Dr. Monk's DIY Electronics Blog

Snootlab Zombadge

2012-02-10T07:13:00.000-08:00

If you want a nice simple board to solder up for fun, or just to learn a bit of soldering, then you might like to consider a Zombadge Kit from Snootlabs. They are kind of fun!

They come as a complete kit, with a lithium cell that fits in a holder on the back.

The instructions for building the kit are clear and simple, in Snootlab's usual photo-cartoon style. They also tell you how to identify the components.

For novices, the RGB LED is a little tricky to solder as the leads are close together, so check for solder bridges when you are finished.

The badge is powered by an ATTiny85 microcontroller fitted in a DIL socket. It has an RGB LED (left) an IR sender and an IR receiver as well as ICSP programming headers.

The ATTiny comes ready programmed and when you turn the badge on, it cycles the LED through its colors.

There are some instructions on installing various games on it here. Theses instructions are mostly in French, with an abbreviated version in English, but I had to refer to the French version to try and see what was going on. Better game translation please Snootlabs.

If you have a number of these badges, you can play some interesting interactive games.

Sadly I only had one, so I had to make do with a flashing LED.

The boards are designed to be programmed using an Arduino as an ICSP, and there are instructions for doing this (in English). Unlike the approach of Hi Low Tech, you do not use the Arduino IDE to program them, but rather run 'make' files after configuring them for the port to use.

I wanted to try programming the boards using the Arduino IDE and a USB Tiny ISP as I have with some home made ATTiny boards, but All I could get was:

Binary sketch size: 658 bytes (of a 8192 byte maximum)
avrdude: initialization failed, rc=-1
Double check connections and try again, or use -F to override
this check.

The schematic for the Zombadge is available on the downloads tab of the product page.

I would be interested to see if anyone gets any further with this. I can see some interesting hacks for this gadget, along the lines of TV be Gone!

Anyway - irrespective of my failed attempts to hack it, this is a nice little gadget!

Arduino Timer Library

2012-01-31T05:40:00.000-08:00

I have developed a simple to use library that gets around a load of problems that arise when you start trying to do much inside 'loop'. It can change pin values or run a callback function. It seems like such an obvious thing that I doubt its original, so I would like to hear of similar projects.

DOWNLOAD Thanks to Jack Christensen for hosting it and the improvements and version management he has added to it.

The library does not interfere with the built-in timers, it just uses 'millis' in a crude type of scheduler to decide when something needs doing.

Examples

The Arduino 'delay' function is both a blessing and a curse. Its great for showing beginners how to make an LED flash. But as soon as you get more complex and start slowing down your 'loop' function you will run into problems.

A classic example is turning a relay on for 10 minutes. The 'delay'-way looks like this:

int pin = 13;

void setup()
{
pinMode(13, OUTPUT);
digitalWrite(pin, HIGH);
delay(10 * 60 * 60 * 1000);
digitalWrite(pin, LOW);
}

void loop()
{
}

The disadvantage of the delay approach is that nothing else can go on while the 'delay' is happening. You cannot update a display, or check for key presses for example.

My 'Timer' library version looks like this:

#include "Timer.h"

Timer t;
int pin = 13;

void setup()
{
pinMode(pin, OUTPUT);
t.pulse(pin, 10 * 60 * 1000, HIGH); // 10 minutes
}

void loop()
{
t.update();
}

The 'pulse' method takes arguments of a pin to change, the period to change it for and its initial state.

The call to t.update() will take a matter of microseconds to run, unless the appropriate period of time has passed.

Lets look at another example that uses two timer events. One to flash an LED and another that reads A0 and displays the result in the Serial Monitor.

#include "Timer.h"

Timer t;
int pin = 13;

void setup()
{
Serial.begin(9600);
pinMode(pin, OUTPUT);
t.oscillate(pin, 100, LOW);
t.every(1000, takeReading);
}

void loop()
{
t.update();
}

void takeReading()
{
Serial.println(analogRead(0));
}

The first thing to notice is that we are using a callback function called 'takeReading'. We connect it to the Timer using the 'every' command, which in this case, will call the function every second.

We have also attached another event to the timer using the method 'oscillate'. This will cause the LED to toggle state every 100 milliseconds.

Each of the events has an integer ID associated with it, so that you can stop an event, as we do in this example below, which will write to the serial monitor every 2 seconds, flash the LED and after 5 seconds, stop the LED flashing fast, and flash it 5 times slowly.

#include "Timer.h"

Timer t;

int ledEvent;

void setup()
{
Serial.begin(9600);
int tickEvent = t.every(2000, doSomething);
Serial.print("2 second tick started id=");
Serial.println(tickEvent);

pinMode(13, OUTPUT);
ledEvent = t.oscillate(13, 50, HIGH);
Serial.print("LED event started id=");
Serial.println(ledEvent);

int afterEvent = t.after(10000, doAfter);
Serial.print("After event started id=");
Serial.println(afterEvent);

}

void loop()
{
t.update();
}

void doSomething()
{
Serial.print("2 second tick: millis()=");
Serial.println(millis());
}

void doAfter()
{
Serial.println("stop the led event");
t.stop(ledEvent);
t.oscillate(13, 500, HIGH, 5);
}

You can attach up to 10 events to a timer.

Installation

As with all libraries, unzip the file into the 'libraries' folder in your Arduino directory, which will be in something like 'My Documents\Arduino' on Windows, 'Documents/Arduino' on Mac etc. If this is the first library you have installed, you will need to create a directory there called 'libraries'.

The library is compatible with both Arduino 1.0 and earlier versions.

Reference

int every(long period, callback)
Run the 'callback' every 'period' milliseconds.
Returns the ID of the timer event.

int every(long period, callback, int repeatCount)
Run the 'callback' every 'period' milliseconds for a total of 'repeatCount' times.
Returns the ID of the timer event.

int after(long duration, callback)
Run the 'callback' once after 'period' milliseconds.
Returns the ID of the timer event.

int oscillate(int pin, long period, int startingValue)

Toggle the state of the digital output 'pin' every 'period' milliseconds. The pin's starting value is specified in 'startingValue', which should be HIGH or LOW.

Returns the ID of the timer event.

int oscillate(int pin, long period, int startingValue, int repeatCount)

Toggle the state of the digital output 'pin' every 'period' milliseconds 'repeatCount' times. The pin's starting value is specified in 'startingValue', which should be HIGH or LOW.

Returns the ID of the timer event.

int pulse(int pin, long period, int startingValue)

Toggle the state of the digital output 'pin' just once after 'period' milliseconds. The pin's starting value is specified in 'startingValue', which should be HIGH or LOW.

Returns the ID of the timer event.

int stop(int id)
Stop the timer event running.
Returns the ID of the timer event.

int update()
Must be called from 'loop'. This will service all the events associated with the timer.

Conclusion

Have a go with the library, please let me know what you think.

A Review of SnootLab's 'Memoire' Arduino Shield

2012-01-23T08:32:00.000-08:00

SnootLabs were kind enough to send me one of their Memoire Shields. This useful little shield combines an SD card slot with a DS1307 Real Time Clock (RTC). If you haven't come across one before, an RTC is a hardware clock with its own battery back-up, so that when your Arduino gets turned off, it does not forget the time.

The rationale for combining SD card with a RTC is that you can read temperatures or whatever and write then to the SD card along with the date and time form the RTC.

This useful card costs about 25 USD in kit form and a bit more ready assembled. I actually enjoy this kind of thing in kit form. It is easy enough to assemble and the instructions are clear and logical. They are found on the 'downloads' tab for the product information and you will also find the schematic and Eagle files there too.

One immediately noticeable feature of the board is the prototyping area. Which gives you can solder in your own temperature sensors or whatever else you want to log along with the time.

Rather than make a logger, I decided to make myself a thick juicy Arduino sandwich and combine it with a Freetronics LCD shield and an Arduino Uno to make a clock. I reviewed LCD Shields a while back.

Its a rather expensive and over-engineered clock - but none the less a clock. You set the time by sending a string from the Serial monitor and from then on, it will keep time for you.

The three boards are shown below.

The Snootlabs shield is placed on the Arduino Uno and then the LCD shield on top of that.

The only potential conflict in pin usage between the two shields is for pin D9 that is used for a general purpose LED on the Snootshield. As the LCD shield uses this for LCD Enable, occasional flickering of the LED was not seen as a problem.

Conclusion
In summary, its a useful shield with good documentation from SnootLabs.

There are other boards including this from AdaFruit. The AdaFruit version is a similar price and even a similar layout. It does however use a buffer chip for the SD interface, where as the Snootlabs design uses potential dividers to drop the SD card levels.

Correction: In an earlier version of this post, I stated that the Snootlabs device did not have its own regulator - actually it does. Its a SMD ready soldered onto the bottom of the board.

The code for the example project was adapted from here. Its Arduinio 1.0 code.

#include "Wire.h"
#include <LiquidCrystal.h>

#define DS1307_ADDRESS 0x68
byte zero = 0x00; //workaround for issue #527
LiquidCrystal lcd(8, 9, 4, 5, 6, 7);

void setup()
{
Wire.begin();
Serial.begin(9600);
Serial.println("Set date sending format: YYMMDD HHMMSS W");
Serial.println("Where W = day of week - 1-7");
lcd.begin(16, 2);
lcd.print("Clock");
}

void loop()
{
if (Serial.available())
{
setTimeFromSerial();
}
printDateTime();
delay(1000);
}

void setTimeFromSerial()
{
byte year = (Serial.read()-'0') * 10 + (Serial.read()-'0');
byte month = (Serial.read()-'0') * 10 + (Serial.read()-'0');
byte day = (Serial.read()-'0') * 10 + (Serial.read()-'0');
Serial.read();
byte hour = (Serial.read()-'0') * 10 + (Serial.read()-'0');
byte minute = (Serial.read()-'0') * 10 + (Serial.read()-'0');
byte second = (Serial.read()-'0') * 10 + (Serial.read()-'0');
Serial.read();
byte weekDay = (Serial.read()-'0');

Wire.beginTransmission(DS1307_ADDRESS);
Wire.write(zero); //stop Oscillator

Wire.write(decToBcd(second));
Wire.write(decToBcd(minute));
Wire.write(decToBcd(hour));
Wire.write(decToBcd(weekDay));
Wire.write(decToBcd(day));
Wire.write(decToBcd(month));
Wire.write(decToBcd(year));

Wire.write(zero); //start

Wire.endTransmission();

}

byte decToBcd(byte val){
// Convert normal decimal numbers to binary coded decimal
return ( (val/10*16) + (val%10) );
}

byte bcdToDec(byte val) {
// Convert binary coded decimal to normal decimal numbers
return ( (val/16*10) + (val%16) );
}

void printDateTime(){

// Reset the register pointer
Wire.beginTransmission(DS1307_ADDRESS);
Wire.write(zero);
Wire.endTransmission();

Wire.requestFrom(DS1307_ADDRESS, 7);

int second = bcdToDec(Wire.read());
int minute = bcdToDec(Wire.read());
int hour = bcdToDec(Wire.read() & 0b111111); //24 hour time
int weekDay = bcdToDec(Wire.read()); //0-6 -> sunday - Saturday
int monthDay = bcdToDec(Wire.read());
int month = bcdToDec(Wire.read());
int year = bcdToDec(Wire.read());

lcd.clear();
lcd.setCursor(0, 0);
lcd.print(hour);
lcd.print(":");
if (minute < 10) lcd.print("0");
lcd.print(minute);
lcd.print(":");
if (second < 10) lcd.print("0");
lcd.print(second);

}

DIY Coilgun

2012-01-17T08:41:00.000-08:00

Here is one of the projects from the book '15 Dangerously Mad Projects for the Evil Genius'. You can actually download the chapter in full, free of charge, from here so I will just give an overview of it here.

Its pretty simple to make and safe. I kept the voltage low (36V), although it does pack about 100A through the coil in 10mS and it will fire a small section of nail at a maximum of about 30 mph.

WARNING: BE SENSIBLE! DONT FIRE IT AT ANYONE, INCLUDING YOURSELF.

Here is the schematic.

And this is how it is wired together.

If you fancy having a go, be my guest and download the chapter and if you like it, then you might like to try some of the other projects. There is a real mixture. Some like the Trebuchet don't actually involve any electronics at all and three of them use Arduinos.

Projects List

Chapter 01. Coil Gun

Chapter 02. Trebuchet

Chapter 03. Ping Pong Ball Minigun

Chapter 04. Mini Laser Turret

Chapter 05. Balloon-popping Laser Gun

Chapter 06. Laser sight

Chapter 07. Laser Intruder Alarm

Chapter 08. Persistence of Vision **** Arduino

Chapter 09. Covert Radio Bug

Chapter 10. Laser Voice Transmitter

Chapter 11. Flash Bomb

Chapter 12. LED Strobe

Chapter 13. Levitation Machine **** Arduino

Chapter 14. Light Seeking Microbot

Chapter 15. Surveillance Robot **** Arduino

There is also a video on youtube showing the more interesting projects.

Laser Cutting at FabLab Manchester

2012-01-15T12:26:00.000-08:00

Manchester FabLab allows anyone to go along and use their kit for free on Fridays and Saturdays on condition that we make public what we do. So I paid them a visit on Friday to cut myself a new enclosure for my Arduino Lilypad Binary Clock.

The clock is one of the projects from my book '30 Arduino Projects for the Evil Genius'. Its a binary clock with four red LEDs indicating the hour, six blue LEDs the minute and six green LEDs the second. They all fan out from the Arduino Lilypad. A reed switch is used to advance the clock by holding a magnet close to it.

Its a little difficult to photograph, so here it is again on a white background. I quite like the effect of the white background and may fit a backing to the acrylic.

The clock was formerly housed in a picture frame. Which looked okay, but I thought it should be possible to make something nicer:

The new enclosure does not really do much enclosing. Its just a sheet of 3mm clear acrylic, cut in the shape below. This allows the LEDs to sit in the channels and allows a space in the center for the Lilypad.

The PDF for the clock face is available on the book's website in the download section.

The laser cutter is a Epilog Mini 24 Laser Cutter and I wasn't really taxing it much to cut the acrylic.

As well as a laser cutter, Fab Lab has a 3D printer, a Desktop Milling machine, a Vinyl cutter, a large CNC Router, a vacuum former and well equipped electronic workstations.

This is all backed up with a knowledgeable and helpful set of staff as well as well as lots of people around happy to help out.

Power Over Ethernet (PoE)

2012-01-12T05:22:00.000-08:00

Power over Ethernet or PoE is one of those things that sound difficult but actually at its simplest is very easy to use and a great way to reduce the number of cables. For all I know, when you get into more advanced PoE it does become scary, but all I wanted to do was to be able to do away with a wall-wart power supply lead for my little Altoids tin project.

If you look next to the 'L' of Altoids, you can see the lens of a Luxeon LED poking through. What I have here is a modification of my web morse flasher project described in my earlier blog about the EtherTen. The EtherTen is a combined Arduino and Ethernet board.

This project runs the EtherTen as a web server that gives you an interface like this:

And when you press 'Send' it flashes out the message on the LED in Morse code.

By using PoE I could mount my useful messenger device on the wall, with only a single wire coming out of it (the Ethernet cable). This would provide both power and network connection.

The module I used to accomplish this magic trick is the Freetronics 4-Channel Power-over-Ethernet Midspan Injector. This device costs about 25USD.

To use it, you insert it between your device and your home hub and plug it into a power adaptor. Hey presto, it then supplied power over the Ethernet cable.

I used a 12V DC power supply. SO you still need a separate power supply, but at least it and its wire can be kept out of sight.

You need to insert two jumpers on the EtherTen just behind the RJ45 socket. These are supplied with the EtherTen, but are not connected when shipped. You just bridge the top two connections together and also the bottom two connections.

Note to UK readers - you can buy Altoids in Tescos.

I cut bits out of the bottom with a Dremell - lots of sparks - wear glasses - and drilled a hole in the lid for the LED. I also had to cut a bit off the protpshield so that it fitted flat and fully into the EtherTen's sockets.

I put lots of PVC insulating tape anywhere where electronics might come into contact with metal.

The EtherTen fits perfectly into the Altoids box, making a perfect little web server.

Conclusion

PoE does not have to be difficult or expensive to use. If you are using an Arduino as a web server then this approach could simplfy your wiring - so consider it.

Disclosure: Freetronics gave me the Midspan Injector. I did however have to buy my own mints - and very tasty they were too!

Canine Radio Direction Finder - Part 2

2012-01-06T01:54:00.000-08:00

Its been a long time coming, but my son Matt and I finally finished the radio direction finder project. I described part 1 (the transmitter back in November 2011. This post describes the receiver.

The basic idea is that the transmitter sends beeps and you turn the directional antenna until you get maximum signal and that is the direction of the transmitter.

It doesn't work terribly well. The reason being the antenna is quite sensitive, so even though it is directional, if the transmitter is close then you cant tell which way it is. So it only works in the sweet spot where the transmitter is far enough away for the signal to be smaller when the the antenna is pointing the wrong way but not so far away that you cannot get a signal at all. For us, this range was perhaps 30 to 100 yards.

What is really needed is some means of varying the gain of the antenna. We ran out of enthusiasm before solving this problem.

Anyway, it does work after a fashion and its quite fun and cheap to make.

This is the schematic.

Its just an audio amplifier that amplifies the signal from the RF module. The module is the other half of the transmitter module and something like this. Make sure you get an AM module - that matches the frequency of the transmitter.

If you want to use a speaker, omit R3, but we found headphones better. So in the diagram above the speaker is actually a headphone socket.

The directional antenn is made from a piece of wood, with lengths of retractable steel ruler attached to it. The design was taken from a posting on an Australian forum that I now cannot find. But I'm sure they wouldn't mind my repeating it here.

The second element takes the connection to the receiver circuit and this is made with a short length of TV antenna lead.

You can also see how the strips of ruler are just screwed onto the wood.

As I mentioned the results were a little disappointing. But then the whole project cost about 20 USD and we had some fun. Especially wandering around the neighbourhood wearing headphones and clutching what looks like a home made TV antenna. This is the kind of situation where it is best to just to cultivate a wild look in the eye and hope people don't bother you or call the police.

Arduino Screw Shield Review

2012-01-01T03:26:00.000-08:00

This is a review of the Freetronics Terminal Shield and the SnootLabs Power Screw Shield.

Introduction.
The Arduino socket strips are okay for attaching components, but sometimes, when putting together a quick prototype it would be useful to be able to have something more substantial - like a screw terminal.

These shield boards provide just such a feature.

Snootlabs Freetronics

The shields are intended for the Arduino Uno and earlier versions of Arduino. They break out all the terminal sockets into screw terminals.

Prices
The Snootlabs shield costs around 21 USD as a kit and 28 USD fully assembled.
The Freetronics shiled is only available fully assembled and costs around 17 USD

In Common
Both boards use straight through headers that mean as well as having screw terminals, you can also fit another shield on top. In both cases, the designers have left enough room to easily access the screw terminals even with a big shield like an LCD shield attached.

Both boards have a reset button.

SnootLabs Power Screw Shield
This is the larger and more expensive of the two shields. It has a large prototyping area where you can solder in components. It also has special areas of the board for soldering in a SMD chip and for DIL through hole ICs.

The other noticeable difference is the power connector. This is the same type of four pin connectors that you used to find on PATA Hard Disks to supply the power.

Jumpers allow you to configure this socket to either provide the power to the Arduino, or to pass through the Vin 2.1mm socket on the Arduino to the 4 pin socket to provide power to other devices.

There is also an LED that can either be linked to an IO pin of your choice or to 5V to act as a power-on indicator.

The Snootlabs website has very good information on this shield, including a photographic style sheet of instructions for constructing the board and a useful datasheet that explains what all the jumpers do without having to start working out whats going on from the schematics.

Providing the board in kit form is a nice idea. As well as being cheaper, its a nice easy project for someone new to electronics wanting to practice their soldering.

Freetronics Terminal Shield

As with all Freetronics kit. This is a high quality board that is sold fully assembled. Its smaller and cheaper than the Snootlabs shield and does not have a dedicated IC area for SMD or 0.1inch DIL. It does exactly what it says on the tin.

The board comes with a number of surface mount components already attached to it. This includes three (red, green and blue) LEDs and their current limiting resistors. These are positioned on the back ende of the shield where they are easily visible and can be wired to any of the IO pins.

Conclusion

Both products are good quality and neither will dispoint.

If you need to use an SMD IC for your project then the dedicated area for this makes the Snootlabs shield a good choice. The same applies if you need all the prototyping area you can get.

If this is not a consideration then the cheaper Freetronics shield will serve you just fine.

Other Options

Other screw shields are available of course and if you do not need the prototyping area then something like the WingShield may be of use to you. http://wingshieldindustries.com/products/screwshield/

Sparkfun and Adafruit both sell shields similar to the Freetronics offering: http://www.sparkfun.com/products/9729 and http://www.adafruit.com/products/196

Arduino Oscilloscope Update

2011-12-28T05:24:00.000-08:00

Project 18 in my book 30 Arduino Evil Genius Projects for the Evil Genius, is a very crude Arduino-based Oscilloscope - well more of an experiment really.

It just reads data from A0, divides it by 4 so it would fit in a byte and then sent it over USB to a receiving program that I wrote in Ruby and Tk.

// Project 18 - Oscilloscope

#define CHANNEL_A_PIN 0

void setup()
{
Serial.begin(115200);
//Serial.begin(9600);

}

void loop()
{
int value = analogRead(CHANNEL_A_PIN);
value = (value >> 2) & 0xFF;
Serial.print(value, BYTE);
delayMicroseconds(100);
}

Here is the schematic - it just creates a 2.5V reference and AC coupling.

Note that there is no overvoltage protection, so understand what you try and measure with it, or you could damage or destroy your Arduino.

A few people have been having trouble using Tk and Ruby, so I decided to redo the sketch in Processing.

As I said, very crude, but feel free to improve it and make something of it.

If you haven't had a play then do so, its great! If you are used to Arduino, then the IDE will be very familiar to you. Instead of 'setup' and 'loop' you have 'setup' and 'draw'.

The full processing sketch is listed below and if you just want an executable (mac, Linux and Windows), you can download this from the 'downloads' page on the book's website.

import processing.serial.*;

final int dt = 5;
final int width = 800;
final int height = 600;
final int messageHeight = 30;

Serial myPort;
int reading;
int t = 0;
int a_ = 128;

void setup()
{
size(width, height);
background(255, 255, 255);
makeConnection();
}

void draw()
{
if (t == 0)
{
while (getNextReading() != 128) {}; // wait for zero crossing
}
int a = (256 - getNextReading()) * 2 + messageHeight;
// clear a vertical strip just infront of waveform
fill(255, 255, 255);
noStroke();
rect(t, messageHeight+1, dt, height-messageHeight);
// draw 0V line
fill(0, 255, 0);
stroke(1);
line(t, 256 + messageHeight, t+dt, 256 + messageHeight);
// draw the waveform line
fill(255, 0, 0);
stroke(2);
line(t, a_, t+dt, a);
t += dt;
a_ = a;
if (t > width) t = 0; // flyback to start
}

int getNextReading()
{
try
{
int readAttempts = 0;
while ( myPort.available() < 0 && readAttempts < 10000)
{
readAttempts ++;
}
return myPort.read();
}
catch (Exception e)
{
makeConnection();
}
return 128;
}

void makeConnection()
{
// I know that the first port in the serial list on my mac
// is always my FTDI adaptor, so I open Serial.list()[0].
// On Windows machines, this generally opens COM1.
// Open whatever port is the one you're using.
String portName = "None";
try
{
portName = Serial.list()[0];
myPort = new Serial(this, portName, 115200);
notify("Port: " + portName);
}
catch (Exception e)
{
warn("Not Connected: " + portName);
}
}

void notify(String message)
{
fill(255, 255, 255);
stroke(0);
rect(0, 0, width, messageHeight);
fill(0, 0, 255);
text(message, 0, 20);
}

void warn(String message)
{
fill(255, 0, 0);
stroke(0);
rect(0, 0, width, messageHeight);
fill(0, 0, 0);
text(message, 0, 20);
}

Freetronics EtherTen Review

2011-12-21T02:01:00.000-08:00

If you have read some of my other blog posts, you will know that I am a bit of a fan of Freetronics.

They may not be the cheapest Arduino boards and shields, but the quality of both design and manufacture is of the highest standard.

This is a review of the Freetronics EtherTen board. This board effectively combines an Arduino Uno with an Ethernet shield. This board costs AUD 69.95 (about USD 70) which is cheaper than an Uno + Ethernet card (29.95 + 45.95 = USD 79) and a lot smaller and more convenient.

Features

The EtherTen has a Micro SD slot (why would you need anything bigger?). This is very handy if you are using the EtherTen to serve a lot of content or are using it for any kind of data logging application.

Connection to your computer is by a miniUSB which saves space. There are various headers that allow you to do clever things like use PoE (Power over Ethernet) as well as status LEDs that let you know what's going on.

In common with all Ethernet devices it gets pretty warm, and I left my project (see below) running all night, with no ill effects.

The board functions just like an Arduino Uno + Ethernet shield. I used it on Arduino 1.0 and standard Ethernet library without having to change anything. It all just worked first time.

Conclusion

This is a terrific little board and if you have an Ethernet Arduino project in mind, I would recommend it over using separate Uno and Ethernet shield combination. Its cheaper and it will keep your Arduino sandwhich from looking like something Scooby-Doo would eat.

If you want to see how I used it in a little test project then read on....

Mini-Project

In reviewing a product, I always like to try it out with some little project I, rather than use simple example sketches, so I decided to try out an Ethernet Telegraph. A bit silly really, but the idea is that the EtherTen would act as a web server connected to my home hub (next to my desk) and would have a homemade Luxeon LED shield attached to it. Then when my beloved wanted to contact me, she could open a browser page (even from work if I open up the firewall) and type in a message, that would be relayed to me as the Luxeon LED flashing me in Morse Code.

I used to know a little Morse, but actually, I'd probably have to note it down then decode each letter. Still, thats not the point.

This is the web page:

Here is the shield attached to the EtherTen:

The shield is from my book '30 Arduino Projects for the Evil Genius'. I had to change the pin it uses from 11 (which is used by the EtherTen) to pin 8. Here are the schematic and protoshield layouts for the shield.

The sketch for all this is listed below. It is a modified version of a sketch from my book 'Programming Arduino' see page 74 for an explanation of the Morse part and Chapter 10 for the Ethernet part.

You may need to change the IP address on line 6, to something compatible with your home network.

#include <SPI.h>

#include <Ethernet.h>

int ledPin = 8;

byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };

IPAddress ip(192, 168, 1, 177);

EthernetServer server(80);

char line1[256];

int dotDelay = 100;

char* letters[] = {

".-", "-...", "-.-.", "-..", ".", "..-.", "--.", "....", "..", // A-I

".---", "-.-", ".-..", "--", "-.", "---", ".--.", "--.-", ".-.", // J-R

"...", "-", "..-", "...-", ".--", "-..-", "-.--", "--.." // S-Z

};

char* numbers[] = {"-----", ".----", "..---", "...--", "....-", ".....", "-....", "--...", "---..", "----."};

void setup()

{

pinMode(ledPin, OUTPUT);

digitalWrite(ledPin, LOW);

Ethernet.begin(mac, ip);

Serial.begin(9600);

}

void loop()

{

EthernetClient client = server.available();

if (client)

{

while (client.connected())

{

readHeader(client);

if (! pageNameIs("/"))

{

client.stop();

return;

}

client.println("HTTP/1.1 200 OK");

client.println("Content-Type: text/html");

client.println();

// send the body

client.println("<html><body>");

client.println("<h1>Morse Sender</h1>");

client.println("<form method='GET'>");

client.println("Message:    ");

client.println("<input type='TEXT' name='m' size='100'>");

client.println("<input type='submit' value='Send Morse'/>");

client.println("</form>");

client.println("</body></html>");

client.stop();

processHeader();

}

void processHeader()

{

// header lloks like this:

// GET /?m=Happy+Christmas HTTP/1.1

// so Morse flash everything from [=] to [space]

int n = strlen(line1);

int i = 0;

while (i < n && line1[i] != '=') i++; // skip to =

while (i < n && line1[i] != ' ')

{

flashCharacter(line1[i]);

i++;

}

boolean pageNameIs(char* name)

{

// page name starts at char pos 4

// ends with space

int i = 4;

char ch = line1[i];

while (ch != ' ' && ch != '\n' && ch != '?')

{

if (name[i-4] != line1[i])

{

return false;

}

i++;

ch = line1[i];

}

return true;

}

void readHeader(EthernetClient client)

{

// read first line of header

char ch;

int i = 0;

while (ch != '\n')

{

if (client.available())

{

ch = client.read();

line1[i] = ch;

i ++;

}

line1[i] = '\0';

Serial.println(line1);

}

void flashCharacter(char ch)

{

if (ch >= 'a' && ch <= 'z')

{

flashSequence(letters[ch - 'a']);

}

else if (ch >= 'A' && ch <= 'Z')

{

flashSequence(letters[ch - 'A']);

}

else if (ch >= '0' && ch <= '9')

{

flashSequence(numbers[ch - '0']);

}

else if (ch == '+')

{

delay(dotDelay * 4); // gap between words

}

void flashSequence(char* sequence)

{

int i = 0;

while (sequence[i] != NULL)

{

flashDotOrDash(sequence[i]);

i++;

}

delay(dotDelay * 3); // gap between letters

}

void flashDotOrDash(char dotOrDash)

{

digitalWrite(ledPin, HIGH);

if (dotOrDash == '.')

{

delay(dotDelay);

}

else // must be a -

{

delay(dotDelay * 3);

}

digitalWrite(ledPin, LOW);

delay(dotDelay); // gap between flashes

}

Note: In the interests of transparency, Freetronics did supply me with a board for review, but I can honestly say that this has not biased my opinion of the board.

.NET Gadgeteer - First Impressions

2011-12-13T07:35:00.000-08:00

It shows just how far Arduino and the other open source hardware platforms have come, when Microsoft wants to get in on the act.

The question often posed is 'is .NET Gadgeteer an Arduino Killer?'

vs.

The answer is an emphatic NO, it isn't. In the same way that a Rolls-Royce isn't a pedal cycle killer. They are both vehicles and some people will own one of each, but they are very different beasts.

It is rare that you get very far with an Arduino without a bit of soldering. It has a laughably feeble processor, tiny amounts of RAM and program storage. However, thats often all you need. Its 'lightness' is part of its charm.

The .NET Gadgeteer is a quite different beast. The kit I have is the 'Fez Spider Starter Kit' from GHI electronics. And it comes with a fantastic range of things to connect to your Controller board.

Yup, thats right, there is a camera, a large LCD touch screen, a joystick, multicolor LED, USB host, SD card and even a little push button. And they all have little DIL connectors, so you assemble your project by plugging things together. Nearly all the components actually have their own microcontroller, and I suspect there are more transistors in one of these kits than a thousand Arduinos.

So whereas an Arduino project will often involve a shield, that has a few components on, say a screen and a joystick, in the Gadgeteer world, you plug in separate components using lengths of ribbon cable. So the front of a Gadgeteer controller board is covered in sockets into which things can be plugged.

There are rules about what can be plugged into what, but we will come to that in a moment.

You can see the separate programmer, which yes, you guessed it uses one of those little sockets to connect it to your computer via USB. When I say your computer, obviously I mean your Windows computer. You program the Gadgeteer using the Visual Studio integrated development environment, and this is only available for Windows. However, Mac and Linux users do not despair. I had no problems running the development environment on Virtual Box and Windows on my Mac.

I have to say that programming the Gadgeteer was a very pleasant surprise. The libraries are very well though out and easy to use and backed up by a really excellent hardware designer. Let me show you.

In this mini project I am connecting a joystick and a RGB LED. So, as I change the position of the joystick, it will use the X position of the joystick to control the brightness of the blue channel of the LED.

So, before I actually plug together the physical hardware, I plug together virtual hardware on the designer. This does nice things like tell me which of the sockets are compatible with the peripheral I am plugging in.

Then, when I am done designing the hardware, I hit save, and a load of boilerplate code is generated for me. All I need to do then is add in a Timer and a single line that reads the X position, scales it and assigns it to the blue channel of the LED and I am done.

Installing it in the actual hardware is a button press and what's more I can use a proper debugger and set break-points in my code and everything.

Very cool.

Conclusion.

I can see .NET Gadgeteer working really well in educational settings. Its a great way of getting kids to understand that their gadgets don't just fall ready formed from the sky, but they get designed by people like them. The ability to make things without soldering is sadly another win in our safety conscious society.

It is a very well thought out and consistent system that provides another approach to hardware development for the masses.

Arduino 1.0 First Impressions

2011-12-06T02:31:00.001-08:00

The Arduino software - the development environment that you run on your computer to be able to write programs and program your Arduino has bumped versions. It has gone from version 23 to version 1.0

The first thing to say that while this is a major (if slightly confusing) update in version numbering, it is more of a tidy up and general stability release than any major change in functionality. The rewrite as a stand-alone Eclipse RCP, would have been my choice, but never mind.

The two IDE's are shown side by side below:

Arduino 1.0 Arduino 23

I know these are too small to see properly, but I wanted to illustrate one of the changes. The color! Does anyone else think that IDE's should be a more macho color like black or silver, rather than the color of over-boiled brocoli?

Anyway, here is a bigger picture of the new IDE:

The first thing I noticed (apart from the horrendous color) was the really useful text at the bottom of the editor that correctly told me I had a Mega attached to a serial port, and the serial port's name. This is a nice touch.

Another improvement, for beginners especially, is that the toolbar items have been given an overhaul.

Old Arduino 23 Tool bar.

New Toolbar:

The new icons make a lot more sense. The Play button of earlier versions that compiles without uploading to the board just becomes a 'check' icon. The button next to it uploads to the board and the other three icons allow you to start a new sketch, open and save sketches respectively.

So, what's new then?

Looking at the release notes, the main new features are:

The sketch file names extension has changed from .pde to .ino. See later where I talk about compatibility.
Serial Communications using the standard UART (Rx and Tx pins) has been improved
The SoftwareSerial library has been supplanted by the superior NewSofwareSerial library. This allows you to have several serial connections on the go at the same time.
The String class has been reimplemented - if you like that kind of thing
There is a nice new syntax for putting your strings into flash (PROGMEM) rather than having to use up valuable RAM. You just wrap it in F() like this: Serial.print(F("hello world")). Very cool!
The Ethernet library now has DHCP and DNS support - thanks to Adrian McEwen. This is a great improvement, although it does unavoidably swell the library size.
The Wire and SD libraries have been improved and tidied up.

Compatability

The one thing that scared me in the release notes was the change in extension from .pde to .ino. But I needn't have worried. When I started up Arduino 1.0 IDE, the sketches that I had previously left open in Arduino 23 opened too.

If you create any new sketches, they will automatically get saved with the .ino extension, however, it is only when you come to save an existing sketch after modifying it, that you will get the following prompt.

Which is fine. But if you have an important sketch, make a backup of it somewhere before changing it in 1.0 in case you need to go back to 23.

One issue is the amount of flash the sketches take up when deployed fo an Arduino board. All these improvements come at the cost of bigger fiels, especially if you use some of the new libraries (http://arduino.cc/forum/index.php/topic,81070.0.html)

Conclusion

The Arduino team have been brave in adressing some overdue tidying up and enhancements. But with all such changes, the is likely to be some disruption.

There are likely to be problems with some existing libraries, so my plan is to stick with 23 for all my exisiting projects, for any minor changes and use Arduino 1.0 for any new developments. There is no problem having both IDE's available, just edit their names so that you can tell them apart.

Oh, and Arduin team - please do something about that color! A Preferences setting would be great.

Photo Etching: Part 3 - Make a Timer

2011-12-05T03:22:00.001-08:00

Now that we can create our own circuit boards, lets improve our UV Light Box, by adding an automatic timer to it.

The PCB is designed in EagleCAD. A free version is available for non-commercial use. It is not the easiest software to use, but you will soon get the hang of it with a bit of patience. The Eagle project files are available here.

We will use the famous and much used 555 timer and a variable resistor to control the length of the exposure. We will also have two indicator LEDs. A red one to indicate that power is supplied to the Light Box and a blue one that will only be illuminated when the UV LEDs are lit.

You will need the following parts:

1 x NE 555 time

1 x 8 pin DIL IC socket

1 x MΩ Log potentiometer

2 x 470Ω 0.5W metal film resistor

1 x 33KΩ 0.5W metal film resistor

1 x 100µF 16V electrolytic capacitor

1 x Red 3mm LED

1 x Blue 3mm LED

1 x FQP7N10 N-Channel MOSFET 1

1 x Push to make switch

The schematic diagram for the board is shown below, along with the board itself.

The board design is included in this zip. Its also shown below, but not to the correct scale.

Print off the timer board design onto transparency film and expose it in the same way as you did for your test strip, using the exposure you decided on in the previous section.

Make sure that you put the transparency on top of the board the right way up. I.e. it should have the rougher side on which the image was printed to the top, as the PCB layout shown at the end of the document is from the perspective of looking through the board from above and so we need to reverse it.

When the transparency is on the board in a position for printing, the text should read correctly rather than be mirror image.

Once the board is etched, you will need to drill the board using a 1mm drill bit. Use the diagram below to identify the position of each component. Solder the components into place, starting with the lowest components first.

The potentiometer is attached to short wires to make it stand far enough away from the board to fit into our enclosure. Depending on the design of your index box, you may not need to do this. Similarly, wires are soldered between the termination points on the circuit board and the switch. This also applies to the connection to the UV LED Array and the power socket.

Note that you could use screw connectors for J1, J2 and J3 on the board, but I just soldered leads directly to the board.

Note also the two red jumper links that are required.

Test the board connected to the power supply and the switch using just the blue LED, before fitting everything into the box and connecting up the UV LED panel.

Line up the completed board against the inside of the box and mark the position in which to drill the holes for the potentiometer, the push switch and the LEDs. The collar of the potentiometer and the snug fit of the LEDs into their holes is used to keep the board in place.

After it is all assembled, we need to calibrate the timer. I used a paper label onto which I marked the times, including the optimal time for my set of equipment of 30 seconds.

A stop watch and trial and error was used to calibrate the dial.

Conclusion

It is beyond the scope of this article to go any further into PCB design. The author uses the free (for home use and small boards) Eagle CAD software. This excellent software takes a little getting used to, but is very powerful and will attempt to automatically create board layouts from your schematic diagrams.

Have fun, but above all, be careful - almost everything in this project is dangerous!

Photo Etching: Part 2 - Exposure and Etching

2011-11-29T01:38:00.001-08:00

We have a functioning light box, so, now its time to do some etching!

WARNING: IN THIS SECTION WE ARE USING POISONOUS CHEMICALS, THAT CAN ALSO BURN. WEAR PROTECTIVE GOGGLES AND GLOVES WHILE HANDLING THESE CHEMICALS.

ALWAYS FOLLOW THE INSTRUCTIONS INCLUDED WITH THE CHEMICALS EVEN WHERE THEY DIFFER FROM THE INSTRUCTIONS BELOW.

You will need:

An assembled light box from Part 1 of this blog entry
Small single-sided pre-sensitised copper-clad board 100mmx75mm
Craft knife
Steel rule
Scissors
Sodium persulphate etch powder
Universal photo-etch developer
Disposable latex gloves
Safety goggles
Empty bottles to contain the mixed chemicals (not the bottles should be clearly labelled POISON - DO NOT DRINK)
A bucket
Developer trays, I use recycled plastic food tubs

Everyone learns by making mistakes. Every exposure box is likely to have a slightly different intensity, and need different lengths of exposure. Also your inkjet printer, transparency film and copper-clad board are all likely to be different to mine. Although there is actually quite a wide margin or error, we need to try and find the optimal exposure for our set of equipment without wasting too much copper clad board.

So, to avoid frustration, just accept that you are not going to get anything except knowledge out of your first few dollars worth of copper-clad board and transparency film.

We are going to start by making a test strip to determine the best exposure for our printer / board / lightbox combination. This is a technique taken from ‘good old fashioned’ film photography. The idea is that we will have a test pattern printed onto transparency film that we will partially cover up with the first exposure and then gradually move the card to expose more of the board for the subsequent exposures.

But first, let’s print the test strip onto transparency film.

Printing

First of all, we need to create a test strip pattern. The test strip below can be printed directly by printing the last page of these instructions onto transparency film. This film used to be used extensively for presentations on over-head projectors.

I use an inkjet printer, but if you have a laser printer then you can also get transparency film for them. Be sure to get film for your correct type of printer. You cannot put inkjet film into a laser printer and vice-versa. Any major office supplier will sell transparent film.

We need to print as boldly onto the transparency film as possible to ensure as little UV as possible leaks through to the coper clad board. To do this, make sure that you set:

the media type to ‘Transparency’

document type to ‘Monochrome’

quality to ‘Maximum’

The transparency sheets are relatively expensive, so I tend to print at the top of the page and then cut the top of the film and use the remainder for the next board, getting three or four boards out of one film.

When you have printed the film, try to keep it clean until you are ready to use it, as any little specs of dust will end up as copper.

A Test Strip

Firstly we need to cut up our sacrificial copper clad board into test strip sized pieces. You can do this with a craft knife and metal rule. Score the board top and bottom, where you want to cut it and then snap it over the edge of a table.

You will notice that the copper side of the board has a thick layer of light-proof plastic covering. This will need to be removed from the test strip before exposing it.

Here are the steps for creating your test strip.

Mix water into the developer powder according to the instructions on the packet. Mixing them into a storage bottle. If the chemicals are designed to work at a higher than room temperature then place the bottle it in a bucket of hot water to bring them up to temperature.
Do the same for the etch solution.
Trim the transparency film to be about the same size as the copper-clad board.
Disassemble the clip frame
Peel the protective layer off the board and place is sensitized side up on the base of the clip-frame
Place the test strip over the board
Fix the glass lid of the frame back into place.
Place the whole photo frame into the bottom of the light box.

Now we can begin making the exposures.

We are going to make four exposures, for the first three covering successively less and less of the test board.

The sequence is:

Cover sections D, C and B with a thick piece of card (on top of the glass) and expose for 40 seconds.
Move the board to cover just the sections D and C and expose for 20 seconds
Move the board to just cover section D and expose for 10 seconds
Remove the board completely and expose for 10 seconds

Developing

By this time your chemicals will be at the right temperature and we can develop the board. If you are not quite ready to develop yet, then it does not matter, as long as you cover the board to prevent any further exposure from ambient light. Turning it upside-down is sufficient.

Put on your protective eye-ware and latex gloves and place the board copper side up in the tray that you are going to develop in.

Pour some developer onto the board enough to cover it with about half an inch of developer. Then gently rock the tray back and forth. You should soon see a picture starting to develop. Do not remove the board from the developer until the test strip image is clearly visible and well defined on the board. It is much easier to under-develop the board than to over-develop it, so if in doubt leave it in the developer a bit longer.

When its ready, it should look something like this:

When you are happy that the board is ok, then remove it and wash it in the water in your bucket. Pour your developer back into its storage bottle ready for next time.

Etching

Either use a separate tray from the developing tray or clean your developer tray very carefully, then place the board in copper side up again and pour the etchant over it. Again a depth of about half an inch is ideal. The etchant solution will gradually go blue as it dissolves the copper that is not protected by the photo-resist image, so it is much easier to see what is going on if you don’t fill the tray right up.

You may have to fish the board out of the etchant form time to time to check on it.

Almost immediately, you will notice the exposed copper areas to start to go pink. You know when the board is ready when all the pink areas have gone. The two pictures below show a board that is not quite ready yet followed by a board that is fully etched.

When the etching is complete, put it back into the bottle and put your chemicals away safely out of the reach of children. Especially the etchant, which turns an attractive blue color when used.

Wash the board again, and you are done!

Assessing the Test Strip

An example test strip is shown below.

On the left had side of the board, 10 seconds was not enough as most of the copper is still there. On the other hand 80 seconds was too much as the UV clearly went straight through the printed mask.

40 seconds was still a bit much, but 20 seconds was just about right. Echos of Goldilocks there!

In the final part of the blog entry we will use our new toy to create a PCB for a timer to control the the UV exposure box.

Now I call that bootstrapping!

Photo Etching: Part 1 - UV Light Box

2011-11-27T08:52:00.001-08:00

Before I get started, I first need to say that I haven't forgotten about part 2 of my 'Canine Direction Finder'. The receiver is on breadboard and all that remains is to build a directional antenna. So, watch this space.

In the mean time, I thought I would add this article I wrote a while back about making your own PCBs using photo etching. Starting by creating your own UV light box using UV LEDs.

Creating your own printed circuit boards is not as difficult or expensive as you might think. In this article, I describe how you can use pre-sensitised boards and a home made light box to create your own boards.

Introduction

Photo etching uses a transparency with an image of the PCB to be created printed onto transparency film, that is then placed over copper-clad board that has been pre-sensitised. These boards are not much more expensive than plain boards. The board is then exposed to UV light through the transparency film.

The board is then put into a tray of developer and the image of the PCB tracks will become visible on the board just like an old fashioned photograph being developed.

Next, the board is etched in a chemical that dissolves the copper except where it is protected by the photographic image of the PCB tracks.

A Light box

WARNING: ULTRAVIOLET LIGHT IS DANGEROUS IT CAN DAMAGE YOUR EYESIGHT. WHEN ASSEMBLING THIS PROJECT DO NOT LOOK DIRECTLY AT A LIT UV LED. IF YOU HAVE TO CHECK THAT THE LEDS ARE WORKING, THEN POINT THE BOARD AWAY FROM YOU AND LOOK AT THE LIGHT REFLECTED ON A PIECE OF PAPER. YOU CANNOT SEE IT, BUT THIS LED PANEL PRODUCES VERY BRIGHT UV.

Rather than buy a light box I decided to save some money and have some fun by designing my own. To start with the light box will have no timer, but rather the exposure that normally needs to be about 30 seconds will just be timed by hand. The first job of the light box will be to create a PCB for a simple timer to control our exposure more accurately.

Traditionally, UV light boxes are built using florescent UV tubes. These are relatively expensive and the tubes have to be replaced, so I decided to use a large array of UV LEDs sourced from eBay as a lot of 100 at a cost of about USD 20 - by far the biggest single outlay for the project.

The light box itself is going to be housed in an 7x5 inch index card box and the copper clad board and photo mask transparency will be sandwiched together in a cheap clip-style photo frame.

Power is supplied by a 12V wall-wart power supply.

You will need

84 (buy 100) x 400nm (at least 3000 mcd) UV LEDs

28 x 56Ω 0.5W resistors

Strip board 15cm x 10 cm (roughly 6” x 4”)

6” x 4” photo clip frame

7” x 5” index card box

12V 1.5A ‘wall-wart’ power supply

2.1mm power socket

When buying the LEDs, it does not really matter whether they are 5mm or 2mm diameter, but do ensure that they are 400nm wavelength and bright enough (at least 3000 mcd).

The LEDs will be mounted in the top of the index box and the copper clad board will be a good 6 inches away in the bottom of the box, and so the angle of the LEDs is not critical.

The LEDs are arranged in sets of 3 LED in series each with their own current limiting resistor. These series sets are all arranged in parallel on the strip board in a hexagonal pattern.

You will need to make breaks in the copper track of the strip board. The easiest way to do this is by hand using a drill bit. Put the bit at the hole where you want to make the cut and twist it between forefinger and thumb, just enough to break the track.

There are a lot of LEDs and resistors to solder into place. Start with the linking wires and then the resistors and finally the LEDs.

Since there is a significant risk of accidentally creating a short-circuit, I found a good way of working to be to solder up a batch of three LEDs and then make sure that they lit before moving onto the next set.

Hold the board away from you or upside-down and shine the LEDs onto a sheet of paper and look at the sheet of paper when testing them. Although they do not look bright, these LEDs are emitting a lot of ultraviolet and could easily damage your eyesight.

Make a hole in the index card box for the power supply and attach the LED board to the top of the index box. I used strips of self adhesive velcro to attach the board to the box, but you could also use self adhesive pads.

So there we have it, our own light box. The next step is to try out some test exposures and learn how to etch some boards.

New book: 'Programming Arduino: Getting Started with Sketches'

2011-11-18T07:54:00.000-08:00

My new book 'Programming Arduino: Getting Started with Sketches' is just out on Amazon.

http://www.amazon.com/Programming-Arduino-Getting-Started-Sketches/dp/0071784225

It is intended as a companion to Massimo's book, but it concentrates on how to program the Arduino.

It is intended for non-programmers and programmers alike.

The book is organized into the following chapters:

Chapter 1. This is Arduino. An introduction the Arduino hardware, what it is capable of and the various types of Arduino board that are available.

Chapter 2. Getting Started. First experiments with your Arduino board, installing the software, powering it up and uploading your first sketch.

Chapter 3. C Language Basics. The basics of the C language and for complete programming beginners an introduction to programming in general.

Chapter 4. Functions. This chapter explains the key concept of using and writing functions in Arduino sketches. Demonstrated throughout with runnable code examples.

Chapter 5. Arrays and Strings. How to make and use more advanced data structures than simple integer variables. A Morse Code example project is slowly developed to illustrate the concepts being explained.

Chapter 6. Input and Output. How to use the digital and analog inputs and outputs on the Arduino in your programs. A multimeter will be useful to see what is happening on the Arduino’s input output connections.

Chapter 7. The Standard Arduino Library. Making use of the Arduino functions that come in the Arduino’s standard library.

Chapter 8. Data Storage. Writing sketches that can save data in EEPROM memory and make use of the Arduino’s built-in Flash memory.

Chapter 9. LCD Displays. Programming with the LCD Shield library to make a simple USB message board example.

Chapter 10. Arduino Ethernet Programming. Making the Arduino behave like a web server, including a little

background on HTML and the HTTP protocol.

Chapter 11. C++ and Libraries. Beyond C, looking at adding object-orientation and writing your own Arduino libraries.

Handbag - Android and Arduino without the Java

2011-11-17T10:28:00.000-08:00

I saw a great presentation by Philip Lindsay on a technology that he had developed called 'Handbag' at the Android Open conference last month.

Handbag is another way to write the code part of an Android Accessory. That is to link an Android phone that supports Open Accessory to an Arduino. The Arduino part might be an Arduino Uno with a USB Host shield, or a specialist board such as the Freetronics USBDroid board that I reviewed a few weeks ago (http://srmonk.blogspot.com/2011/10/freetronics-usb-droid-review.html).

I decided to try out Handbag to control a couple of servos that raise little paper flags in a project I developed for my book 'Arduino + Android Projects for the Evil Genius'. In the book, the servos were attached to an Arduino / Ethernet shield combination. In this case, I decided to attach them to a USBDroid board, although an Uno and USB host shield would work just as well.

Philip's stroke of genius was to realise that if the Arduino is acting as the host in the USB relationship (as it does) then it might as well be in charge of telling the Android phone what to do. In other words, there is zero programming to be done on the Android side, instead you put code in your Arduino script that tells a general purpose Android app what to display in its UI and to do when someone presses a button etc.

I'll just say that again! Genius!

Step 1. Downloading the Handbag App onto my Android Phone.

So, my first task was to fetch the general purpose Handbag app down for my Android phone.

Its not on the Android Market, so I downloaded the APK binary from here. For your convenience here is a QR code for it.

Note that because this App is not from the Market, you have to allow your phone to download apps from 'Unknown Sources'. You will find this in Settings->Applications.

When the App starts, it should look like this.. Philip, I stole that image from your web site - hope thats okay.

Step 2. Setup the Arduino Environment

If you haven't used the Android ADK, then you will need to install the necessary libraries onto your Arduino IDE. To do this, you just unzip the library files here into your libraries folder which will be in the Arduino folder in your documents folder, so on a Mac thats in ~/Documents/Arduino. If there isn't a 'libraries' folder there, make one.

Then unzip this file and copy its 'Handbag' folder into the libraries folder.

You will also need to install the ADK library and a modified USB host library. These live in these two locations.

Note that if you are using a Uno and USB host shield or a USB Droid board then, when installing the ADK (first link) don't install the USB Host library that comes with the ADK download, use the one that come in the second link instead.

Step 3. Upload this minimal sketch to your Uno or USBDroid.

You will also need to attach an LED and resistor to pin 4, as shown below.

Initially I tried to use 13 as the LED pin to make use of the built-in LED, but that seems to be reserved for use somewhere, so I had to resort to using an LED on pin 4.

Anyway, here is the minimal sketch.

#include <Max3421e.h>
#include <Usb.h>
#include <AndroidAccessory.h>
#include "Handbag.h"
#define ledPin 4

AndroidAccessory acc("rancidbacon.com",
"Handbag",
"Handbag (Arduino Board)",
"0.1",
"http://rancidbacon.com",
"0000000000000001");

HandbagApp Handbag(acc);

void setupHandbagUI()
{
Handbag.addLabel("Minimal Handbag Example");
Handbag.addButton("Toggle LED", toggleLED);
}

void setup()
{
pinMode(ledPin, OUTPUT);
Handbag.begin(setupHandbagUI);
}

void loop()
{
Handbag.refresh();
}

void toggleLED()
{
digitalWrite(ledPin, !digitalRead(ledPin));
}

Lets just pause for a moment. We have 37 lines of code here. If you want to see the equivalent is writing it long hand in Android, you could add at least one zero to the lines of code.

Have a quick read through the code above. Its really very easy to see how to use Handbag.

So, lets change my flags code to use Handbag.

Here is the wiring diagram, it shows an Ethernet Board, but its the same pin numbers as an Uno or USB Droid.

And here is the sketch:

#include <Servo.h>

#include <Max3421e.h>

#include <Usb.h>

#include <AndroidAccessory.h>

#include "Handbag.h"

#define REQUEST_BUFFER_SIZE 700

#define MIN_ANGLE 30

#define MAX_ANGLE 175

// pins 10, 11, 12 and 13 used by Ethernet

#define SERVO_1_PIN 2

#define SERVO_2_PIN 3

Servo servo1;

Servo servo2;

int servo1pos = MIN_ANGLE;

int servo2pos = MIN_ANGLE;

AndroidAccessory acc("rancidbacon.com",

"Handbag",

"Handbag (Arduino Board)",

"0.1",

"http://rancidbacon.com",

"0000000000000001");

HandbagApp Handbag(acc);

void setupHandbagUI()

{

Handbag.addLabel("Evil Genius Flags");

Handbag.addButton("Raise Flag 1", raiseFlag1);

Handbag.addButton("Lower Flag 1", lowerFlag1);

Handbag.addButton("Raise Flag 2", raiseFlag2);

Handbag.addButton("Lower Flag 2", lowerFlag2);

}

void setup()

{

Handbag.begin(setupHandbagUI);

servo1.attach(SERVO_1_PIN);

servo2.attach(SERVO_2_PIN);

}

void loop()

{

Handbag.refresh();

servo1.write(servo1pos);

servo2.write(servo2pos);

delay(100);

}

void raiseFlag1()

{

servo1pos = MAX_ANGLE;

}

void lowerFlag1()

{

servo1pos = MIN_ANGLE;

}

void raiseFlag2()

{

servo2pos = MAX_ANGLE;

}

void lowerFlag2()

{

servo2pos = MIN_ANGLE;

}

And here is a short video of the flags in action. It all worked like a dream.

In short, Handbag is a wonderfully simple way to make Android accessories without having to learn large amounts about Java programming and the Android libraries.

Arduino LCD Shield Review

2011-11-08T14:13:00.000-08:00

In this review I look at two 16x2 LCD modules at opposite ends of the price spectrum. Both have very similar display modules, both is size and visual clarity.

Freetronics LCD and Keypad Shield AUD 29.95 (approx 31 USD)
http://www.freetronics.com/products/lcd-keypad-shield

DFRobot LCD Shield 17 USD
http://www.dfrobot.com/index.php?route=product/product&product_id=51

That is quite a difference in price spread, with the Freetronics device being almost twice the price of the DFRobot shield.

However, the Freetronics shield is much better made and is well thought out. features that I particularly liked are:

* Extra long headers mean it will fit onto an Ethernet Shield.
* Pins used and init string for LCD are marked on the board itself.
* Long stalk switches.
* LCD Module firmly attached with nuts and bolts.

My only dislikes are that the in the module I received, the trim-pot used to adjust the contrast of the display was not included on the board. This could easily be added, and the 'default' contrast was okay, but I would have preferred this component to be included.

The DFRobot shield is very good value, but there are a few features that let it down.
* Not compatible with Ethernet Shield
* Reset button next to user definable buttons
* LCD module just attached by solder connections on one side
* Trim pot sticks up too high

This first feature was a problem for me, because I bought it with the intention of attaching it to an Ethernet Shield to display my current book Amazon ranking (yes, I know, the vanity of the man!). No conflict in the main control pins, so fine I thought. Unfortunately, the DFRobot module uses D10 for backlight which is used as SPI CS on Ethernet shield. In addition, while the board fits snuggly on an Arduino Uno, the pins are to short to fit square on an Ethernet shield.

The height of the trim-pot causes a problem because it sticks up to the same height as the LCD panel, so I think it would be difficult to mount it in a case with a cutout and bezel for the display.

In conclusion, if you need a low cost display shield and you are not using an Ethernet shield or worried about fitting it in a box then buy the DFRobot shield, otherwise, go for the much better designed and built Freetronics shield.

You will find many other LCD shields out there too, but when selecting one, be careful to check for pin compatibility with any other shields that you may be using.

Disclosure: While I have tried to be completely unbiassed in this review, I do need to point out that the Freetronics module was provided to me free of charge from Freetronics.

Canine Radio Direction Finder - Part 1

2011-11-06T13:58:00.000-08:00

After our new dog ran off when we were out, I decided it might be fun to make a radio direction finder, so that we can at least see in which direction he is.

So far, I have made the radio transmitter end of the project. In the second part of this blog I will look at the receiver and the directional antenna.

The transmitter is built using a low cost 433MHz AM Radio Frequency transmitter module. This is the module that I used RF SOLUTIONS - QAM-TX1 - MODULE TRANSMITTER AM 433MHZ but theses modules are pretty standard in their pinouts and features.

To provide pulses to the RF transmitter, I use an ATTiny45 programmed using an Arduino board as described here: http://hlt.media.mit.edu/?p=1229

The pulses are are a continuous series of 'Sputnik-style' beeps at a frequency of 300Hz.

The 3.7V battery and tiny slide switch were scavenged from a broken RC helicopter and the antanna is made by wrapping 17cm of solid core wire around a screwdriver.

To test out the transmitter, its corresponding 433MHz receiver module (RF SOLUTIONS - QAM-RX2 - MODULE RECEIVER AM 433MHZ) was fitted to some breadboard and an oscilloscope attached.

So there we go! We are receiving the signal. The next step is to build a directional antenna with ajustable gain, so that by sweeping it back and forth we can find the point of maximum signal strength.

The sketch:

int pin = 3;

void setup()
{
pinMode(pin, OUTPUT);
}

void loop()
{
beep();
delay(500);
}

void beep()
{
for (int i = 0; i < 100; i++)
{
digitalWrite(pin, HIGH);
delayMicroseconds(200);
digitalWrite(pin, LOW);
delayMicroseconds(200);
}
}

Copyright Theft - a good outcome

2011-11-02T14:53:00.000-07:00

My book writing take me a lot of time, and while I do enjoy it, I probably wouldn't do it if it were not for the handy extra income it gives me.

As such its distressing when a friend sends me an URL for a free download of one of my books. The whole thing as a PDF was there on a web site in full with a load of other hobby electronic books.

I used 'whois' to find the ISP for the web site and wrote a polite letter like this:

One of the companies you host (******.****) is hosting illegal electronic copies of books including my own book '30 Arduino Projects for the Evil Genius' at this address: http://********.***/

As a reputable ISP I am sure you do not want to be associated with copyright theft.

I would appreciate it if you could take action to stop this.

Thanks, Simon.

The sent back an immediate reply saying that they had contacted the host and asked them to take the books down.

I went back to they site and yes the books had gone!

I love it when things like that just work.

Freetronics USB Droid Review

2011-10-28T11:54:00.000-07:00

5 Stars! The best thing to come out of Australia since Rolf Harris!

I was given one of these boards at Android Open, and rather like the IOIO of my previous Blog, I have only just got around to having a play with it.

It is intended as an alternative to the Android ADK reference board which is Arduino Mega-based and so probably overkill for most Android Accessories that you are likely to make. The USB Droid is far more practical in size.

It comes in a nice retail pack, with a Mini USB lead which is used to connect it to your computer rather than the 'normal' Arduino USB-B connector - good choice.

And that is where the magic starts...

The board is extremely well made, and well thought out. When I plugged the Mini USB into my computer I was surprised to see a green LED light along with the blue power LED.

The green LED is labelled VBUS and yes, the USB 5V is passed through from your computer and out of the USB-A connector to your phone. A really nice touch as you don't have to use an external power supply while you are developing.

I am not sure Putting a Micro SD card on there is much use for making Android accessories, as effectively all the storage of the phone is available to you. But I guess you could make a data logger that worked off-line until you connected it to the Android phone to send the data to Pachube. Also it could come in handy for other types of USB host projects.

I have a minimal Android Open Accessory test app that I describe in my Arduino + Android book. You can download it from here (the app that is, not the book). There are also slides from my talk at Android Open here that describe the app. All it does is send a number to the Arduino that increments it and sends it back.

The sketch installed and ran perfectly.

I am very impressed with this board, its certainly a lot neater than an Uno with a USB host shield on the top.

I see that Freetronics have done similar things with an Ethernet board. I look forward to trying out one of these.

IOIO First Impressions

2011-10-23T09:17:00.000-07:00

I picked up a IOIO (apparently pronounced YoYo) from Android Open and I have just had chance to play with it.

Unlike the Arduino, IOIO is not intended to operate independently. It has to be paired with an Android phone. While it can use the Android Open Accessory protocol, it can also use plain old ADB which means that it works on most phones rather than the smaller choice of phones that Open Accessory works on.

I even tried an old Android 1.6 LG phone that one of my kids cast off six months ago and it works just fine.

When creating a project, you do not change the firmware on the IOIO, but rather you issue commands that read values from pins and turn pins on and off from the Android app.

It took 10 minutes to get the example working that turns the on-board LED on and off from a little Android app. Although I had Eclipse and the Android SDK already installed. These are probably the most complex part of setting up.

IOIO sets out to do just one job and do it well. It is not a general purpose board like the Arduino, and for $50, it is just cheaper than an Arduino and USB host shield and smaller and neater.

I like it a lot and it looks great. Far more IO ports than you are ever likely to use. In fact, I will probably solder 0.2 inch screw terminals onto the connectors and just use make every other IO available.

Pros.
Pot to adjust charging current to phone
Nice looking board
Good documentation set on the Wiki (https://github.com/ytai/ioio/wiki)

Cons.
Only 20mA output current per IO pin (Arduino can do 40mA)
3.3V logic, but some pulls can cope with being pulled up to 5V
No Power socket, you have to solder power leads on. This means that to do anything with the board, you will need to solder.

Edit: I forgot to mention that IOIOs with the latest firmware can accept a cheap Bluetooth dongle and work seamlessly over BT. Even switching connection without restart if you plug in with USB.

Android Open Conference 2011

2011-10-13T09:01:00.000-07:00

Super conference.

As well as the day job aspect of it promoting Meme IDE http://www.memeide.com I also got to present on my favourite hobby topic of Arduino http://androidopen.com/android2011/public/schedule/detail/20972

The talk went well and I was surprised how many people knew about Arduino. I met several people who I had exchanged messages with and it was good to put some faces to conversations. Someone even got me to sign a copy of my book that they had brought. For a moment there I felt like a real author!

I was really impressed by Handbag (http://rancidbacon.com/p/android-arduino-handbag/). Its a great way to solve the problem of the Android end of Open Accessory programming. I look forward to seeing how this project develops.

Well the conference is over now and I am taking the rest of the week-off to enjoy San Francisco - which isn't hard!

Arduino + Android Projects for the Evil Genius

2011-09-26T05:29:00.000-07:00

My new book 'Arduino + Android Projects for the Evil Genius' is now available for pre-order from Amazon. See the link to Amazon in the right-hand panel (scroll down a bit).

The cover on Amazon hasn't been updated yet, so it looks a little different.

The first books should be shipped around the start of December.

The projects are:

Chapter	Project	Notes
1	Bluetooth Robot	Control a small rover from your Android Phone using Bluetooth and an Arduino and Motor shield.
2	Android Geiger Counter	An Android Open Accessory Project using a USB host shield and Arduino Uno.
3	Android Light Show	A powered Open Accessory dock for your Android phone that drives three LED panels to make a sound sensitive light show.
4	Android TV Remote	Programmable Infrared remote control accessory for your Android phone.
5	Temperature Logger	A temperature logger that uses the Android phone to wirelessly send readings to Pachube.
6	Ultrasonic Range Finder	An Android Open Accessory for measuring distance.
7	Home Automation Controller	The Android tablet base unit with a audio jack interface to Arduino.
8	Home Automation Power Control	Add control of AC outlets and lights to the Home Automation Controller from Chapter 7.
9	Home Automation Thermostat	Add control of domestic heating to the Home Automation Controller using low cost RF data modules.
10	Remote Door Lock	Control access to your home using RFID tags, also with a RF link to the Home Automation Controller
11	Ethernet Flag	Network control of two flags that can be activated from any Internet device. Useful for the Evil Genius to summon minions.
12	Delay Timer	A simple to make Arduino-based delay timer.

Pimp Your Slot Car Racer

2011-09-25T00:52:00.000-07:00

A while ago my son's school entered a competition where they made their own slot cars with vacuum formed plastic bodies. They were allowed to bring them home and 'pimp' them.

So being British we decided to interpret 'pimping' rather conservatively and take it to mean adding headlights and working brake lights.

Here is the schematic:

When there is power on the tracks, the headlights are always on, but the diode will bypass the Brake LEDs and charge the capacitor. When the controller is released and the supply voltage drops to zero or open circuit, then the current flows out of the capacitor lighting the brake LEDs discharging through the stationary motor for a couple of seconds.

We didn't win the race competition, but actually I think the electronics was more fun anyway.

Arduino Solar Radio

2011-09-19T01:21:00.000-07:00

I have finished my Arduino Solar Radio.

* Solar charging, via the panel on the back.
* 12 position switch to select channel number
* Seek up / seek down controls and 'store' button
* RDS display of call sign
* Frequency display
* Battery voltage display
* Solar charging current display

The software still needs a bit of attention. Its fine if the signal is good and RDS comes in quickly, but if not, then adjusting the volume or changing channel takes a few seconds to kick in. As I only really listen to Radio 4, its not a problem, but I'll get round to updating it some time.

Here are the circuit diagrams and the stripboard layout as will as a picture of the breaks in the back.

Also, here is the sketch. It uses the library I described in my previous post.

#include <EEPROM.h>
#include <LiquidCrystal.h>
#include <Si4703_Breakout.h>
#include <Wire.h>

int resetPin = 4;
int SDIO = A4;
int SCLK = A5;
int volumePin = A2;
int rotaryPin = A3;
int upSwitchPin = 5;
int downSwitchPin = 6;
int setSwitchPin = 7;
int lcdRSPin = 3;
int lcdEPin = 2;

Si4703_Breakout radio(resetPin, SDIO, SCLK);
LiquidCrystal lcd(lcdRSPin, lcdEPin, 12, 11, 10, 9);
int channel[12];
int currentChannel = 0;
int channelNumber = 3;
int volume = 1;
long autoUpdatePeriod = 5000l;
long lastUpdate;

void setup()
{
pinMode(upSwitchPin, INPUT);
digitalWrite(upSwitchPin, HIGH);
pinMode(downSwitchPin, INPUT);
digitalWrite(downSwitchPin, HIGH);
pinMode(setSwitchPin, INPUT);
digitalWrite(setSwitchPin, HIGH);
radio.powerOn();
radio.setVolume(0);
lcd.begin(16, 2);
lcd.clear();
readChannelsFromEEPROM();
updateChannel();
setVolume();
displayRDS();
}

void loop()
{
int newChannelNumber = 11 - (analogRead(rotaryPin) / 90);
if (newChannelNumber != channelNumber)
{
channelNumber = newChannelNumber;
updateChannel();
displayRDS();
}

int up = ! digitalRead(upSwitchPin);
int down = ! digitalRead(downSwitchPin);
int set = ! digitalRead(setSwitchPin);

if (up)
{
currentChannel = radio.seekUp();
updateDisplay();
}
if (down)
{
currentChannel = radio.seekDown();
updateDisplay();
}

if (set)
{
channel[channelNumber] = currentChannel;
saveChannel(channelNumber, currentChannel);
flashSet();
displayRDS();
}

setVolume();

if (millis() > lastUpdate + autoUpdatePeriod)
{
lastUpdate = millis();
updateDisplay();
displayRDS();
}
delay(50);
}

void updateChannel()
{
clearRDS();
currentChannel = channel[channelNumber];
updateDisplay();
radio.setChannel(currentChannel);
}

void setVolume()
{
volume = (analogRead(volumePin) + 35) / 70;
radio.setVolume(volume);
}

void updateDisplay()
{
lcd.setCursor(0, 0);
if ((channelNumber + 1) < 10) lcd.print(" ");
lcd.print(channelNumber + 1);

lcd.setCursor(12, 0);
lcd.print(currentChannel / 10); lcd.print("."); lcd.print(currentChannel % 10);

lcd.setCursor(0, 1); lcd.print("Batt ");
int v = getBatteryVolts();
lcd.print(v / 10); lcd.print("."); lcd.print(v % 10); lcd.print("V");

int i = getChargeCurrent();
lcd.setCursor(11, 1); lcd.print(" ");
lcd.setCursor(11, 1);
lcd.print(i / 10); lcd.print("mA");

char rdsBuffer[10];
getRDS(rdsBuffer);
lcd.setCursor(3, 0);
lcd.print(rdsBuffer);
}

void displayRDS()
{
char rdsBuffer[10];
getRDS(rdsBuffer);
lcd.setCursor(3, 0);
lcd.print(rdsBuffer);
}

void flashSet()
{
lcd.setCursor(3, 0);
lcd.print(" SET ");
delay(500);
clearRDS();
}

void clearRDS()
{
lcd.setCursor(3, 0);
lcd.print(" ");
}

int getBatteryVolts()
{
// volts * 10
// potential divider 33k:10k
// Vcc 3.3V
// Vin 10V, Vout = 2.326V, raw at 10V = 1023 * 2.326 / 3.3 = 721
// V*10 = raw / 72
int raw = analogRead(1);
return raw / 7;
}

int getChargeCurrent()
{
// current mA * 10
int battVoltsTen = getBatteryVolts();
int solarVoltsTen = analogRead(0) / 7;
int mV = (solarVoltsTen - battVoltsTen) * 100;
int mA10 = mV / 10;
if (mA10 < 0)
{
mA10 = 0;
}
return mA10;
}

void getRDS(char* buffer)
{
radio.readRDS(buffer, 2000);
}

void saveChannel(int i, int channel)
{
byte high = highByte(channel);
byte low = lowByte(channel);

EEPROM.write(i * 2, high);
EEPROM.write(i * 2 + 1, low);
}

void readChannelsFromEEPROM()
{
for (int i = 0; i < 12; i++)
{
byte high = EEPROM.read(i*2);
byte low = EEPROM.read(i*2 + 1);
int ch = high * 256 + low;
if (ch > 700 && ch < 1500)
{
channel[i] = ch;
}
}
}

New Arduino Library for Sparkfun Si4703 FM Receiver Breakout Board

2011-09-16T05:19:00.000-07:00

The Sparkfun Si4703 FM Receiver Breakout Board is a great little FM radio, complete with RDS and a 100mW stereo amp.

There is example code for using it and top marks to Nathan Seidle from Sparkfun for working out how to use the pesky thing from the largely opaque datasheet for the receiver chip.

I have been making myself the 'ultimate' FM receiver. Arduino-based and using nice controls, solar-charging of battery with charging data and an LCD display for the RDS data. I will post on this when its finished.

The software engineer in me railed at just hacking away at Nathan's example. So I put his code in a library and also fixed some of the problems with RDS and did a bit of tidying.

You can download it from here. Continuing Nathan's licensing arrangement, I also offer it as 'Beer-ware'. If you are feeling extremely grateful then by all means buy one of my books (see right panel).

Here is an example app, just connect up the three pins at the top of the sketch but remember Vcc for the breakout board is 3.3V NOT 5V. 5V will kill it:

#include <Si4703_Breakout.h>
#include <Wire.h>

int resetPin = 2;
int SDIO = A4;
int SCLK = A5;

Si4703_Breakout radio(resetPin, SDIO, SCLK);
int channel;
int volume;
char rdsBuffer[10];

void setup()
{
Serial.begin(9600);
Serial.println("\n\nSi4703_Breakout Test Sketch");
Serial.println("===========================");
Serial.println("a b Favourite stations");
Serial.println("+ - Volume (max 15)");
Serial.println("u d Seek up / down");
Serial.println("r Listen for RDS Data (15 sec timeout)");
Serial.println("Send me a command letter.");

radio.powerOn();
radio.setVolume(0);
}

void loop()
{
if (Serial.available())
{
char ch = Serial.read();
if (ch == 'u')
{
channel = radio.seekUp();
displayInfo();
}
else if (ch == 'd')
{
channel = radio.seekDown();
displayInfo();
}
else if (ch == '+')
{
volume ++;
if (volume == 16) volume = 15;
radio.setVolume(volume);
displayInfo();
}
else if (ch == '-')
{
volume --;
if (volume < 0) volume = 0;
radio.setVolume(volume);
displayInfo();
}
else if (ch == 'a')
{
channel = 930; // Rock FM
radio.setChannel(channel);
displayInfo();
}
else if (ch == 'b')
{
channel = 974; // BBC R4
radio.setChannel(channel);
displayInfo();
}
else if (ch == 'r')
{
Serial.println("RDS listening");
radio.readRDS(rdsBuffer, 15000);
Serial.print("RDS heard:");
Serial.println(rdsBuffer);
}
}
}

void displayInfo()
{
Serial.print("Channel:"); Serial.print(channel);
Serial.print(" Volume:"); Serial.println(volume);
}

Here is the public part of the class definition.

class Si4703_Breakout
{
public:
Si4703_Breakout(int resetPin, int sdioPin, int sclkPin);
void powerOn(); // call in setup
void setChannel(int channel); // 3 digit channel number
int seekUp(); // returns the tuned channel or 0
int seekDown();
void setVolume(int volume); // 0 to 15
void readRDS(char* message, long timeout);
// message should be at least 9 chars
// result will be null terminated
// timeout in milliseconds

Android Open Conference

2011-08-17T05:37:00.000-07:00

I shall be giving a presentation on the subject of: 'Building Android Accessories using the Open Accessory Development Kit and Arduino' at the Android Open Conference in October.

The talk is a 40 minute session that describes how to use Open Accessory with standard Arduino hardware to create accessories for Android devices. Both the Arduino and the Android ends of the solution are explained in detail, with example code.

I'm also going to bring along a few examples of projects that I have made while doing the research for my next book 'Arduino + Android Projects for the Evil Genius' - see right.

The Geiger Counter is my favourite:

Ultrasonic Range Finder

Bright LED panel light show - sound sensitive.

There may be a few awkward conversations with customs officials!

It promises to be a really good event, so I hope to see you there.

Hack a USB Computer Keyboard to Make a Synth Pedal Board

2011-08-02T12:31:00.000-07:00

My son asked me if I could make a pedal board to connect to his laptop to use with his synth software, so that he can switch loops while performing -- or something musical like that.

Fortunately for him he does not get his musical ability from his Dad.

The brief was 10 big buttons to be pressed with his feet, while on stage. The buttons to be arranged in three groups of three and one button on the end, that he would map to mute on his software.

You will need:
* A USB keyboard that you do not mind destroying.
* 10 stout push to make switches
* 20 spade terminals (if thats the connection on your switches)
* A 1KΩ resistor
* A length of plastic ducting
* Stripboard - for size see description below
* Soldering tools and patience
* Twin multicore wire - as for a door bell (when door bells used to have wires)

Rather than try and do anything with an Arduino - which was my first throught - I decided to hack an old keyboard I had lying around:

The only bit of the keyboard I kept was the USB controller module:

The connectors at the top normally press against the conductive plastic of the keyboard connections and were coated with some kind of conductive polymer. So, to be able to solder them, I rubbed them with glass paper, to bring up the raw copper.

There then followed the tedious problem of working out how to simulate the pressing of one of the keys '0' to '9'. The keys are arranged in a matrix, so connecting the right row to the right column would simulate a press. But, you do not want to accidentally connect one row to another, so rather than experiment with a wire to find out the combination that simulated a digit, I used a 1K resistor to test connecting two points together.

To keep track of which combinations produced the desired results, I made up a matrix, assigning each contact a number.

With the controller connected to my computer and a word processor open, every time I got a digit by connecting two of the connections with a resistor, I added it to the table. So, connecting the resistor between pins 22 and 17 caused the digit '1' to appear on the screen. [ignore the rogue 0 to the left].

This is not actually as tedious as it sounds, you will rapidly home in on clusters of combinations that work.

There is not enough room to solder the leads for the switches directly onto the connectors on the controller, so I found a bit of stripboard and carried the connections across.

Using the matrix as a guide, I soldered up leads to the spade terminals and to the appropriate connections on the stripboard.

Loosely attaching the switches, I tested them all before fitting them into the box.

The box is made from a length of ventilation ducting with holes drilled for the switches.

There now follows the tricky task of threading the wires through to the appropriate holes in the box. Labelling each pair of wires and using a stronger guide wire to pull the wires through helped with this.

All that remains is to reattach the switches, test again and then push all the switches into the holes.

The tennis ball is just for scale.

Have fun and post me pictures if you have a go for yourself. I'm always interested in ideas for version 2!

Si.

Android Open Accessory without charging the phone

2011-06-18T04:16:00.000-07:00

I have been spending some time recently working on Android Open Accessory using an Uno and the Sparkfun USB host shield. I'm including a range of accessories, Geiger counter, ultrasonic distance meter etc. in my soon to be released (well Dec 2011) book Arduino + Android Projects for the Evil genius

Although the feature that the accessory should provide half an amp at 5V to charge the phone is all very well for AC outlet powered accessories, it means battery powered accessories need a big battery.

Or does it?

I decided to do a bit of experimenting with a surplus USB extension lead that came with a USB modem dongle and just extends the USB lead a couple of inches.

Firstly simply cutting the red 5V USB power lead. This stopped the accessory being recognised and the charge indicator on my Nexus One did not indicate any charging (no surprise there).

If, however, I put a 1k resistor in line on the red 5V wire, everything works fine as an accessory, but the phone does not draw anything significant from the accessories battery, allowing it to be powered from a small 9V battery. At least it does if the phone is well charged.

WARNING: This result was derived experimentally. This may well void your phone warranty, if you connect it up like this. It didn't hurt my phone, but do it at your own risk. Also your wire may not use the same color coding as mine did, so red might be the wrong lead for you.

The following sequence of photos shows the construction of the lead.

Carefully cut away some of the outer plastic with a sharp knife on one side and tease out the shielded bundle of wires.

Scrape a gap between the shielding to get at the +5V wire.

Cut the red wire and strip and tin the ends.

Solder the 1k resistor into place. Then wrap it all up with insulating tape. Wrap the part behind the tape carefully, so that there is no chance of the bare leads from either side of the resistor making contact with the shielding wires or foil.

Trebuchet concerns

2011-06-03T03:58:00.000-07:00

There have been some concerns that my son was hurt during the making of this trebuchet video from the new book.

I would like to reassure everyone that while he was struck, the projectile was a tennis ball, and while it did hit him squarely on the chest, there was a certain amount of acting involved ;)

15 Dangerously Mad Projects for the Evil Genius

2011-05-10T06:09:00.000-07:00

.. its finally for sale on Amazon.com

I had a lot of fun writing this one. What is this instinctive urge to make weapons?

The website for the book is here.

Westinghouse Dynamotor

2011-04-02T13:03:00.000-07:00

As well as the Radio (as it turns out) from the previous post to this, my brother and I also uncovered a Westinghouse Dynamotor.

This wonderful contraption is a low voltage DC motor coupled to a high voltage DC generator. These things were used in WW2 and may well have found its way back from the war with my Dad, along with assorted bits of mine, which I remember being used as door stops around the house. He was in the Royal Navy on a motor launch - mine sweeper in the Adriatic for most of the war.

My brother remembers my Dad taking this on camping holidays so that he could use his electric shaver.

So, why not I thought, lets fire it up! And it still works well and here is the video evidence to prove it.

Surgery - similarities with programming?

2011-03-31T02:17:00.000-07:00

Over the years, people have tried to label the people who write software professionally as:
* Engineers
* Programmers
* Analyst / Programmers
* Software Engineers
* Hackers

One of the many excellent ideas that came with eXtreme Programming is that writing code does not really have a neat metaphor in other walks of life. Its a creative process, part craft, part engineering is fairly close.

Having listened to a program on BBC Radio 4 about how surgeons work and learn, it stuck me that there are some similarities with the way a writer of code works and learns within a modern agile process.

Surgeons save lives and loose lives on a daily basis. There work is clearly far more important than that of someone writing some code, but the similarities are there.

* Surgeons tend to be arrogant - there are good reasons for this, and it is not as bad a thing as it may sound. This is because they must quickly decide on the best course of action for a patient. Most writers of code will quickly form an opinion of the best way to go about something and get on with it.

* Surgeons start with 'standard' training. Their medical degree and then learn on the job, from each other and by honing their technique, trying out variations. Ditto coders. After the usual degree in Computer Science, most learning codes from the rest of the team and for experimentation.

* They mostly share their knowledge in an informal manner when cooperating, but also disseminate more widely in journals, but usually in a qualitative rather than quantitate way. Surgeons by and large are not overly keen on controlled clinical trials. This is a bit like coders in an agile team avoiding to much up front design, doing just enough to clarify thought, share the vision and get on with it.

Writing this down, it doesn't sound as good as it did in my head when I was listening to the program. It may be as simple as they are both jobs that have a high degree of pragmatism and a distrust of organisational culture.

Oh well, I'll throw it out there anyway.

Mystery solved

2011-03-29T05:38:00.000-07:00

The Philips museum came up trumps:

the apparatus is an old radio receiver without loudspeaker.

Probably the type number is Philips 2501, Philips 2502, Philips 2514 or Philips 2515 produced in 1927/1928.

I asked if they wanted it for their collection, but they already have several.

Anyone interested in it as a restoration project,? Its yours for the cost of postage. It currently resides in York - England.

What on earth is this?

2011-03-28T02:26:00.000-07:00

Over the weekend, I helped my brother clear out his loft, because they are moving home. In it, we found this ancient bit of valve equipment, which we have totally failed to be able to identify.

Any ideas?

Its heavy and a peek behind the back board looks like some seriously big tubes, but interestingly very little in the way of ventilation.

The big control in the middle is a 3 position switch labelled 200/400, 300/600, 1000/2000

Its made by Phillips - and both ends are the same, each with a big knob and a small knob.

One big knob changes the dial setting labelled 'S' and the other the dial labelled 'P'

Its very very odd.

Any help identifying this would be much appreciated.

New web site

2011-01-24T10:16:00.001-08:00

There is a new website for '30 Arduino Projects for the Evil Genius'.

http://www.arduinoevilgenius.com

Google sites is excellent!

Make Your Own PCBs

2011-01-23T12:52:00.000-08:00

I wrote this a while back and thought it might be of interest...

Creating your own printed circuit boards is not as difficult or expensive as you might think. In this article, I describe how you can use pre-sensitised boards and a home made light box to create your own boards.

http://dl.dropbox.com/u/3993179/pcbs.pdf

Broken banking site

2010-12-29T03:54:00.000-08:00

Humm. This scares me.

A better quality of grammer

2010-12-02T14:31:00.000-08:00

Most supermarkets in the UK have special checkouts for '10 items of less'.

I recently went to Booths, a higher quality supermarket and was very please to see that the quality of the food was not the only thing that was better. Their grammar was better too.

Their equivalent said '10 items or fewer'.

2 MOSFETS and split power to drive motors

2010-11-16T23:54:00.000-08:00

I am working on a robot project and started down the design of an H-bridge. After I had counted up that I would need 4 MOSFETS plus 4 bipolar transistors, I decided there must be an easier way.

I know there are chips for this, but I feel like thats cheating.

So I decided that I could more than halve what I needed if I took a centre-tap on the batteries to split the power supply.

It works well.

A-GND, B-GND - motor off
A-5V, B-GND - motor turns one way
A-GND, B-5V - motor turns the other way
A-5V, B-5V - HEAT SMOKE AND DEAD TRANSISTORS

I haven't tried it, but it should work fine with PWM outputs too. As long as your PWM off is really 0% duty cycle!

Errata page on Arduino book web site

2010-11-05T03:08:00.000-07:00

I have added a page to http://www.arduinoevilgenius.com for Errata.

I would be grateful if people would pass on any other errors they find to me directly at simon@arduinoevilgenius.com

Amateur's and Open Source

2010-10-21T14:42:00.000-07:00

There was an interesting programme of BBC Radio 4 yesterday. 'The Long View' that looked amongst other things at the Amateur movement. The idea of which was that sport should be carried out for the love of it and not the money. Prior to its invention by the Victorians, sports such as boxing were highly commercial.

The amateur movement has largely reverted to commercialism these days and I guess the experiment and the ideals have faded. It was founded with the best of intentions, but was always something of a sham.

It struck me that there are interesting parallels with the open source movement. Originally, it was founded with the best of intentions and great things were created by amateurs. These days, the big boys have taken over projects like MySQL and everything seems to me to be becoming more and more commercial.

Will open source eventually go the way of amateur sport?

Even busses suffer from 500 errors

2010-10-11T05:32:00.000-07:00

The other day, I was following a bus that had broken down and was being towed back to be repaired. Interestingly the big matrix sign on the back of the bus said 500.

It seems even busses suffer from Error 500 HTTP response codes.

Book available in the UK

2010-09-20T13:43:00.000-07:00

'30 Arduino Projects for the Evil Genius' is now available in the UK!

http://www.arduinoevilgenius.com

My Arduino book is for sale on Amazon

2010-08-15T02:18:00.000-07:00

On arriving back from holiday (Italy) I was very pleasantly surprised to find '30 Arduino Projects for the Evil Genius' availabe on Amazon. So please go and buy it and write some great customer reviews.

http://www.amazon.com/30-Arduino-Projects-Evil-Genius/dp/007174133X/ref=sr_1_1?ie=UTF8&s=books&qid=1281863328&sr=8-1

There are also more details, youTube videos of some of the projects and the like at www.arduinoevilgenius.com

Embedded Software Crashes

2010-07-01T05:22:00.000-07:00

Warning, this post is a bit childish and demonstrates a certain operating system prejudice that I harbour.

I have a compulsion to photograph ATMs and other embedded software systems, where the software has crashed. Its about the only time you get to see what the underlying operating system is.

Obviously for ultimate reliability you would use some kind of embedded operating system?

Perhaps not judging by these photos I have collected over the last couple of years.

I can't quite place that dialog style, but it does look kind of familiar. Interestingly all the writing would lead me to think that actually, it was responding fairly well.

PLEASE TAKE YOUR CRASH FROM THE SLOT BELOW.

'Unexpected rebooting in the self-sevice area.'

HEY EVERYONE ! I'VE CRASHED AGAIN !

Elderflower Cordial, Citric Acid, Crack and Sherbert

2010-06-18T00:57:00.000-07:00

Its the Elderflower season, and a family tradition is that I make a batch of cordial from the flowers. See last years post on this for the recipe.

But this year, it nearly didn't happen through difficulty in obtaining the essential ingredient of citric acid. It has long been the case that in England, you buy citric acid from a chemist shop (drug store). But this year the first two shops I tried said that they didn't have any and looked at me as if I was asking for heroin.

Finally at the third shop, the assistant said they were only allowed to keep three packets in stock, but they had sold out and would be getting some more the next day. The next day I went back and sure enough, they were willing to sell me two packets. But she actually held them up for the pharmacists permission before she would sell them to me, in the same way as if you are buying pain killers.

Surprised, I asked why there was all this fuss over a harmless home cooking ingredient and the reply was that apparently people use it to make crack cocaine injectable rather than smokeable and furthermore they were under instructions to notify the police if anyone tried to buy a lot.

So, if you go into a chemist shop and ask for citric acid and they look at you as if you were a drug addict, then thats because they think you are a drug addict.

Ho, hum what a complicated world we live in.

Incidentally, a GOOD thing to mix citric acid with is sugar, just put a tiny bit in with some sugar to make your own Sherbert. Yummy, and a bit addictive, but in a harmless way.

Google IO 2010 Some Observations

2010-05-28T07:38:00.000-07:00

This was a well staged event, with good honest technical presentations of the type you would expect from Google. I went there primarily in the hope of finding other people considering Android for the field service type applications that are Momote's bread and butter. This to help inform our current work of extending the MX Platform to include Android. In that respect I failed because the Android developers that I met were all concerned either with developing games, quirky utilities or mobile extensions to existing web apps.

On the other hand, I did learn quite a lot to improve my amateurish experiments in Android development. As well as some important dos and donts for efficient and responsive applications. I discovered that my approach to the relationship between fetching data and presenting it was rather out of date.

Let me explain. Momote's MX Platform for mobile solutions distinguishes between resilient requests (fetching data from web services on a separate thread) and blocking requests. The distinction for us was that, if you were signing in you would block and wait, but when sending status updates, you would just push them off onto the 'resiliency queue'. Fetching bulk data could happen in the background, but you would not try and display it until you had got it all back.

This could lead to the situation where you arrive at a sync point in the application and get nothing but an hour glass until data has finished loading or times out. Users often interpret as 'its crashed' and soft reset the device.

The better approach and something that is very iPhone / Android is to just render the list and let the data start to appear as it becomes available. That way the user has a much finer level of granularity visible to them. So no more having to trust the 'something is happening, be patient message'.

Stepping back a level, its good to see Apple being given a bit of competition, although I have to say that there were a lot of iPhones and iPads in use by the delegates.

So, come on manufacturers, where's my g-pad!

Maker's Faire, San mateo 2010

2010-05-28T06:58:00.000-07:00

A business trip to Google IO also gave me the chance to go to the Maker Faire.

I particularly liked this:

and this:

and these - there was a whole group of R2D2 makers:

Also, there were lots of kids there learning how to solder. Its great to see that, despite so many fine gadgets being available off-the-shelf, people still want to make their own. Fantastic!

UK Author US Publisher

2010-04-02T11:14:00.000-07:00

I live in the UK, but my publisher McGraw Hill is American. US law says that the publisher must withhold 30% of all payments (advances and royalties) to foreigners. This would then be followed by the Inland Revenue taking its slice, leaving me a tiny little morsel.

Your publisher does not have to deduct the 30% if you have completed a form W-8BEN and given it to the publisher. However, to complete a W-8BEN (the easy part) you must have a valid US tax code (the hard part).

The kind of US Tax Code that you need to get is called an ITIN. To obtain one of these, you must have a supporting letter (see mine below), complete a form W-7 (also see mine below) an SAE and send them special delivery along with your passport to the IRS at the US Embassy. They will then send back your passport (mine came back by return of post).

They pass on the form and letter to the IRS in Texas, who in my case sat on it for 3 months and then said that the letter from the publisher was wrong. After much discussion with the IRS in the US embassy we managed to find out that the problem was that the original letter did not have the phrase 'will be receiving payments for the year X and ongoing'. The publisher sent me another letter with the correct phrasing (the one attached) and a very helpful chap (Carlos) at the IRS in London managed to get the ITIN issued very quickly.

Once you have your ITIN, the W-8BEN is a nice simple one page form.

Now, I'm just trying to get the wire transfer sorted out. But the end is in sight!

Good luck!

Notes:

Don't forget to put the dates in the American MM DD YYYY format on the forms.
If you have a problem email the IRS at the US Embassy (IRS.London@irs.gov)
Don't blame me if this doesn't work, I'm just trying to help out I am not a tax expert.
Be patient

New Arduino book on the way

2010-03-26T01:42:00.000-07:00

My book '30 Arduino Experiments for the Evil Genius' (McGraw Hill) is out the door now and I have nothing to do except wait for the proofs and play with the web page (www.arduinoevilgenius.com).

The book should be on the shelves in August!

Simplified Ethernet Library for 28J60 Shield

2010-03-26T01:21:00.000-07:00

With an Ethernet shield you can transform your Arduino into a tiny little web server. Not only that but a web server with Inputs and Outputs. So you can use it to measure things on an analog input and then access those readings from anywhere on the Internet. Or, if you like, you can use it as a remote control to turn things on and off.

There are two flavours of ethernet shield for the Arduino. There is the official one, based on the Wiznet W5100 chip and the unofficial but significantly cheaper board based on the 28J60 chip.

Nuelectronics sell a board based on this chip and have also produced a library to use it. There are also clones of this to be found on eBay, some of which have a neat little prototying area (see above)

The Nuelectronics library is very thorough, but not the easiest library in the world to use, so I decided to write a library that wrapped up this library with a simpler interface.

You can download the library from here but you will also need to download the Nuelectronics library from here.

Install both libraries into your Arduino environment by unzipping them into a folder called 'libraries' in your sketches directory.

You can now create a simple sketch like this hello world web server example:

#include "etherShield.h"

#include "ETHER_28J60.h"

static uint8_t mac[6] = {0x54, 0x55, 0x58, 0x10, 0x00, 0x24};

static uint8_t ip[4] = {192, 168, 1, 15};

static uint16_t port = 80;

ETHER_28J60 ethernet;

void setup()

{

ethernet.setup(mac, ip, port);

}

void loop()

{

if (ethernet.serviceRequest())

{

ethernet.print("<H1>Hello World</H1>");

ethernet.respond();

}

This example just displays Hello World when you connect to it in a browser.

I have included some other examples that display the values at the analog ports, set a digital output and also echo the request parameters.

This is all heavily influenced by a posting I saw and now cannot find by some who had done a very similar thing to this. If you are reading this, please let me know so that I can give you the credit you deserve. I just kind of did things a slightly different way, and put it in a library rather than a set of functions.

The API is documented below:

Setup.
void setup(uint8_t macAddress[], uint8_t ipAddress[], uint16_t port);

Example:

static uint8_t mac[6] = {0x54, 0x55, 0x58, 0x10, 0x00, 0x24};

static uint8_t ip[4] = {192, 168, 1, 15};

static uint16_t port = 80;

ETHER_28J60 ethernet;

void setup()

{

ethernet.setup(mac, ip, port);

}

You will need to find an ipAddress that is both in a valid range and unused on your local network.

The mac address just has to be unique on your network, so unless you have two of these boards on the network, the value above will be fine.

Servicing Web Requests

char* serviceRequest();

Example:

void loop()
{
  char* params;
  if (params = e.serviceRequest())
  {
   e.print("<H1>Web Remote</H1>");
   if (strcmp(params, "?cmd=on") == 0)
   {
   digitalWrite(outputPin, HIGH);
   e.print("<A HREF='?cmd=off'>Turn off</A>");
   }
   else
   {
   digitalWrite(outputPin, LOW);
   e.print("<A HREF='?cmd=on'>Turn on</A>");
   }
   e.respond();
  }
}

serviceRequest either returns null if there has not been an incoming web request to service, or it returns a string containing the request parameter string for the incoming request. The request string includes the '?' character.

In the example above, if the request parameter string is '?cmd=on' then the digital output is set high and the hyperlink to turn the output off is rendered. Otherwise, the digital output is set low and the hyperlink to turn it on is rendered.

This also shows how to write the response and make the final response to the browser's request.

Writing the Response

void print(char* text)
- adds a string of HTML to the response to be returned.

void print(int value);
- adds an integer displayed in decimal form to the response.

void respond();
- commits the response back to the requesting browser.

Some things to watch.
The board consumes about 250mA which seems a lot to me. When driven from a power adaptor rather than USB, that makes the Arduino board get pretty hot around the voltage regulator. So just be careful, particularly if you plan to put your project in a box.

If you start to get strange things happening with the code, and you are using a 168 Arduino, you may well be running out of memory. The examples in the library will work with a 168, but to do anything more substantial use a 328.

Apple Rant

2010-03-23T08:23:00.000-07:00

I have been using Macs since the days of the 'Multi-Finder' anyone else remember that? When you could actually have more than one application running at a time!

After a time away from Macs I was first in the queue to get a Mac when OS X first came out. I had to put up with a lot of grief from my co-workers and the highly non-standard nature of my computer. Gradually one by one they took to Macs and there is not really any going back to Windows after you have used one.

iPod's - fantastic again very happy to be an early adopter. iPhone - yup I need on of them, and its great.

So, you may be surprised to discover that I am considering trading in my iPhone for an Android phone. The reason for this change of heart, is that Apple are deliberately making it hard for anyone like me to make any kind of hardware that works with the dock connector, without having to buy special licensing chips and give Apple money!

All I want to do is to get at the line-out pins on the dock connector to wire my iPod into my car stereo and have a nice neat single plug dock for my iPod when its in the car, without having to plug a lead into the top for audio.

But you can't! Apple have forbidden it, so my iPod breakout board will be going onto eBay and if it wasn't so damned nice, it would be followed shortly by my iPhone!

Apple, you are supposed to be the good guys, just take a leaf out of Google's book and be nice.

Elderflower Cordial

2008-06-10T14:32:00.000-07:00

Its that time of year again when the Elderflower bushes are all in bloom. Its very easy to make your own cordial.

Ingredients

30 x flower heads from a bush cut in the sunshine

3 x lemons

1 x 60g packet of citric acid

1 kg of sugar

You will also need 2 big pans and a bit of net curtain or a pop-sock or half a pair of tights for straining the flowers through.

Put the flower heads and lemons cut into quarters into the pan.
Cover with boiling water, bring to the boil and leave over-night.
Fish out the bulk of the flowers and lemons with your fingers and put them in the bin.
Attach the pop-sock over a jug so that only the poring lip of the jug escapes the sock. In this way you can pour the unfiltered brew into the sock then pour filterd liqued out of the jug into a second pan.
Pour all the Elderflower tea a bit at a time into the filtering jug described above.
Add the sugar and citric acid to the filtered brew and bring to the boil.
Allow it to cool and bottle it.

You can now use it diluted like you would any squash.

Mmm a taste of summer. Make up a jug of it chilled with slices of lemon and ice cubes or use fizzy water.

Trip to Moscow

2008-06-08T11:40:00.000-07:00

Bit of a retrospective blog, this one.

Last year I presented at SD Best Practice Moscow.

It was a fantastic experience and I very much enjoyed Moscow.

I deliberately stayed near the centre away from the conference hotel so that I could experience a bit more of the real Moscow.

A weekly Metro ticket was very cheap, and I was very please with myself for learning and reciting enough Russian to buy my pass.

The art and decor of the Metro is amazing, as are the escalators, which go up and up and up and ... amazing feats of engineering, far longer than anything in the London underground.

Not many people in the street spoke English, so its worth having a phrase book and learning to pronounce the place you are looking for. Its also polite.

I found people perfectly friendly and willing to help the stupid foreigner find where he was looking for.

Wandering about, sometimes even late at night seemed safe. I didn't see anything untoward. But I may just have been lucky.

I can recommend a visit to the VVTs - see your guide book. Its easily accessible from the Metro and its nice to wander about.

At the far end of the park from the Metro is a Vostok rocket. Just sitting there, unguarded largely ignored by all all except me who - as a lover of all things spacey was mightily impressed. It was smaller than I expected and top marks for courage to Uri Gagarin for sitting on top of what is basically a prototype ICBM.

The contrast was even more start for me as the week after I was in Florida and visited the Kennedy Space Center. The understated and free nature of the Vostok rocket was really refreshing. The informality and complete lack of commerciality was great. It was a real reminder of the achievements of this remarkable nation.

It reminded me of the tale about the urban legend of the Americans spending a million dollars developing a pen that would write in zero gravity. The Russians just used a pencil !

The impression I was left with of Russia was one of a people with brains and pragmatism.

A nation with very much to be proud of.

Debugging a live Ruby on Rails server

2008-06-07T00:09:00.000-07:00

This just something useful that occurred to me that is probably blindingly obvious to seasoned rails people out there.

We have a Rails application hosted with Apache and a Mongrel cluster running in production mode. That means if something goes bang, to see what happened you have to go to /log/production.log to see what happened. This system is for internal use to its considered acceptable to reproduce problems quickly on the server and even fix there and copy back to the repository. Mainly because thats much faster. The problem is that you have to restart the cluster every time you change anything.

What occured to me was that to reproduce bugs I could leave the cluster running normally, but just start another instance of the application running on another port in development mode by doing:

script/server -p 4000

I can then hit the controllers running on those pages and see the error messages and trace.

So there you go - a bit trivial, but it saved me some time yesterday.

Extending core Classes in Ruby on Rails

2008-06-03T23:30:00.000-07:00

While I was tinkering with our agile tracker tool, I had the need of a first_of_month method that would tell me the first day of the month of any particular day. In a less flexible language, you are limited to the choices of:

write a 'utility' class which is just a bucket of useful methods - not very elegant and ugly too use.
extend the built-in Date class and add your own methods - not very convenient because you have to remember too use the class 'MyDate' everywhere

What Ruby lets you do is simply add your own methods to existing classes! This is exactly what's needed.

To do this in rails, simple create a new file in your 'lib' directory called date_extension.rb and put the following code in it.

class Date

  def first_of_month
   return Date.new(self.year, self.month, 1)
  end

end

To get Rails to load this extra method, you need to add the following line to your 'config/environment.rb' file.

require 'date_extension.rb'

Thats it! You'll need to restart Rails to see the change, but then you can use the new method anywhere in your controllers or templates. For example:

first_of_month = Date.today.first_of_month

You can do the same with String and add your favourite starts_with? or whatever methods.