Erlets - Easier Erlang-Java interfacing

I've been helping a friend of mine out with an Erlang project and we needed to interface with Java. JInterface is a great start but it wasn't the easiest to figure out and start using. So I've created 'erlets' a simpler way to create a Java node that erlang can call:

public class MyErletServer {
   @ErlangFunction(module="pinger", function="ping")
   public OtpErlangObject ping(OtpErlangObject arguments) {
       return new OtpErlangString("pong");
   }

   public static void main(String args[]) {
       Erlets server = new Erlets("java@127.0.0.1");
       server.addFunctions(new MyErletServer());
       server.start();
   }
}

This can then be called from Erlang:

$ erl -name 'erl@127.0.0.1'
Eshell V5.7.3  (abort with ^G)
(erl@127.0.0.1)1> rpc:call('java@127.0.0.1', pinger, ping, []).
"pong"

It's available here: http://bitbucket.org/dale.thatcher/erlets

Silly Mii

My talk for barcamplondon4 was "Silly Mii". It's a few ideas I had for silly things to do with the wii-mote. The program includes a simple persistence of vision LED message bar and an 'invisible instrument'. The invisible instrument supports up to four IR sources to play sounds.

Presentation
Program

Ruby: Debugging backticks

I needed to knock up a Ruby script recently that orchestrated some external processes using backticks. However something was going wrong and I need to temporarily peek into the inputs and outputs of the external programs. Ruby bend-ability to the rescue:

module Kernel
  alias_method :real_backticks, :'`'

  def `(cmd) 
    puts "`#{cmd}` => #{output = real_backticks(cmd)}"
    output
  end
end

Four pixel high font

I needed a font that was four pixels high for a project I'm working on and this is what I came up with. Capital B and E and lower case s and z are really difficult but it's just about readable. Free for all commercial or non-commercial use but I'd appreciate a credit if you find it helpful.

HOWTO: Get wii-mote data into Android

In the previous post I demonstrated live wii-mote data going into Google Android. Here is how to replicate this for yourself.

Overview

A C program communicates with the wii-mote over bluetooth and outputs the accelerometer readings to a file. This is then read by a patched version of the OpenIntents sensor simulator and relayed into Android.

The bits

There are four main parts you'll need to get this going:

1. http://dalethatcher.com/android-wii/wiiacc.tar.bz2 A small home grown C app that uses the CWiid library V0.6.
2. http://dalethatcher.com/android-wii/wiimote-sensor-simulator.jar A patched version of the OpenIntents sensor simulator program that supports input from wiiacc.
3. http://openintents.googlecode.com/files/openintents-binary-0.1.5.zip The OpenIntents binaries, which includes the sensors demo program.
4. http://code.google.com/android/download.html The Android emulator.

Setup

Setting up each of the parts.

wiiacc

1. Get cwiid-0.6.00.tgz if you need to and install it.
2. Download wiiacc.tar.bz2 and unpack it.
3. Run bootstrap.sh and then follow the instructions in the INSTALL file to build and install it.
4. Run the program with the output filename as an argument. I use 'wiiacc wii' in my home directory.
5. Follow the instructions from the program and if all is well you should start to see wii accelerometer data in the output file.

Patched Sensor Simulator

1. Download wiimote-sensor-simulator.jar or build from the source if you prefer.
2. Run "java -jar wiimote-sensor-simulator.jar"
3. Scroll down to the bottom of the settings window to the "Real sensor bridge" section.
4. Enter the path to the output file in the text field (I use '/home/dale/wii') and select "Use Wii-mote accelerometer".
5. If all is well you should see the image of the mobile phone in the top left mostly match the movement of the wii-mote. I say mostly because the wii-mote works out it's orientation by gravity which means that it doesn't measure yaw. There is a good explanation here.

OpenIntents and Android

There are some instructions on the OpenIntents wiki here. However this is the short version:

1. Unpack android and run "tools/emulator"
2. Unpack the open intents binary package and install the OpenGL viewer by running: android_install/tools/adb install openintents-binary-0.1.5/OpenIntents.apk android_install/tools/adb install openintents-binary-0.1.5/samples/OpenGLSensors.apk
3. When the emulator starts launch the OpenGL Sensors program and go to the settings menu, enter the most plausible IP address found under 'Possible IP addresses'.
4. You can then test it's working by going to the "Testing" tab and clicking connect, you should see the wii accelerometer data.
5. For some reason I usually find at this point you'll need to come out of the OpenGL Sensors app and go back in. However once I've done this selecting 'connect' in the menu works.

Wii-mote accelerometer into Android

I successfully hooked up my wii-mote to the OpenIntents sensor simulator and then into Android. More information is available here.

MyHelpa New Front Page

We've revamped the front page on MyHelpa today. Have a look and let me know what you think: http://myhelpa.com/.