Saturday, 19 July 2014

Windchill and Scala: a quick dabble

Scala runs on the Java Virtual machine (JVM) and compiles to byte code the same as Java, this means that like jython it can also use Java libraries. One of the nice features of some modern languages is the REPL a console that allows the direct input of code to the interpreter along with instantaneous feedback.

 PTC's Windchill PLM/PDM Application is written in Java and also features an API to allow it to be customised to meet customer requirements. Running the Scala console inside a windchill shell allows access to windchill libraries and hence allows code be run on windchill's Method Servers using remote method server calls.

To give it a try download and install Scala from http://www.scala-lang.org/download/ then open a windchill shell and type scala to access the Scala REPL.

Like Java, before you can make any calls using the Windchill API you need to import the classes, also to be able to run windchill methods we need a remote method server instance, so we can enter

import wc.method.remotemethodserver

 followed by

val remotemethodserver=RemoteMethodServer.getDefault()

 now that we have a method server  we can access it's methods, by entering

println(remotemethodserver.getInfo().startDate()

we can print out the start time of the method server as shown below.


Typing this in line by line would soon get repetitive and boring so we can create our code in a text file and then run it via the Scala console using scala filename.scala in this case scala WindchillExamples.scala

The below code shows some examples of using the windchill api to create a part and query the database, the syntax looks similar to how it would be written in Java with a few differences (specifying the class in the query spec and casting the returned part object from Persistable for instance). 

import wt.part.WTPart
import wt.method.RemoteMethodServer
import wt.fc.PersistenceHelper
import wt.query.QuerySpec
import wt.query.SearchCondition
 
object WindchillExamples {
def main(args: Array[String]) {
  println("Hello, Windchill!")
 
 
  // Get MethodServer
 
  val remotemethodserver=RemoteMethodServer.getDefault() 
  val name="examplePart" 
  createPart(name) 
  countParts(name)
 
}
 
def countParts (name:String){
 
  //example query
 
  var qs=new QuerySpec(classOf[WTPart]) 
  qs.appendWhere(new SearchCondition(classOf[WTPart], WTPart.NAME,SearchCondition.LIKE, name))
  val qr = PersistenceHelper.manager.find(qs)
  println("Query results count: "+qr.size())
  val resultantPart=qr.nextElement()
  println(resultantPart.asInstanceOf[WTPart].getNumber())
 
}

def createPart(name:String){
 
  //example create part
 
  var part=WTPart.newWTPart()
  part.setName(name)
  PersistenceHelper.manager.store(part)
 
}
 
}

Sunday, 16 February 2014

Controlling a Berry Clip from Node.js

I am looking to try and run a workshop session at my local developers group, the group contains developers form a range of background and hence a number of languages, this makes workshops interesting. To be able to do any interesting projects with a Raspberry Pi I would prefer people are spend their thinking about problems and not battling which ever language is currently running on my RPi devices. A recent pole suggested that javascript was the most widely used language among the group so I decided to see could be achieved in Node.js.

I found a few libraries/modules that allowed gpio access and decided to try onoff since it the example code included using an event to trap button pushes.

I am not quite sure currently what my final project will be but starting off with a simple project I decided to try and control my Berry Clip 6 LED addon board.

The below code selects a random LED to turn on and turns off the previously lit one. Full Information and a run script can be found in the README.ME
var Gpio = require('onoff').Gpio,
    ledA = new Gpio(04, 'out'),
    ledB = new Gpio(17, 'out'),
    ledC = new Gpio(22, 'out'),
    ledD = new Gpio(10, 'out'),
    ledE = new Gpio(09, 'out'),
    ledF = new Gpio(11, 'out'),
    button = new Gpio(07, 'in', 'both');
var leds=new Array(ledA,ledB,ledC,ledD,ledE,ledF);
var lastLed=ledA;

button.watch(function(err, value) {
  var activeLed=Math.floor(Math.random() * 6);
  lastLed.writeSync(0);
  lastLed=leds[activeLed];
  leds[activeLed].writeSync(value);
});

Code:
https://github.com/qubecad/berry_clip_node

References:

https://github.com/fivdi/onoff
http://www.raspberrypi-spy.co.uk/

Tuesday, 11 February 2014

Analog Thumbstick and the Raspberry Pi


For a while now I have wanted to try using analog inputs with my Raspberry Pi. The Pi hardware only supports digital inputs, but it is also capable of communicating with expansion chips using an interface called Serial Peripheral Interface (SPI) . I decided to try my hand at getting a ThumbStick from a GamePad to work They are available for a few pounds from ebay and so would not require me to destroy an existing console controller. 

Some internet research pointed me in the direction of using a MCP3008 10 bit Digital to Analogue converter. The first guide I found for using one of these was on the Adafruit learning system and used something called Bit Banging, further research showed that later Pi do not need to do this and a guide on Raspberry Pi Spy gave me a starting point using a library called py-spidev. This lead to the below circuit diagram. The 2 direction (X & Y) signals are fed into the A/D converter. When the AD converter is queried by the python code a value between 0 and 1023 is returned representing the position of the stick ie 0 is extreme left, around 500 centre and 1023 extreme  right.



The next part was to make my stick work like a joystick. I decided to have a play with PyGame (PyGame is installed as default on the Raspbian image) and see what I could come up with. At IWDEV 2 Gareth Williams gave a Introduction to Monogame and created a simply shooter based on an alien and his cat. Trying to recreate this in python on the Pi would provide me with a suitable test for my joystick.


Once this was working I started to create some code to act as a bridge between the A/D and the normal Joystick functions. Luckily this proved to just be a case of setting range of the A/D converter values when initialising the uniput library and then passing in the value received by querying the chip. I used a third analog channel for the switch activated by pressing down the stick but it should really be a digital GPIO input and I was being lazy. 



The results as a Google + Auto Awesome montage

The python uinput library download and install details can be found at:


Matt Hawkins guide to the MCP 3008 including enabling the kernel modules and installing py-spidev can be found at:


My final python listener script can be found on github at:


To start,  run the .setup.sh script which loads the uniput module and then start the python script with the command:

sudo python analog_joycestick.py &

this should start the script as a background process (requested via the &) and display the process id of the script. If you later want to quit the script you can stop it using sudo kill -9

Sources:
http://www.raspberrypi-spy.co.uk

Sunday, 24 November 2013

Snap N Paint

After a recent visit to see my niece and nephew I wanted to see if I could come up with an app that they might use. My idea was to create a paint by numbers style app but to source the picture to be coloured from an image.

The result is Snap N Paint, the picture is captured via the camera and processed using the OpenCV library sobel function, this provides an outline which can then be coloured in.

To make sure the correct colours are available in the palette, the original image is used. The user selects the area they would like to colour and the correct colour is set active.  

My current results are shown below (and my dodgy colouring skills), it is still a work in progress and I will probably never release it but it is quite fun if you have a stylus and a tablet. 


Sunday, 27 October 2013

Setting the Raspberry Pi's JAVA_HOME

The new Raspberry Pi build of Raspbian now comes with Java 1.7 pre installed.

If you need to set JAVA_HOME it can be set by carrying out the following to your ~/.bashrc

nano ~/.bashrc

then add the following and save the changes

export JAVA_HOME="/usr/lib/jvm/jdk-7-oracle-armhf"
export PATH=$PATH:$JAVA_HOME/bin

when you next login try typing:

 export

you will see a list of values, one of which should be

declare -x JAVA_HOME="/usr/lib/jvm/jdk-7-oracle-armhf"

A guide for installing and setting up the java 8 preview is available at :
http://www.savagehomeautomation.com/raspi-jdk8

Sunday, 6 October 2013

MineCraft: Pi Edition Java Api

I saw a recent post on Raspberry Pi Spy about the Pi edition of MineCraft having a python API and thought it might be fun to play with. After installing, it seems it also has a Java Api which closely follows the Python. The next question was what to write, always a sticking point. I decided upon flipping things on their head a little and have a joystick in MineCraft control my trusty PiBot (I've tried to control it with everything else why not this). Hitting one of the blocks via a right click would launch the Bot into action.




The Bot is controlled by a Web service, so no changes were needed from the code previously written to talk to an android tablet.

The Api includes some examples written by Daniel Frisk along with a Javadoc and Martin O'Hanlon has written some good Python tutorials on his blog http://www.stuffaboutcode.com.


My resulting code can be found at
:https://bitbucket.org/chughes42/minecraft-pi

and the Pibot code is at

https://bitbucket.org/chughes42/remotepibot






Sunday, 4 August 2013

Useful Android adb Network debugging commands



Capture network traffic to pcap file:

adb -e shell tcpdump -s 1500 -w /sdcard/capture.pcap

Transfer pcap file from emulator to host pc

adb pull /sdcard/capture.pcap

The pcap file can then be opened in Wireshark.