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Kit Plummer
Software Engineer :: Techitect :: Evangelist
kitplummer@gmail.com
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Well, I’ve been looking for a reason to play with JRuby for some time now. It finally came time, in the shape of a Phidgets servo. Ok, so maybe it isn’t “Phidgets and Ruby” exactly. I can’t say what I’m using the Phidgets for but being able to access them from Ruby is a huge bonus (if for no other reason than I prefer looking at Ruby). Problem is…no Ruby API to access them directly. Python yes, Ruby no. Although I really have nothing against Python this particular project already implicates Java. So, what’s one more library like JRuby?

I will admit that I had quite a few problems getting through outdated documentation for JRuby. Just getting setup with the initial ‘include Java’ instead of ‘require java’ was almost torture. Ruby community’s documentation is already suspect – therefore JRuby must just want to follow suit [Ruby itself, is fairly well documented – thanks to James and the Happy Camper guys]. Then I had to figure out how to work the Java interfaces for the servo’s “attach” listener. The documentation for how to do this is a bit of a struggle too. Just need to remember that JRuby is early 1.x version.

I was actually able to get Phidget servo to respond and set it to a given position. Cool. And, I will admit the code is much cleaner, simpler and a lot less of it.


include Java

require 'phidget21.jar'

include_class Java::com.phidgets.ServoPhidget
include_class Java::com.phidgets.event.AttachListener
include_class Java::com.phidgets.event.AttachEvent
include_class Java::com.phidgets.PhidgetException

class ServoAttachListener
   
  servo = ServoPhidget.new()
    
  def attached(ae)
    begin
      puts "Getting Device Name..."
      servo = ae.getSource()
      puts "Device Name: " + servo.getDeviceName()

      puts "Getting Servo Count..."
      puts "Servo Count: " + servo.getMotorCount().to_s

      puts "Getting Servo Max Position..."
      puts "Position: " + servo.getPositionMax(0).to_s
      
      puts "Getting Servo Min Position..."
      puts "Position: " + servo.getPositionMin(0).to_s
      
      puts "Setting Servo to Max Position..."
      servo.setPosition(0, 232.0)
      
    rescue PhidgetException => e
      puts "Java or Ruby exception: #{e}"
      raise
    end
  end
  
end

puts "Hello Phidget Servo"

servo = ServoPhidget.new()
attach_listener = ServoAttachListener.new()

servo.addAttachListener(attach_listener)
servo.openAny()

while true
  
end
puts "Goodbye Phidget Servo"


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