Language - Ruby

Ruby is an interpreted and object oriented scripting language with simple syntax created by Yukihiro Matsumoto.

Introduction

If this is your first time working with a Phidget, we suggest starting with the Getting Started page for your specific device. This can be found in the user guide for your device. That page will walk you through installing drivers and libraries for your operating system, and will then bring you back here to use Ruby specifically.

Ruby is capable of using the complete Phidget API, including events. We also provide example code in Ruby for all Phidget devices.

Ruby can be developed with Linux and OS X.

You can compare Ruby with our other supported languages.

Just need the Ruby documentation, drivers, libraries, and examples? Here they are:

Documentation

• RubyDoc API Manual

Example Code

• Example Code (@RubyGems)

Libraries and Drivers

• Ruby Libraries (@RubyGems)
• OS X Drivers Installer
• Linux Libraries (Source Code)

Getting started with Ruby

If you are new to writing code for Phidgets, we recommend starting by running, then modifying existing examples. This will allow you to:

• Make sure your libraries are properly linked
• Go from source code to a test application as quickly as possible
• Ensure your Phidget is hooked up properly

Instructions for OS X and Linux are similar, so they will be combined into the same section.

The first step in using Ruby on Mac or Linux is to install the Phidget libraries. Compile and install them as explained on the getting started guide for your device.

The next step is to install the phidgets-ffi gem. This is the library that allows you to program Phidgets with Ruby. For more information, please see phidgets-ffi at RubyGems and GitHub.

Description of Library Files

Ruby programs on OS X and Linux depend on the following files, which the installers put into your system.

If you are using OS X, you will need the:

• Phidget21.framework contains the actual Phidgets library for OS X, which is used at run-time.

If you are using Linux, you will need the:

• libphidget21.so contains the actual Phidgets library for Linux, which is used at run-time.

For both OS X and Linux, you will need the phidgets-ffi gem.

• phidgets-ffi is the Phidgets gem for Ruby. This gem contains the library as well as example code.

Installing phidgets-ffi

The phidgets-ffi gem relies on the ffi gem. So, if you do not already have it installed, please do so. A version of ffi 1.0.9 or greater is needed. Type the following to install ffi:

  gem install ffi

Next, please install the phidgets-ffi gem by typing the following into command line:

  gem install phidgets-ffi

For OS X systems, the gem will be installed into /Library/Ruby/Gems/1.x/phidgets-ffi-x.x.x.

For typical Linux systems, the gem will be installed into var/lib/gems/1.9/gems/phidgets-ffi-x.x.x.

Use Our Examples

Open a command line terminal and navigate to the phidgets-ffi gem directory. cd into the examples folder. Here, you will find all of the examples available for Ruby. If you aren't sure what the software example for your device is called, check the software object listed in the Getting Started guide for your device.

The easiest way to confirm that your environment is set up properly will be to compile and run the HelloWorld Ruby example.

The only thing left to do is to run the examples! Type the following into command line:

  ruby HelloWorld.rb

This program will detect for devices that are attached/detached on the computer. Go ahead, and attach or detach your devices! Here is an example output:

After confirming that the HelloWorld example is working, you can proceed to run the example for your device. If you aren't sure what the software example for your device is called, check the software object listed in the Getting Started Guide for your Device. Please ensure that you have set your start up project to be the one that matches your device before compiling.

Once you have the Ruby examples running, we have a teaching section below to help you follow them.

Write Your Own Code

When you are building a project from scratch, or adding Phidget function calls to an existing project, you'll need to configure your environment to properly link the Phidget Ruby libraries.

Simply, add the following two lines to the beginning of any .rb script to make use of the phidgets-ffi gem

  require 'rubygems'
  require 'phidgets-ffi'

The project now has access to the Phidget21 function calls and you are ready to begin coding.

The same teaching section which describes the examples also has further resources for programming your Phidget.

Follow the Examples

By following the instructions for your operating system and compiler above, you probably now have a working example and want to understand it better so you can change it to do what you want. This teaching section has resources for you to learn from the examples and write your own.

Next, comes our API information. These resources outline the Ruby Phidget functions:

• Ruby API (This is the complete set of functions you have available for all Phidgets)
• Device Specific APIs - The one for your Phidget can be found in its user guide.

To learn the details behind opening, configuring, using, and closing your Phidget, try the General Phidget Programming page. That page also describes using the Phidget in an event-driven manner and in a traditional manner, both of which are available in Ruby.

Example Flow

The Hello World example has this general structure so you can follow along. We also have an in-depth general introduction to writing Phidget code (like open, read data, etc), as well as the Ruby API for specific syntax:

// ----- Event and Other Functions ----- Create any Language-Specific Functions (exception handling) Create General Attach, Detach, and Error Handling Functions: On attach: Print Hello Message On detach: Print Goodbye Message		In Ruby, you can name these event functions whatever you like. You will then pass them as function pointers to the Phidget library below in the Main Code section. This hooks them into the actual events when they occur. In the example code, the event functions common to all Phidgets are called things like AttachHandler() and DetachHandler(), etc. Some event functions will be specific to each device, like when a tag is read on an RFID board, or when a sensor value changes on an Interface Kit. Other functions are given in the examples to show you more detail on using your Phidget. For example, DeviceInitialize() will show what needs to be set up for your Phidget before using it.
// ----- Main Code ----- Create Manager Software Object Hook Event Functions created above to Device Open Device Wait for 'Enter' key character input Handle on-going attach and detach events Print Hello and Goodbye messages Exit upon input Close Device Delete Device		Creating a Phidget software object in Ruby is specific to the Phidget. For a Phidget Spatial, for example, this would involve creating a Spatial object. The examples show how to do this and other API functions. The object provides device specific methods and properties which are available from the API for your specific Phidget.

Common Problems and Solutions/Workarounds

Here you can put various frequent problems and our recommended solutions.