Phidgets

Phidgets are are a set of interfaces, sensors and actuators that have readily made connectors (USB or 3-line). Phidgets let you avoid soldering and microcontroller programming so you can put together an installation pretty quickly. Good for prototyping.

"Physical Widgets"

How to set up for Java:

• Phidget USB driver installation, follow the instructions for your platform
• Then go to Java download page
• Put Phidget21.jar in your project classpath
  • if you encouter problems with the Phidget21.jar file on the Java download page you can use this, which is taken from the example zip
    

• supported in Windows, Mac OS X, Linux, Windows Mobile
• USB devices, installation and re-configuration is "plug and play"
  
• support available from a number of programming environments:
• Visual Basic
• Visual Basic for Applications (VBA)
• C/C++ (available in Windows, Linux, MacOS)
• Borland Delphi
• ActionScript (Flash)
• Java (Windows, MacOS, Linux) , which we will work with
  
• etc
• no Processing support, though you can fix that with some form of inter-process communication (e.g. a TCP socket)
  

USB

• universal serial bus, i.e. lets you hang devices in any order
• needs Phidget driver installation
• Phidgets use the USB HID (Human Interface Device) protocol
• use the "phidget manager" on your platform to see a list of successfully connected Phidgets
  • PC: start from the Ph icon in the system tray
  • Mac: System Preferences, select Phidgets
• power issues: some phidgets will need separate power (6-12 V DC) in certain heavier-load conditions, others will simply take their power from USB
• you have to wait a bit more the first time you connect a new type of Phidget (or any other USB device for that matter) in a certain USB connector
• sometimes you will get an error the first time, try disconnecting and reconnecting the device, it may work without errors

8/8/8 "Phidget Interface Kit" (8 digital inputs, 8 digital outputs, 8 analog inputs; there exist boards of other sizes)

• we have 4 boards
• will need external power in some USB connectors
• will surely need external power when other phidgets are connected to the board. If you want to avoid this, connect the phidget directly to the computer or use a powered USB hub
• you can monitor the Phidget Interface Kit with the manager applications
• 8 digital inputs (see page 16) , basically reading the state of a switch. Returns True when the switch is connected to GND, False otherwise.
• 8 digital outputs (see page 19)
  • basically turns a switch on and off
  • simple and frequent example: LEDs
  • a LED is a diode, will let current pass in only one direction
    
  • shorter pin to the ground (cathode), the longer one (anode) to the digital output
    
  • to avoid short, 300 Ohm resistor included in the phidget output
    
• 8 analog inputs (page 12)
• you can connect a number of packaged sensors
• but any other sensor that can be fed with 5V and produce voltage between 0 and 5V will work. See details below.
• we have 3 sensors for each of: force, light, mini joystick, rotation, slider, temperature, touch
• besides these, we can also detect acceleration and presence of RFID tags (see specific phidgets below)
  
• always disconnect the USB to the computer before modifying the interface kit circuit! (attaching analog inputs, digital inputs or outputs)

• if you encouter problems with the Phidget21.jar file on the Java download page you can use this, which is taken from the example zip
• package com.phidgets
  • all USB devices have their own class, a subclass of from com.phidgets.Phidget
    
• the ones we use are the classes corresponding to the devices we have
• InterfaceKitPhidget, ServoPhidget, RFIDPhidget, AccelerometerPhidget
• important Phidget methods
• info: getSerialNumber(), getLibraryVersion(), getDeviceVersion()
  
• useful when software and hardware evolve
  
• getSerialNumber() identifies the device uniquely
  
• open() looks for the physical USB device
• you can specify the serial number of the device, in case there are more Phidget interface kits attached
• openAny() will return the first available Phidget of the respective type
• you can open Phidghets connected to another computer by indicating an IP address (the Phidget Web Service should be started on that machine)
• open is pervasive. It will keep the device open even if it is attached or detached
• open is asynchronous, it returns immediately. You can call waitForAttachment()or use events (see below) to
• isAttached() tells whether the device is really attached
  
• Events: AttachEvent, DetachEvent, ServerConnectEvent, ServerDisconnectEvent, ErrorEvent
  • use addEEEEListener(EEEEListener) where EEEE is the type of event
  • removeEEEEListener(EEEEListener)
• close() gives away resources needed by your program to access the device. No more events are sent.
• device-specific methods depend on the actual device function
• most devices let you register listeners that will have a method called when a device changes state
  

• we look at a Java example and the way it is set up in a IDE (Eclipse)
  
• board size
  
• getOutputCount() the number of digital outputs (8 for our board)
• getInputCount() the number of digital inputs (8)
• getSensorCount() the number of analog inputs (8)
• digital input reading: getInputState(int index)
• digital output setting: setOutputState(int index, boolean value)
  • this may lead to timeout PhidgetException... It looks a lot like harware incompatible with latest software
  • happens also to other setting methods (for e.g. servo motors)
  • especially if you call them in rapid sequence
• digital output reading: getOutputState(int index)
  
• analog input reading
  
• getSensorValue(int index) returns 0-1000
• getSensorRawValue(int index) returns 0-4095 (10 bit Analog-Digital Converter)
• polling vs event subscription
• event subscription for:
  • InputChangeEvent, OutputChangeEvent, SensorChangeEvent
• the event object will give information on
• which Phidget produced the event: getSource()
• which input has changed: getIndex()
• what is the new value: getValue() for analog inputs, getState() for digital inputs our outputs
  

• 4 servo motor driver
  • we have 3, and a large number of servo motors
  • can turn in fine-tuned angles
  • can be tested from the Phidget manager
  • USB power only goes to motor 0. If you want to drive other servos, you need to give 6-12V DC power to the board
  • API (ServoPhidget)
    • getMotorCount()
    • double getPosition(int index)
    • getPositionMax(int index), getPositionMin(int index)
    • setPosition(int index, double angle)
    • getMotorOn(index), setMotorOn(index, boolean)
  • Event: ServoPositionChangeEvent
  • Java example
    
  • initial position is not always zero (or minimum), always set the servo to the desired position initially! The position of a newly connected motor cannot be known, you have to set it.
  • Beware of multiple Java programs running at the same time (esp in Eclipse)
  • other types of motors: stepper motors (turn with a precise number of steps)
    
• LCD and LED output

• RFID board
  • we have 3
  • detects when a certain tag is within 3 inches of the RFID receiver
  • can be tested from the Phidget manager
    
  • one tag can be present only. If more tags are present, one or none will be reported
    
  • API: (RFIDPhidget):
    
  • the latest RFID tag seen: String getLastTag() 
  • TagGainEvent, TagLossEvent
    
  • the device also has some outputs, e.g. a LED
  • getOutputCount(), getOutputState(int index), setOutputState(int index, boolean value), OutputChangeEvent
  • setAntenaOn(boolean), getAntennaOn()
    
  • Java example
    
  • issues
    
  • some older Phidget RFID receivers do not work with the USB hub of  the newer Phidget Interface Kits
  • connect them directly to a computer USB instead
  • setAntennaOn(true) seems to be always needed for old boards.
    
• accelerometer
  • we have one
  • can be tested from the Phidget manager
  • API (AccelerometerPhidget)
  • number of axes: getAxisCount()
  • sensor value reading: double GetAcceleration(int axis)
  • change trigger for acceleration: setAccelerationChangeTrigger(int axis, double value)
    
  • AccelerationChangeEvent
    • contains information on the axis where acceleration changed (getIndex()) and the acceleration value (double getValue())
  • Java example
    
• Other sensors

• sensor data sheets
• resistive and active sensors
  • resistive sensors are simply given a voltage to measure their resistance
  • some resistive sensors only have 2 pins and an extra resistance is needed
  • active sensors are given a voltage and will output a voltage proportional to what is measured
  • in all cases, analog-digital conversion takes place inside the phidget
• guide to phidget analog input cable

• do you want to drive bulbs?
• external supply
• large voltages
• a problem: common ground with the digital circuit
• you can avoid this problem with optocouplers
• using relays: up to 240V
• using 16/16 phidget interface kit: up to 30V DC

Arduino Firmata is suggested as an alternative. Like Phidgets, Firmata can be easily driven from a computer , from various programming environments (it's a so-called sensorbox), with no need for external power. Unlike Phidgets, with Firmata the sensors and actuators are not packaged, they need more wiring and/or soldering. An Arduino Phidget shield might address that.

Moving towards higher-fidelity prototypes.
Microcontrollers

• allow you to skip the PC if needed
• allow programming via a serial/USB connection
  
• sensors/outputs are connected to microcontroller pins, via specific circuits