Prerequisites

You should review the following before moving on:

• Introduction to Pygame Zero
• Getting Started Kit - Advanced Lessons - Smart Phidget Events
• Getting Started Kit - Advanced Lessons - Data Interval

Setup

Install Pygame Zero

In order to use Pygame Zero, you first have to install it. You do this in the same way you previously installed the Phidget22 library. Simply navigate to your package manager, search for pgzero and press install!

Create Project Structure

Create the following project structure on your computer in the location of your choice.

Download the following files and place them in the appropriate location.

• alien.png
• alien_hurt.png
• eep.wav

Finally, create a new python file named phidgets_pygame.py and save it in the same location

Write Code (Python)

Copy the code below into phidgets_pygame.py.

  
#Add Phidgets Library
from Phidget22.Phidget import *
from Phidget22.Devices.Encoder import *
from Phidget22.Devices.DigitalInput import *

import pgzrun

alien = Actor('alien')
alien.pos = 100, 56

WIDTH = 500
HEIGHT = alien.height + 20

def draw():
    screen.clear()
    alien.draw()
    
def update():
    if(dial.alienMovement > 0):
        alien.left += 5
    elif(dial.alienMovement < 0):
        alien.left -= 5    

def set_alien_hurt():
    alien.image = 'alien_hurt'
    sounds.eep.play()

def set_alien_normal():
    alien.image = 'alien'
    
#Phidgets Code Start
#Button Event
def onStateChange(self, state):
    if(state):
        set_alien_hurt()
    else:
        set_alien_normal()
        
def onPositionChange(self, positionChange, timeChange, indexTriggered):
    #position change is only availble through this event, so store the data for use in the update event
    dial.alienMovement = positionChange 
    
#Create, Address, Subscribe to Events and Open
dial = Encoder()
button = DigitalInput()
button.setOnStateChangeHandler(onStateChange)
dial.setOnPositionChangeHandler(onPositionChange)
dial.alienMovement = 0 #create this property on the fly to store movement information
dial.openWaitForAttachment(5000)
button.openWaitForAttachment(5000)
#Set data interval to minimum | This will increase the data rate from the sensor and allow for smoother movement
dial.setDataInterval(dial.getMinDataInterval())
#Phidgets Code End    
    
pgzrun.go()
  

Run Your Program

When you move the dial, the alien will also move. When you press the dial down, you will hear a sound and the alien sprite will change to an unhappy alien.

Code Review

As you may have noticed, the program above is based on the program from the Introduction to Pygame Zero. The main difference is that the code to handle mouse clicks has been removed. To replace mouse clicks, the Dial Phidget is used.

When using the Dial Phidget, you have two objects to create and use:

• Encoder
• Push Button

When using the Encoder, it's important to set the data interval to the minimum as shown in the code above. This will ensure your sensor is as responsive as possible. In this program, you are controlling the alien based on the dial movement (left or right). The easiest way to do this is to subscribe to the position change event and store the position change value as shown in the code above. If the change is positive, move the alien to the right, if negative, move it to the left.

When using the push button, it's a good idea to use events. Events will allow you to easily determine when the button has been pushed or released. Polling can also be used, however, extra code will be required

Practice

1. Try commenting out the section of your code that sets the data interval. What is the result?
2. Try increasing how fast the alien moves when the dial is turned.