Examples

Basic usage

Hello, World!:

>>> import pifacecad

>>> cad = pifacecad.PiFaceCAD()    # create PiFace Control and Display object
>>> cad.lcd.backlight_on()         # turns the backlight on
>>> cad.lcd.write("Hello, world!") # writes hello world on to the LCD

Reading the switches:

>>> cad.switches[3].value  # reads the value of switch 3
1
>>> cad.switch_port.value  # reads the value of the switch port
4

Cursor control:

>>> cad.lcd.set_cursor(4, 1)  # set the cursor to col 4 on the second row
>>> cad.lcd.cursor_off()      # turns the cursor off
>>> cad.lcd.write("3.141592") # writes π to the LCD

>>> cad.lcd.blink_off()       # turns the blinking off
>>> cad.lcd.cursor_on()       # turns the cursor on
>>> cad.lcd.home()            # send the cursor home

>>> cad.lcd.write("PiFace Control\nand Display")  # '\n' starts a new line
>>> cad.lcd.clear()           # clear the screen (also sends the cursor home)

The LCD has more RAM than just the 16x2 characters that you can see:

>>> cad.lcd.write("Something really, really long.")
>>> cad.lcd.move_right()
>>> cad.lcd.move_left()
>>> cad.lcd.see_cursor()  # move the display so that we can see the cursor

The viewport_corner variable describes which column the top left display character is showing from RAM:

>>> cad.lcd.viewport_corner       # inspect the viewport_corner variable
8
>>> cad.lcd.viewport_corner = 15  # set the viewport_corner variable

You can also create your own custom bitmaps.

IR Receiver

You need to add your LIRC client (your program) to ~/.lircrc:

$ cat ~/.lircrc
begin
  prog = pifacecadexample
  button = 1
  config = one
end

begin
  prog = pifacecadexample
  button = 2
  config = two
end

Then, register IR codes to functions using IREventListener:

>>> import pifacecad

>>> def print_ir_code(event):
...     print(event.ir_code)
...
>>> pifacecad.PiFaceCAD()  # initialise a PiFace Control and Display board
>>> listener = pifacecad.IREventListener(prog="pifacecadexample")
>>> listener.register('one', print_ir_code)
>>> listener.register('two', print_ir_code)
>>> listener.activate()

Now when you press 1 or 2 on your remote, “one” or “two” is printed.

Interrupts

Instead of polling the switches we can use the SwitchEventListener to register actions that we wish to be called on certain switch events.

>>> import pifacecad
>>> def update_pin_text(event):
...     event.chip.lcd.set_cursor(13, 0)
...     event.chip.lcd.write(str(event.pin_num))
...
>>> cad = pifacecad.PiFaceCAD()
>>> cad.lcd.write("You pressed: ")
>>> listener = pifacecad.SwitchEventListener(chip=cad)
>>> for i in range(8):
...     listener.register(i, pifacecad.IODIR_FALLING_EDGE, update_pin_text)
>>> listener.activate()

The screen should update as buttons are pressed. To stop the listener, call it’s deactivate method:

>>> listener.deactivate()

The Event object has some interesting attributes. You can access them like so:

>>> import pifacecad
>>> cad = pifacecad.PiFaceCAD()
>>> listener = pifacecad.InputEventListener(chip=cad)
>>> listener.register(0, pifacecad.IODIR_RISING_EDGE, print)
>>> listener.activate()

This would print out the event informaion whenever you unpress switch 0:

interrupt_flag:    0b1
interrupt_capture: 0b11111111
pin_num:           0
direction:         1
chip:              <pifacecad.core.PiFaceCAD object at 0xb682dab0>
timestamp:         1380893579.447889