PiFace Example 1

#!/usr/bin/env python
import time, threading
import pifaceio

# Width and number of output pulses in sequence
PULSE_ON  = 2 # secs
PULSE_OFF = 1 # secs
PULSE_NUM = 3 # count of ON pulses in sequence

PIN_TRANSITIONS = PULSE_NUM * 2

# Global lock for threads
lock = threading.Lock()

# Fetch instance of and initialize PiFace board
pf = pifaceio.PiFace()

# Initialize all board pin outputs to 0
pin_outputs = 0x0
pf.write(pin_outputs)

# Currently active pins
pin_active = 0x0

def send_output(pin_mask):
    'Runs in thread to drive a single output pin through transitions'
    global pin_outputs, pin_active

    for count in range(PIN_TRANSITIONS):
        with lock:
            if count & 1:
                pin_outputs &= ~pin_mask
                delay = PULSE_OFF
            else:
                pin_outputs |= pin_mask
                delay = PULSE_ON

            pf.write(pin_outputs)

        # Don't delay on final off
        if count != PIN_TRANSITIONS - 1:
            time.sleep(delay)

    with lock:
        pin_active &= ~pin_mask

# Forever ..
while True:
    with lock:
        inputs = pf.read()

    # Iterate through all 8 inputs pins and start output thread if input on
    for pin in range(8):
        pin_mask = 1 << pin
        if inputs & pin_mask and not (pin_active & pin_mask):
            with lock:
                pin_active |= pin_mask

            t = threading.Thread(target=send_output, args=[pin_mask])
            t.daemon = True
            t.start()

    time.sleep(0.05)