PiFace Example 2

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

# Pressing a Piface board input pin starts a sequence of output pins + delays.

# Define output sequences here. Format is:
#   in_pin: ((out_pin1, on_time), (out_pin2, on_time), [ .. ])
# if out_pin = -1 then delay for on_time only.
# It's up to you to define/use output sequences that don't conflict.
# Input and output pins are numbered 0 to 7.
# Times are in seconds (and can be float, e.g. 0.1 sec).
sequences = {
    0: ((0,4), (-1,2), (1,3), ),
    1: ((2,4), (5,3), ),
}

# 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 input pins
in_active = 0x0

def send_output(in_pin):
    'Runs in thread to drive output pins + delays for given input pin sequence'
    global pin_outputs, in_active

    for out_pin, delay in sequences[in_pin]:

        # Set this output pin ON
        if out_pin >= 0:
            pin_mask = 1 << out_pin
            with lock:
                pin_outputs |= pin_mask
                pf.write(pin_outputs)

        time.sleep(delay)

        # Set this output pin OFF
        if out_pin >= 0:
            with lock:
                pin_outputs &= ~pin_mask
                pf.write(pin_outputs)

    with lock:
        in_active &= ~(1 << in_pin)

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

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

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

    time.sleep(0.05)