scrapeboard/gpio.py

# [SCRAPEBOARD] is an arcade game in development by [@diskmem] & [@snakesandrews]
#
# It requires custom hardware to play but can be tested in keyboard mode without
# the hardware. For more information on setting up and running the game, see 
# README.md. For information on the game in general, see <https://scrape.nugget.fun/>.
#
# Full open source code is available at <https://git.nugget.fun/scrape/scrapeboard>.
#
# This module can be imported and used to check on the status of connections between four GPIO
# inputs on the Raspberry Pi for detecting the pads in Scrapeboard.
#
# It can also be run as a diagnostic script, in which case it prints connections detected between
# the input GPIO pins. Use the `-h` flag to print the options.
#
#     $ python3 gpio.py -h
#
# Original algorithm by Dr. Clement Shimizu is taken from his Arduino code in serial/serial.ino

import time, itertools, argparse
import RPi.GPIO as GPIO

# These represent the game pads and the GPIO pins they're connected to
LNW, LNE, LSE, LSW = range(4)
pins = {
    LNW: 26,
    LNE: 19,
    LSE: 13,
    LSW: 6
}

def initialize_gpio():
    """
    Set pin numbering mode to GPIO and initialize all pins to input pullup.
    """
    # Use GPIO numbering
    GPIO.setmode(GPIO.BCM)

    # Set all pins to pullup
    for pin_id, pin in pins.items():
        GPIO.setup(pin, GPIO.IN, pull_up_down=GPIO.PUD_UP)

def connection2(pin_a, pin_b):
    """
    Set `pin_a` to output a low signal, and set every other pin to pullup. If `pin_b` reads a low signal even though
    it's set to pullup, that means `pin_a` is connected to it, so return `True`.

    @param pin_a   Pin which will be set to output LOW
    @param pin_b   Pin which will be read
    @return        `True` if a low signal is sent from `pin_a` to `pin_b`, `False` otherwise
    """
    for pin_id, pin in pins.items():
        if pin == pin_a:
            # Set pin_a to output LOW
            GPIO.setup(pin, GPIO.OUT)
            GPIO.output(pin, GPIO.LOW)
        else:
            # Set all other pins to input pullup
            GPIO.setup(pin, GPIO.IN, pull_up_down=GPIO.PUD_UP)

    # Force 25ns delay between comparisons
    time.sleep(0.025)

    # pin_b can now be tested to see if if reads the LOW signal from pin_a
    return GPIO.input(pin_b) == GPIO.LOW

def connection(pin_a, pin_b):
    """
    Tests low signals connect from both A to B and from B to A

    @param pin_a   Test if this pin is connected to `pin_b`
    @param pin_b   Test if this pin is connected to `pin_a`
    @return        `True` if `pin_a` and `pin_b` are connected, `False` otherwise
    """
    return connection2(pin_a, pin_b) and connection2(pin_b, pin_a)

def connections():
    """
    Look at all six possible connections between the four pins and return the state of each as a single dict.

    @return   A dict with one entry per combination of pins, the key is a tuple of pin IDs, and the value is the state of connection
    """
    state = {}
    for pin_id_a, pin_id_b in itertools.combinations(pins, 2):
        if connection(pins[pin_id_a], pins[pin_id_b]):
            state[(pin_id_a, pin_id_b)] = True
        else:
            state[(pin_id_a, pin_id_b)] = False
    return state

def activity():
    """
    Look at all six possible connections between the four pins, and if a pin appears in any active connection, consider it active.
    Return the active state of all four pins as a dict.

    @return   A dict with one entry per pin. The key is the pin ID, and the value is the state of whether it's active (a.k.a. pressed)
    """
    # Create a dict of pins all at False
    state = pins.copy()
    for pin in state.keys():
        state[pin] = False

    # Check all six combinations. If a pin appears in a connection, update its state to True.
    for pin_id_a, pin_id_b in itertools.combinations(pins, 2):
        if connection(pins[pin_id_a], pins[pin_id_b]):
            state[pin_id_a] = True
            state[pin_id_b] = True

    return state

if __name__ == "__main__":
    # Set up and parse CLI
    parser = argparse.ArgumentParser()
    parser.add_argument("--connections", action="store_true")
    parser.add_argument("--activity", action="store_true")
    arguments = parser.parse_args()

    initialize_gpio()
    
    while True:
        if arguments.connections or not arguments.activity:
            # Try all connections once each frame
            for connection_ids, connection_state in connections().items():
                # Only print connected combinations of pins
                if connection_state:
                    pin_id_a, pin_id_b = connection_ids
                    print(f"{pin_id_a} ({pins[pin_id_a]}) <-> {pin_id_b} ({pins[pin_id_b]})")
        else:
            pin_activity = activity()
            print(f"LNW {int(pin_activity[LNW])} LNE {int(pin_activity[LNE])} LSE {int(pin_activity[LSE])} LSW {int(pin_activity[LSW])}")