Reading an NES controller using RP2040's PIO

NES_controller_PIO_polling.py

import time
import rp2
from machine import Pin
from ucollections import OrderedDict

led_1 = Pin(25, Pin.OUT)


@rp2.asm_pio(set_init=(rp2.PIO.OUT_LOW, rp2.PIO.OUT_LOW), push_thresh=8, autopush=True)
def read_NES_buttons():
    wrap_target()
    set(x, 7)
    set(pins, 0b10) [1]
    set(pins, 0b00)

    label("btn_loop")
    in_(pins, 1)
    set(pins, 0b01) [1]
    set(pins, 0b00)
    jmp(x_dec, "btn_loop")

    set(pins, 0b01) [1]
    set(pins, 0b00)
    wrap()


def get_buttons_from_state(state):
    buttons = OrderedDict([
        ("A", False),
        ("B", False),
        ("SELECT", False),
        ("START", False),
        ("UP", False),
        ("DOWN", False),
        ("LEFT", False),
        ("RIGHT", False),
    ])
    for i, button in enumerate(buttons.keys()):
        buttons[button] = not bool(state & (1 << 7 - i))
    return buttons


state_machine = rp2.StateMachine(
    0, read_NES_buttons, freq=2000, set_base=Pin(0), in_base=Pin(15)
)
state_machine.active(1)
while True:
    buttons = get_buttons_from_state(state_machine.get())
    print(list(filter(lambda x: buttons[x], buttons.keys())))
    led_1.value(buttons["B"])
    time.sleep(0.01)