LEGO Power Functions IR control with HIP badge

hip-badge-lego-power-functions.py

from esp32 import RMT
from machine import Pin, Timer

button3 = Pin(9, Pin.IN, Pin.PULL_UP)
button4 = Pin(10, Pin.IN, Pin.PULL_UP)
ir = Pin(2, Pin.OUT)
rmt = RMT(0, pin=ir, clock_div=191, tx_carrier=(38000, 50, 1))
tim = Timer(3)

def send_command(nibble1, nibble2, nibble3):
    nibble4 = 0xF ^ nibble1 ^ nibble2 ^ nibble3 # LRC nibble
    command = (nibble1 << 12) | (nibble2 << 8) | (nibble3 << 4) | nibble4
    pulses = []
    pulses.append(6)
    pulses.append(39)
    for shift in range(15, -1, -1):
        pulses.append(6)
        bit = (command >> shift) & 1
        pulses.append(19 if bit else 10)
    pulses.append(6)
    pulses.append(39)
    rmt.write_pulses([11*j for j in pulses], 1)

def speed_to_nibble(v):
    if v < 0:
        return (-v) | 0b1000
    elif v > 0:
        return v
    else:
        return 0b1000

def set_speed(channel, red, blue):
    send_command(
        (channel & 0b11) | 0b100,
        speed_to_nibble(red) & 0b1111,
        speed_to_nibble(blue) & 0b1111)

red = 0
blue = 0

def irq_handler(*args):
    global red, blue
    red = 1 - button3.value()
    blue = 1 - button4.value()
    set_speed(0, red, blue)
    red = 1 - button3.value()
    blue = 1 - button4.value()
    if red or blue:
        # Retransmit after 500ms if any of the buttons is still pressed
        tim.init(period=200, mode=Timer.ONE_SHOT, callback=irq_handler)
    else:
        set_speed(0, 0, 0)

button3.irq(trigger=Pin.IRQ_FALLING | Pin.IRQ_RISING, handler=irq_handler)
button4.irq(trigger=Pin.IRQ_FALLING | Pin.IRQ_RISING, handler=irq_handler)