from machine import Pin, Timer
import time

led = Pin(25, Pin.OUT)

btn_blu = Pin(2, Pin.IN, Pin.PULL_UP)
btn_red = Pin(3, Pin.IN, Pin.PULL_UP)

def user_interaction(timeout):
    def _toggle_leds(timer):
        led.toggle()
    tmr = Timer()
    tmr.init(freq=2, mode=Timer.PERIODIC, callback=_toggle_leds)
    startime = time.ticks_ms()
    timeout *= 1000
    while time.ticks_diff(time.ticks_ms(), startime) < timeout:
        b, r = btn_blu.value(), btn_red.value()
        if (b + r) < 2:
            tmr.deinit()
            return 'B' if not b else 'R'
    tmr.deinit()
    return 'T'   # Timeout

if __name__ == '__main__':
    print(user_interaction(20))