import machine
import utime

pot = machine.ADC(26)
led = machine. PWM(machine.Pin(13))
heart_min = 40
heart_max = 180
heart_range = heart_max - heart_min

while True:
    pot_value = pot.read_u16()
    bpm = heart_min + ((pot_value / 65535) * heart_range)
    print (bpm)

    beat = 60/bpm
    brighter_time = beat / 2
    dimmer_time = beat /2

    led.duty_u16(0)
    led.freq(500)
    led.duty_ns(int(brighter_time * 500_000))
    utime.sleep(brighter_time)
    led.duty_ns(int (dimmer_time * 50_000))
    utime.sleep(dimmer_time)