Light alarm clock with raspberry pi pico

from machine import Pin, PWM, Timer
import utime # utime is the micropython brother of time

# Setup
onboard_led = Pin(25, Pin.OUT)
# blink onboard led 3 times to make sure the pico works
for i in range(3):
    onboard_led.value(1)
    utime.sleep(0.2)
    onboard_led.value(0)
    utime.sleep(0.2)
    

# see https://datasheets.raspberrypi.org/pico/raspberry-pi-pico-python-sdk.pdf chapter 3.1
tim = Timer()

# the timer works with seconds. To make it more human readable I calculate hours
m = 60 # 60 seconds = 1 minute
h = 60*m # 60 minutes = 1 hour
sleeptime = 7.7*h # my preferred sleeping duration is 7.7 hours

# Pulse Width Modulation setup
duty = 0
pwm = PWM(Pin(15))
pwm.freq(1000)

# flash external led once to make sure it still works
duty = 40000
pwm.duty_u16(duty)
utime.sleep(1)
duty = 0
pwm.duty_u16(duty)

def tick(timer):
    global duty
    global pwm
    
    while duty < 255:
        duty +=1
        pwm.duty_u16(duty*duty)
        utime.sleep(0.3)
    
tim.init(freq=1/sleeptime, mode=Timer.ONE_SHOT, callback=tick)