from machine import Pin, PWM
from time import sleep

pwmPin15 = PWM(Pin(15))
pwmPin15.freq(1000)

while 1/1 == 1:
    for duty in range(65025):
        pwmPin15.duty_u16(duty)
        sleep(0.0001)
    for duty in range(65025, 0, -1):
        pwmPin15.duty_u16(duty)
        sleep(0.0001)