from machine import Pin,PWM
from time import sleep

myPin=Pin(0,Pin.OUT)

myServo=PWM(myPin)
myServo.freq(100)
i=1800
diff=10

while True:
    myServo.duty_u16(i)
    print(i)
    i+=diff
    if i>18000 or i<1800:
        diff*=-1
        i+=diff
    sleep(0.001)