from machine import Pin , PWM
import time

servo = PWM(Pin(5) , freq = 50)
while True:
    for i in range(20,121,1):
        servo.duty(i)
        time.sleep_ms(15)
    time.sleep(1)
    for j in range(120,-1,-1):
        servo.duty(j)
        time.sleep_ms(15)