from machine import Pin,PWM
from time import sleep

pin = Pin(4,Pin.OUT)
servo_pwm = PWM(pin,freq=50,duty=0)

def rotate(servo_pwm,degree):
    val = int(degree*0.54)+25
    servo_pwm.duty(val)

while True:
    rotate(servo_pwm,0)
    sleep(1)
    rotate(servo_pwm,180)
    sleep(1)