from machine import Pin,PWM
from utime import sleep_ms
servo = PWM(Pin(15))
servo.freq(50)
def interval_mapping(x,in_min,in_max,out_min,out_max):
    return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min
def servo_write(pin,angle):
    pulse_width = interval_mapping(angle,0,180,0.5,2.5)
    duty = int(interval_mapping(pulse_width,0,20,0,65535))
    pin.duty_u16(duty)
while True:
    for angle in range(180):
        servo_write(servo,angle)
        sleep_ms(20)
    for angle in range(180,-1,-1):
        servo_write(servo,angle)
        sleep_ms(20)