from machine import Pin,PWM
from time import sleep
sg90 = PWM(Pin(12, mode=Pin.OUT))
sg90.freq(50)
# 0.5ms/20ms = 0.025 = 2.5% duty cycle
# 2.4ms/20ms = 0.12 = 12% duty cycle
# 0.025*65535=1638
# 0.12*65535=7864
while True:
  sg90.duty_u16(1638)
  sleep(1)
  sg90.duty_u16(7864)
  sleep(1)