import machine, time
from machine import Pin, PWM
servo=PWM(Pin(14, Pin.OUT))
servo.freq(50)
led=Pin(26, Pin.OUT)
class HCSR04:
  # echo_timeout_us is based in chip range limit (400cm)
  def __init__(self, trigger_pin, echo_pin, echo_timeout_us=500*2*30):
    self.echo_timeout_us = echo_timeout_us
    # Init trigger pin (out)
    self.trigger = Pin(trigger_pin, mode=Pin.OUT, pull=None)
    self.trigger.value(0)
    # Init echo pin (in)
    self.echo = Pin(echo_pin, mode=Pin.IN, pull=None)
  def _send_pulse_and_wait(self):
    self.trigger.value(0) # Stabilize the sensor
    time.sleep_us(5)
    self.trigger.value(1)
    # Send a 10us pulse.
    time.sleep_us(10)
    self.trigger.value(0)
    try:
      pulse_time = machine.time_pulse_us(self.echo, 1, self.echo_timeout_us)
      return pulse_time
    except OSError as ex:
      if ex.args[0] == 110: # 110 = ETIMEDOUT
        raise OSError('Out of range')
      raise ex
  def distance_cm(self):
    pulse_time = self._send_pulse_and_wait()
    cms = (pulse_time / 2) / 29.1
    return cms
hcsr=HCSR04(trigger_pin=18 , echo_pin=19 , echo_timeout_us=500*2*30)
while True:
  d=hcsr.distance_cm()
  print(d)
  if d<300 :
    led.value(1)
    servo.duty(100)
    time.sleep(1)
  else:
    servo.duty(75)
    led.value(0)
    time.sleep(1)