import math 
import time
from machine import Pin, PWM

pwm=PWM(Pin(1))
pwm.freq(50)

trigger_pin = Pin(2, Pin.OUT)
echo_pin = Pin(3, Pin.IN)

def measure_dist():
    trigger_pin.low()
    time.sleep_us(2)
    trigger_pin.high()
    time.sleep_us(10)
    trigger_pin.low()

    while echo_pin.value()==0:
        pulse_start = time.ticks_us()
    while echo_pin.value()==1:
        pulse_end = time.ticks_us()
    
    pulse_duration = pulse_end - pulse_start
    distance_cm = (pulse_duration * 0.0340)/2
    return round(distance_cm)

while True:
    distance = measure_dist()
    print("Distance:", distance, "cm")
    if(distance<=100):
        for position in range(1000, 9000, 50):
            pwm.duty_u16(position)
            time.sleep(0.01)
        print("Gate Opened")
        time.sleep(5)
        for position in range(9000, 1000, -50):
            pwm.duty_u16(position)
            time.sleep(0.01)
        print("Gate closed")
    time.sleep(0.5)