from machine import Pin,PWM
import utime

trigger = Pin(2, Pin.OUT)
echo = Pin(4, Pin.IN)
buzzer_pin = Pin(21, Pin.OUT)

WATER_LEVEL_HIGH = 400
WATER_LEVEL_LOW = 100

def ultra():
    trigger.low()
    utime.sleep_us(2)
    trigger.high()
    utime.sleep_us(5)
    trigger.low()

    while echo.value() == 0:
        signaloff = utime.ticks_us()
    while echo.value() == 1:
        signalon = utime.ticks_us()
    timespeed = signalon-signaloff
    distance = (timespeed*0.0343)/2
    return distance

def activate_buzzer():
    buzzer = PWM(Pin(buzzer_pin))
    buzzer.freq(500)
    buzzer.duty_u16(45618)
    utime.sleep(1)

def deactivate_buzzer():
    buzzer = PWM(Pin(buzzer_pin))
    buzzer.duty_u16(0)

def water_level():
    distance = ultra()
    print("Distance measured is:",distance,"cm")

    if distance < WATER_LEVEL_LOW:
        print("Water level is low")
        activate_buzzer()
    elif distance > WATER_LEVEL_HIGH:
        print("Water level is high")
        activate_buzzer()
    else:
        print("The distance is normal")
        deactivate_buzzer()

while True:
    water_level()
    utime.sleep(1)