# Project objectives:
# Detect water level using ultrasonic sensor, display results on the console,
# and trigger a buzzer if water level is 10 cm or less.
#
# Hardware connections used:
# Ultrasonic sensor VCC to 5V, GND to GND, Trig to GPIO 16, Echo to GPIO 17
# Buzzer Signal to GPIO 18

from machine import Pin, I2C
from time import sleep, ticks_us

# Ultrasonic sensor setup
trigger = Pin(16, Pin.OUT)
echo = Pin(17, Pin.IN)

# Buzzer setup
buzzer = Pin(18, Pin.OUT)

# function to measure distance using ultrasonic sensor
def get_distance():
    # trigger pulse
    trigger.low()
    sleep(0.02)
    trigger.high()
    sleep(0.00001)  # 10 microseconds pulse
    trigger.low()

    # wait for echo response
    while echo.value() == 0:
        signal_off = ticks_us()
    while echo.value() == 1:
        signal_on = ticks_us()

    # calculate pulse duration and distance
    time_passed = signal_on - signal_off
    distance = (time_passed * 0.0343) / 2  # convert time to distance (cm)
    return distance

# function to control the buzzer
def trigger_buzzer(state):
    buzzer.value(state)  # state is 1 for ON and 0 for OFF

# continuously get sensor readings while the board has power
while True:
    # Measure distance dynamically using the ultrasonic sensor
    distance = get_distance()

    # check if water level is 10 cm or less
    if distance <= 10:
        print(f"Water level: {distance:.1f} cm - ALERT!")
        trigger_buzzer(1)  # turn the buzzer ON
    else:
        print(f"Water level: {distance:.1f} cm")
        trigger_buzzer(0)  # turn the buzzer OFF

    # delay of 1 second between readings
    sleep(1)