from machine import Pin, PWM
from time import sleep
import utime

# Initialize ultrasonic sensor pins
trigger = Pin(28, Pin.OUT)
echo = Pin(27, Pin.IN)

# Initialize buzzer with PWM
buzzer = PWM(Pin(20))

# Function to measure distance using ultrasonic sensor
def measure_distance():
    # Send a 10 microsecond pulse to trigger pin
    trigger.value(1)
    utime.sleep_us(10)
    trigger.value(0)
    
    # Wait for the echo pin to go high
    while echo.value() == 0:
        pulse_start = utime.ticks_us()
    
    # Wait for the echo pin to go low again
    while echo.value() == 1:
        pulse_end = utime.ticks_us()
    
    # Calculate pulse duration
    pulse_duration = utime.ticks_diff(pulse_end, pulse_start)
    
    # Convert pulse duration to distance 
    distance = (pulse_duration * 0.0343) / 2  
    
    return distance

# Function to turn on the buzzer with a specific frequency
def buzzer_on(frequency):
    buzzer.freq(frequency)
    buzzer.duty_u16(32768)  # Set duty cycle to 50%

# Function to turn off the buzzer
def buzzer_off():
    buzzer.duty_u16(0)  # Set duty cycle to 0%

# Main loop
while True:
    # Measure distance
    distance = measure_distance()
    
    # Print distance
    print("Distance:", distance, "cm")
    
    # Check if distance is less than or equal to 20 cm
    if distance <= 20:
        # Activate buzzer
        buzzer_on(1000)  # You can change the frequency as needed
        print("Buzzer ON")
    else:
        # Deactivate buzzer
        buzzer_off()
        print("Buzzer OFF")
    
    # Wait for a short period before taking the next measurement
    sleep(0.1)