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#include <stdio.h>
#include <pigpio.h>
#include <unistd.h>

// Define the GPIO pins for LED and Ultrasonic sensor
#define LED_PIN 2     // GPIO pin for LED
#define TRIG_PIN 23   // GPIO pin for Trig (ultrasonic sensor)
#define ECHO_PIN 24   // GPIO pin for Echo (ultrasonic sensor)

int main() {
    // Initialize the pigpio library
    if (gpioInitialise() < 0) {
        printf("PIGPIO initialization failed\n");
        return 1;
    }

    // LED Control: Turn the LED on and off
    printf("LED Control: Turning LED ON...\n");
    gpioSetMode(LED_PIN, PI_OUTPUT);  // Set LED pin as output
    gpioWrite(LED_PIN, 1);            // Turn LED ON
    getchar();                        // Wait for Enter key to turn LED off
    gpioWrite(LED_PIN, 0);            // Turn LED OFF
    printf("LED Control: LED OFF\n");
    
    // Wait a moment before ultrasonic sensor starts
    usleep(1000000); // Wait for 1 second before starting ultrasonic measurement

    // Ultrasonic Sensor: Measure distance
    printf("Ultrasonic Sensor: Measuring Distance...\n");

    // Set up Trig pin as output and Echo pin as input
    gpioSetMode(TRIG_PIN, PI_OUTPUT);
    gpioSetMode(ECHO_PIN, PI_INPUT);

    // Ensure the Trig pin is low before sending pulse
    gpioWrite(TRIG_PIN, 0);
    usleep(2000);  // Wait for 2 milliseconds to ensure pin is low

    // Send a pulse on the Trig pin to start the measurement
    gpioWrite(TRIG_PIN, 1);  // Set Trig pin high
    usleep(10);               // Wait for 10 microseconds
    gpioWrite(TRIG_PIN, 0);   // Set Trig pin low

    // Measure the time the Echo pin is high
    while (gpioRead(ECHO_PIN) == 0); // Wait for the Echo pin to go high
    int start = gpioTick();          // Record the start time

    while (gpioRead(ECHO_PIN) == 1); // Wait for the Echo pin to go low
    int stop = gpioTick();           // Record the stop time

    // Calculate the duration of the pulse
    double pulseDuration = (stop - start) / 1000000.0; // Convert microseconds to seconds

    // Calculate the distance (speed of sound ~ 343m/s at 20C)
    double distance = pulseDuration * 34300.0 / 2.0; // Divide by 2 because it's the round-trip distance

    // Output the distance measured
    printf("Distance: %.2f cm\n", distance);

    // Clean up and terminate the pigpio library
    gpioTerminate();
    
    return 0;
}