[arduino code examples for F24]-12 How to control one relay

Code:
/*

 * Made by KinCony IoT: https://www.kincony.com

 *

 * This program controls a 24-channel relay board via two PCF8575 I/O expanders.

 * It toggles relay 24 every 2 seconds and prints its status via the serial port.

 * 

 * Pin Definitions:

 * - SDA: GPIO 8

 * - SCL: GPIO 18

 * 

 * Relay 24 is controlled through the first PCF8575 (I2C_ADDRESS_R1).

 */



#include <Wire.h>        // Include the Wire library for I2C communication

#include <PCF8575.h>     // Include the PCF8575 library to control the I/O expander



#define SDA 8            // Define the SDA pin

#define SCL 18           // Define the SCL pin

#define TOGGLE_DELAY 2000  // Define the toggle delay time (2 seconds)



// Set I2C addresses of the PCF8575 modules

#define I2C_ADDRESS_R1 0x25 // I2C address of the first PCF8575 module (for relays 9-24)

#define I2C_ADDRESS_R2 0x26 // I2C address of the second PCF8575 module (for relays 1-8)



PCF8575 pcf8575_R1(I2C_ADDRESS_R1); // Create a PCF8575 object for the first module (for relays 9-24)

PCF8575 pcf8575_R2(I2C_ADDRESS_R2); // Create a PCF8575 object for the second module (for relays 1-8)



bool relay24State = HIGH; // Initialize relay 24 state to OFF (assuming HIGH is OFF)



void setup() {

  // Initialize I2C communication

  Wire.begin(SDA, SCL); // SDA on GPIO 8, SCL on GPIO 18 (according to your board's configuration)

  

  // Initialize serial communication for debugging

  Serial.begin(115200);

  Serial.println("PCF8575 Relay 24 Toggle Program: Starting...");



  // Initialize the PCF8575 modules

  pcf8575_R1.begin();

  pcf8575_R2.begin();



  // Ensure that all relays are turned off initially (set all pins HIGH)

  for (int i = 0; i < 16; i++) {

    pcf8575_R1.write(i, HIGH); // Set relays 9-24 to OFF (assuming HIGH means OFF for relays)

    pcf8575_R2.write(i, HIGH); // Set relays 1-8 to OFF (assuming HIGH means OFF for relays)

  }

}



void loop() {

  // Toggle relay 24 state (relay 24 corresponds to pin 15 on pcf8575_R1)

  relay24State = !relay24State; // Toggle the state

  pcf8575_R1.write(15, relay24State); // Write the new state to relay 24



  // Print the current state of relay 24 to the serial port

  if (relay24State == LOW) {

    Serial.println("Relay 24 is ON");

  } else {

    Serial.println("Relay 24 is OFF");

  }



  // Wait for 2 seconds before toggling again

  delay(TOGGLE_DELAY);

}