[arduino code examples for AIO Hybrid]-01 Turn ON/OFF relay

Code:
/*

 * PCF8574 Relay Control Example

 * 

 * Controls 5 relays connected to PCF8574 via I2C bus.

 * 

 * Made By KinCony

 * https://www.kincony.com

 */



#include <Arduino.h>

#include <Wire.h>

#include "PCF8574.h"



// I2C pin definitions

#define I2C_SDA 8

#define I2C_SCL 18



// Create PCF8574 object with I2C address 0x26

PCF8574 pcf8574(0x26);



void setup() {

  Serial.begin(115200);

  delay(500);



  // Initialize I2C with specified SDA and SCL pins

  Wire.begin(I2C_SDA, I2C_SCL);



  // Set PCF8574 P3~P7 as OUTPUT (Relays)

  pcf8574.pinMode(P3, OUTPUT);

  pcf8574.pinMode(P4, OUTPUT);

  pcf8574.pinMode(P5, OUTPUT);

  pcf8574.pinMode(P6, OUTPUT);

  pcf8574.pinMode(P7, OUTPUT);



  Serial.print("Init pcf8574...");

  if (pcf8574.begin()) {

    Serial.println("OK");

  } else {

    Serial.println("KO");

    while (1); // Stop if initialization fails

  }



  // Turn OFF all relays at startup

  for (int pin = P3; pin <= P7; pin++) {

    pcf8574.digitalWrite(pin, LOW);

  }

}



void loop() {

  // Turn ON all relays one by one

  for (int pin = P3; pin <= P7; pin++) {

    pcf8574.digitalWrite(pin, HIGH);

    delay(500);

  }



  delay(1000); // Keep all relays ON for a while



  // Turn OFF all relays

  for (int pin = P3; pin <= P7; pin++) {

    pcf8574.digitalWrite(pin, LOW);

  }



  delay(1000); // Keep all relays OFF for a while

}