# I2C Expander rev_01

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    - Project: # I2C Expander
    - Source Code NOT compiled for: ESP8266 NodeMCU V1.0
    - Source Code created on: 2026-02-05 14:51:45

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/****** SYSTEM REQUIREMENTS *****/
/****** SYSTEM REQUIREMENT 1 *****/
    /* add i2c gpio expander PCF8574 */
/****** END SYSTEM REQUIREMENTS *****/


// Create PCF8574 instance with default I2C address 0x20
// Address range: 0x20 to 0x27 depending on A0, A1, A2 pins
PCF8574 expander;

/****** FUNCTION PROTOTYPES *****/
void setup(void);
void loop(void);

void setup(void)
{
    // Initialize Serial communication
    Serial.begin(115200);
    delay(100);

    Serial.println("\n\nPCF8574 I2C GPIO Expander Initialization...");

    // Initialize PCF8574 with I2C address 0x20
    // Using default ESP8266 pins: SDA=4 (D2), SCL=5 (D1)
    if (expander.begin()) {
        Serial.println("PCF8574 initialized successfully!");
        Serial.print("I2C Address: 0x");
        Serial.println(0x20, HEX);

        // Initialize all pins to HIGH (default state)
        expander.writePort(0xFF);
        Serial.println("All pins set to HIGH");
    } else {
        Serial.println("Failed to initialize PCF8574!");
        Serial.println("Please check I2C connections and address configuration");
    }

    delay(500);
}


void loop(void)
{
    // Check if PCF8574 is still connected
    if (expander.isConnected()) {
        // Example: Set pins individually
        // Set pin 0 to HIGH
        expander.setPin(0);
        delay(500);

        // Set pin 1 to HIGH
        expander.setPin(1);
        delay(500);

        // Clear pin 0 to LOW
        expander.clearPin(0);
        delay(500);

        // Clear pin 1 to LOW
        expander.clearPin(1);
        delay(500);

        // Toggle pin 2 multiple times
        expander.togglePin(2);
        delay(250);
        expander.togglePin(2);
        delay(250);

        // Read entire port state
        uint8_t portState = expander.readPort();
        Serial.print("Port state: 0x");
        Serial.println(portState, HEX);

        // Read individual pin states
        for (int i = 0; i < 8; i++) {
            Serial.print("Pin ");
            Serial.print(i);
            Serial.print(": ");
            Serial.println(expander.getPinState(i) ? "HIGH" : "LOW");
        }

        Serial.println("---");
        delay(2000);
    } else {
        Serial.println("PCF8574 device not connected!");
        delay(2000);
    }
}

/* END CODE */