A comprehensive, professional-grade Arduino library for the MAX7300 I²C GPIO port expander chip manufactured by Analog Devices (formerly Maxim Integrated). This library provides complete access to all features of the MAX7300 with an intuitive, user-friendly API.

• Complete Access to All Functionality:

  • Individual pin configuration (input, output, high-impedance)
  • Individual and batch pin read/write operations
  • Full transition detection support
  • Power management (normal/shutdown modes)

• High Performance:

  • Efficient register caching to minimize I2C traffic
  • Optimized read/write operations

• Developer Friendly:

  • Clear, consistent API
  • Comprehensive error reporting and handling
  • Detailed documentation and examples
  • Input validation to prevent errors

• Configurable:

  • Multiple chip support with different I2C addresses
  • Compatible with all Arduino platforms
  • Support for multiple I2C buses

The MAX7300 is a 28-port I²C-interfaced GPIO expander that allows microcontrollers to control up to 28 additional general-purpose input/output (GPIO) pins through an I²C serial interface. Key features of the MAX7300:

• 28 I/O ports configurable as inputs or outputs
• 2.5V to 5.5V operating voltage range
• 400kHz I²C-compatible interface
• Transition detection capability on pins 4-27
• Low power consumption (<1µA in shutdown mode)
• Configurable I²C address (4 possible addresses)
• Small 24-pin QSOP or 36-pin TQFN packages

1. Open the Arduino IDE
2. Go to Sketch > Include Library > Manage Libraries...
3. Search for "MAX7300"
4. Click "Install"

1. Download the latest release
2. Extract the ZIP file
3. Copy the folder to your Arduino libraries directory
   • Windows: Documents/Arduino/libraries/
   • Mac/Linux: ~/Documents/Arduino/libraries/
4. Restart the Arduino IDE

Connect your MAX7300 to your Arduino or compatible board:

* Make sure to use a voltage compatible with your microcontroller's I/O levels.
† Use the appropriate I2C pins for your Arduino board:

• Arduino Uno/Nano: A4 (SDA), A5 (SCL)
• Arduino Mega: 20 (SDA), 21 (SCL)
• Arduino Leonardo/Micro: 2 (SDA), 3 (SCL)
• Arduino ESP8266/ESP32: Check your board's documentation

#include <Wire.h>
#include <MAX7300.h>

// Create a MAX7300 object with default address (0x40)
MAX7300 gpio;

void setup() {
  Serial.begin(115200);
  
  // Initialize the MAX7300
  if (gpio.begin() != MAX7300_OK) {
    Serial.println("Error: Could not initialize MAX7300");
    while (1);
  }
  
  // Configure pins
  gpio.pinMode(10, MAX7300_PIN_OUTPUT);     // Set pin 10 as output
  gpio.pinMode(11, MAX7300_PIN_INPUT);      // Set pin 11 as input
  
  // Set output pin high
  gpio.digitalWrite(10, HIGH);
}

void loop() {
  // Read input pin
  int value = gpio.digitalRead(11);
  Serial.print("Pin 11 value: ");
  Serial.println(value);
  
  delay(1000);
}

The MAX7300's I²C address is determined by the A0, A1, and A2 pins:

To use a specific address:

// Create MAX7300 with address 0x44 (A2=L, A1=H, A0=L)
MAX7300 gpio(0x44);

Constructor for creating a MAX7300 object.

Parameters:

• addr: I2C address of the device (default: 0x40)
• wire: TwoWire instance for platforms with multiple I2C buses (default: Wire)

Initialize the MAX7300 device.

Parameters:

• resetPins: If true, resets all pins to high-impedance mode (default: true)

Returns:

• MAX7300_OK (0) on success, or a negative error code

Reset the device to default state.

Parameters:

• hardReset: If true, performs a full software reset (default: false)

Returns:

• MAX7300_OK (0) on success, or a negative error code

Set device to normal operation mode.

Returns:

• MAX7300_OK (0) on success, or a negative error code

Set device to shutdown/low-power mode.

Returns:

• MAX7300_OK (0) on success, or a negative error code

Check if the device is in normal operation mode.

Returns:

• true if device is enabled (normal mode), false if disabled (shutdown mode)

Configure a pin's mode (input, output, high-impedance).

Parameters:

• pin: Pin number (0-27)
• mode: Mode (MAX7300_PIN_HIGHZ, MAX7300_PIN_OUTPUT, MAX7300_PIN_INPUT, or MAX7300_PIN_INPUT_PULLUP)

Returns:

• MAX7300_OK (0) on success, or a negative error code

Get the current mode of a pin.

Parameters:

• pin: Pin number (0-27)

Returns:

• Pin mode or negative error code

Configure multiple pins at once with the same mode.

Parameters:

• pinMask: Bit mask of pins to configure (bit 0 = pin 0, etc.)
• mode: Mode to set for all selected pins

Returns:

• MAX7300_OK (0) on success, or a negative error code

Read from a GPIO pin.

Parameters:

• pin: Pin number (0-27)

Returns:

• Pin state (0 or 1) or negative error code

Write to a GPIO pin.

Parameters:

• pin: Pin number (0-27)
• value: Value to write (0 or 1)

Returns:

• MAX7300_OK (0) on success, or a negative error code

Read all pin states and return as a 32-bit value.

Returns:

• 32-bit value where bits 0-27 represent pins 0-27

Write values to multiple pins at once.

Parameters:

• values: 32-bit value where bits 0-27 represent pins 0-27
• mask: 32-bit mask where 1 means update that pin (default: all pins)

Returns:

• MAX7300_OK (0) on success, or a negative error code

Enable transition detection functionality.

Returns:

• MAX7300_OK (0) on success, or a negative error code

Disable transition detection functionality.

Returns:

• MAX7300_OK (0) on success, or a negative error code

Check if transition detection is enabled.

Returns:

• true if enabled, false if disabled

Configure transition detection for a specific pin.

Parameters:

• pin: Pin number (4-27, pins 0-3 don't support transition detection)
• mode: Detection mode (MAX7300_TRANSITION_NONE, MAX7300_TRANSITION_LOW, MAX7300_TRANSITION_HIGH, or MAX7300_TRANSITION_BOTH)

Returns:

• MAX7300_OK (0) on success, or a negative error code

Get the transition detection configuration for a pin.

Parameters:

• pin: Pin number (4-27)

Returns:

• Transition mode or negative error code

Check if a transition has been detected.

Returns:

• true if a transition was detected, false otherwise

Read the transition event register to determine which pins triggered an event.

Returns:

• 32-bit value where bits represent which pins had transitions

Clear transition events.

Returns:

• MAX7300_OK (0) on success, or a negative error code

Direct register access for advanced users.

Parameters:

• reg: Register address

Returns:

• Register value or negative error code

Direct register write for advanced users.

Parameters:

• reg: Register address
• value: Value to write

Returns:

• MAX7300_OK (0) on success, or a negative error code

Get the last error that occurred.

Returns:

• Error code

Set I2C communication timeout.

Parameters:

• timeout: Timeout in milliseconds

Get current I2C timeout setting.

Returns:

• Timeout in milliseconds

#include <Wire.h>
#include <MAX7300.h>

MAX7300 gpio;

void setup() {
  Serial.begin(115200);
  
  if (gpio.begin() != MAX7300_OK) {
    Serial.println("Error: Could not initialize MAX7300");
    while (1);
  }
  
  gpio.pinMode(10, MAX7300_PIN_OUTPUT);  // LED pin
  gpio.pinMode(11, MAX7300_PIN_INPUT);   // Button pin
}

void loop() {
  // Read button state
  int buttonState = gpio.digitalRead(11);
  
  // Control LED based on button state
  gpio.digitalWrite(10, buttonState);
  
  delay(10);  // Short delay for debouncing
}

#include <Wire.h>
#include <MAX7300.h>

MAX7300 gpio;

void setup() {
  Serial.begin(115200);
  
  if (gpio.begin() != MAX7300_OK) {
    Serial.println("Error: Could not initialize MAX7300");
    while (1);
  }
  
  // Configure pins 8-15 as outputs (for LEDs)
  uint32_t ledPins = 0xFF00;  // Pins 8-15
  gpio.setMultiplePinMode(ledPins, MAX7300_PIN_OUTPUT);
  
  // Configure pins 16-23 as inputs (for buttons)
  uint32_t buttonPins = 0xFF0000;  // Pins 16-23
  gpio.setMultiplePinMode(buttonPins, MAX7300_PIN_INPUT);
}

void loop() {
  // Read all buttons at once
  uint32_t buttonStates = gpio.digitalReadAll() & 0xFF0000;
  
  // Light LEDs based on button states (shifted to match LED pins)
  uint32_t ledStates = buttonStates >> 8;
  gpio.digitalWriteAll(ledStates, 0xFF00);
  
  delay(10);
}

#include <Wire.h>
#include <MAX7300.h>

MAX7300 gpio;

void setup() {
  Serial.begin(115200);
  
  if (gpio.begin() != MAX7300_OK) {
    Serial.println("Error: Could not initialize MAX7300");
    while (1);
  }
  
  // Configure pin 5 as input
  gpio.pinMode(5, MAX7300_PIN_INPUT);
  
  // Enable transition detection for pin 5
  gpio.enableTransitionDetection();
  gpio.configureTransitionDetection(5, MAX7300_TRANSITION_BOTH);
  
  Serial.println("Waiting for transitions on pin 5...");
}

void loop() {
  // Check if a transition occurred
  if (gpio.transitionDetected()) {
    // Get which pins had transitions
    uint32_t events = gpio.getTransitionEvents();
    
    if (events & (1UL << 5)) {
      int state = gpio.digitalRead(5);
      Serial.print("Pin 5 changed to: ");
      Serial.println(state);
    }
    
    // Clear the transition flag
    gpio.clearTransitionEvents();
  }
  
  delay(10);
}

#include <Wire.h>
#include <MAX7300.h>

// Create two MAX7300 objects with different addresses
MAX7300 gpio1(0x40);  // A0=0, A1=0, A2=0
MAX7300 gpio2(0x42);  // A0=1, A1=0, A2=0

void setup() {
  Serial.begin(115200);
  
  if (gpio1.begin() != MAX7300_OK) {
    Serial.println("Error: Could not initialize MAX7300 #1");
    while (1);
  }
  
  if (gpio2.begin() != MAX7300_OK) {
    Serial.println("Error: Could not initialize MAX7300 #2");
    while (1);
  }
  
  // Configure pins on first device
  gpio1.pinMode(0, MAX7300_PIN_OUTPUT);
  gpio1.pinMode(1, MAX7300_PIN_OUTPUT);
  
  // Configure pins on second device
  gpio2.pinMode(0, MAX7300_PIN_INPUT);
  gpio2.pinMode(1, MAX7300_PIN_INPUT);
}

void loop() {
  // Read inputs from second device
  int input1 = gpio2.digitalRead(0);
  int input2 = gpio2.digitalRead(1);
  
  // Write values to first device
  gpio1.digitalWrite(0, input1);
  gpio1.digitalWrite(1, input2);
  
  delay(10);
}

For advanced users who need direct access to the MAX7300 registers:

// Read Configuration Register (0x04)
int16_t configReg = gpio.readRegister(0x04);
if (configReg >= 0) {
  Serial.print("Config Register: 0x");
  Serial.println(configReg, HEX);
}

// Write to Configuration Register (0x04)
gpio.writeRegister(0x04, 0x01);  // Normal operation mode

void performOperation() {
  int8_t result = gpio.pinMode(10, MAX7300_PIN_OUTPUT);
  
  if (result != MAX7300_OK) {
    Serial.print("Error occurred: ");
    switch (result) {
      case MAX7300_ERR_COMM_FAIL:
        Serial.println("Communication failure");
        break;
      case MAX7300_ERR_INVALID_PIN:
        Serial.println("Invalid pin number");
        break;
      case MAX7300_ERR_INVALID_MODE:
        Serial.println("Invalid pin mode");
        break;
      default:
        Serial.println("Unknown error");
        break;
    }
  }
}

#include <Wire.h>
#include <MAX7300.h>

TwoWire secondBus = TwoWire(1);  // Create a second I2C instance (for ESP32)
MAX7300 gpio(&secondBus);        // Use the second I2C bus

void setup() {
  Serial.begin(115200);
  
  // Initialize the second I2C bus on custom pins (ESP32 example)
  secondBus.begin(SDA_PIN, SCL_PIN, 400000);
  
  if (gpio.begin() != MAX7300_OK) {
    Serial.println("Error: Could not initialize MAX7300");
    while (1);
  }
  
  // Rest of your setup code
}

This library is licensed under the MIT License. See the LICENSE file for details.

1. No Communication

   • Check wiring and I2C address
   • Verify pull-up resistors on SDA/SCL lines (typically 4.7kΩ)
   • Try a slower I2C speed (lower than 400kHz)

2. Inconsistent Readings

   • Check for proper power supply decoupling capacitors
   • Ensure the I2C bus isn't too long or noisy
   • Verify that all chips share a common ground reference

3. Pin Configuration Issues

   • Remember that pins start in high-impedance mode after power-up
   • Make sure to enable the device with gpio.enable()
   • Pins 0-3 have special functions on some variants of the chip

4. Transition Detection Not Working

   • Only pins 4-27 support transition detection
   • Make sure to enable transition detection with enableTransitionDetection()
   • Clear transition events with clearTransitionEvents()

Contributions to improve the library are welcome. Please follow these steps:

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add some amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

Library developed by danel32 /erbolite@gmail.com/.

• 1.0.0 (2023-04-23): Initial release
  • Complete implementation of all MAX7300 features
  • Extensive documentation and examples
  • Error handling and input validation

If you find this library helpful, please consider starring the repository on GitHub!