MCP23017Control Class

The MCP23017Control class provides an interface for interacting with the MCP23017 I/O expander chip over I²C on Arduino platforms. This class includes methods for initializing the chip, configuring pin modes, and reading/writing digital values to individual pins or entire banks.

Constructor

MCP23017Control(byte address = 0x20)
- address: I²C address of the MCP23017. Default is 0x20.

Methods

begin(bool initWire = true)

Initializes the MCP23017 I/O expander. This method sets up the I²C communication and configures all pins on the MCP23017 as inputs for safety.

initWire: A boolean parameter that determines whether the Wire (I²C) library should be initialized within this method. Defaults to true.
- If true, Wire.begin() will be called to initialize the I²C communication.
- If false, Wire.begin() will not be called, allowing for manual initialization of the I²C bus elsewhere in your code.

pinMode(byte pinNumber, byte mode)

Sets the mode of a specific pin.

pinNumber: Pin number (0-15).
mode: Mode of the pin (INPUT, OUTPUT, INPUT_PULLUP).

digitalWrite(byte pinNumber, byte state)

Writes a digital value (HIGH or LOW) to a specified output pin. If the pin is set as an input, it automatically changes the pin mode to INPUT or INPUT_PULLUP.

pinNumber: Pin number (0-15).
state: State to write (HIGH or LOW).

digitalRead(byte pinNumber)

Reads and returns the state (HIGH or LOW) of a specified input pin.

pinNumber: Pin number (0-15).

setPinHigh(byte outputNumber)

Sets a specified output pin to high.

outputNumber: Pin number (0-15).

setBankMode(byte bank, byte mode)

Sets the mode for all pins in a specified bank (Bank A or Bank B) of the MCP23017.

bank: Bank number (0 for Bank A, 1 for Bank B).
mode: Mode to set for all pins in the specified bank (INPUT, OUTPUT, INPUT_PULLUP).

writeBank(byte bank, byte value)

Writes a byte value to all pins of either Bank A or Bank B.

bank: Bank number (0 for Bank A, 1 for Bank B).
value: Byte value to write to the bank.

readBank(byte bank)

Reads and returns the state of all pins in either Bank A or Bank B.

bank: Bank number (0 for Bank A, 1 for Bank B).

setAllPinsMode(byte mode)

Sets the mode for all pins across both Bank A and Bank B of the MCP23017.

mode: Mode to set for all pins (INPUT, OUTPUT, INPUT_PULLUP).

readAllPins()

Returns the combined state of all 16 pins as a 16-bit value.

writeAllPins(uint16_t value)

Writes a 16-bit value to set the states of all 16 pins.

value: 16-bit value representing the state of each pin.

static uint16_t getBitmask(byte bitPosition)

Returns a 16-bit number with only one bit set, based on the specified position.

bitPosition: Position of the bit to set (0-15).

Usage Examples

Initializing the MCP23017

#include "MCP23017Control.h"

MCP23017Control mcp(0x20); // Replace 0x20 with your MCP23017's I2C address

void setup() {
    mcp.begin(); // Initialize the MCP23017 with default Wire.begin()
    // or
    mcp.begin(false); // Skip Wire.begin() if I²C has been initialized elsewhere
}

Configuring Pin Modes

// Set pin 0 as an output and pin 8 as an input with pull-up
mcp.pinMode(0, OUTPUT);
mcp.pinMode(8, INPUT_PULLUP);

Writing to and Reading from Pins

// Write HIGH to pin 0 (e.g., to turn on an LED)
mcp.digitalWrite(0, HIGH);

// Read the state of pin 8
byte state = mcp.digitalRead(8);
if (state == HIGH) {
    // Pin 8 is HIGH
}

Setting a Specific Pin High

// Set pin 3 to HIGH
mcp.setPinHigh(3);

Configuring a Bank Mode

// Set all pins in Bank A to OUTPUT
mcp.setBankMode(0, OUTPUT);

// Set all pins in Bank B to INPUT_PULLUP
mcp.setBankMode(1, INPUT_PULLUP);

Writing to and Reading from Banks

// Write a byte value to Bank A
mcp.writeBank(0, 0xFF); // Set all pins in Bank A to HIGH

// Read the current state of Bank B
byte bankBState = mcp.readBank(1);

Configuring All Pins Mode

// Set all pins to be inputs with pull-up resistors
mcp.setAllPinsMode(INPUT_PULLUP);

Reading the State of All Pins

uint16_t allAllPins = mcp.readAllPins();

Writing to All Pins

// Set the first 8 pins to HIGH and the rest to LOW
mcp.writeAllPins(0x00FF);

Using the getBitmask Utility

// Get a bitmask with only the 5th bit set
uint16_t bitmask = MCP23017Control::getBitmask(5);

Advanced Usage Example

Toggle All Pins

This example demonstrates toggling all pins on and off in an alternating pattern.

void setup() {
    mcp.begin();
    mcp.setAllPinsMode(OUTPUT); // Set all pins as outputs
}

void loop() {
    mcp.writeAllPins(0xFFFF); // Set all pins HIGH
    delay(500);
    mcp.writeAllPins(0x0000); // Set all pins LOW
    delay(500);
}

Error Handling and Limitations

The MCP23017Control class does not currently provide explicit error handling for I²C communication failures.
Ensure that the I²C address provided to the constructor matches the hardware configuration.
The class is designed for standard Arduino boards and may require modifications for use with other microcontroller platforms.

Versioning and Updates

Current Version: 1.0.0

Changelog

1.0.0

Initial release of MCP23017Control.
Support for basic I/O operations, bank-level control, and pin mode configurations.

Jabur-Consulting/MCP23017Control