libmcp23016 Documentation

libmcp23016 provides a simple and straightforward API for accessing Microchip MCP23016 I/O expanders from userspace. It relies on the libgpiod and libi2cd libraries to interface with the Linux kernel.

libmcp23016 development is hosted on GitHub. A code coverage report is also available.

Getting Started

libmcp23016's main data structures and functions are documented in the Main API module. Most uses of the API are straightforward: a MCP23016 device handle is first created by calling mcp23016_open(), which is then passed to supporting functions followed by a call to mcp23016_close() to close the handle and free associated memory. As the MCP23016 lacks a hardware reset, it is advised that a software reset be issued by calling mcp23016_reset() after opening the device handle to ensure the device is in a consistent state. Interrupt output is managed separately to support multiple devices. See the Interrupt Output module for more details.

The following example demonstrates getting the port value from a MCP23016 device at position 0 (I2C slave address 0x20):

#include <stdio.h>
#include <stdlib.h>
#include <mcp23016.h>
 
int main(void)
{
    struct mcp23016_device *dev;
    uint16_t port;
 
    /* Open MCP23016 device */
    dev = mcp23016_open("/dev/i2c-1", 0);
    if (dev == NULL) {
        perror(NULL);
        return EXIT_FAILURE;
    }
 
    /* Reset registers to POR defaults */
    if (mcp23016_reset(dev) < 0) {
        perror(NULL);
        mcp23016_close(dev);
        return EXIT_FAILURE;
    }
 
    /* Get the port value */
    if (mcp23016_get_port(dev, &port) < 0) {
        perror(NULL);
        mcp23016_close(dev);
        return EXIT_FAILURE;
    }
 
    printf("port value: %#" PRIx16 "\n", port);
 
    /* Close MCP23016 device handle */
    mcp23016_close(dev);
 
    return EXIT_SUCCESS;
}

Care should be taken if the device handle is shared between threads as libmcp23016 is not inherently thread-safe. Calls using the same handle should be restricted to a single thread or synchronized using a mutual exclusion mechanism.

License

libmcp23016 is distributed under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or any later version. See COPYING for more details.