Deprecated !

A more complete implementation was introduced in kernel source around June 2017

mcp230xx

Device driver kernel module for mcp23008 & mcp23017 (i²C GPIO expanders)

This is a slight modification of gpio-mcp23s08 linux kernel module. Original source code supports both SPI and I²C but doesn't seem to behave well when both protocols are activated. So I remove all SPI specific code and made an I²C only version.

Module usage

We'll consider the mcp230xx chip is actually well hooked on an I²C bus. This module requires i2c-dev to be loaded.

modprobe i2c-dev

And the module itself.

modprobe gpio-mcp23xx

Register the device.

echo [chip-address] > /sys/bus/i2c/devices/[i2c-bus-number]/new_device

Where chip-address is the address of the chip on the i²c bus. (0x20 if all 3 address pins are shorted to GND) And i2c-bus-number is the i2c bus identifier on your machine.

This should register a new folder in /sys/class/gpio named gpiochipX. Where X is the base gpio address of this chip. In this folder the following files give important information :

• base : gives the starting gpio address
• ngpio : gives the number of gpio pins handled by this device
• label : the chip name (should contain either mcp23008 or mcp23017)

Finally we need to register the gpio device :

  echo [gpio-address] > /sys/class/gpio/epxport

Here gpio-address is base + [0..ngpio] This creates a new folder in /sys/class/gpio named gpio[gpio-address]. Voilà !