This is a small library to interface the popular I²C MCP23017 portexpander with a Raspberry Pi and Python. A threaded approach makes sure, that interrupt capability of the expander works properly.

There are just these three python dependencies:

• python>=3.6
• smbus
• RPi.GPIO

Just install the package with pip or your favorite package manager:
pip install pi-mcp23017

Connect the Port Expander to your Raspberry Pi and find out the address. If you haven't configured the address pins, it should be under 0x20. Also make sure to note the GPIO pin to which the interrupt pin is connected.

Pins are numbered from 0 to 15 and mapped as follows
PORTA: 0 to 7 with PORTA_0 = Pin 0
PORTB: 8 to 15 with PORTB_0 = Pin 8

The library merges the both interrupt pins of the MCP23017 for the sake of simplicity.

For a working example that uses most of the functions, see the example below.
For docs, see the docstrings in mcp23017.py. It is planned to add some kind of proper documentation if needed.

# This example registers one callback that toggles a pin
# on each press

from pi_mcp23017.mcp23017 import MCP23017, Banks, Directions, PullUp
from time import sleep

# example address and pin,
# change to your own data
ADDRESS = 0x20
PIN = 27


# define an interrupt callback
def callback(pin_number):
    print(f"got interrupt on pin {pin_number}!")
    state = port_expander.read_pin(8)
    port_expander.write_pin(8, not state)


# if you have multiple busses choose the right one!
port_expander = MCP23017(ADDRESS, int_pin=PIN, bus=0)

# set PORTA to Input and enable interrupts
port_expander.setup_port(Banks.A, Directions.INPUT, PullUp.ENABLED)
port_expander.attach_interrupt(0, callback)

# set PORTB_0 to Output and set it to LOW
port_expander.setup_pin(8, Directions.OUTPUT, PullUp.DISABLED)
port_expander.write_pin(8, False)

try:
    while True:
        sleep(.1)
except KeyboardInterrupt:
    print("Cleaning up automatically and exiting")

The testsuite is pretty small at the moment