Python 2.x and 3.x module to use the MCP23017 or MCP23008 GPIO expander chip and the Raspberrypi. This module supports using the interrupt capabilities on the MCP230XX chips

This requires the smbus module for the i2c connection and the RPi.GPIO or compatible module to use the interrupt capabilities.

Included at the end of the module are some example uses of the module

Connection to the MCP230XX from the Pi are as follows

• Pi SCL to MCP SCL
• Pi SDA to MCP SDA
• Pi 3.3V to MCP VDD
• Pi Gnd to MCP Vss
• Pi 3.3V to MCP RESET (Could be tied to a Pi GPIO if you want active control of the RESET)
• Pi 3.3V to MCP A0
• Pi Gnd to MCP A1
• Pi Gnd to MCP A2
• Pi GPIO # to MCP INTA
• Pi GPIO # to MCP INTB

With the above A0-A2 connections the i2c address is 0x21

For the MCP23008 the MCP GPIOA 0-7 are IO 0-7 in this module For the MCP23017 the MCP GPIOA 0-7 are IO 0-7 and the MCP GPIOB 0-7 are IO 8-15 in this module

Current functions include:

• interrupt_options(outputType = 'activehigh', bankControl = 'separate')
• set_register_addressing(regScheme='8bit')
• set_mode(pin, mode, pullUp='disable')
• invert_input(pin, invert = False)
• output(pin, value)
• input(pin)
• add_interrupt(pin, callbackFunctLow='empty', callbackFunctHigh='empty')
• remove_interrupt(pin)
• register_reset()

Example uses

to initialize the chip

MCP = MCP230XX('MCP23017', i2cAddress, '16bit')

to set up an input and output

MCP.set_mode(0, 'output') # set IO 0 to an output MCP.set_mode(1, 'input') # set IO 1 to an input MCP.set_mode(10, 'input', 'enable') # set IO 10 to an input with the pullup enabled

to set an output

MCP.output(0,1) # set IO 0 high MCP.output(0,0) # set IO 0 low

to read an input

MCP.input(1) # reads current value on IO 1, return 0 for low and 1 for high

to set interrupt options

MCP.interrupt_options(outputType = 'activehigh', bankControl = 'separate')

• the interrupt pins can be set as either activehigh, activelow or opendrain
• for the MCP23017 the interrupts for IO 0-7 and IO 8-15 can be trigger INTA and INTB respectively with bankControl = 'seperate' or and an intterupt on any of the IO (0-15) can be sent to both INTA and INTB with bankControl = 'both'

to add and remove an interrupt to an input

MCP.add_interrupt(10, callbackFunctLow=functA, callbackFunctHigh=functB) # add interrupt to IO 10 with call back functions functA and functB

• separate callback functs can be set for when the pin goes high and low, the same function can be used for callbackFunctLow and callbackFunctHigh

On the Raspberry Pi side using the RPi.GPIO module as IO, the following needs to be included in your program IO.add_event_detect(intPin,IO.RISING,callback=MCP.callbackB)

callback = either MCP.callbackA or MCP.callbackB if using the bankControl = 'seperate' or callback = MCP.callbackBoth if using the bankControl = 'both'

MCP.remove_interrupt(10) # remove interrupt from IO 10