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