The AB Electronics UK Knowledge Base provides support solutions, tutorials and troubleshooting guides.
Python Library to use with IO Pi Plus Raspberry Pi development board.
The example python files can be found in /ABElectronics_Python_Libraries/IOPi/demos
Note: Microchip recommends that pin 8 (GPA7) and pin 16 (GPB7) are used as outputs only. This change was made for revision D MCP23017 chips manufactured after June 2020. See the MCP23017 datasheet for more information.
Downloading and Installing the library
Python 3
To install the library you will need the Python3 build and install packages. To install them run the following command.
sudo apt update
sudo apt install python3-build python3-installer git
Download the ABElectronics_Python_Libraries to your Raspberry Pi:
git clone https://github.com/abelectronicsuk/ABElectronics_Python_Libraries.git
To install the python library navigate into the ABElectronics_Python_Libraries folder and run:
python3 -m build
sudo python3 -m installer dist/*.whl
Python 2
If you want to install the library on older versions of Linux using Python 2 you can run the following command.
sudo python setup.py install
If you have PIP installed you can install the library directly from GitHub with the following command replacing python2.7 with the version of Python on your computer:
sudo python2.7 -m pip install git+https://github.com/abelectronicsuk/ABElectronics_Python_Libraries.git
Using classes without installing the library
To use a specific part of our Python library in your project without installing the entire library, you can simply copy the needed class file into your project's directory. For example, to use the IO Pi Plus, copy the IOPi.py file from the IOPi directory to where your project files are located. After doing this, you can use the class in your program by adding an import statement at the beginning of your Python code. This allows you to directly utilize the class's functionality in your project.
from IOPi import IOPi
Required Libraries
The library requires smbus2 or python-smbus to be installed
For Python 2.7:
sudo pip install smbus2
For Python 3:
sudo pip3 install smbus2
Classes:
IOPi(address, initialise, bus)
Parameters:
address: i2c address for the target device. 0x20 to 0x27
initialise (optional): True = direction set as inputs, pull-ups disabled, ports not inverted. False = device state unaltered., defaults to True
bus (optional): I2C bus number (integer). If no value is set the class will try to find the i2c bus automatically using the device name.
Functions:
set_pin_direction(pin, value):
Sets the IO direction for an individual pin
Parameters:
pin: 1 to 16
value: 1 = input, 0 = output
Returns: null
get_pin_direction(pin)
Get the IO direction for an individual pin
Parameters:
pin: pin to read, 1 to 16
Returns: 1 = input, 0 = output
set_port_direction(port, value):
Sets the IO direction for the specified IO port
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16
value: number between 0 and 255 or 0x00 and 0xFF. Each bit in the 8-bit number represents a pin on the port. 1 = input, 0 = output
Returns: null
get_port_direction(port):
Get the direction from an IO port
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16
Returns: number between 0 and 255 (0xFF)
set_bus_direction(value):
Sets the IO direction for all pins on the bus
Parameters:
value: 16-bit number 0 to 65535 (0xFFFF). For each bit 1 = input, 0 = output
Returns: null
get_bus_direction()
Get the direction for an IO bus
Returns: 16-bit number 0 to 65535 (0xFFFF). For each bit 1 = input, 0 = output
set_pin_pullup(pin, value)
Set the internal 100K pull-up resistors for an individual pin
Parameters:
pin: pin to update, 1 to 16 value: 1 = enabled, 0 = disabled
Returns: null
get_pin_pullup(pin)
Get the internal 100K pull-up resistors for an individual pin
Parameters:
pin: pin to read, 1 to 16
Returns: 1 = enabled, 0 = disabled
set_port_pullups(port, value)
Set the internal 100K pull-up resistors for the selected IO port
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16
value: number between 0 and 255 or 0x00 and 0xFF. Each bit in the 8-bit number represents a pin on the port. 1 = Enabled, 0 = Disabled
Returns: null
get_port_pullups(port):
Get the internal pull-up status for the selected IO port
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16
Returns: number between 0 and 255 (0xFF)
set_bus_pullups(value)
Set internal 100K pull-up resistors for an IO bus
Parameters:
value: 16-bit number 0 to 65535 (0xFFFF). For each bit 1 = enabled, 0 = disabled
Returns: null
get_bus_pullups()
Get the internal 100K pull-up resistors for an IO bus
Returns: 16-bit number 0 to 65535 (0xFFFF). For each bit 1 = enabled, 0 = disabled
write_pin(pin, value)
Write to an individual pin 1 - 16
Parameters:
pin: 1 to 16
value: 1 = logic high, 0 = logic low
Returns: null
write_port(port, value)
Write to all pins on the selected port
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16
value: number between 0 and 255 or 0x00 and 0xFF. Each bit in the 8-bit number represents a pin on the port. 1 = logic high, 0 = logic low
Returns: null
write_bus(value)
Write to all pins on the selected bus
Parameters:
value: 16-bit number 0 to 65535 (0xFFFF). For each bit 1 = logic high, 0 = logic low
Returns: null
read_pin(pin)
Read the value of an individual pin 1 - 16
Parameters:
pin: 1 to 16
Returns: 0 = logic low, 1 = logic high
read_port(port)
Read all pins on the selected port
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16
Returns: number between 0 and 255 or 0x00 and 0xFF. Each bit in the 8-bit number represents a pin on the port. 0 = logic low, 1 = logic high
read_bus()
Read all pins on the bus
Returns: 16-bit number 0 to 65535 (0xFFFF) Each bit in the 16-bit number represents a pin on the port. 0 = logic low, 1 = logic high
invert_pin(pin, value)
Invert the polarity of the selected pin
Parameters:
pin: 1 to 16
value: 0 = same logic state of the input pin, 1 = inverted logic state of the input pin
Returns: null
get_pin_polarity(pin)
Get the polarity of the selected pin
Parameters:
pin: pin to read, 1 to 16
Returns: 0 = same logic state of the input pin, 1 = inverted logic state of the input pin
invert_port(port, value)
Invert the polarity of the pins on a selected port
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16
value: number between 0 and 255 or 0x00 and 0xFF. Each bit in the 8-bit number represents a pin on the port. 0 = same logic state of the input pin, 1 = inverted logic state of the input pin
Returns: null
get_port_polarity(port):
Get the polarity for the selected IO port
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16
Returns: number between 0 and 255 (0xFF)
invert_bus(value)
Invert the polarity of the pins on the bus
Parameters:
value: 16-bit number 0 to 65535 (0xFFFF). For each bit 0 = same logic state of the input pin, 1 = inverted logic state of the input pin
Returns: null
get_bus_polarity()
Get the polarity of the pins on the bus
Returns: 16-bit number 0 to 65535 (0xFFFF). For each bit 0 = same logic state of the input pin, 1 = inverted logic state of the input pin
mirror_interrupts(value)
Sets whether the interrupt pins INT A and INT B are independently connected to each port or internally connected
Parameters:
value: 1 = The INT pins are internally connected, 0 = The INT pins are not connected. INT A is associated with PortA and INT B is associated with PortB
Returns: null
set_interrupt_polarity(value)
Sets the polarity of the INT output pins
Parameters:
value: 0 = Active Low, 1 = Active High
Returns: null
get_interrupt_polarity()
Get the polarity of the INT output pins
Returns: 1 = Active-high. 0 = Active-low.
set_interrupt_type(port, value)
Sets the type of interrupt for each pin on the selected port
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16
value: number between 0 and 255 or 0x00 and 0xFF. Each bit in the 8-bit number represents a pin on the port. 1 = interrupt is fired when the pin matches the default value, 0 = the interrupt is fired on state change
Returns: null
get_interrupt_type(port):
Get the type of interrupt for each pin on the selected port
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16
Returns: number between 0 and 255 (0xFF)
For each bit 1 = interrupt is fired when the pin matches the default value, 0 = interrupt fires on state change
set_interrupt_defaults(port, value)
These bits set the compare value for pins configured for interrupt-on-change on the selected port.
If the associated pin level is the opposite from the register bit, an interrupt occurs.
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16, value: compare value between 0 and 255 or 0x00 and 0xFF. Each bit in the 8-bit number represents a pin on the port.
Returns: null
get_interrupt_defaults(port):
Get the interrupt default value for each pin on the selected port
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16
Returns: number between 0 and 255 (0xFF)
set_interrupt_on_pin(pin, value)
Enable interrupts for the selected pin
Parameters:
pin: 1 to 16
value: 0 = interrupt disabled, 1 = interrupt enabled
Returns: null
get_interrupt_on_pin(pin)
Gets whether the interrupt is enabled for the selected pin
Parameters:
pin: pin to read, 1 to 16
Returns: 1 = enabled, 0 = disabled
set_interrupt_on_port(port, value)
Enable interrupts for the pins on the selected port
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16
value: number between 0 and 255 or 0x00 and 0xFF. Each bit in the 8-bit number represents a pin on the port.
Returns: null
get_interrupt_on_port(port):
Gets whether the interrupts are enabled for the selected port
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16
Returns: number between 0 and 255 (0xFF). For each bit 1 = enabled, 0 = disabled
set_interrupt_on_bus(value)
Enable interrupts for the pins on the bus
Parameters:
value: 16-bit number 0 to 65535 (0xFFFF). For each bit 1 = enabled, 0 = disabled
Returns: null
get_interrupt_on_bus()
Gets whether the interrupts are enabled for the bus
Returns: 16-bit number 0 to 65535 (0xFFFF). For each bit 1 = enabled, 0 = disabled
read_interrupt_status(port)
Read the interrupt status for the pins on the selected port
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16
Returns: number between 0 and 255 or 0x00 and 0xFF. Each bit in the 8-bit number represents a pin on the port. 1 = Enabled, 0 = Disabled
read_interrupt_capture(port)
Read the value from the selected port at the time of the last interrupt trigger
Parameters:
port: 0 = pins 1 to 8, 1 = pins 9 to 16
Returns: number between 0 and 255 or 0x00 and 0xFF. Each bit in the 8-bit number represents a pin on the port. 1 = Enabled, 0 = Disabled
reset_interrupts()
Set the interrupts A and B to 0
Parameters: null
Returns: null
Usage
To use the IO Pi library in your code you must first import the library:
from IOPi import IOPi
Next, you must initialise the IO object with the I2C address of the I/O controller chip. The default addresses for the IO Pi are 0x20 and 0x21:
bus1 = IOPI(0x20)
We will read the inputs 1 to 8 from bus 2 so set port 0 as inputs and enable the internal pull-up resistors
bus1.set_port_direction(0, 0xFF)
bus1.set_port_pullups(0, 0xFF)
You can now read pin 1 with:
print('Pin 1: ' + str(bus1.read_pin(1)))
Note: documents in Portable Document Format (PDF) require Adobe Acrobat Reader 5.0 or higher to view, download Adobe Acrobat Reader or other PDF reading software for your computer or mobile device.
