The AB Electronics UK Knowledge Base provides support solutions, tutorials and troubleshooting guides.
Node.js Library to use with IO Pi Raspberry Pi development board.
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.
Install
To download to your Raspberry Pi type in the terminal:
git clone https://github.com/abelectronicsuk/ABElectronics_NodeJS_Libraries.git
The IO Pi library is located in the /lib/iopi/ directory
The example files are located in the /examples/iopi/ directory
The IO Pi library requires the i2c-bus library to run.
Install i2c-bus from npm package repository i2c-bus with
npm install i2c-bus
Classes:
IoPi(address, initialise)
Parameters:
address: (number) i2c address for the target device. 0x20 to 0x27
initialise (optional): (boolean) true = direction set as inputs, pull-ups disabled, ports not inverted. false = device state unaltered. defaults to true
Functions:
setPinDirection(pin, direction):
Sets the IO direction for an individual pin
Parameters:
pin: (number) 1 to 16
direction: (number) 1 = input, 0 = output
Returns: null
getPinDirection(pin)
Get the IO direction for an individual pin
Parameters:
pin: (number) pin to read, 1 to 16
Returns: (number) 1 = input, 0 = output
setPortDirection(port, direction):
Sets the IO direction for the specified IO port
Parameters:
port: (number) 0 = pins 1 to 8, 1 = pins 9 to 16
direction: (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
getPortDirection(port):
Get the direction from an IO port
Parameters:
port: (number) 0 = pins 1 to 8, 1 = pins 9 to 16
Returns: (number) between 0 and 255 (0xFF)
setBusDirection(direction):
Sets the IO direction for all pins on the bus
Parameters:
direction: (number) 16-bit number 0 to 65535 (0xFFFF). For each bit 1 = input, 0 = output
Returns: null
getBusDirection()
Get the direction for an IO bus
Returns: (number) 16-bit number 0 to 65535 (0xFFFF). For each bit 1 = input, 0 = output
setPinPullup(pin, value)
Set the internal 100K pull-up resistors for an individual pin
Parameters:
pin: (number) pin to update, 1 to 16 value: (number) 1 = enabled, 0 = disabled
Returns: null
getPinPullup(pin)
Get the internal 100K pull-up resistors for an individual pin
Parameters:
pin: (number) pin to read, 1 to 16
Returns: (number) 1 = enabled, 0 = disabled
setPortPullups(port, value)
Set the internal 100K pull-up resistors for the selected IO port
Parameters:
port: (number) 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
getPortPullups(port):
Get the internal pull-up status for the selected IO port
Parameters:
port: (number) 0 = pins 1 to 8, 1 = pins 9 to 16
Returns: (number) between 0 and 255 (0xFF)
setBusPullups(value)
Set internal 100K pull-up resistors for an IO bus
Parameters:
value: (number) 16-bit number 0 to 65535 (0xFFFF). For each bit 1 = enabled, 0 = disabled
Returns: null
getBusPullups()
Get the internal 100K pull-up resistors for an IO bus
Returns: (number) 16-bit number 0 to 65535 (0xFFFF). For each bit 1 = enabled, 0 = disabled
writePin(pin, value)
Write to an individual pin 1 - 16
Parameters:
pin: (number) 1 to 16
value: (number) 1 = logic high, 0 = logic low
Returns: null
writePort(port, value)
Write to all pins on the selected port
Parameters:
port: (number) 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
writeBus(value)
Write to all pins on the selected bus
Parameters:
value: (number) 16-bit number 0 to 65535 (0xFFFF). For each bit 1 = logic high, 0 = logic low
Returns: null
readPin(pin)
Read the value of an individual pin 1 - 16
Parameters:
pin: (number) 1 to 16
Returns: (uint8_t) 0 = logic low, 1 = logic high
readPort(port)
Read all pins on the selected port
Parameters:
port: (number) 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
readBus()
Read all pins on the bus
Returns: (number) 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
invertPin(pin, polarity)
Invert the polarity of the selected pin
Parameters:
pin: (number) 1 to 16
polarity: (number) 0 = same logic state of the input pin, 1 = inverted logic state of the input pin
Returns: null
getPinPolarity(pin)
Get the polarity of the selected pin
Parameters:
pin: (number) pin to read, 1 to 16
Returns: (number) 0 = same logic state of the input pin, 1 = inverted logic state of the input pin
invertPort(port, polarity)
Invert the polarity of the pins on a selected port
Parameters:
port: (number) 0 = pins 1 to 8, 1 = pins 9 to 16
polarity: (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
getPortPolarity(port):
Get the polarity for the selected IO port
Parameters:
port: (number) 0 = pins 1 to 8, 1 = pins 9 to 16
Returns: (number) between 0 and 255 (0xFF)
invertBus(polarity)
Invert the polarity of the pins on the bus
Parameters:
polarity: (number) 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
getBusPolarity()
Get the polarity of the pins on the bus
Returns: (number) 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
mirrorInterrupts(value)
Sets whether the interrupt pins INT A and INT B are independently connected to each port or internally connected
Parameters:
value: (number) 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
setInterruptPolarity(value)
Sets the polarity of the INT output pins
Parameters:
value: (number) 0 = Active Low, 1 = Active High
Returns: null
getInterruptPolarity()
Get the polarity of the INT output pins
Returns: (number) 1 = Active-high. 0 = Active-low.
setInterruptType(port, value)
Sets the type of interrupt for each pin on the selected port
Parameters:
port: (number) 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
getInterruptType(port):
Get the type of interrupt for each pin on the selected port
Parameters:
port: (number) 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
setInterruptDefaults(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 of the register bit, an interrupt occurs.
Parameters:
port: (number) 0 = pins 1 to 8, 1 = pins 9 to 16
value: (number) 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
getInterruptDefaults(port):
Get the interrupt default value for each pin on the selected port
Parameters:
port: (number) 0 = pins 1 to 8, 1 = pins 9 to 16
Returns: (number) number between 0 and 255 (0xFF)
setInterruptOnPin(pin, value)
Enable interrupts for the selected pin
Parameters:
pin: (number) 1 to 16
value: (number) 0 = interrupt disabled, 1 = interrupt enabled
Returns: null
getInterruptOnPin(pin)
Gets whether the interrupt is enabled for the selected pin
Parameters:
pin: (number) pin to read, 1 to 16
Returns: (number) 1 = enabled, 0 = disabled
setInterruptOnPort(port, value)
Enable interrupts for the pins on the selected port
Parameters:
port: (number) 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
getInterruptOnPort(port):
Gets whether the interrupts are enabled for the selected port
Parameters:
port: (number) 0 = pins 1 to 8, 1 = pins 9 to 16
Returns: (number) between 0 and 255 (0xFF). For each bit 1 = enabled, 0 = disabled
setInterruptOnBus(value)
Enable interrupts for the pins on the bus
Parameters:
value: (number) 16-bit number 0 to 65535 (0xFFFF). For each bit 1 = enabled, 0 = disabled
Returns: null
getInterruptOnBus()
Gets whether the interrupts are enabled for the bus
Returns: (number) 16-bit number 0 to 65535 (0xFFFF). For each bit 1 = enabled, 0 = disabled
readInterruptStatus(port)
Read the interrupt status for the pins on the selected port
Parameters:
port: (number) 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
readInterruptCapture(port)
Read the value from the selected port at the time of the last interrupt trigger
Parameters:
port: (number) 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
resetInterrupts()
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:
var iopi = require('../../lib/iopi/iopi');
Next, you must initialise the IO object
var bus1 = new IoPi(0x20);
We will read the inputs 1 to 8 from bus 1 so set port 0 as inputs and enable the internal pull-up resistors
bus1.setPortDirection(0, 0xFF);
bus1.setPortPullups(0, 0xFF);
You can now read pin 1 with:
console.log('Pin 1: %d', bus1.readPin(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.
