This softtware library is designed to interface with the MCP2307 and MCP23S17 chips that are made by Microchip. This library makes use of the interrupt pins on the mcp23x17 chips to allow the developer to write event driven functions.
Copyright (c) 2019 Wade Ryan
On your Raspberry Pi, please use the raspi-config program to enable the I2C interface. Then use the gpio command to make sure your i2c devices can be found. The default address for an MCP23017 chip is 0x20.
$ sudo raspi-config
$ gpio i2cd
This Library is based on WiringPi, so, you'll need make sure you have WiringPi installed before you can succesfully compile this library.
To compile this library, navigate into the src folder and use the make utility to compile and install the library.
$ cd [project folder]
$ cd src
$ make && sudo make install
$ cd ../utility
$ make && sudo make install
Complie your applications using these command line arguments: -lwiringPi -lwiringPiMCP23x17
There is an accopmaning command line utility, which will allow you to view the status of the mcp23017 chip. Before the Utility can be used, the chip must be initialized using the -x option. Once a chip has been initizalzed, there should not be a need to initialize it again, unless you use a different library which may change the settings required for this utility to work.
$ mcp23x17
usage: mcp23017 -i i2c_address
Options:
-a = port-a [pin]
-b = port-b [pin]
-c = configuration
-d = debug
-i = i2c address; default=0x20
-m = mode input/output
-o = read olat
-r = read pin values
-v = verbose
-w = write 0/1
-x = reset device
Note: Using write automatically forces
output mode on the specified pin
Caution: Reading the GPIO pins will
clear the interrupts
$ mcp23x17 -xi 20
$ mcp23x17 -ri 20
+--------------++--------------+
| IIC Address 0x20 |
+--------------++--------------+
| Port-B || Port-A |
+---+------+---++---+------+---+
| n | Mode | V || V | Mode | n |
+---+------+---++---+------+---+
| 0 | OUT | 0 || 1 | OUT | 7 |
| 1 | OUT | 1 || 0 | OUT | 6 |
| 2 | OUT | 0 || 0 | OUT | 5 |
| 3 | OUT | 0 || 0 | OUT | 4 |
| 4 | OUT | 0 || 1 | IN | 3 |
| 5 | IN | 1 || 1 | IN | 2 |
| 6 | IN | 1 || 1 | IN | 1 |
| 7 | IN | 1 || 1 | IN | 0 |
+---+------+---++---+------+---+
The example program "main.cpp" shows how to use the library to both detect events on input pins as well as modify the output on other pins. belown is a sample of the program running while the switches are being tripped on/off.
$ ./example
enable txs0108
initialization complete
init input pins
init led to match switch, value = 0
event pin<a0> value=1
event pin<a0> value=0
event pin<a0> value=1
event pin<a0> value=0
