Universal GPIO Access

The library libgpiod provides universal access to GPIOs of any device running Linux. It detects available GPIO, can read and write data to them, and wait for events to be triggered. With this, you can write ow code to talk UART to any connected device.

To install it, run the following commands:

apt-get install autoconf autoconf-archive libtool libkmod-dev pkg-config
git clone https://github.com/brgl/libgpiod.git

cd libgpiod
./autogen.sh --enable-tools=yes --prefix=/usr/local/bin
make
sudo make install

If compilation and installation is successful, in the subfolder ./tools you will find binaries like gpiodetect and gpioinfo that you can use to explore the GPIOs. See the following examples.

$> ./tools/gpiodetect
gpiochip0 [pinctrl-bcm2711] (58 lines)
gpiochip1 [raspberrypi-exp-gpio] (8 lines)

./tools/gpioinfo
gpiochip0 - 58 lines:
 line   0:     "ID_SDA"       unused   input  active-high
 line   1:     "ID_SCL"       unused   input  active-high
 line   2:       "SDA1"       unused   input  active-high
 line   3:       "SCL1"       unused   input  active-high
 line   4:  "GPIO_GCLK"       unused   input  active-high
 line   5:      "GPIO5"       unused   input  active-high
...

If you want to work with the library, read this article for a detailed introduction.

Conclusion

For working with I2C, SPI and UART on the Raspberry Pi, not only Python, but C++ libraries can be used as well. Specifically, you need to activate the I2C and SPI functions via raspi-config, which infernally loads the appropriate Kernel modules. Then you choose a client library and other necessary C++ headers. Working with the libraries follows the same principles: Determine the connected device file, configure a connection object, open the device file, then read from/write to it. Finally, the handy library libgpiod can help you to access all GPIO pins directly, which can be helpful for debugging.