Summary

Platform independent driver for the NRF24L01(+) complient with ANSI C99. Tested on the ESP32 using ESP-IDF release/v4.3

Documentation

Driver documentation generated by Doxygen is available here

Documentation health is updated on commit:

Inspiration

To my knowledge, a platform-independent driver for the NRF24L01(+) is not available although there are plenty of samples on Arduino. Based on code provided at https://github.com/elmot/nrf24l01-lib and https://github.com/LonelyWolf/stm32/tree/master/nrf24l01

Install Tools

Install all the vsCode extensions specified in the .vscode/extensions.json file

Install CppCheck

• Windows: Use Chocolatey by running choco install cppcheck

Automated testing

To successfully run the build script the runner needs 'build-essential' installed. Since this dependency cannot be installed from the action due to the lack of root permissions, run following command from SSH: sudo apt-get install build-essential -y

Additionally, the GPIO controller is not available from userspace

Configuring Self-Hosted GitHub Runner

By default on the Raspberry Pi the SPI and GPIO controllers are not available from userspace.

Running as Root

Using LibCap (Not working)

The author of the bcm2835 library recommends using LibCap if the program needs to run without root. See the section called Running as root within the Documentation.

Unfortunately this method will not persist across rebuilds and the project needed to be completely rebuilt on each invokation of the CI pipeline.

By Permissions (Not working)

Granting Permissions for SPI

1. Create a new group for SPI access

   sudo groupadd spi
   

2. Identify the name of the spi controllers

   ls /dev | grep spi
   

3. Transfer ownership of the SPI controllers to the new spi group

   sudo chown :spi /dev/spidev0.0
   sudo chown :spi /dev/spidev0.1
   

4. Add read/write permissions to the SPI controllers

   sudo chmod g+rw /dev/spidev0.0
   sudo chmod g+rw /dev/spidev0.1
   

5. Add the user which owns the github runner process to the spi group

   sudo usermod -aG spi jared
   

Granting Permissions for GPIO

1. Create a new group for GPIO access

   sudo groupadd gpio
   

2. Transfer ownership of the GPIO controller to the new gpio group

   sudo chown :gpio /dev/gpiomem
   

3. Add read/write permissions to the GPIO controller

   sudo chmod g+rw /dev/gpiomem
   

4. Add the user which owns the github runner process to the gpio group

   sudo usermod -aG gpio <username>
   

Persistence

Likely the above changes will not persist a reboot. The solution is to create additional udev rules which will run on boot.

1. Change to the udev rules directory

   cd /etc/udev/rules.d
   

2. Create a new file

   vi local.rules
   

3. Add the rules

   ACTION=="add", KERNEL=="gpio*", MODE="0660", OWNER="root", GROUP="gpio" 
   ACTION=="add", KERNEL=="mem", MODE="0660", OWNER="root", GROUP="gpio" 
   ACTION=="add", KERNEL=="spidev0.0", MODE="0660", OWNER="root", GROUP="spi" 
   ACTION=="add", KERNEL=="spidev0.1", MODE="0660", OWNER="root", GROUP="spi"