Optimized high speed nRF24L01+ driver class documentation  1.4.2
TMRh20 2020 - Optimized fork of the nRF24L01+ driver
Using CMake

A more modern approach instead of using hand-crafted Makefiles & configure scripts to build & install software. Please note that these instructions are not needed if you have already installed the library using these older instructions

Installing the library

Using a package manager

The RF24 library now (as of v1.4.1) has pre-built packages (_.deb_ or _.rpm_ files) that can be installed on a Raspberry Pi. These packages can be found on the library's GitHub release page

Warning
If you have previously installed the library from source code, then you will need to uninstall it manually to avoid runtime conflicts.
sudo rm /usr/local/lib/librf24.*
sudo rm /usr/local/lib/librf24-bcm.so
sudo rm -r /usr/local/include/RF24

The librf24-bcm.so file may not exist if you used CMake to install the library.

  1. Download the appropriate package for your machine

    Go to the library's GitHub release page, and look for the latest release's assets.

    For all Raspberry Pi variants using the Raspberry Pi OS (aka Raspbian), you need the file marked for armhf architecture.

    For Raspberry Pi variants using a 64-bit OS (like Ubuntu), you need the file marked for arm64 architecture.

    Notice that the filenames will include the name of the utility driver that the package was built with. This does not mean that the LittleWire, MRAA, or wiringPi libraries are included in the package (you will still need to install those yourself beforehand).

  2. Install the downloaded pkg

    If you downloaded the file directly from your target machine using the desktop environment, then you only need to double-click the package (deb or rpm) file, and the OS should do the rest.

    If you downloaded the file remotely and want to copy it over ssh, then use the scp command in a terminal.

    scp pkg_filename.deb pi@host_name:~/Downloads
    Note
    You do not need to do this from within an ssh session. Also, you can use the target machine's IP address instead of its host name.

    The scp command will ask you for a password belonging to the user's name on the remote machine (we used pi in the above example).

    Now you can open up a ssh session and install the copied package from the terminal.

    ssh pi@host_name
    cd Downloads
    dpkg -i pkg_filename.deb

Building from source code

  1. Install prerequisites if there are any (wiringPi, MRAA, LittleWire libraries, setup SPI device etc)

    CMake may need to be installed

    sudo apt-get install cmake
    Note
    See the MRAA documentation for more information on installing MRAA
  2. Make a directory to contain the RF24 library and possibly other RF24* libraries and enter it
    mkdir ~/rf24libs
    cd ~/rf24libs
  3. Clone the RF24 repo and navigate to it
    git clone https://github.com/nRF24/RF24.git RF24
    cd RF24
  4. Create a build directory inside the RF24 directory and navigate to it.
    mkdir build
    cd build
  5. Configure build environment

    Note
    When using these instructions to install RF24Mesh, RF24Network, or RF24Gateway, the following RF24_DRIVER option is not needed (it is only for the RF24 library).
    cmake .. -D RF24_DRIVER=SPIDEV

    Instead of using SPIDEV driver (recommended), you can also specify the RPi, wiringPi, MRAA, or LittleWire as alternative drivers.

    If the RF24_DRIVER option is not specified, then it will be automatically configured based on the detected CPU or installed libraries (defaults to SPIDEV when auto-detection fails).

  6. Build and install the library
    make
    sudo make install
  7. Build the examples

    Navigate to the examples_linux directory

    cd ../examples_linux

    Make sure the pins used in the examples match the pins you used to connect the radio module

    nano gettingstarted.cpp

    and edit the pin numbers as directed in the linux/RPi general documation. Create a build directory in the examples_linux directory and navigate to it.

    mkdir build
    cd build

    Now you are ready to build the examples.

    cmake ..
    make

    If using the MRAA or wiringPi drivers, then you may need to specify the RF24_DRIVER option again.

    cmake .. -D RF24_DRIVER=wiringPi
    make
  8. Run an example file
    sudo ./gettingstarted

Cross-compiling the library

The RF24 library comes with some pre-made toolchain files (located in the RF24/cmake/toolchains directory) to use in CMake. To use these toolchain files, additional command line options are needed when configuring CMake to build the library (step 5 in the above instructions to build from source).

cmake .. -D CMAKE_TOOLCHAIN_FILE=cmake/toolchains/armhf.cmake
make

If you plan on using the cross-compiled library with your personal cross-compiled project, then it is advised to specify the path that your project will look in when linking to the RF24 library:

cmake .. -D CMAKE_INSTALL_PREFIX=/usr/arm-linux-gnueabihf -D CMAKE_TOOLCHAIN_FILE=cmake/toolchains/armhf.cmake
make
sudo make install

Remember to also specify the RF24_DRIVER option if not using the auto-configuration feature (see step 5 in the above instructions to build from source).

Installing the library remotely

To install remotely, you can create an installable package file using CMake's built-in program called CPack.

cmake .. -D CMAKE_TOOLCHAIN_FILE=cmake/toolchains/armhf.cmake
make
cpack

This will create a deb file and a rpm file in a new sub-directory called "pkgs" within the build directory. You can use either of these packages to install the library to your target machine (see the above instructions about using a package manager).