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¶

You can install the library in a few different ways.

• Building and installing the library from source code is preferable since it will include all the latest changes.

• Installing the library (via a package manager) from a pre-built package is mostly for cross-compiling purposes, but it can be useful for environments that don’t have all the build-time dependencies (namely CMake).

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

Automatic Installation¶

There is a newer automatic install script that makes use of the CMake approach.

1. Download the install.sh file from https://github.com/nRF24/.github/blob/main/installer/install.sh

   wget https://raw.githubusercontent.com/nRF24/.github/main/installer/install.sh
   

2. Make it executable

   chmod +x install.sh
   

3. Run it and choose your options

   ./install.sh
   

   It will also ask to install a python package named pyRF24. This is not the same as the traditionally provided python wrappers as the pyRF24 package can be used independent of the C++ installed libraries. For more information on this newer python package, please check out the pyRF24 documentation.

4. Try an example from one of the libraries

   cd ~/rf24libs/RF24/examples_linux
   

   Edit the gettingstarted example, to set your pin configuration

   nano gettingstarted.cpp
   

   Build the examples. Remember to set the RF24_DRIVER option according to the one that was selected during the scripted install.

   mkdir build && cd build
   cmake .. -D RF24_DRIVER=SPIDEV
   make
   

   Run the example

   sudo ./gettingstarted
   

Building from source code¶

1. Install prerequisites if there are any (PiGPIO, WiringPi, MRAA, LittleWire libraries, and enable the SPI bus(es) in the OS).

   CMake may need to be installed

   sudo apt-get install cmake
   

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

   Instead of specifying the RF24_DRIVER option in the CLI, it is recommended to use a environment variable named RF24_DRIVER.

export RF24_DRIVER=SPIDEV

These instructions assume you have not set an environment variable.

cmake .. -D RF24_DRIVER=SPIDEV

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

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

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
   

   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
   

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 (via CLI or environment variable) 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).

sudo rm /usr/local/lib/librf24.*
sudo rm /usr/local/lib/librf24-bcm.so
sudo rm -r /usr/local/include/RF24