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Minimal example

CMakeLists.txt:

# Can be setted in cli
set(CMAKE_TOOLCHAIN_FILE ${CMAKE_CURRENT_SOURCE_DIR}/../../nrf52.cmake)

cmake_minimum_required(VERSION 3.8)

project(example C ASM)

add_executable(example main.c)
set_target_properties(example PROPERTIES NRF52_CHIP NRF52832)
nrf52_target(example)

main.c:

int main()
{
    for(;;);
    return 0;
}

configure:

$ cmake ./
-- No TOOLCHAIN_PATH specified, using default: /usr
-- No TOOLCHAIN_TRIPLET specified, using default: arm-none-eabi
-- No NRF5_SDK_PATH specified, using default: /opt/nRF5_SDK
-- The C compiler identification is GNU 9.2.0
-- The ASM compiler identification is GNU
-- Found assembler: /bin/arm-none-eabi-gcc
-- Check for working C compiler: /bin/arm-none-eabi-gcc
-- Check for working C compiler: /bin/arm-none-eabi-gcc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to:

build:

$ cmake --build ./
Scanning dependencies of target example
[ 25%] Building C object CMakeFiles/example.dir/main.c.obj
[ 50%] Building ASM object CMakeFiles/example.dir/opt/nRF5_SDK/modules/nrfx/mdk/gcc_startup_nrf52.S.obj
[ 75%] Building C object CMakeFiles/example.dir/opt/nRF5_SDK/modules/nrfx/mdk/system_nrf52.c.obj
[100%] Linking C executable example
[100%] Built target example

nrf52-cmake features reference

The main piece of nrf52-cmake is toolchain file nrf52.cmake. It setups cross-compiling enviroment and defines some useful functions. This file should be passed to cmake using CMAKE_TOOLCHAIN_FILE variable, either using command line or in CMakeLists.txt. This toolchain file uses following variables:

  • TOOLCHAIN_PATH (default: /usr) - path to ARM GCC toolchain, compiler should be located in ${TOOLCHAIN_PATH}/bin

  • TOOLCHAIN_TRIPLET (default: arm-none-eabi) - compiler target triplet, cmake will search for ${TOOLCHAIN_TRIPLET}-gcc executable

  • NRF5_SDK_PATH (default: /opt/nRF5_SDK) - optional path to NRF5 SDK. Required if you're going to use startup code and linker script from SDK (most common scenario)

Target properties

Besides toolchain setup nrf52-cmake defines some useful functions, which works on cmake targets and target properties. Some properties can (or should) be setted on target to use nrf52-cmake functions:

  • NRF52_CHIP - mandatory property to specify NRF52 device. Can be either NRF52xxx or NRF52xxx-xxxx form. Currently only NRF52840, NRF52832, NRF52811, NRF52810 are supported.

  • NRF52_NO_SDK - optional tells nrf52-cmake not to use any source code from NRF5 SDK. You'll have to provide all startup sources by yourself.

  • NRF52_NO_LINKER_SCRIPT - optional tells nrf52-cmake not to use common autogenerated linker script.

Functions

nrf52-cmake adds following useful functions:

  • nrf52_get_chip(<target> <chip> <variant>) - parses NRF52_CHIP property on <target> and outputs some useful information:

    • <chip> - specific chip code (840, 832, etc.)
    • <variant> - chip variant (AA, AB, etc), default will be AA.

  • nrf52_add_sdk_startup(<target>) - search and adds startup sources to target from nRF5 SDK.

  • nrf52_linker_sizes_from_device(<chip> <variant> <ram_size> <flash_size>) - get flash and ram size from chip name and variant.

  • nrf52_linker_generate_script(<target> <script> [RAM_SIZE <size>] [FLASH_SIZE <size>] [RAM_START <addr>] [FLASH_START <addr>]) - generate linker script.

  • nrf52_add_linker_script(<target> <script>) - add (custom) linker script file to target.

  • nrf52_generate_linker_script(<target>) - generate (using nrf52_linker_sizes_from_device and nrf52_linker_generate_script) and add linker script for target.

  • nrf52_configure_compiler(<target>) - configure all compiler options

  • nrf52_target(<target>) - process target and and make everything listed above.

SoftDevice

nrf52-cmake provides support for SoftDevice firmware. Minimal example can be found here

SoftDevice support implemented as cmake package, so you'll need to use find_package first:

find_package(SoftDevice COMPONENTS <variant> REQUIRED)

where <variant> - SoftDevice variant(s) (S112, S132, S140, etc.) Package will add following IMPORTED targets, that can be linked using target_link_libraries:

  • SoftDevice::<variant> - header only library that adds include directories and compiler definitions

  • SoftDevice::<variant>Firmware - library that will link SoftDevice firmware (extracted from .hex file) into final executable. Link those if you want complete image with SoftDevice included.

SoftDevice package also defines some functions:

  • softdevice_generate_linker_script(<target> SOFTDEVICE <variant> RAM <size>) - generates correct linker script for using with SoftDevice. RAM argument specifies amount of RAM that will be used by SoftDevice firmware.

  • softdevice_add_flash_target(<target> SOFTDEVICE <variant> [ADAPTER <adapter>]) - add custom target <target> that will flash SoftDevice firmware to device using openocd and <adapter> hardware adapter (jlink by default). SoftDevice variant (S140, S132, S332, etc) should be specified by SOFTDEVICE parameter.

ChibiOS

nrf52-cmake provides support for ChibiOS RTOS building. Example located here

You'll need both ChibiOS (version 19.1.x) and ChibiOS-Contrib to run ChibiOS on NRF52 platform. Only NRF52832 is currently supported by ChibiOS.

ChibiOS support implemented as cmake package:

find_package(ChibiOS COMPONENTS Core HAL NRF5 REQUIRED)

To use this package you'll need to specify ChibiOS location:

$ cmake -DChibiOS_ROOT=<path> -DChibiOS_Contrib_ROOT=<path> ../

Package will add many IMPORTED libraries with ChibiOS modules' source code:

  • ChibiOS::RT and ChibiOS::NIL - kernel core (NIL or RT)

  • ChibiOS::HAL - ChibiOS HAL

  • ChibiOS::NRF52832 - kernel support for NRF52832

  • ChibiOS::HAL::NRF52832 - HAL support for NRF52832

  • ChibiOS::HAL::* and ChibiOS::HAL::NRF52832::* - HAL drivers (e.g. ChibiOS::HAL::I2C and ChibiOS::HAL::NRF52832::I2C - support for I2C driver)

To help with HAL modules there is function nrf52_linker_generate_script(<target> PLATFORM NRF52832 CONFIG <path to halconf.h>) which links <target> with HAL drivers listed in halconf.h

Currently, nrf52-cmake does not generates linker script for ChibiOS, you'll need to provide own (see examples/chibios).

Also, there is function ChibiOS_set_stack_sizes(<target> [DEFAULT] [MAIN <size> PROCESS <size>]) which sets stack sizes for ChibiOS linker script. Calling ChibiOS_set_stack_sizes is mandatory for now.