Essential CMake Techniques for Effective Embedded Build Systems

The world of embedded systems is a dynamic landscape filled with constant evolution. Over my two decades in this field, I've witnessed significant transformations in how we build and manage our software. With the rise of complex applications, the demand for efficient build systems has never been greater. Enter CMake—a powerful tool that can help streamline your development process and ensure your projects remain maintainable and scalable.

In this blog post, we’ll explore essential CMake techniques to enhance your embedded build systems. Whether you’re setting up a new project or refining an existing one, these tips and tricks will help you leverage CMake to boost productivity and software quality. We’ll also dive into toolchain files—an essential aspect of CMake that can simplify cross-compilation for embedded systems.

And plan now to attend my free Design News CEC course, “Introduction to Build Systems and CMake” from August 26 – 30, 2024.

What is a build system?

At its core, a build system automates the process of converting your source code into executable software. It manages dependencies, compiles your code, links libraries, and produces the final binaries. A well-designed build system is crucial for any embedded project, as it can significantly impact productivity, software quality, and time-to-market.

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A robust build system becomes essential with modern embedded systems increasingly reliance on multiple libraries and dependencies. CMake, an open-source build system generator, excels at managing complex projects and is particularly well-suited for embedded systems development.

Why use CMake for embedded build systems?

CMake offers several advantages that make it a compelling choice for embedded developers:

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Setting up your CMake build system

Let’s explore how to set up a basic CMake build system for an embedded project, focusing on essential components and best practices.

Step 1: Create a CMakeLists.txt file

The heart of any CMake project is the CMakeLists.txt file. This file contains instructions for CMake on how to build your project. Here’s a simple example:

cmake_minimum_required(VERSION 3.10)

# Set project name and version

project(MyEmbeddedProject VERSION 1.0)

# Specify the C++ standard

set(CMAKE_CXX_STANDARD 17)

set(CMAKE_CXX_STANDARD_REQUIRED True)

# Add source files

add_executable(my_executable main.cpp utils.cpp)

In this example, we define the project name, version, and C++ standard. We then specify the source files that should be compiled into the final executable.

Step 2: Organize your project structure

A well-organized project structure enhances maintainability and collaboration. There are as many ways to organize a project as there are developers! However, for a small starter project, the project structure might look something like the following:

MyEmbeddedProject/

├── CMakeLists.txt

├── src/

│   ├── main.cpp

│   └── utils.cpp

├── include/

│   └── utils.h

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└── lib/

    └── external_lib/

        └── CMakeLists.txt

To include headers from the include/ directory, add the following line to your main CMakeLists.txt:

include_directories(include)

Step 3: Adding external libraries

Using third-party libraries can speed up development, but managing dependencies can be challenging. CMake simplifies this process with find_package(). For example, if you’re using the Boost library, you can include it as follows:

find_package(Boost REQUIRED)

if (Boost_FOUND)

    include_directories(${Boost_INCLUDE_DIRS})

    target_link_libraries(my_executable ${Boost_LIBRARIES})

endif()

This snippet checks if Boost is found on your system and links it to your executable.

Introducing toolchain files

When developing embedded applications, you often need to cross-compile your code for different target architectures. For example, you’ll need to cross-compile the code for your target, but you also might need to compile it on a host for unit testing, DevOps, and simulation. Toolchain files in CMake enable you to specify the compiler, linker, and other tools needed for a specific target platform.

What is a toolchain file?

A toolchain file is a CMake script that defines the tools and configurations needed for cross-compilation. It specifies paths to compilers, flags, and the target system. Here’s an example of a simple toolchain file for an ARM Cortex-M microcontroller:

set(CMAKE_SYSTEM_NAME Generic)

set(CMAKE_SYSTEM_PROCESSOR arm)

# Specify the cross compiler

set(CMAKE_C_COMPILER arm-none-eabi-gcc)

set(CMAKE_CXX_COMPILER arm-none-eabi-g++)

set(CMAKE_LINKER arm-none-eabi-ld)

# Specify the path to the toolchain

set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mcpu=cortex-m4 -mthumb")

set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -T linker_script.ld")

To use this toolchain file, invoke CMake with the -DCMAKE_TOOLCHAIN_FILE option:

cmake -DCMAKE_TOOLCHAIN_FILE=path/to/toolchain.cmake ..

Step 4: Building and running your project

With your CMakeLists.txt configured and toolchain file set up, you can now build your project. Follow these steps:

Tips for effective CMake usage

Here are some additional tips to help you make the most of CMake in your embedded projects:

Conclusion

Building effective embedded systems requires a well-designed build system that can handle the complexities of modern software development. CMake offers powerful features that streamline the build process, improve productivity, and ensure software quality. By mastering essential CMake techniques and toolchain files, you can enhance your development workflow and position yourself for success in the embedded systems industry.

If you’re ready to take your embedded build systems to the next level, I invite you to join my free Design News CEC course, “Introduction to Build Systems and CMake” from August 26 – 30, 2024. If you can’t make it live, don’t worry, the recordings will be provided!  

Together, we’ll explore the intricacies of CMake and build systems, empowering you to create optimized, maintainable, and efficient embedded applications. Transform your build process—streamline, modernize, and boost productivity with CMake!