modm

Features

• Object-oriented C++23 API designed for high performance and low memory overhead.

• Modular HAL generation using the lbuild data-driven code generator for over 3,800 microcontrollers.

• Support for multiple vendors including STMicroelectronics (STM32), Microchip (SAM, AVR), and Raspberry Pi (RP2040).

• Build system agnostic design supporting CMake, SCons, and Makefiles.

• Zero-allocation HAL implementation to minimize RAM consumption in deeply embedded systems.

• Cross-platform peripheral interfaces for GPIO, ADC, DAC, UART, I2C, SPI, CAN, and Ethernet.

• Integrated cooperative, stackful fibers and a lightweight task scheduler.

• Target-independent drivers for a wide range of external I2C and SPI sensors and devices.

• Debug and logging system providing IOStream and printf-compatible interfaces.

• Functional partial libstdc++ implementation specifically optimized for AVR architectures.

• Integration with FreeRTOS and FreeRTOS+TCP for real-time multitasking and networking.

• Native support for TinyUSB stack for both host and device roles.

• Support for FatFS to enable FAT/exFAT filesystem operations on block devices.

• Integration with LVGL for building embedded graphical user interfaces.

• Support for Nanopb to handle Protocol Buffers in memory-constrained environments.

• Built-in lightweight unit testing system suitable for execution on 8-bit AVRs.

• Crash reporting via CrashCatcher for debugging HardFaults on ARM Cortex-M.

• Support for Segger Real-Time Transport (RTT) for high-speed logging.

Architecture

modm follows a modular, data-driven architectural pattern centered around the lbuild code generator. Unlike traditional static libraries, modm generates a custom library instance tailored specifically to the target microcontroller and project requirements. The architecture is layered to provide maximum portability while maintaining hardware-specific optimizations. At the lowest level, the library generates startup code and a Hardware Abstraction Layer (HAL) that provides a unified C++23 interface for peripherals like GPIO, UART, and SPI across different vendors.

Above the HAL, modm provides target-independent drivers for external components (sensors, displays, etc.) and high-level communication protocols. A key architectural principle is the avoidance of dynamic memory allocation within the HAL, ensuring predictable RAM consumption. The system also includes a cooperative multitasking layer based on stackful fibers, allowing for complex asynchronous logic without the overhead of a full preemptive RTOS, though integration with FreeRTOS is provided for more demanding applications.

Use Cases

This library is ideal for:

• Autonomous Robotics: Specifically optimized for high-reliability requirements in competitions like Eurobot where predictable program flow is critical.
• Resource-Constrained Devices: Ideal for 8-bit AVR and small ARM Cortex-M0+ devices where low RAM and flash consumption are paramount.
• Cross-Platform Development: Projects that need to maintain a single codebase across different microcontroller families (e.g., STM32 and SAM).
• Rapid Prototyping: Developers using supported development boards (Nucleo, Discovery, Arduino) who need a high-level C++ API without sacrificing performance.
• Industrial Communication: Applications requiring robust CAN, CAN-FD, or Ethernet stacks with integrated third-party networking libraries.
• Embedded GUI Development: Systems requiring graphical interfaces via LVGL integration on various display controllers.

Getting Started

To begin using modm, developers must clone the repository recursively to include all necessary submodules: git clone --recurse-submodules https://github.com/modm-io/modm.git. The library relies on the lbuild tool to generate the specific library files for your target; this process involves creating a project configuration file that specifies the microcontroller and required modules.

Comprehensive documentation, including installation guides for the required toolchains and a detailed “Discover” guide, is available at modm.io. The repository also contains hundreds of up-to-date examples for various architectures and development boards, which serve as the primary reference for implementing peripheral drivers and third-party integrations.