CMSIS

CMSIS, the Cortex Microcontroller Software Interface Standard, is a vendor-independent software framework for Arm Cortex-M microcontrollers. It provides standardized interfaces to core processor features and common peripherals, enabling code portability and reuse across devices from different vendors. CMSIS is maintained by Arm and widely supported by toolchains and MCU vendors.

The core component, CMSIS-Core, offers the core peripheral access layer, including definitions for core registers, the Nested Vectored Interrupt Controller, SysTick, and core architecture functions. CMSIS-SVD describes device registers in XML to aid configuration and debugging. CMSIS-Pack is a packaging format that describes devices, middleware, and tools for easy installation and management.

CMSIS also includes libraries and APIs. CMSIS-DSP provides optimized digital signal processing routines for Cortex-M cores. CMSIS-NN offers neural network kernels for efficient ML on constrained devices. CMSIS-Driver defines a common API for peripherals such as SPI, I2C, UART, and USB, enabling vendor-agnostic driver integration. For real-time operating systems, CMSIS-RTOS defines a portable API (with CMSIS-RTOS and CMSIS-RTOS2 variants) so applications can run on multiple RTOS implementations. CMSIS-DAP refers to the debug interface standard used by Cortex targets for programming and debugging.

In practice, CMSIS reduces porting effort, accelerates development, and promotes code reuse by providing a common foundation for core access, device descriptions, and middleware. It is commonly used with toolchains such as Keil MDK, Arm Development Studio, IAR, and GCC-based environments.