Arm CMSIS Ethos-U

This repository contains the source of the CMSIS software pack ARM::CMSIS-Ethos-U containing the Arm Ethos-U NPU core driver and supporting documentation. The driver supplies the low-level interface between embedded software and Arm Ethos-U55, Ethos-U65, and Ethos-U85 NPUs.

The pack provides a single-variant driver component for each supported NPU family and a multi-variant component containing support for all three families. A single-variant build selects the NPU at compile time. A multi-variant build selects the NPU product and MAC configuration for each driver instance at run time.

Applications can use the driver to initialize an NPU, configure memory access, invoke Vela-optimized ML models synchronously or asynchronously, handle interrupts, and collect performance-monitoring data.

Refer to the CMSIS-Ethos-U documentation for architecture concepts, Vela configuration, driver usage, and system-integration guidance.

Supported NPUs

NPU support	Component variant	Backend implementation
Arm Ethos-U55	Generic U55	source/src/ethosu_backend_u55.c
Arm Ethos-U65	Generic U65	source/src/ethosu_backend_u65.c
Arm Ethos-U85	Generic U85	source/src/ethosu_backend_u85.c
Ethos-U55, Ethos-U65, and Ethos-U85	Multi-Variant	All three backends

The selected single-variant component supplies the corresponding configuration header and NPU-family definition. The Multi-Variant component supplies all three backends and defines ETHOSU_MULTI_VARIANT.

Documentation

The documentation is organized into five sections:

• General introduces the architecture, terminology, memory modes, and deployment lifecycle.
• Vela covers compiler installation, model compilation, configuration, memory placement, and diagnostics.
• Driver describes single-variant and multi-variant configuration, memory access, the core-driver API, execution contract, platform hooks, PMU, and bring-up checks.
• Integration connects Vela output to linker placement, memory attributes, cache policy, driver configuration, and system memory budgeting.
• Zephyr explains how to configure, build, and run Ethos-U-accelerated Zephyr applications.

Files and Directories

This is a list of the relevant files and directories.

File or directory	Description
source	Core-driver source, public headers, single- and multi-variant NPU support, CMake build files, and Zephyr module metadata.
interface	CMSIS-RTOS2 and data-cache interface templates supplied by the driver components.
examples	CMSIS-Toolbox integration-test solutions for Ethos-U55, Ethos-U65, and Ethos-U85, including Corstone targets, TFLM models, and self-checking tests.
documentation	Doxygen sources for the general, Vela, driver, integration, and Zephyr guides, plus generated web content, styles, and authoring guidance.
overview	Pack overview content and images displayed by CMSIS tooling.
.github	Workflows that test the example, build the pack, and publish documentation.

Building the Driver using CMake

Projects that build a single-variant driver directly with CMake select the target through ETHOSU_TARGET_NPU_CONFIG, for example ethos-u55-128.

The driver is intended to be cross-compiled for the Arm Cortex-M processor used by the target system. Configure the toolchain, processor, and Ethos-U configuration before building:

cmake -S source -B build \
  -DCMAKE_TOOLCHAIN_FILE=<toolchain> \
  -DCMAKE_SYSTEM_PROCESSOR=cortex-m<nr><features> \
  -DETHOSU_TARGET_NPU_CONFIG=ethos-u<nr>-<macs>
cmake --build build

For a multi-variant build, set ETHOSU_MULTI_VARIANT=ON instead of selecting ETHOSU_TARGET_NPU_CONFIG. The build includes support for all three NPU families. Applications use ethosu_init_ex() and ethosu_reserve_driver_ex() to select the product and MAC configuration at run time.

When using a toolchain from the Ethos-U core platform, set TARGET_CPU instead of CMAKE_SYSTEM_PROCESSOR. See the driver README for API examples and integration requirements.

Pack and Documentation Generation

Generate the documentation from a Bash shell with:

./documentation/doxygen/gen_doc.sh

Generate the CMSIS-Ethos-U software pack with:

./gen_pack.sh

The pack script builds the documentation as a preprocessing step and writes the resulting archive to output by default. See the documentation authoring guide for prerequisites and document structure.

Continuous Integration (CI)

CI workflow	Description
pack	Generates the documentation and software pack for pull requests, pushes to main, and published releases.
gh-pages	Deploys the generated content from the gh-pages branch to GitHub Pages.
test-ethos-u	Builds and runs the Ethos-U55, Ethos-U65, and Ethos-U85 integration tests with Arm Compiler 6 and GCC.

The Test Ethos-U workflow pins Arm GNU Toolchain 14.2.1 in vcpkg-configuration.json. TensorFlow Lite Micro 1.26.5 is built as C++17 with exceptions and RTTI disabled, matching the compiler settings supplied by the TensorFlow Lite Micro pack. Newer GCC versions diagnose the pack's private class-specific operator delete when exceptions are enabled.

License

The CMSIS-Ethos-U pack and core driver are licensed under the Apache License 2.0.

Contributions and Issues

Contributions are accepted under the Apache License 2.0 and must include a Developer Certificate of Origin sign-off. See the driver contribution guidance for details.

Use GitHub Issues to report defects, request enhancements, or discuss documentation improvements. For security-related matters, follow the security policy.