Edge Impulse IMU Inference on Zephyr

This repository demonstrates how to run IMU-based Edge Impulse models on Zephyr using the Edge Impulse Zephyr Module.
Drop in your model > build > flash > get real-time motion inference.

Initialize This Repo

west init https://github.com/edgeimpulse/ei-zephyr-imu-inference.git
cd ei-zephyr-imu-inference
west update

This fetches:

• Zephyr RTOS
• Edge Impulse Zephyr SDK module
• All module dependencies

Update the Model

In Edge Impulse Studio go to:
Deployment > Zephyr library > Build

Download the generated .zip

Extract into the model/ folder:

unzip -o ~/Downloads/your-model.zip -d model/

Your model/ directory should contain:

• CMakeLists.txt
• edge-impulse-sdk/
• model-parameters/
• tflite-model/

Supported shield

The project support the following sensor shield:

• X-NUCLEO-IKS02A1 enabled passing -DCONFIG_EI_IKS02A1=y
• IKS01A3 enabled passing -DCONFIG_EI_IKS01A3=y

Build

Choose your board and the shield you are targeting,

For example: Nucleo U585ZI + IKS01A3

west build --pristine -b nucleo_u585zi_q -- -DCONFIG_EI_IKS01A3=y

Or Renesas EK RA6M5 + IKS02A1

west build --pristine -b ek_ra6m5 -- -DCONFIG_EI_IKS02A1=y

Note

You need to define one of the supported shield otherwise the build will fail with an error.

Flash

west flash

Or specify runner:

west flash --runner jlink
west flash --runner nrfjprog
west flash --runner openocd

Sensors Supported

All sensors accessible through I²C/SPI + Zephyr sensor drivers are compatible.

Project Structure

├── CMakeLists.txt          # Build configuration
├── prj.conf                # Zephyr config
├── west.yml                # Manifest (declares Edge Impulse SDK module)
├── model/                  # Your Edge Impulse model (Zephyr library)
└── src/
    ├── main.cpp
    ├── inference/          # Inference state machine
    └── sensors/            # IMU interface

How It Works

1. Initialize - Sensor setup via Zephyr sensor API
2. Sample - Continuous data collection at model frequency
3. Buffer - Circular buffer stores samples
4. Infer - Run classifier when buffer full
5. Output - Print classification results
6. Loop - Repeat

Configuration

Key settings in prj.conf:

CONFIG_EDGE_IMPULSE_SDK=y        # Enable Edge Impulse SDK
CONFIG_MAIN_STACK_SIZE=8192      # Adjust for your model size
CONFIG_SENSOR=y                  # Enable sensor subsystem
CONFIG_I2C=y                     # Enable I2C for sensors

For larger models, increase stack size:

CONFIG_MAIN_STACK_SIZE=16384

Using in Your Own Project

Add to your west.yml:

projects:
  - name: edge-impulse-sdk-zephyr
    path: modules/edge-impulse-sdk-zephyr
    revision: v1.75.4  # See https://github.com/edgeimpulse/edge-impulse-sdk-zephyr/tags
    url: https://github.com/edgeimpulse/edge-impulse-sdk-zephyr

Then:

west update

Add to your CMakeLists.txt:

list(APPEND ZEPHYR_EXTRA_MODULES ${CMAKE_CURRENT_SOURCE_DIR}/model)

Troubleshooting

Module not found

west update

Insufficient memory

# In prj.conf
CONFIG_MAIN_STACK_SIZE=16384

Sensor not detected

# In prj.conf - enable debug logging
CONFIG_I2C_LOG_LEVEL_DBG=y
CONFIG_SENSOR_LOG_LEVEL_DBG=y

Cyclic Dependency Error

Symptom:

CMake Error at .../zephyr/cmake/modules/zephyr_module.cmake:73 (message):
  Unmet or cyclic dependencies in modules:
  /path/to/your-project/model
  depends on: ['edge-impulse-sdk-zephyr']

Cause: Your project has two module.yml files registering different parts of your application as Zephyr modules. This creates a hierarchical conflict where the module system can't determine the correct dependency resolution order.

How to Check: From your project root, run:

find . -maxdepth 2 -name "module.yml"

You should see only ONE result:

./model/zephyr/module.yml  ✓ CORRECT

If you see both of these:

./zephyr/module.yml        DELETE THIS
./model/zephyr/module.yml  KEEP THIS

Fix: Delete the zephyr/module.yml file at your project root:

rm zephyr/module.yml

Then run:

west update
west build -b <your_board> -p

Why This Happens:

• model/zephyr/module.yml correctly registers your trained ML model as a module
• zephyr/module.yml incorrectly registers the entire application as a module
• The build system finds the project-level module first, then encounters the model module nested inside, creating a circular dependency

Key Principle: Only the model should be a Zephyr module. Your application project is a Zephyr application, not a module.

Resources

• Edge Impulse SDK for Zephyr

Clear BSD License - see LICENSE file
Copyright (c) 2025 EdgeImpulse Inc.