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Firmware variants

The BHI385 IMU chip can handle processing directly on-board, which is why Bosch Sensortec offers several firmware variants tailored for different projects. You can find the full list of firmware versions in their GitHub repository.

Understanding the Firmware Names​

Here is how to read a firmware file name, using Bosch_Shuttle3_BHI385_BMM350C_bsxsam_ndof.fw.h as an example:

  • Bosch_Shuttle3_BHI385: Designed for the Bosch Shuttle Board 3.0 with the BHI385 as the primary sensor.
  • _BMM350C (or BMP58X, BME688): Supports external slave sensors connected directly to the BHI385.
  • _bsxsam (or *_lite, *_turbo, *_lite_Klio): Includes the full Bosch BSX Sensor Fusion library. It does all the math to turn raw sensor data into clean, usable physical orientation tracking.
    ℹ️
    *_Klio offers the Klio machine learning engine to learn repetitive motions and recognize activities, like gym exercises.
  • _ndof: N-degrees of Freedom. This usually means 9-DoF absolute orientation fusion if you connect the BMM350 magnetometer.
  • .fw.h (.fw): A C/C++ header version of the binary file, wrapped in a const unsigned char array so you can include it directly in your Arduino or embedded projects.

Choosing the Right Firmware​

You can change the BHI385's firmware depending on what your project needs.

Firmware variantUse when...
bsxsam_liteYou only need accelerometer and gyroscope. It saves the most memory (smallest footprint).
bsxsamYou want accelerometer and gyroscope data combined with full BSX sensor fusion.
bsxsam_turboYou need a high output data rate (up to 800 Hz) with BSX fusion.
bsxsam_lite_KlioYou need accelerometer, gyroscope, and Klio motion pattern recognition.

Writing Your Own Firmware​

Why write custom firmware? You might want to create your own firmware if you need to:

  • Create a virtual sensor: Calculate specific metrics directly on the chip, like golf swing angles or precise vibration patterns.
  • Connect unsupported hardware: Write custom drivers for new external sensors connected to the BHI385's master I2C or SPI pins.
  • Free up your main microcontroller: Move heavy math and filtering from your ESP32 or STM32 to run entirely inside the low-power BHI385.

To build your own firmware, you will need Bosch's official development tools:

  1. Bosch BHI3xx SDK (Software Development Kit): A C-based development kit with the framework, RTOS headers, and drivers.
  2. ARC GNU Toolchain: Required because the BHI385 runs on a Synopsys ARC EM4 architecture. You can download it here.
  3. Bosch Motion AI Studio: Use this to design, train, and run custom machine learning models (like gesture recognition) directly on the sensor.

For a step-by-step guide, check out the BHI3xx SDK Quick Start Guide.