Fully featured I2C and SPI driver for CEVA (Hilcrest)'s BNO080 and FSM300 Inertial Measurement Units.

Dependents:   BNO080-Examples BNO080-Examples


BNO080 Driver

by Jamie Smith / USC Rocket Propulsion Lab

After lots of development, we are proud to present our driver for the Hilcrest BNO080 IMU! This driver is inspired by SparkFun and Nathan Seidle's Arduino driver for this chip, but has been substantially rewritten and adapted.

It supports the main features of the chip, such as reading rotation and acceleration data, as well as some of its more esoteric functionality, such as counting steps and detecting whether the device is being hand-held.


  • Support for 15 different data reports from the IMU, from acceleration to rotation to tap detection
  • Support for reading of sensor data, and automatic checking of update rate against allowed values in metadata
  • BNO_DEBUG switch enabling verbose, detailed output about communications with the chip for ease of debugging
  • Ability to tare sensor rotation and set mounting orientation
  • Can operate in several execution modes: polling I2C, polling SPI, and threaded SPI (which handles timing-critical functions in a dedicated thread, and automatically activates when the IMU has data available)
    • Also has experimental support for using asynchronous SPI transactions, allowing other threads to execute while communication with the BNO is occurring. Note that this functionality requires a patch to Mbed OS source code due to Mbed bug #13941
  • Calibration function
  • Reasonable code size for what you get: the library uses about 4K of flash and one instance of the object uses about 1700 bytes of RAM.


Full Doxygen documentation is available online here

Example Code

Here's a simple example:

BNO080 Rotation Vector and Acceleration

#include <mbed.h>
#include <BNO080.h>

int main()
	Serial pc(USBTX, USBRX);

	// Create IMU, passing in output stream, pins, I2C address, and I2C frequency
	// These pin assignments are specific to my dev setup -- you'll need to change them
	BNO080I2C imu(&pc, p28, p27, p16, p30, 0x4a, 100000); 


	// Tell the IMU to report rotation every 100ms and acceleration every 200ms
	imu.enableReport(BNO080::ROTATION, 100);
	imu.enableReport(BNO080::TOTAL_ACCELERATION, 200);

	while (true)
		// poll the IMU for new data -- this returns true if any packets were received
			// now check for the specific type of data that was received (can be multiple at once)
			if (imu.hasNewData(BNO080::ROTATION))
				// convert quaternion to Euler degrees and print
				pc.printf("IMU Rotation Euler: ");
				TVector3 eulerRadians = imu.rotationVector.euler();
				TVector3 eulerDegrees = eulerRadians * (180.0 / M_PI);
				eulerDegrees.print(pc, true);
			if (imu.hasNewData(BNO080::TOTAL_ACCELERATION))
				// print the acceleration vector using its builtin print() method
				pc.printf("IMU Total Acceleration: ");
				imu.totalAcceleration.print(pc, true);


If you want more, a comprehensive, ready-to-run set of examples is available on my BNO080-Examples repository.


This driver makes use of a lightweight, public-domain library for vectors and quaternions available here.


Version 2.1 (Nov 24 2020)

  • Added BNO080Async, which provides a threaded implementation of the SPI driver. This should help get the best performance and remove annoying timing requirements on the code calling the driver
  • Added experimental USE_ASYNC_SPI option
  • Fixed bug in v2.0 causing calibrations to fail

Version 2.0 (Nov 18 2020)

  • Added SPI support
  • Refactored buffer system so that SPI could be implemented as a subclass. Unfortunately this does substantially increase the memory usage of the driver, but I believe that the benefits are worth it.

Version 1.3 (Jul 21 2020)

  • Fix deprecation warnings and compile errors in Mbed 6
  • Fix compile errors in Arm Compiler (why doesn't it have M_PI????)

Version 1.2 (Jan 30 2020)

  • Removed accidental IRQ change
  • Fixed hard iron offset reading incorrectly due to missing cast

Version 1.1 (Jun 14 2019)

  • Added support for changing permanent orientation
  • Add FRS writing functions
  • Removed some errant printfs

Version 1.0 (Dec 29 2018)

  • Initial Mbed OS release

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