STM32-BNO055

STM32 library for the Bosch BNO055 IMU with integrated sensor fusion algorithm

Usage example

Simple Code

#include "BNO055.hpp"

// Create BNO object with I2C interface and I2C address
BNO055 bno(&hi2c1, 0x28);

// (Optional) Specify the reset GPIO pin if connected
bno.set_reset_pin(BNO_RST_GPIO_Port, BNO_RST_Pin);

// Perform a sensor reset
bno.reset();

// Perform your configurations here while the sensor is in CONFIGMODE
// [...]

// Start the sensor in full fusion mode, configurations are now disabled
bno.set_operation_mode(BNO_OPERATION_MODE::NDOF);

// Simple loop to read fused angle data every 100ms
while(true)
{
  bno_vec_3_t euler_angles = bno.euler_angles();
  HAL_Delay(100);
}

Build

Copy the BNO055.cpp, BNO55.hpp, I2C.cpp and I2C.hpp to your source and include directory.

To build, specify a build flag for your STM32 MCU. For a STM32F1XXX for example, use -D STM32F1.

In the Cube IDE, paste the flag in the Preprocessor tab in the C/C++ build settings under Project > Properties

API

Constructor

Construct a BNO sensor object using the hi2c interface and the I2C address (e.g. 0x28)

BNO055(I2C_HandleTypeDef *hi2c, uint8_t address)

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Specify a reset pin

Specify a GPIO pin that is connected to the BNO reset pin for hardware resets. The reset is performed by setting the pin low for 100ms and then back to high. If invert is true, the pin is set high and then kept low.

void set_reset_pin(GPIO_TypeDef *port, uint16_t pin, bool invert);   // Specify a STM32 GPIO pin using port and pin number
void set_reset_pin(GPIO_TypeDef *port, uint16_t pin);                // Same as above with invert=false

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Sensor Reset

The sensor can be reset via the reset pin or through a reset bit. After a reset, the method blocks for 900ms to ensure that the sensor has started.

void reset();            // Perform a hardware reset or a software reset if no reset pin is defined
void hardware_reset();   // Perform a hardware reset by toggeling the reset pin, then wait 900ms. If no pin is defined, method returns.
void software_reset();   // Perform a software reset by setting RST_SYS in SYS_TRIGGER and wait 900ms

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Get sensor IDs

uint16_t unique_id();     // Get the BNO           unique id
uint8_t  bno_chip_id();   // Get the BNO           chip id, fixed value: 0xA0
uint8_t  acc_chip_id();   // Get the accelorometer chip id, fixed value: 0xFB
uint8_t  mag_chip_id();   // Get the magnetometer  chip id, fixed value: 0x32
uint8_t  gyro_chip_id();  // Get the gyroscope     chip id, fixed value: 0x0F

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Software versions

uint16_t  software_revision();   // Get the current BNO software version, format: [MSB].[LSB]
uint8_t   bootloader_version();  // Get the current BNO bootloader version

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Sensor self test

void     self_test();             // Trigger a self test
uint8_t  get_selftest_results();  // Returns selftest result bits

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Operation Mode

The operation mode defines which sensors and algorithms are active.

BNO_OPERATION_MODE	Description	ACC	MAG	GYR	Fusion
CONFIGMODE	This is the only mode in which setting registers are writable, default mode after reset	❌	❌	❌	❌
ACC_ONLY	Only accelerometer enabled	✔️	❌	❌	❌
MAG_ONLY	Only magnetometer enabled	❌	✔️	❌	❌
GYRO_ONLY	Only gyroscope enabled	❌	❌	✔️	❌
ACC_MAG	Both accelerometer and magnetometer enabled	✔️	✔️	❌	❌
ACC_GYRO	Both accelerometer and gyroscope enabled	✔️	❌	✔️	❌
MAG_GYRO	Both magnetometer and gyroscope enabled	❌	✔️	✔️	❌
AMG	All three sensors enabled	✔️	✔️	✔️	❌
IMU	Relative orientation from accelerometer and gyroscope	✔️	❌	✔️	✔️
COMPASS	Heading calculation from gravity vector and magnetometer	✔️	✔️	❌	✔️
M4G	Same as IMU, but magnetometer is used instead of gyroscope	✔️	✔️	❌	✔️
NDOF_FMC_OFF	9 DoF fusion without fast magnetometer calibration (FMC)	✔️	✔️	✔️	✔️
NDOF	9 DoF fusion with fast magentometer calibration (FMC)	✔️	✔️	✔️	✔️

⚠️ Switching operation modes takes around 20 ms

void                 set_operation_mode(BNO_OPERATION_MODE mode);  // Sets the operation mode and blocks for 20 ms
BNO_OPERATION_MODE   get_operation_mode();                         // Get the current operation mode

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Power Mode

The BNO allows for three general power modes.

BNO_POWER_MODE	Description
NORMAL	All sensors required for the selected operation mode are always switched ON
LOW_POWER	If no activity, low power mode is entered. Only accelerometer is active. If motion is detected, normal mode is entered.
SUSPEND	System is paused and all sensors are halted. Microcontroller is in sleep mode. No registers are updated.

void             set_power_mode(BNO_POWER_MODE mode);   // Set the power mode
BNO_POWER_MODE   get_power_mode();                      // Get the current power mode

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Sensor calibration

uint8_t get_calib_status();      // Get the sensor calibration status, 0xFF means fully calibrated

Check individual sensor calibration status:

uint8_t get_mag_calibrated();    // calibration state, 0 - 3 where 3 means fully calibrated
uint8_t get_acc_calibrated();    // calibration state, 0 - 3 where 3 means fully calibrated
uint8_t get_gyr_calibrated();    // calibration state, 0 - 3 where 3 means fully calibrated
uint8_t get_sys_calibrated();    // calibration state, 0 - 3 where 3 means fully calibrated

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Interrupts

Interrupt Enable

To enable certain interrupts, set the respective bits. For all bits see BNO_INT_MASK or the datasheet.

void set_interrupt_enable(uint8_t int_en_bits);   // Set the interrupt enable bits, see BNO_INT_MASK for all bits

Example:

set_interrupt_enable(ACC_NM | ACC_HIGH_G); // Enable accelerometer no motion and high-g interrupt

To disable all interrupts, set the interrupt enable byte to 0.

Interrupt Mask

With the interrupt mask you can control which interrupts trigger a change of the INT pin. When disabled, only the INT_STA bit will be updated.

void set_interrupt_mask(uint8_t int_msk_bits);   // Set the interrupt mask, see BNO_INT_MASK for all bits

To clear all mask bits, set the interrupt mask byte to 0.

Interrupt Status and Reset

uint8_t get_interrupt_status();  // Get the interrupt status bits
void reset_interrupts();         // Reset all interrupt status bits

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System Clock

The BNO can run using its internal or an external oscillator.

bool set_sys_clk(BNO_CLK_SOURCE clk_source);  // Set the system oscillator source (INTERNAL or EXTERNAL)
bool get_sys_clk_status();                    // Get the system clock status

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Temperature

Both the accelerometer and the gyroscope have an integrated temperature sensor. You can select which one should be used for readings.

void set_temperature_source(BNO_TEMP_SOURCE source); // TEMP_ACCELEROMETER or TEMP_GYROSCOPE

Reading the temperature is done using

int16_t temperature(); // Returns temperature in °C or °F, see set_temperature_unit

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Unit selection

You can select different output units for different data types by calling the set_[...]_unit methods. The following units are available.

Unit Struct Name	Influenced Data	Available units
BNO_ACC_UNIT	acceleration linear acceleration gravity	m/s^2 or mg
BNO_ANG_UNIT	euler angles	deg or rad
BNO_ANG_RATE_UNIT	angular rate	deg/s or rad/s
BNO_TEMP_UNIT	temperature	°C or °F

⚠️ Changing units is only possible in CONFIGMODE
ℹ️ Quaternion data is unitless
ℹ️ Magnetometer data unit is always uT and cannot be changed

The selected units are tracked internally by the sensor class. When you read the data the correct unit conversion is performed.
temperature() for example will return either °C or °F, depending on your selection.

bool set_acceleration_unit(BNO_ACC_UNIT unit);          // either METERS_PER_SECOND2 or MILLI_G
bool set_angle_unit(BNO_ANG_UNIT unit);                 // either DEG                or RAD
bool set_angular_rate_unit(BNO_ANG_RATE_UNIT unit);     // either DEG_PER_SECOND     or RAD_PER_SECOND
bool set_temperature_unit(BNO_TEMP_UNIT unit);          // either CELSIUS            or FAHRENHEIT

All functions return true if the unit was updated sucessfully. If false, make sure that you are in CONFIGMODE

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Axis output settings

⚠️ Changing axis settings is only possible in CONFIGMODE

Orientation output format

Two different fusion data output formats are available.

Rotation Angle	Range (Android)	Range (Windows)
Pitch	+180° to -180° (cw = value decrease)	-180° to +180° (cw = value increase)
Roll	-90° to +90°	-90° to +90°
Yaw	0° to 360°	0° to 360°

void set_orientation_format(BNO_ORI_FORMAT format); // either WINDOWS or ANDROID

Axis signs

You can change the sign of every axis to invert its direction.

void set_axis_sign_invert(bool x, bool y, bool z);  // false = no invert, true = invert axis
uint8_t get_axis_sign_invert();                     // Get the current signs, bits are: 0bxxxxxXYZ

Axis remap

You can remap axes to new axes. The default map is: X Axis = X, Y Axis = Y, Z Axis = Z. Mapping one axis to two or more is not allowed and will be ignored by the BNO.

void set_axis_remap(BNO_AXIS new_x, BNO_AXIS new_y, BNO_AXIS new_z); // use BNO_X_AXIS, BNO_Y_AXIS or BNO_Z_AXIS

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System Status

Get the system status byte.

uint8_t get_system_status();

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System Error

Get the system error byte.

uint8_t get_system_error();

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Output IMU data

Accelerometer data

Get the acceleration data for x, y and z axis.

bno_vec_3_t get_acceleration();

ℹ️ The unit is either m/s^2 or mg, see Unit selection

Linear Acceleration

Get the linear acceleration for x, y and z axis.

bno_vec_3_t get_linear_acceleration();

ℹ️ The unit is either m/s^2 or mg, see Unit selection
⚠️ Linear acceleration integration for velocity and position estimation is too inaccurate.

Gravity vector

Get the gravity vector estimation.

bno_vec_3_t get_gravity_vector();

ℹ️ The unit is either m/s^2 or mg, see Unit selection
⚠️ Only available in fusion mode

Gyroscope data

Get the gyroscope data (angular rate) for x, y and z axis.

bno_vec_3_t get_gyro_data();

ℹ️ The unit is either deg/s or rad/s, see Unit selection

Magnetometer data

Get the magnetometer data for x, y and z axis.

bno_vec_3_t get_mag_data();

ℹ️ The unit is always uT

Euler angles

Get the fused orientation as euler angles for each axis.

bno_vec_3_t get_euler();

ℹ️ The unit is either deg or rad, see Unit selection
⚠️ Only available in fusion mode

Quaternion data

Get the fused orientation as quaternion (w + ix + jy + kz)

bno_vec_4_t get_quaternion_data();

ℹ️ Quaternions are unitless
⚠️ Only available in fusion mode

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