File content as of revision 0:8a8f44689157:

/**
 * A simple single-file program to test the BNO055 breakout board from Adafruit.
 * There are two BNO055 libraries on MBED, as well as Arduino source code on the Adafruit website,
 * but none of it worked for me, so I wrote this simple example.
 *
 * Some notes:
 * 1.) You will probably need to reset your microcontroller a few times. The BNO055 is correctly initialized when
 *      the ID is read correctly and the temperature is not zero (i.e. initBNO055() should return true).
 * 2.) The BNO055 breakout board uses an external crystal. If you are not using an external crystal, delete the
 *      I2C write message that sets the chip to using external crystal.
 */

#include "mbed.h"

Serial pc(USBTX,USBRX);
I2C i2c(D7, D6);

const int bno055_addr = 0x28 << 1;

const int BNO055_ID_ADDR                                          = 0x00;
const int BNO055_EULER_H_LSB_ADDR                                 = 0x1A;
const int BNO055_TEMP_ADDR                                        = 0x34;
const int BNO055_OPR_MODE_ADDR                                    = 0x3D;
const int BNO055_CALIB_STAT_ADDR                                  = 0x35;
const int BNO055_SYS_STAT_ADDR                                    = 0x39;
const int BNO055_SYS_ERR_ADDR                                     = 0x3A;
const int BNO055_AXIS_MAP_CONFIG_ADDR                             = 0x41;
const int BNO055_SYS_TRIGGER_ADDR                                 = 0x3F;

typedef struct CalibStatus_t
{
    int mag;
    int acc;
    int gyr;
    int sys;
} CalibStatus;

typedef struct Euler_t
{
    float heading;
    float pitch;
    float roll;
} Euler;


/**
 * Function to write to a single 8-bit register
 */
void writeReg(int regAddr, char value)
{
    char wbuf[2];
    wbuf[0] = regAddr;
    wbuf[1] = value;
    i2c.write(bno055_addr, wbuf, 2, false);  
}

/**
 * Function to read from a single 8-bit register
 */
char readReg(int regAddr)
{
    char rwbuf = regAddr;
    i2c.write(bno055_addr, &rwbuf, 1, false);
    i2c.read(bno055_addr, &rwbuf, 1, false);
    return rwbuf;
}

/**
 * Returns the calibration status of each component
 */
CalibStatus readCalibrationStatus()
{
    CalibStatus status;
    int regVal = readReg(BNO055_CALIB_STAT_ADDR);
        
    status.mag = regVal & 0x03;
    status.acc = (regVal >> 2) & 0x03;
    status.gyr = (regVal >> 4) & 0x03;
    status.sys = (regVal >> 6) & 0x03;
    
    return status;
}


/**
 * Checks that there are no errors on the accelerometer
 */
bool bno055Healthy()
{
    int sys_error = readReg(BNO055_SYS_ERR_ADDR);
    wait(0.001);
    int sys_stat = readReg(BNO055_SYS_STAT_ADDR);
    wait(0.001);
    
    if(sys_error == 0 && sys_stat == 5)
        return true;
    else
        return false;
}
    

/**
 * Configure and initialize the BNO055
 */
bool initBNO055()
{
    unsigned char regVal;
    i2c.frequency(400000);
    bool startupPass = true;
    
    // Do some basic power-up tests
    regVal = readReg(BNO055_ID_ADDR);
    if(regVal == 0xA0)
        pc.printf("BNO055 successfully detected!\r\n");
    else {
        pc.printf("ERROR: no BNO055 detected\r\n");
        startupPass = false;
    }
        
    regVal = readReg(BNO055_TEMP_ADDR);
    pc.printf("Chip temperature is: %d C\r\n", regVal);
    
    if(regVal == 0)
        startupPass = false;
 
    // Change mode to CONFIG
    writeReg(BNO055_OPR_MODE_ADDR, 0x00);
    wait(0.2);
    
    regVal = readReg(BNO055_OPR_MODE_ADDR);
    pc.printf("Change to mode: %d\r\n", regVal);
    wait(0.1);
    
    // Remap axes
    writeReg(BNO055_AXIS_MAP_CONFIG_ADDR, 0x06);    // b00_00_01_10
    wait(0.1);    

    // Set to external crystal
    writeReg(BNO055_SYS_TRIGGER_ADDR, 0x80);
    wait(0.2);    

    // Change mode to NDOF
    writeReg(BNO055_OPR_MODE_ADDR, 0x0C);
    wait(0.2);
 
    regVal = readReg(BNO055_OPR_MODE_ADDR);
    pc.printf("Change to mode: %d\r\n", regVal);
    wait(0.1);
    
    return startupPass;
}

/**
 * Reads the Euler angles, zeroed out
 */
Euler getEulerAngles()
{
    char buf[16];
    Euler e;
    
    // Read in the Euler angles
    buf[0] = BNO055_EULER_H_LSB_ADDR;
    i2c.write(bno055_addr, buf, 1, false);
    i2c.read(bno055_addr, buf, 6, false);
    
    short int euler_head = buf[0] + (buf[1] << 8);
    short int euler_roll = buf[2] + (buf[3] << 8);
    short int euler_pitch = buf[4] + (buf[5] << 8);
    
    e.heading = ((float)euler_head) / 16.0;
    e.roll = ((float)euler_roll) / 16.0;
    e.pitch = ((float)euler_pitch) / 16.0;
    
    return e;
}

int main() {

    bool startupPassed;
    Euler e;

    // Initialize
    pc.baud(115200);
    wait(0.5);
    startupPassed = initBNO055();   // Note: set LED to RED if this fails
 
    // Read orientation values
    while(true)
    {
        // Make sure that there are no errors
        if(!bno055Healthy())
            pc.printf("ERROR: BNO055 has an error/status problem!!!\r\n");
        
        // Read in the Euler angles
        e = getEulerAngles();
 
        wait(0.001);
 
        // Read in the calibration status
        CalibStatus calStat = readCalibrationStatus();
        
        printf("Heading: %7.2f \tRoll: %7.2f \tPitch: %7.2f \tMAG: %d ACC: %d GYR: %d SYS: %d\r\n", e.heading, e.roll, e.pitch,
            calStat.mag, calStat.acc, calStat.gyr, calStat.sys);
        
        wait(0.05);
    }
}