LSM9DS1.cpp

/******************************************************************************
  SFE_LSM9DS1.cpp
  SFE_LSM9DS1 Library Source File
  Jim Lindblom @ SparkFun Electronics
  Original Creation Date: February 27, 2015
https://github.com/sparkfun/LSM9DS1_Breakout

This file implements all functions of the LSM9DS1 class. Functions here range
from higher level stuff, like reading/writing LSM9DS1 registers to low-level,
hardware reads and writes. Both SPI and I2C handler functions can be found
towards the bottom of this file.

This code is beerware; if you see me (or any other SparkFun employee) at the
local, and you've found our code helpful, please buy us a round!

Distributed as-is; no warranty is given.
 ******************************************************************************/

#include "LSM9DS1.hpp"
#include "LSM9DS1_Registers.h"
#include "LSM9DS1_Types.h"

// Sensor Sensitivity Constants
// Values set according to the typical specifications provided in
// table 3 of the LSM9DS1 datasheet. (pg 12)
#define SENSITIVITY_ACCELEROMETER_2  0.000061
#define SENSITIVITY_ACCELEROMETER_4  0.000122
#define SENSITIVITY_ACCELEROMETER_8  0.000244
#define SENSITIVITY_ACCELEROMETER_16 0.000732
#define SENSITIVITY_GYROSCOPE_245    0.00875
#define SENSITIVITY_GYROSCOPE_500    0.0175
#define SENSITIVITY_GYROSCOPE_2000   0.07
#define SENSITIVITY_MAGNETOMETER_4   0.00014
#define SENSITIVITY_MAGNETOMETER_8   0.00029
#define SENSITIVITY_MAGNETOMETER_12  0.00043
#define SENSITIVITY_MAGNETOMETER_16  0.00058

LSM9DS1::LSM9DS1()
{
    init(IMU_MODE_I2C, LSM9DS1_AG_ADDR(1), LSM9DS1_M_ADDR(1));
}

LSM9DS1::LSM9DS1(interface_mode interface, uint8_t xgAddr, uint8_t mAddr)
{
    init(interface, xgAddr, mAddr);
}

void LSM9DS1::init(interface_mode interface, uint8_t xgAddr, uint8_t mAddr)
{
    settings.device.commInterface = interface;
    settings.device.agAddress = xgAddr;
    settings.device.mAddress = mAddr;

    settings.gyro.enabled = true;
    settings.gyro.enableX = true;
    settings.gyro.enableY = true;
    settings.gyro.enableZ = true;
    // gyro scale can be 245, 500, or 2000
    settings.gyro.scale = 245;
    // gyro sample rate: value between 1-6
    // 1 = 14.9    4 = 238
    // 2 = 59.5    5 = 476
    // 3 = 119     6 = 952
    settings.gyro.sampleRate = 6;
    // gyro cutoff frequency: value between 0-3
    // Actual value of cutoff frequency depends
    // on sample rate.
    settings.gyro.bandwidth = 0;
    settings.gyro.lowPowerEnable = false;
    settings.gyro.HPFEnable = false;
    // Gyro HPF cutoff frequency: value between 0-9
    // Actual value depends on sample rate. Only applies
    // if gyroHPFEnable is true.
    settings.gyro.HPFCutoff = 0;
    settings.gyro.flipX = false;
    settings.gyro.flipY = false;
    settings.gyro.flipZ = false;
    settings.gyro.orientation = 0;
    settings.gyro.latchInterrupt = true;

    settings.accel.enabled = true;
    settings.accel.enableX = true;
    settings.accel.enableY = true;
    settings.accel.enableZ = true;
    // accel scale can be 2, 4, 8, or 16
    settings.accel.scale = 2;
    // accel sample rate can be 1-6
    // 1 = 10 Hz    4 = 238 Hz
    // 2 = 50 Hz    5 = 476 Hz
    // 3 = 119 Hz   6 = 952 Hz
    settings.accel.sampleRate = 6;
    // Accel cutoff freqeuncy can be any value between -1 - 3. 
    // -1 = bandwidth determined by sample rate
    // 0 = 408 Hz   2 = 105 Hz
    // 1 = 211 Hz   3 = 50 Hz
    settings.accel.bandwidth = -1;
    settings.accel.highResEnable = false;
    // accelHighResBandwidth can be any value between 0-3
    // LP cutoff is set to a factor of sample rate
    // 0 = ODR/50    2 = ODR/9
    // 1 = ODR/100   3 = ODR/400
    settings.accel.highResBandwidth = 0;

    settings.mag.enabled = true;
    // mag scale can be 4, 8, 12, or 16
    settings.mag.scale = 4;
    // mag data rate can be 0-7
    // 0 = 0.625 Hz  4 = 10 Hz
    // 1 = 1.25 Hz   5 = 20 Hz
    // 2 = 2.5 Hz    6 = 40 Hz
    // 3 = 5 Hz      7 = 80 Hz
    settings.mag.sampleRate = 7;
    settings.mag.tempCompensationEnable = false;
    // magPerformance can be any value between 0-3
    // 0 = Low power mode      2 = high performance
    // 1 = medium performance  3 = ultra-high performance
    settings.mag.XYPerformance = 3;
    settings.mag.ZPerformance = 3;
    settings.mag.lowPowerEnable = false;
    // magOperatingMode can be 0-2
    // 0 = continuous conversion
    // 1 = single-conversion
    // 2 = power down
    settings.mag.operatingMode = 0;

    settings.temp.enabled = true;
    for (int i=0; i<3; i++)
    {
        gBias[i] = 0;
        aBias[i] = 0;
        mBias[i] = 0;
        gBiasRaw[i] = 0;
        aBiasRaw[i] = 0;
        mBiasRaw[i] = 0;
    }
    _autoCalc = false;
}


uint16_t LSM9DS1::begin()
{
    _xgAddress = settings.device.agAddress;
    _mAddress = settings.device.mAddress;

    constrainScales();
    // Once we have the scale values, we can calculate the resolution
    // of each sensor. That's what these functions are for. One for each sensor
    calcgRes(); // Calculate DPS / ADC tick, stored in gRes variable
    calcmRes(); // Calculate Gs / ADC tick, stored in mRes variable
    calcaRes(); // Calculate g / ADC tick, stored in aRes variable

    // Now, initialize our hardware interface.
    if (settings.device.commInterface == IMU_MODE_I2C)  // If we're using I2C
        initI2C();  // Initialize I2C
    else if (settings.device.commInterface == IMU_MODE_SPI)     // else, if we're using SPI
        initSPI();  // Initialize SPI

    // To verify communication, we can read from the WHO_AM_I register of
    // each device. Store those in a variable so we can return them.
    uint8_t mTest = mReadByte(WHO_AM_I_M);      // Read the gyro WHO_AM_I
    uint8_t xgTest = xgReadByte(WHO_AM_I_XG);   // Read the accel/mag WHO_AM_I
    uint16_t whoAmICombined = (xgTest << 8) | mTest;

    if (whoAmICombined != ((WHO_AM_I_AG_RSP << 8) | WHO_AM_I_M_RSP))
        return 0;

    // Gyro initialization stuff:
    initGyro(); // This will "turn on" the gyro. Setting up interrupts, etc.

    // Accelerometer initialization stuff:
    initAccel(); // "Turn on" all axes of the accel. Set up interrupts, etc.

    // Magnetometer initialization stuff:
    initMag(); // "Turn on" all axes of the mag. Set up interrupts, etc.

    // Once everything is initialized, return the WHO_AM_I registers we read:
    return whoAmICombined;
}

void LSM9DS1::initGyro()
{
    uint8_t tempRegValue = 0;

    // CTRL_REG1_G (Default value: 0x00)
    // [ODR_G2][ODR_G1][ODR_G0][FS_G1][FS_G0][0][BW_G1][BW_G0]
    // ODR_G[2:0] - Output data rate selection
    // FS_G[1:0] - Gyroscope full-scale selection
    // BW_G[1:0] - Gyroscope bandwidth selection

    // To disable gyro, set sample rate bits to 0. We'll only set sample
    // rate if the gyro is enabled.
    if (settings.gyro.enabled)
    {
        tempRegValue = (settings.gyro.sampleRate & 0x07) << 5;
    }
    switch (settings.gyro.scale)
    {
        case 500:
            tempRegValue |= (0x1 << 3);
            break;
        case 2000:
            tempRegValue |= (0x3 << 3);
            break;
            // Otherwise we'll set it to 245 dps (0x0 << 4)
    }
    tempRegValue |= (settings.gyro.bandwidth & 0x3);
    xgWriteByte(CTRL_REG1_G, tempRegValue);

    // CTRL_REG2_G (Default value: 0x00)
    // [0][0][0][0][INT_SEL1][INT_SEL0][OUT_SEL1][OUT_SEL0]
    // INT_SEL[1:0] - INT selection configuration
    // OUT_SEL[1:0] - Out selection configuration
    xgWriteByte(CTRL_REG2_G, 0x00); 

    // CTRL_REG3_G (Default value: 0x00)
    // [LP_mode][HP_EN][0][0][HPCF3_G][HPCF2_G][HPCF1_G][HPCF0_G]
    // LP_mode - Low-power mode enable (0: disabled, 1: enabled)
    // HP_EN - HPF enable (0:disabled, 1: enabled)
    // HPCF_G[3:0] - HPF cutoff frequency
    tempRegValue = settings.gyro.lowPowerEnable ? (1<<7) : 0;
    if (settings.gyro.HPFEnable)
    {
        tempRegValue |= (1<<6) | (settings.gyro.HPFCutoff & 0x0F);
    }
    xgWriteByte(CTRL_REG3_G, tempRegValue);

    // CTRL_REG4 (Default value: 0x38)
    // [0][0][Zen_G][Yen_G][Xen_G][0][LIR_XL1][4D_XL1]
    // Zen_G - Z-axis output enable (0:disable, 1:enable)
    // Yen_G - Y-axis output enable (0:disable, 1:enable)
    // Xen_G - X-axis output enable (0:disable, 1:enable)
    // LIR_XL1 - Latched interrupt (0:not latched, 1:latched)
    // 4D_XL1 - 4D option on interrupt (0:6D used, 1:4D used)
    tempRegValue = 0;
    if (settings.gyro.enableZ) tempRegValue |= (1<<5);
    if (settings.gyro.enableY) tempRegValue |= (1<<4);
    if (settings.gyro.enableX) tempRegValue |= (1<<3);
    if (settings.gyro.latchInterrupt) tempRegValue |= (1<<1);
    xgWriteByte(CTRL_REG4, tempRegValue);

    // ORIENT_CFG_G (Default value: 0x00)
    // [0][0][SignX_G][SignY_G][SignZ_G][Orient_2][Orient_1][Orient_0]
    // SignX_G - Pitch axis (X) angular rate sign (0: positive, 1: negative)
    // Orient [2:0] - Directional user orientation selection
    tempRegValue = 0;
    if (settings.gyro.flipX) tempRegValue |= (1<<5);
    if (settings.gyro.flipY) tempRegValue |= (1<<4);
    if (settings.gyro.flipZ) tempRegValue |= (1<<3);
    xgWriteByte(ORIENT_CFG_G, tempRegValue);
}

void LSM9DS1::initAccel()
{
    uint8_t tempRegValue = 0;

    //  CTRL_REG5_XL (0x1F) (Default value: 0x38)
    //  [DEC_1][DEC_0][Zen_XL][Yen_XL][Zen_XL][0][0][0]
    //  DEC[0:1] - Decimation of accel data on OUT REG and FIFO.
    //      00: None, 01: 2 samples, 10: 4 samples 11: 8 samples
    //  Zen_XL - Z-axis output enabled
    //  Yen_XL - Y-axis output enabled
    //  Xen_XL - X-axis output enabled
    if (settings.accel.enableZ) tempRegValue |= (1<<5);
    if (settings.accel.enableY) tempRegValue |= (1<<4);
    if (settings.accel.enableX) tempRegValue |= (1<<3);

    xgWriteByte(CTRL_REG5_XL, tempRegValue);

    // CTRL_REG6_XL (0x20) (Default value: 0x00)
    // [ODR_XL2][ODR_XL1][ODR_XL0][FS1_XL][FS0_XL][BW_SCAL_ODR][BW_XL1][BW_XL0]
    // ODR_XL[2:0] - Output data rate & power mode selection
    // FS_XL[1:0] - Full-scale selection
    // BW_SCAL_ODR - Bandwidth selection
    // BW_XL[1:0] - Anti-aliasing filter bandwidth selection
    tempRegValue = 0;
    // To disable the accel, set the sampleRate bits to 0.
    if (settings.accel.enabled)
    {
        tempRegValue |= (settings.accel.sampleRate & 0x07) << 5;
    }
    switch (settings.accel.scale)
    {
        case 4:
            tempRegValue |= (0x2 << 3);
            break;
        case 8:
            tempRegValue |= (0x3 << 3);
            break;
        case 16:
            tempRegValue |= (0x1 << 3);
            break;
            // Otherwise it'll be set to 2g (0x0 << 3)
    }
    if (settings.accel.bandwidth >= 0)
    {
        tempRegValue |= (1<<2); // Set BW_SCAL_ODR
        tempRegValue |= (settings.accel.bandwidth & 0x03);
    }
    xgWriteByte(CTRL_REG6_XL, tempRegValue);

    // CTRL_REG7_XL (0x21) (Default value: 0x00)
    // [HR][DCF1][DCF0][0][0][FDS][0][HPIS1]
    // HR - High resolution mode (0: disable, 1: enable)
    // DCF[1:0] - Digital filter cutoff frequency
    // FDS - Filtered data selection
    // HPIS1 - HPF enabled for interrupt function
    tempRegValue = 0;
    if (settings.accel.highResEnable)
    {
        tempRegValue |= (1<<7); // Set HR bit
        tempRegValue |= (settings.accel.highResBandwidth & 0x3) << 5;
    }
    xgWriteByte(CTRL_REG7_XL, tempRegValue);
}

// This is a function that uses the FIFO to accumulate sample of accelerometer and gyro data, average
// them, scales them to  gs and deg/s, respectively, and then passes the biases to the main sketch
// for subtraction from all subsequent data. There are no gyro and accelerometer bias registers to store
// the data as there are in the ADXL345, a precursor to the LSM9DS0, or the MPU-9150, so we have to
// subtract the biases ourselves. This results in a more accurate measurement in general and can
// remove errors due to imprecise or varying initial placement. Calibration of sensor data in this manner
// is good practice.
void LSM9DS1::calibrate(bool autoCalc)
{  
    uint8_t data[6] = {0, 0, 0, 0, 0, 0};
    uint8_t samples = 0;
    int ii;
    int32_t aBiasRawTemp[3] = {0, 0, 0};
    int32_t gBiasRawTemp[3] = {0, 0, 0};

    // Turn on FIFO and set threshold to 32 samples
    enableFIFO(true);
    setFIFO(FIFO_THS, 0x1F);
    while (samples < 0x1F)
    {
        samples = (xgReadByte(FIFO_SRC) & 0x3F); // Read number of stored samples
    }
    for(ii = 0; ii < samples ; ii++) 
    {   // Read the gyro data stored in the FIFO
        readGyro();
        gBiasRawTemp[0] += gx;
        gBiasRawTemp[1] += gy;
        gBiasRawTemp[2] += gz;
        readAccel();
        aBiasRawTemp[0] += ax;
        aBiasRawTemp[1] += ay;
        aBiasRawTemp[2] += az - (int16_t)(1./aRes); // Assumes sensor facing up!
    }  
    for (ii = 0; ii < 3; ii++)
    {
        gBiasRaw[ii] = gBiasRawTemp[ii] / samples;
        gBias[ii] = calcGyro(gBiasRaw[ii]);
        aBiasRaw[ii] = aBiasRawTemp[ii] / samples;
        aBias[ii] = calcAccel(aBiasRaw[ii]);
    }

    enableFIFO(false);
    setFIFO(FIFO_OFF, 0x00);

    if (autoCalc) _autoCalc = true;
}

void LSM9DS1::calibrateMag(bool loadIn)
{
    int i, j;
    int16_t magMin[3] = {0, 0, 0};
    int16_t magMax[3] = {0, 0, 0}; // The road warrior

    for (i=0; i<128; i++)
    {
        while (!magAvailable())
            ;
        readMag();
        int16_t magTemp[3] = {0, 0, 0};
        magTemp[0] = mx;        
        magTemp[1] = my;
        magTemp[2] = mz;
        for (j = 0; j < 3; j++)
        {
            if (magTemp[j] > magMax[j]) magMax[j] = magTemp[j];
            if (magTemp[j] < magMin[j]) magMin[j] = magTemp[j];
        }
    }
    for (j = 0; j < 3; j++)
    {
        mBiasRaw[j] = (magMax[j] + magMin[j]) / 2;
        mBias[j] = calcMag(mBiasRaw[j]);
        if (loadIn)
            magOffset(j, mBiasRaw[j]);
    }

}
void LSM9DS1::magOffset(uint8_t axis, int16_t offset)
{
    if (axis > 2)
        return;
    uint8_t msb, lsb;
    msb = (offset & 0xFF00) >> 8;
    lsb = offset & 0x00FF;
    mWriteByte(OFFSET_X_REG_L_M + (2 * axis), lsb);
    mWriteByte(OFFSET_X_REG_H_M + (2 * axis), msb);
}

void LSM9DS1::initMag()
{
    uint8_t tempRegValue = 0;

    // CTRL_REG1_M (Default value: 0x10)
    // [TEMP_COMP][OM1][OM0][DO2][DO1][DO0][0][ST]
    // TEMP_COMP - Temperature compensation
    // OM[1:0] - X & Y axes op mode selection
    //  00:low-power, 01:medium performance
    //  10: high performance, 11:ultra-high performance
    // DO[2:0] - Output data rate selection
    // ST - Self-test enable
    if (settings.mag.tempCompensationEnable) tempRegValue |= (1<<7);
    tempRegValue |= (settings.mag.XYPerformance & 0x3) << 5;
    tempRegValue |= (settings.mag.sampleRate & 0x7) << 2;
    mWriteByte(CTRL_REG1_M, tempRegValue);

    // CTRL_REG2_M (Default value 0x00)
    // [0][FS1][FS0][0][REBOOT][SOFT_RST][0][0]
    // FS[1:0] - Full-scale configuration
    // REBOOT - Reboot memory content (0:normal, 1:reboot)
    // SOFT_RST - Reset config and user registers (0:default, 1:reset)
    tempRegValue = 0;
    switch (settings.mag.scale)
    {
        case 8:
            tempRegValue |= (0x1 << 5);
            break;
        case 12:
            tempRegValue |= (0x2 << 5);
            break;
        case 16:
            tempRegValue |= (0x3 << 5);
            break;
            // Otherwise we'll default to 4 gauss (00)
    }
    mWriteByte(CTRL_REG2_M, tempRegValue); // +/-4Gauss

    // CTRL_REG3_M (Default value: 0x03)
    // [I2C_DISABLE][0][LP][0][0][SIM][MD1][MD0]
    // I2C_DISABLE - Disable I2C interace (0:enable, 1:disable)
    // LP - Low-power mode cofiguration (1:enable)
    // SIM - SPI mode selection (0:write-only, 1:read/write enable)
    // MD[1:0] - Operating mode
    //  00:continuous conversion, 01:single-conversion,
    //  10,11: Power-down
    tempRegValue = 0;
    if (settings.mag.lowPowerEnable) tempRegValue |= (1<<5);
    tempRegValue |= (settings.mag.operatingMode & 0x3);
    mWriteByte(CTRL_REG3_M, tempRegValue); // Continuous conversion mode

    // CTRL_REG4_M (Default value: 0x00)
    // [0][0][0][0][OMZ1][OMZ0][BLE][0]
    // OMZ[1:0] - Z-axis operative mode selection
    //  00:low-power mode, 01:medium performance
    //  10:high performance, 10:ultra-high performance
    // BLE - Big/little endian data
    tempRegValue = 0;
    tempRegValue = (settings.mag.ZPerformance & 0x3) << 2;
    mWriteByte(CTRL_REG4_M, tempRegValue);

    // CTRL_REG5_M (Default value: 0x00)
    // [0][BDU][0][0][0][0][0][0]
    // BDU - Block data update for magnetic data
    //  0:continuous, 1:not updated until MSB/LSB are read
    tempRegValue = 0;
    mWriteByte(CTRL_REG5_M, tempRegValue);
}

uint8_t LSM9DS1::accelAvailable()
{
    uint8_t status = xgReadByte(STATUS_REG_1);

    return (status & (1<<0));
}

uint8_t LSM9DS1::gyroAvailable()
{
    uint8_t status = xgReadByte(STATUS_REG_1);

    return ((status & (1<<1)) >> 1);
}

uint8_t LSM9DS1::tempAvailable()
{
    uint8_t status = xgReadByte(STATUS_REG_1);

    return ((status & (1<<2)) >> 2);
}

uint8_t LSM9DS1::magAvailable(lsm9ds1_axis axis)
{
    uint8_t status;
    status = mReadByte(STATUS_REG_M);

    return ((status & (1<<axis)) >> axis);
}

void LSM9DS1::readAccel()
{
    uint8_t temp[6]; // We'll read six bytes from the accelerometer into temp   
    if ( xgReadBytes(OUT_X_L_XL, temp, 6) == 6 ) // Read 6 bytes, beginning at OUT_X_L_XL
    {
        ax = (temp[1] << 8) | temp[0]; // Store x-axis values into ax
        ay = (temp[3] << 8) | temp[2]; // Store y-axis values into ay
        az = (temp[5] << 8) | temp[4]; // Store z-axis values into az
        if (_autoCalc)
        {
            ax -= aBiasRaw[X_AXIS];
            ay -= aBiasRaw[Y_AXIS];
            az -= aBiasRaw[Z_AXIS];
        }
    }
}

int16_t LSM9DS1::readAccel(lsm9ds1_axis axis)
{
    uint8_t temp[2];
    int16_t value;
    if ( xgReadBytes(OUT_X_L_XL + (2 * axis), temp, 2) == 2)
    {
        value = (temp[1] << 8) | temp[0];

        if (_autoCalc)
            value -= aBiasRaw[axis];

        return value;
    }
    return 0;
}

void LSM9DS1::readMag()
{
    uint8_t temp[6]; // We'll read six bytes from the mag into temp 
    if ( mReadBytes(OUT_X_L_M, temp, 6) == 6) // Read 6 bytes, beginning at OUT_X_L_M
    {
        mx = (temp[1] << 8) | temp[0]; // Store x-axis values into mx
        my = (temp[3] << 8) | temp[2]; // Store y-axis values into my
        mz = (temp[5] << 8) | temp[4]; // Store z-axis values into mz
    }
}

int16_t LSM9DS1::readMag(lsm9ds1_axis axis)
{
    uint8_t temp[2];
    if ( mReadBytes(OUT_X_L_M + (2 * axis), temp, 2) == 2)
    {
        return (temp[1] << 8) | temp[0];
    }
    return 0;
}

void LSM9DS1::readTemp()
{
    uint8_t temp[2]; // We'll read two bytes from the temperature sensor into temp  
    if ( xgReadBytes(OUT_TEMP_L, temp, 2) == 2 ) // Read 2 bytes, beginning at OUT_TEMP_L
    {
        int16_t offset = 25;  // Per datasheet sensor outputs 0 typically @ 25 degrees centigrade
        temperature = offset + ((((int16_t)temp[1] << 8) | temp[0]) >> 8) ;
    }
}

void LSM9DS1::readGyro()
{
    uint8_t temp[6]; // We'll read six bytes from the gyro into temp
    if ( xgReadBytes(OUT_X_L_G, temp, 6) == 6) // Read 6 bytes, beginning at OUT_X_L_G
    {
        gx = (temp[1] << 8) | temp[0]; // Store x-axis values into gx
        gy = (temp[3] << 8) | temp[2]; // Store y-axis values into gy
        gz = (temp[5] << 8) | temp[4]; // Store z-axis values into gz
        if (_autoCalc)
        {
            gx -= gBiasRaw[X_AXIS];
            gy -= gBiasRaw[Y_AXIS];
            gz -= gBiasRaw[Z_AXIS];
        }
    }
}

int16_t LSM9DS1::readGyro(lsm9ds1_axis axis)
{
    uint8_t temp[2];
    int16_t value;

    if ( xgReadBytes(OUT_X_L_G + (2 * axis), temp, 2) == 2)
    {
        value = (temp[1] << 8) | temp[0];

        if (_autoCalc)
            value -= gBiasRaw[axis];

        return value;
    }
    return 0;
}

float LSM9DS1::calcGyro(int16_t gyro)
{
    // Return the gyro raw reading times our pre-calculated DPS / (ADC tick):
    return gRes * gyro; 
}

float LSM9DS1::calcAccel(int16_t accel)
{
    // Return the accel raw reading times our pre-calculated g's / (ADC tick):
    return aRes * accel;
}

float LSM9DS1::calcMag(int16_t mag)
{
    // Return the mag raw reading times our pre-calculated Gs / (ADC tick):
    return mRes * mag;
}

void LSM9DS1::setGyroScale(uint16_t gScl)
{
    // Read current value of CTRL_REG1_G:
    uint8_t ctrl1RegValue = xgReadByte(CTRL_REG1_G);
    // Mask out scale bits (3 & 4):
    ctrl1RegValue &= 0xE7;
    switch (gScl)
    {
        case 500:
            ctrl1RegValue |= (0x1 << 3);
            settings.gyro.scale = 500;
            break;
        case 2000:
            ctrl1RegValue |= (0x3 << 3);
            settings.gyro.scale = 2000;
            break;
        default: // Otherwise we'll set it to 245 dps (0x0 << 4)
            settings.gyro.scale = 245;
            break;
    }
    xgWriteByte(CTRL_REG1_G, ctrl1RegValue);

    calcgRes(); 
}

void LSM9DS1::setAccelScale(uint8_t aScl)
{
    // We need to preserve the other bytes in CTRL_REG6_XL. So, first read it:
    uint8_t tempRegValue = xgReadByte(CTRL_REG6_XL);
    // Mask out accel scale bits:
    tempRegValue &= 0xE7;

    switch (aScl)
    {
        case 4:
            tempRegValue |= (0x2 << 3);
            settings.accel.scale = 4;
            break;
        case 8:
            tempRegValue |= (0x3 << 3);
            settings.accel.scale = 8;
            break;
        case 16:
            tempRegValue |= (0x1 << 3);
            settings.accel.scale = 16;
            break;
        default: // Otherwise it'll be set to 2g (0x0 << 3)
            settings.accel.scale = 2;
            break;
    }
    xgWriteByte(CTRL_REG6_XL, tempRegValue);

    // Then calculate a new aRes, which relies on aScale being set correctly:
    calcaRes();
}

void LSM9DS1::setMagScale(uint8_t mScl)
{
    // We need to preserve the other bytes in CTRL_REG6_XM. So, first read it:
    uint8_t temp = mReadByte(CTRL_REG2_M);
    // Then mask out the mag scale bits:
    temp &= 0xFF^(0x3 << 5);

    switch (mScl)
    {
        case 8:
            temp |= (0x1 << 5);
            settings.mag.scale = 8;
            break;
        case 12:
            temp |= (0x2 << 5);
            settings.mag.scale = 12;
            break;
        case 16:
            temp |= (0x3 << 5);
            settings.mag.scale = 16;
            break;
        default: // Otherwise we'll default to 4 gauss (00)
            settings.mag.scale = 4;
            break;
    }   

    // And write the new register value back into CTRL_REG6_XM:
    mWriteByte(CTRL_REG2_M, temp);

    // We've updated the sensor, but we also need to update our class variables
    // First update mScale:
    //mScale = mScl;
    // Then calculate a new mRes, which relies on mScale being set correctly:
    calcmRes();
}

void LSM9DS1::setGyroODR(uint8_t gRate)
{
    // Only do this if gRate is not 0 (which would disable the gyro)
    if ((gRate & 0x07) != 0)
    {
        // We need to preserve the other bytes in CTRL_REG1_G. So, first read it:
        uint8_t temp = xgReadByte(CTRL_REG1_G);
        // Then mask out the gyro ODR bits:
        temp &= 0xFF^(0x7 << 5);
        temp |= (gRate & 0x07) << 5;
        // Update our settings struct
        settings.gyro.sampleRate = gRate & 0x07;
        // And write the new register value back into CTRL_REG1_G:
        xgWriteByte(CTRL_REG1_G, temp);
    }
}

void LSM9DS1::setAccelODR(uint8_t aRate)
{
    // Only do this if aRate is not 0 (which would disable the accel)
    if ((aRate & 0x07) != 0)
    {
        // We need to preserve the other bytes in CTRL_REG1_XM. So, first read it:
        uint8_t temp = xgReadByte(CTRL_REG6_XL);
        // Then mask out the accel ODR bits:
        temp &= 0x1F;
        // Then shift in our new ODR bits:
        temp |= ((aRate & 0x07) << 5);
        settings.accel.sampleRate = aRate & 0x07;
        // And write the new register value back into CTRL_REG1_XM:
        xgWriteByte(CTRL_REG6_XL, temp);
    }
}

void LSM9DS1::setMagODR(uint8_t mRate)
{
    // We need to preserve the other bytes in CTRL_REG5_XM. So, first read it:
    uint8_t temp = mReadByte(CTRL_REG1_M);
    // Then mask out the mag ODR bits:
    temp &= 0xFF^(0x7 << 2);
    // Then shift in our new ODR bits:
    temp |= ((mRate & 0x07) << 2);
    settings.mag.sampleRate = mRate & 0x07;
    // And write the new register value back into CTRL_REG5_XM:
    mWriteByte(CTRL_REG1_M, temp);
}

void LSM9DS1::calcgRes()
{
    switch (settings.gyro.scale)
    {
        case 245:
            gRes = SENSITIVITY_GYROSCOPE_245;
            break;
        case 500:
            gRes = SENSITIVITY_GYROSCOPE_500;
            break;
        case 2000:
            gRes = SENSITIVITY_GYROSCOPE_2000;
            break;
        default:
            break;
    }
}

void LSM9DS1::calcaRes()
{
    switch (settings.accel.scale)
    {
        case 2:
            aRes = SENSITIVITY_ACCELEROMETER_2;
            break;
        case 4:
            aRes = SENSITIVITY_ACCELEROMETER_4;
            break;
        case 8:
            aRes = SENSITIVITY_ACCELEROMETER_8;
            break;
        case 16:
            aRes = SENSITIVITY_ACCELEROMETER_16;
            break;
        default:
            break;
    }
}

void LSM9DS1::calcmRes()
{
    switch (settings.mag.scale)
    {
        case 4:
            mRes = SENSITIVITY_MAGNETOMETER_4;
            break;
        case 8:
            mRes = SENSITIVITY_MAGNETOMETER_8;
            break;
        case 12:
            mRes = SENSITIVITY_MAGNETOMETER_12;
            break;
        case 16:
            mRes = SENSITIVITY_MAGNETOMETER_16;
            break;
    }   
}

void LSM9DS1::configInt(interrupt_select itrpt, uint8_t generator,
        h_lactive activeLow, pp_od pushPull)
{
    // Write to INT1_CTRL or INT2_CTRL. [interupt] should already be one of
    // those two values.
    // [generator] should be an OR'd list of values from the interrupt_generators enum
    xgWriteByte(itrpt, generator);

    // Configure CTRL_REG8
    uint8_t temp;
    temp = xgReadByte(CTRL_REG8);

    if (activeLow) temp |= (1<<5);
    else temp &= ~(1<<5);

    if (pushPull) temp &= ~(1<<4);
    else temp |= (1<<4);

    xgWriteByte(CTRL_REG8, temp);
}

void LSM9DS1::configInactivity(uint8_t duration, uint8_t threshold, bool sleepOn)
{
    uint8_t temp = 0;

    temp = threshold & 0x7F;
    if (sleepOn) temp |= (1<<7);
    xgWriteByte(ACT_THS, temp);

    xgWriteByte(ACT_DUR, duration);
}

uint8_t LSM9DS1::getInactivity()
{
    uint8_t temp = xgReadByte(STATUS_REG_0);
    temp &= (0x10);
    return temp;
}

void LSM9DS1::configAccelInt(uint8_t generator, bool andInterrupts)
{
    // Use variables from accel_interrupt_generator, OR'd together to create
    // the [generator]value.
    uint8_t temp = generator;
    if (andInterrupts) temp |= 0x80;
    xgWriteByte(INT_GEN_CFG_XL, temp);
}

void LSM9DS1::configAccelThs(uint8_t threshold, lsm9ds1_axis axis, uint8_t duration, bool wait)
{
    // Write threshold value to INT_GEN_THS_?_XL.
    // axis will be 0, 1, or 2 (x, y, z respectively)
    xgWriteByte(INT_GEN_THS_X_XL + axis, threshold);

    // Write duration and wait to INT_GEN_DUR_XL
    uint8_t temp;
    temp = (duration & 0x7F);
    if (wait) temp |= 0x80;
    xgWriteByte(INT_GEN_DUR_XL, temp);
}

uint8_t LSM9DS1::getAccelIntSrc()
{
    uint8_t intSrc = xgReadByte(INT_GEN_SRC_XL);

    // Check if the IA_XL (interrupt active) bit is set
    if (intSrc & (1<<6))
    {
        return (intSrc & 0x3F);
    }

    return 0;
}

void LSM9DS1::configGyroInt(uint8_t generator, bool aoi, bool latch)
{
    // Use variables from accel_interrupt_generator, OR'd together to create
    // the [generator]value.
    uint8_t temp = generator;
    if (aoi) temp |= 0x80;
    if (latch) temp |= 0x40;
    xgWriteByte(INT_GEN_CFG_G, temp);
}

void LSM9DS1::configGyroThs(int16_t threshold, lsm9ds1_axis axis, uint8_t duration, bool wait)
{
    uint8_t buffer[2];
    buffer[0] = (threshold & 0x7F00) >> 8;
    buffer[1] = (threshold & 0x00FF);
    // Write threshold value to INT_GEN_THS_?H_G and  INT_GEN_THS_?L_G.
    // axis will be 0, 1, or 2 (x, y, z respectively)
    xgWriteByte(INT_GEN_THS_XH_G + (axis * 2), buffer[0]);
    xgWriteByte(INT_GEN_THS_XH_G + 1 + (axis * 2), buffer[1]);

    // Write duration and wait to INT_GEN_DUR_XL
    uint8_t temp;
    temp = (duration & 0x7F);
    if (wait) temp |= 0x80;
    xgWriteByte(INT_GEN_DUR_G, temp);
}

uint8_t LSM9DS1::getGyroIntSrc()
{
    uint8_t intSrc = xgReadByte(INT_GEN_SRC_G);

    // Check if the IA_G (interrupt active) bit is set
    if (intSrc & (1<<6))
    {
        return (intSrc & 0x3F);
    }

    return 0;
}

void LSM9DS1::configMagInt(uint8_t generator, h_lactive activeLow, bool latch)
{
    // Mask out non-generator bits (0-4)
    uint8_t config = (generator & 0xE0);    
    // IEA bit is 0 for active-low, 1 for active-high.
    if (activeLow == INT_ACTIVE_HIGH) config |= (1<<2);
    // IEL bit is 0 for latched, 1 for not-latched
    if (!latch) config |= (1<<1);
    // As long as we have at least 1 generator, enable the interrupt
    if (generator != 0) config |= (1<<0);

    mWriteByte(INT_CFG_M, config);
}

void LSM9DS1::configMagThs(uint16_t threshold)
{
    // Write high eight bits of [threshold] to INT_THS_H_M
    mWriteByte(INT_THS_H_M, uint8_t((threshold & 0x7F00) >> 8));
    // Write low eight bits of [threshold] to INT_THS_L_M
    mWriteByte(INT_THS_L_M, uint8_t(threshold & 0x00FF));
}

uint8_t LSM9DS1::getMagIntSrc()
{
    uint8_t intSrc = mReadByte(INT_SRC_M);

    // Check if the INT (interrupt active) bit is set
    if (intSrc & (1<<0))
    {
        return (intSrc & 0xFE);
    }

    return 0;
}

void LSM9DS1::sleepGyro(bool enable)
{
    uint8_t temp = xgReadByte(CTRL_REG9);
    if (enable) temp |= (1<<6);
    else temp &= ~(1<<6);
    xgWriteByte(CTRL_REG9, temp);
}

void LSM9DS1::enableFIFO(bool enable)
{
    uint8_t temp = xgReadByte(CTRL_REG9);
    if (enable) temp |= (1<<1);
    else temp &= ~(1<<1);
    xgWriteByte(CTRL_REG9, temp);
}

void LSM9DS1::setFIFO(fifoMode_type fifoMode, uint8_t fifoThs)
{
    // Limit threshold - 0x1F (31) is the maximum. If more than that was asked
    // limit it to the maximum.
    uint8_t threshold = fifoThs <= 0x1F ? fifoThs : 0x1F;
    xgWriteByte(FIFO_CTRL, ((fifoMode & 0x7) << 5) | (threshold & 0x1F));
}

uint8_t LSM9DS1::getFIFOSamples()
{
    return (xgReadByte(FIFO_SRC) & 0x3F);
}

void LSM9DS1::constrainScales()
{
    if ((settings.gyro.scale != 245) && (settings.gyro.scale != 500) && 
            (settings.gyro.scale != 2000))
    {
        settings.gyro.scale = 245;
    }

    if ((settings.accel.scale != 2) && (settings.accel.scale != 4) &&
            (settings.accel.scale != 8) && (settings.accel.scale != 16))
    {
        settings.accel.scale = 2;
    }

    if ((settings.mag.scale != 4) && (settings.mag.scale != 8) &&
            (settings.mag.scale != 12) && (settings.mag.scale != 16))
    {
        settings.mag.scale = 4;
    }
}

void LSM9DS1::xgWriteByte(uint8_t subAddress, uint8_t data)
{
    // Whether we're using I2C or SPI, write a byte using the
    // gyro-specific I2C address or SPI CS pin.
    if (settings.device.commInterface == IMU_MODE_I2C)
        I2CwriteByte(_xgAddress, subAddress, data);
    else if (settings.device.commInterface == IMU_MODE_SPI)
        SPIwriteByte(_xgAddress, subAddress, data);
}

void LSM9DS1::mWriteByte(uint8_t subAddress, uint8_t data)
{
    // Whether we're using I2C or SPI, write a byte using the
    // accelerometer-specific I2C address or SPI CS pin.
    if (settings.device.commInterface == IMU_MODE_I2C)
        return I2CwriteByte(_mAddress, subAddress, data);
    else if (settings.device.commInterface == IMU_MODE_SPI)
        return SPIwriteByte(_mAddress, subAddress, data);
}

uint8_t LSM9DS1::xgReadByte(uint8_t subAddress)
{
    // Whether we're using I2C or SPI, read a byte using the
    // gyro-specific I2C address or SPI CS pin.
    if (settings.device.commInterface == IMU_MODE_I2C)
        return I2CreadByte(_xgAddress, subAddress);
    else if (settings.device.commInterface == IMU_MODE_SPI)
        return SPIreadByte(_xgAddress, subAddress);
    return -1;
}

uint8_t LSM9DS1::xgReadBytes(uint8_t subAddress, uint8_t * dest, uint8_t count)
{
    // Whether we're using I2C or SPI, read multiple bytes using the
    // gyro-specific I2C address or SPI CS pin.
    if (settings.device.commInterface == IMU_MODE_I2C)
        return I2CreadBytes(_xgAddress, subAddress, dest, count);
    else if (settings.device.commInterface == IMU_MODE_SPI)
        return SPIreadBytes(_xgAddress, subAddress, dest, count);
    return -1;
}

uint8_t LSM9DS1::mReadByte(uint8_t subAddress)
{
    // Whether we're using I2C or SPI, read a byte using the
    // accelerometer-specific I2C address or SPI CS pin.
    if (settings.device.commInterface == IMU_MODE_I2C)
        return I2CreadByte(_mAddress, subAddress);
    else if (settings.device.commInterface == IMU_MODE_SPI)
        return SPIreadByte(_mAddress, subAddress);
    return -1;
}

uint8_t LSM9DS1::mReadBytes(uint8_t subAddress, uint8_t * dest, uint8_t count)
{
    // Whether we're using I2C or SPI, read multiple bytes using the
    // accelerometer-specific I2C address or SPI CS pin.
    if (settings.device.commInterface == IMU_MODE_I2C)
        return I2CreadBytes(_mAddress, subAddress, dest, count);
    else if (settings.device.commInterface == IMU_MODE_SPI)
        return SPIreadBytes(_mAddress, subAddress, dest, count);
    return -1;
}

// TODO: Implement SPI
// void LSM9DS1::initSPI()
// {
//     pinMode(_xgAddress, OUTPUT);
//     digitalWrite(_xgAddress, HIGH);
//     pinMode(_mAddress, OUTPUT);
//     digitalWrite(_mAddress, HIGH);
// 
//     SPI.begin();
//     // Maximum SPI frequency is 10MHz, could divide by 2 here:
//     SPI.setClockDivider(SPI_CLOCK_DIV2);
//     // Data is read and written MSb first.
//     SPI.setBitOrder(MSBFIRST);
//     // Data is captured on rising edge of clock (CPHA = 0)
//     // Base value of the clock is HIGH (CPOL = 1)
//     SPI.setDataMode(SPI_MODE0);
// }
// 
// void LSM9DS1::SPIwriteByte(uint8_t csPin, uint8_t subAddress, uint8_t data)
// {
//     digitalWrite(csPin, LOW); // Initiate communication
// 
//     // If write, bit 0 (MSB) should be 0
//     // If single write, bit 1 should be 0
//     SPI.transfer(subAddress & 0x3F); // Send Address
//     SPI.transfer(data); // Send data
// 
//     digitalWrite(csPin, HIGH); // Close communication
// }
// 
// uint8_t LSM9DS1::SPIreadByte(uint8_t csPin, uint8_t subAddress)
// {
//     uint8_t temp;
//     // Use the multiple read function to read 1 byte. 
//     // Value is returned to `temp`.
//     SPIreadBytes(csPin, subAddress, &temp, 1);
//     return temp;
// }
// 
// uint8_t LSM9DS1::SPIreadBytes(uint8_t csPin, uint8_t subAddress,
//         uint8_t * dest, uint8_t count)
// {
//     // To indicate a read, set bit 0 (msb) of first byte to 1
//     uint8_t rAddress = 0x80 | (subAddress & 0x3F);
//     // Mag SPI port is different. If we're reading multiple bytes, 
//     // set bit 1 to 1. The remaining six bytes are the address to be read
//     if ((csPin == _mAddress) && count > 1)
//         rAddress |= 0x40;
// 
//     digitalWrite(csPin, LOW); // Initiate communication
//     SPI.transfer(rAddress);
//     for (int i=0; i<count; i++)
//     {
//         dest[i] = SPI.transfer(0x00); // Read into destination array
//     }
//     digitalWrite(csPin, HIGH); // Close communication
// 
//     return count;
// }

void LSM9DS1::initI2C()
{
    // Initialize I2C library
    i2cInit();
    i2cSetMode(i2cREG1, I2C_MASTER);
}

void LSM9DS1::I2CwriteByte(uint8_t address, uint8_t subAddress, uint8_t data)
{
    // Initialize the Tx buffer
    i2cSetSlaveAdd(i2cREG1, address);
    i2cSetDirection(i2cREG1, I2C_TRANSMITTER);
    i2cSetStop(i2cREG1);
    i2cSetStart(i2cREG1);
    // Put slave register address in Tx buffer
    i2cSendByte(i2cREG1, subAddress);
    // Put data in Tx buffer
    i2cSendByte(i2cREG1, data);

    // Send the Tx buffer
    while(i2cIsBusBusy(i2cREG1));

    while(!i2cIsStopDetected(i2cREG1));
}

uint8_t LSM9DS1::I2CreadByte(uint8_t address, uint8_t subAddress)
{
    uint8_t data; // `data` will store the register data
    // Initialize the Tx buffer
    i2cSetSlaveAdd(i2cREG1, address);
    i2cSetDirection(i2cREG1, I2C_TRANSMITTER);
    i2cSetStop(i2cREG1);
    i2cSetStart(i2cREG1);
    // Put slave register address in Tx buffer
    i2cSendByte(i2cREG1, subAddress);
    // Send the Tx buffer, but send a restart to keep connection alive
    while(i2cIsBusBusy(i2cREG1));

    while(!i2cIsStopDetected(i2cREG1));

    i2cClearSCD(i2cREG1);

    // Read one byte from slave register address
    i2cSetDirection(i2cREG1, I2C_RECEIVER);
    i2cSetStop(i2cREG1);
    i2cSetStart(i2cREG1);
    data = i2cReceiveByte(i2cREG1);
    while(i2cIsBusBusy(i2cREG1));

    while(!i2cIsStopDetected(i2cREG1));
    i2cClearSCD(i2cREG1);

    // Return data read from slave register
    return data;
}

uint8_t LSM9DS1::I2CreadBytes(uint8_t address, uint8_t subAddress, uint8_t * dest, uint8_t count)
{
    // Initialize the Tx buffer
    i2cSetSlaveAdd(i2cREG1, address);
    i2cSetDirection(i2cREG1, I2C_TRANSMITTER);
    i2cSetStop(i2cREG1);
    i2cSetStart(i2cREG1);
    // Next send the register to be read. OR with 0x80 to indicate multi-read.
    i2cSendByte(i2cREG1, subAddress | 0x80);
    while(i2cIsBusBusy(i2cREG1));

    while(!i2cIsStopDetected(i2cREG1));

    i2cClearSCD(i2cREG1);

    i2cSetDirection(i2cREG1, I2C_RECEIVER);
    i2cSetStop(i2cREG1);
    i2cSetStart(i2cREG1);
    i2cReceive(i2cREG1, count, dest);
    while(i2cIsBusBusy(i2cREG1));

    while(!i2cIsStopDetected(i2cREG1));

    i2cClearSCD(i2cREG1);
    return 1;
}