How to use an auxiliary sensor or magnetometer with the BMI160.

How to use an auxiliary sensor or magnetometer with the BMI160.

This example configures the accelerometer, gyroscope and magnetometer to measure at 100Hz and the data is read out over BMI160's FIFO every 100ms.

#include "bmi160.h"
#include "bmm150.h"

/* Macros for frames to be read */

#define ACC_FRAMES	10 /* 10 Frames are available every 100ms @ 100Hz */
#define GYR_FRAMES	10
#define MAG_FRAMES	10
/* 10 frames containing a 1 byte header, 6 bytes of accelerometer, 
 * 6 bytes of gyroscope and 8 bytes of magnetometer data. This results in
 * 21 bytes per frame. Additional 40 bytes in case sensor time readout is enabled */
#define FIFO_SIZE	250 

/* Variable declarations */ 

struct bmi160_dev bmi;
struct bmm150_dev bmm;

uint8_t fifo_buff[FIFO_SIZE];
struct bmi160_fifo_frame fifo_frame;
struct bmi160_aux_data aux_data[MAG_FRAMES];
struct bmm150_mag_data mag_data[MAG_FRAMES];
struct bmi160_sensor_data gyro_data[GYR_FRAMES], accel_data[ACC_FRAMES];

int8_t rslt;

/* Auxiliary function declarations */
int8_t bmm150_aux_read(uint8_t id, uint8_t reg_addr, uint8_t *aux_data, uint16_t len);
int8_t bmm150_aux_write(uint8_t id, uint8_t reg_addr, uint8_t *aux_data, uint16_t len);

void main(void)
{
    /* Initialize your host interface to the BMI160 */

    /* This example uses I2C as the host interface */
    bmi.id = BMI160_I2C_ADDR;
    bmi.read = user_i2c_read;
    bmi.write = user_i2c_write;
    bmi.delay_ms = user_delay_ms;
    bmi.interface = BMI160_I2C_INTF;

    /* The BMM150 API tunnels through the auxiliary interface of the BMI160 */
    /* Check the pins of the BMM150 for the right I2C address */
    bmm.dev_id = BMM150_DEFAULT_I2C_ADDRESS;
    bmm.intf = BMM150_I2C_INTF;
    bmm.read = bmm150_aux_read;
    bmm.write = bmm150_aux_write;
    bmm.delay_ms = user_delay_ms;

    rslt = bmi160_init(&bmi);
    /* Check rslt for any error codes */

    /* Configure the BMI160's auxiliary interface for the BMM150 */
    bmi.aux_cfg.aux_sensor_enable = BMI160_ENABLE;
    bmi.aux_cfg.aux_i2c_addr = bmm.dev_id;
    bmi.aux_cfg.manual_enable = BMI160_ENABLE; /* Manual mode */
    bmi.aux_cfg.aux_rd_burst_len = BMI160_AUX_READ_LEN_3; /* 8 bytes */

    rslt = bmi160_aux_init(&bmi);
    /* Check rslt for any error codes */

    rslt = bmm150_init(&bmm);
    /* Check rslt for any error codes */

    /* Configure the accelerometer */
    bmi.accel_cfg.odr = BMI160_ACCEL_ODR_100HZ;
    bmi.accel_cfg.range = BMI160_ACCEL_RANGE_2G;
    bmi.accel_cfg.bw = BMI160_ACCEL_BW_NORMAL_AVG4;
    bmi.accel_cfg.power = BMI160_ACCEL_NORMAL_MODE;

    /* Configure the gyroscope */
    bmi.gyro_cfg.odr = BMI160_GYRO_ODR_100HZ;
    bmi.gyro_cfg.range = BMI160_GYRO_RANGE_2000_DPS;
    bmi.gyro_cfg.bw = BMI160_GYRO_BW_NORMAL_MODE;
    bmi.gyro_cfg.power = BMI160_GYRO_NORMAL_MODE;

    rslt = bmi160_set_sens_conf(&bmi);
    /* Check rslt for any error codes */

    /* Configure the magnetometer. The regular preset supports up to 100Hz in Forced mode */
    bmm.settings.preset_mode = BMM150_PRESETMODE_REGULAR;
    rslt = bmm150_set_presetmode(&bmm);
    /* Check rslt for any error codes */

    /* It is important that the last write to the BMM150 sets the forced mode.
     * This is because the BMI160 writes the last value to the auxiliary sensor 
     * after every read */
    bmm.settings.pwr_mode = BMM150_FORCED_MODE;
    rslt = bmm150_set_op_mode(&bmm);
    /* Check rslt for any error codes */

    uint8_t bmm150_data_start = BMM150_DATA_X_LSB;
    bmi.aux_cfg.aux_odr = BMI160_AUX_ODR_100HZ;
    rslt = bmi160_set_aux_auto_mode(&bmm150_data_start, &bmi);
    /* Check rslt for any error codes */

    /* Link the FIFO memory location */
    fifo_frame.data = fifo_buff;
    fifo_frame.length = FIFO_SIZE;
    bmi.fifo = &fifo_frame;

    /* Clear all existing FIFO configurations */
    rslt = bmi160_set_fifo_config(BMI160_FIFO_CONFIG_1_MASK , BMI160_DISABLE, &bmi);
    /* Check rslt for any error codes */

    uint8_t fifo_config = BMI160_FIFO_HEADER | BMI160_FIFO_AUX |  BMI160_FIFO_ACCEL | BMI160_FIFO_GYRO;
    rslt = bmi160_set_fifo_config(fifo_config, BMI160_ENABLE, &bmi);
    /* Check rslt for any error codes */

    while(rslt != 0) {
        /* Wait for 100ms for the FIFO to fill */
        user_delay_ms(100);

        /* It is VERY important to reload the length of the FIFO memory as after the 
         * call to bmi160_get_fifo_data(), the bmi.fifo->length contains the
         * number of bytes read from the FIFO */
        bmi.fifo->length = FIFO_SIZE;
        rslt = bmi160_get_fifo_data(&bmi);
        /* Check rslt for any error codes */

        uint8_t aux_inst = MAG_FRAMES, gyr_inst = GYR_FRAMES, acc_inst = ACC_FRAMES;
        rslt = bmi160_extract_aux(aux_data, &aux_inst, &bmi);
        /* Check rslt for any error codes */
        rslt = bmi160_extract_gyro(gyro_data, &gyr_inst, &bmi);
        /* Check rslt for any error codes */
        rslt = bmi160_extract_accel(accel_data, &acc_inst, &bmi);
        /* Check rslt for any error codes */

        for (uint8_t i = 0; i < aux_inst; i++) {
            rslt = bmm150_aux_mag_data(&aux_data[i].data[0], &bmm);
            /* Check rslt for any error codes */
            /* Copy the compensated magnetometer data */
            mag_data[i] = bmm.data;
        }
    }
}

/* Auxiliary function definitions */
int8_t bmm150_aux_read(uint8_t id, uint8_t reg_addr, uint8_t *reg_data, uint16_t len) {

    (void) id; /* id is unused here */

    return bmi160_aux_read(reg_addr, reg_data, len, &bmi);
}

int8_t bmm150_aux_write(uint8_t id, uint8_t reg_addr, uint8_t *reg_data, uint16_t len) {

    (void) id; /* id is unused here */

    return bmi160_aux_write(reg_addr, reg_data, len, &bmi);
}