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About mnjirjak
since
05-10-2019
08-08-2024
mnjirjak
Established Member
18
Posts
12
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4
Solutions
09-03-2019
09:47 PM
Hello, I've been playing with BMX160 shuttleboard and got a strage behaviour when testing magnetic distortion. My test consisted of positioning BMX160 shuttleboard in a relatively clean magnetic environment. After that, I acquired measurements from the magnetometer and printed it to the console. Then I used a permanent magnet to generate magnetic interference by putting said magnet really close to the shuttleboard. As expected, magnetometer output changed while the magnet was close to the PCB (that was actually great, since my goal was to detect change in magnetic field based on magnetometer magnitude). Later, I removed the magnet from magnetometer proximity and observed that the data remained distorted. I then unplugged and plugged back the power cable and uploaded my firmware again. There was no change. It looks as if the magnetic interference permanently changes magnetometer offsets. Also, the change in magnetometer output was dependent on the position of the permanent magnet. Each time I did a figure-of-eight motion and plotted the results. It looks to me that hard-iron parameters are affected. I use BMM150 API to fetch magnetometer data. I also tried fetching the data without RHALL compensation, but the problem persisted. Here are two images of the plot, each quazi-sphere represents one test. My expectation was that the magnetometer data will remain severely distorted when in close proximity to the magnet (which was true), but I also expected that the readings will converge back to previous values when the source of magnetic distortion was removed. Is this the expected behaviour or is there a problem somewhere? Kind regards, Marko Njirjak
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08-03-2019
02:28 PM
3 Likes
Hello, I think I figured it out. There were two things that were problematic: 1. BMM150 API returns the data in uT format, it does not return LSB, which is needed for the BSX library. This was solved by removing the division by 16 (since BMM150 resolution is 16 LSB/uT) in functions: compensate_x, compensate_y and compensate_z. static int16_t compensate_x(int16_t mag_data_x, uint16_t data_rhall, const struct bmm150_dev *dev)
{
...
retval = (retval + (((int16_t)dev->trim_data.dig_x1) * 8));// / 16;
...
}
static int16_t compensate_y(int16_t mag_data_y, uint16_t data_rhall, const struct bmm150_dev *dev)
{
...
retval = (retval + (((int16_t)dev->trim_data.dig_y1) * 8));// / 16;
...
}
static int16_t compensate_z(int16_t mag_data_z, uint16_t data_rhall, const struct bmm150_dev *dev)
{
...
//retval = retval / 16;
...
} This made the API return data in LSB format. 2. In BMM150 API, when performing the compensation for the z axis, unsigned and signed integers are compared. if (retval > BMM150_POSITIVE_SATURATION_Z) {
retval = BMM150_POSITIVE_SATURATION_Z;
} else ... Variable retval is of type int32_t, but BMM150_POSITIVE_SATURATION_Z is defined in bmm150_defs.h as UINT16_C(32767). I observed that the comparsion between retval = -916 and BMM150_POSITIVE_SATURATION_Z returns true, although it shouldn't. I believe this relates to comparing signed and unsigned integers. This was mitigated by defining BMM150_POSITIVE_SATURATION_Z as INT16_C(32767). Since the max value of INT16 is 32767, this should not be a problem. After this modification the former comparision between retval and BMM150_POSITIVE_SATURATION_Z returns false, as expected. Magnetometer calibration status now successfully reaches 3 and the offsets are non-zero. In addition, here's some information that might be useful: a) BMM150 magnetometer data is most easily fetched by using this function: bmm150_read_mag_data(&bmm150); where bmm150 is of type 'struct bmm150_dev'. b) After mag data fetch, the data (now in LSB values) is fed to the BSX library like this: libraryInput_ts.mag.data.x = bmm150.data.x;
libraryInput_ts.mag.data.y = bmm150.data.y;
libraryInput_ts.mag.data.z = bmm150.data.z; c) Here's a few samples of raw magnetometer data (fetched by the function mentioned in 'a') for testing purposes (the sensor was standing still): x: -124, y: -11, z: -984
x: -124, y: -11, z: -984
x: -124, y: -11, z: -984
x: -124, y: -11, z: -984
x: -148, y: -35, z: -927
x: -148, y: -35, z: -927
x: -148, y: -35, z: -927
x: -148, y: -35, z: -927
x: -130, y: -35, z: -896
x: -130, y: -35, z: -896
x: -130, y: -35, z: -896
x: -130, y: -35, z: -895
x: -130, y: -17, z: -921
x: -130, y: -17, z: -921
x: -130, y: -17, z: -921
x: -130, y: -17, z: -921
x: -142, y: -23, z: -921
x: -142, y: -23, z: -921
x: -142, y: -23, z: -921
x: -142, y: -23, z: -921
x: -118, y: -23, z: -921
x: -118, y: -23, z: -921 d) Here's a few samples of BSX Lib magnetometer data fetched by the function 'bsx_get_magcordata' for testing purposes (the sensor was standing still): x: -8.125000, y: -1.812500, z: -57.937500
x: -8.125000, y: -1.812500, z: -57.937500
x: -8.125000, y: -1.812500, z: -57.937500
x: -8.875000, y: -1.062500, z: -57.937500
x: -8.875000, y: -1.062500, z: -57.937500
x: -8.875000, y: -1.062500, z: -57.937500
x: -8.875000, y: -1.062500, z: -57.937500
x: -9.625000, y: -1.437500, z: -58.312500
x: -9.625000, y: -1.437500, z: -58.312500
x: -9.625000, y: -1.437500, z: -58.312500
x: -9.625000, y: -1.437500, z: -58.312500
x: -8.875000, y: -1.062500, z: -57.937500
x: -8.875000, y: -1.062500, z: -57.937500
x: -8.875000, y: -1.062500, z: -57.937500
x: -8.875000, y: -1.062500, z: -57.937500
x: -8.125000, y: -1.812500, z: -56.750000
x: -8.125000, y: -1.812500, z: -56.750000
x: -8.125000, y: -1.812500, z: -56.750000
x: -8.125000, y: -1.812500, z: -56.750000
x: -9.625000, y: -1.062500, z: -58.375000
x: -9.625000, y: -1.062500, z: -58.375000
x: -9.625000, y: -1.062500, z: -58.375000 Kind regards, Marko Njirjak
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08-02-2019
09:01 PM
1 Like
Dear coder, here are the settings that I use in my project. //Accelerometer
bmi.accel_cfg.power = BMI160_ACCEL_NORMAL_MODE;
bmi.accel_cfg.bw = BMI160_ACCEL_BW_NORMAL_AVG4;
bmi.accel_cfg.range = BMI160_ACCEL_RANGE_2G;
bmi.accel_cfg.odr = BMI160_ACCEL_ODR_100HZ;
//Gyroscope
bmi.gyro_cfg.odr = BMI160_GYRO_ODR_100HZ;
bmi.gyro_cfg.range = BMI160_GYRO_RANGE_500_DPS;
bmi.gyro_cfg.bw = BMI160_GYRO_BW_NORMAL_MODE;
bmi.gyro_cfg.power = BMI160_GYRO_NORMAL_MODE;
//Magnetometer
bmm.settings.preset_mode = BMM150_PRESETMODE_REGULAR;
APP_ERROR_CHECK(bmm150_set_presetmode(&bmm));
bmm.settings.pwr_mode = BMM150_FORCED_MODE;
APP_ERROR_CHECK(bmm150_set_op_mode(&bmm));
bmi.aux_cfg.aux_odr = 6; // I believe this is 25Hz, but an 8 works OK too (100Hz)
bmi160_config_aux_mode(&bmi); Kind regards, Marko Njirjak
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07-31-2019
09:59 PM
Dear coder, yes, I use Cortex M4F. Here are some sample codes: a) BSX Lib initialization initParam_t s_input;
s_input.accelspec = (BSX_U8 *)&bsxLibConfAcc;
s_input.magspec = (BSX_U8 *)&bsxLibConfMag;
s_input.gyrospec = (BSX_U8 *)&bsxLibConfGyro;
s_input.usecase = (BSX_U8 *)&bsxLibConf;
bsx_init(&s_input); b) Feeding data to BSX lib (this is done every 10ms) libraryInput_ts.acc.data.x = accel_data.x;
libraryInput_ts.acc.data.y = accel_data.y;
libraryInput_ts.acc.data.z = accel_data.z;
libraryInput_ts.acc.time_stamp = accel_data.sensortime*39; // BMX160 timestamp resolution is 39us, hence multiplying by 39
libraryInput_ts.gyro.data.x = gyro_data.x;
libraryInput_ts.gyro.data.y = gyro_data.y;
libraryInput_ts.gyro.data.z = gyro_data.z;
libraryInput_ts.gyro.time_stamp = gyro_data.sensortime*39;
libraryInput_ts.mag.data.x = bmm.data.x;
libraryInput_ts.mag.data.y = bmm.data.y;
libraryInput_ts.mag.data.z = bmm.data.z;
libraryInput_ts.mag.time_stamp = accel_data.sensortime*39;
bsx_dostep(&libraryInput_ts); c) Quaternion acquisition ts_dataquatf32 quaternion;
bsx_get_orientdata_quat(&quaternion); I do use BMI160+BMM150 sensor APIs, i.e. I'm not fetching registers directly. Kind regards, Marko Njirjak
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07-31-2019
09:41 PM
Hi shellywang, I checked everything you said. Here are the results: 1. Yes, I do use the API. Since BMX160 does not yet have a standalone API, I use BMI160 and BMM150 APIs (reference: this topic). 2. All communication with BMX160 is conducted through the APIs mentioned in the first answer. This is how I acquire data: bmi160_read_aux_data_auto_mode(mag_data, &bmi);
bmm150_aux_mag_data(mag_data, &bmm); where bmi and bmm are defined as: struct bmi160_dev bmi;
struct bmm150_dev bmm; 3. The magnetometer is configured as follows: bmm.settings.preset_mode = BMM150_PRESETMODE_REGULAR;
bmm150_set_presetmode(&bmm);
bmm.settings.pwr_mode = BMM150_FORCED_MODE;
bmm150_set_op_mode(&bmm);
bmi.aux_cfg.aux_odr = 6; // also tried an 8 here
bmi160_config_aux_mode(&bmi);
uint8_t aux_addr = 0x42;
bmi160_set_aux_auto_mode(&aux_addr, &bmi);
bmi160_set_sens_conf(&bmi); According to BMX160 datasheet, bmi.aux_cfg.aux_odr of 6 represents 25Hz ODR, while 8 represents 100Hz ODR. I tried both. 4. I logged raw data from the sensor and filtered data from BSX Lib. The sensor was standing still. - Raw data ACC -> x: -12 y: -309 z: 17340
GYRO -> x: 31 y: 10 z: -10
MAG -> x: -2 y: 15 z: 2047
ACC -> x: 3 y: -317 z: 17329
GYRO -> x: 34 y: 11 z: -9
MAG -> x: -2 y: 15 z: 2047
ACC -> x: 7 y: -327 z: 17344
GYRO -> x: 29 y: 12 z: -10
MAG -> x: -2 y: 15 z: 2047
ACC -> x: -37 y: -296 z: 17380
GYRO -> x: 28 y: 12 z: -8
MAG -> x: -2 y: 15 z: 2047
ACC -> x: -29 y: -286 z: 17381
GYRO -> x: 26 y: 10 z: -11
MAG -> x: -3 y: 15 z: 2047
ACC -> x: -21 y: -300 z: 17356
GYRO -> x: 30 y: 9 z: -6
MAG -> x: -3 y: 15 z: 2047
ACC -> x: 5 y: -283 z: 17326
GYRO -> x: 32 y: 8 z: -8
MAG -> x: -3 y: 15 z: 2047 - BSX Lib data ACC -> x: -0.005387 y: -0.184354 z: 10.382455
GYRO -> x: 0.000830 y: 0.000827 z: -0.000552
MAG -> x: -0.125000 y: 0.875000 z: 127.93750
ACC -> x: -0.011372 y: -0.176572 z: 10.369885
GYRO -> x: 0.001105 y: 0.001652 z: -0.000001
MAG -> x: -0.125000 y: 0.875000 z: 127.937500
ACC -> x: -0.017358 y: -0.175974 z: 10.382455
GYRO -> x: 0.001105 y: 0.001652 z: -0.000001
MAG -> x: -0.125000 y: 0.875000 z: 127.93750
ACC -> x: -0.005387 y: -0.185551 z: 10.375872
GYRO -> x: 0.000004 y: 0.002203 z: -0.000001
MAG -> x: -0.125000 y: 0.875000 z: 127.937500
ACC -> x: 0.004788 y: -0.188543 z: 10.370484
GYRO -> x: 0.000004 y: 0.002203 z: -0.000001
MAG -> x: -0.187500 y: 0.937500 z: 127.937500
ACC -> x: 0.004788 y: -0.178368 z: 10.380660
GYRO -> x: 0.000830 y: 0.000827 z: -0.001377
MAG -> x: -0.187500 y: 0.937500 z: 127.937500
ACC -> x: 0.004190 y: -0.173580 z: 10.366294
GYRO -> x: 0.000830 y: 0.000827 z: -0.001377
MAG -> x: -0.187500 y: 0.937500 z: 127.937500 In addition I will post all relevant code connected with BMX160 configuration and data acquistion. a) Declaration struct bmi160_dev bmi;
struct bmm150_dev bmm;
struct bmi160_sensor_data accel_data;
struct bmi160_sensor_data gyro_data;
uint8_t mag_data[8] = {0};
ts_dataxyz accdata, magdata, gyrodata;
libraryinput_t libraryInput_ts; b) Aux interface helper functions int8_t bmm150_aux_read(uint8_t id, uint8_t reg_addr, uint8_t *reg_data, uint16_t len) {
(void) id;
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;
return bmi160_aux_write(reg_addr, reg_data, len, &bmi);
} c) Sensor intialization bmi.id = 0;
bmi.interface = BMI160_SPI_INTF;
bmi.read = spi_read_transfer;
bmi.write = spi_write_transfer;
bmi.delay_ms = delay;
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 = delay;
bmi160_init(&bmi);
bmi.aux_cfg.aux_sensor_enable = BMI160_ENABLE;
bmi.aux_cfg.aux_i2c_addr = bmm.dev_id;
bmi.aux_cfg.manual_enable = BMI160_ENABLE;
bmi160_aux_init(&bmi);
bmm150_init(&bmm); where spi_read_transfer, spi_write_transfer and delay are master chip specific functions related to SPI communication. d) Turning on sensors //Accelerometer
bmi.accel_cfg.power = BMI160_ACCEL_NORMAL_MODE;
bmi.accel_cfg.bw = BMI160_ACCEL_BW_NORMAL_AVG4;
bmi.accel_cfg.range = BMI160_ACCEL_RANGE_2G;
bmi.accel_cfg.odr = BMI160_ACCEL_ODR_100HZ;
//Gyroscope
bmi.gyro_cfg.odr = BMI160_GYRO_ODR_100HZ;
bmi.gyro_cfg.range = BMI160_GYRO_RANGE_500_DPS;
bmi.gyro_cfg.bw = BMI160_GYRO_BW_NORMAL_MODE;
bmi.gyro_cfg.power = BMI160_GYRO_NORMAL_MODE;
//Magnetometer
bmm.settings.preset_mode = BMM150_PRESETMODE_REGULAR;
bmm150_set_presetmode(&bmm);
bmm.settings.pwr_mode = BMM150_FORCED_MODE;
bmm150_set_op_mode(&bmm);
bmi.aux_cfg.aux_odr = 6;
bmi160_config_aux_mode(&bmi);
uint8_t aux_addr = 0x42;
bmi160_set_aux_auto_mode(&aux_addr, &bmi);
bmi160_set_sens_conf(&bmi); e) Sensor data acquisition bmi160_read_aux_data_auto_mode(mag_data, &bmi);
bmm150_aux_mag_data(mag_data, &bmm);
bmi160_get_sensor_data((BMI160_TIME_SEL | BMI160_ACCEL_SEL | BMI160_GYRO_SEL), &accel_data, &gyro_data, &bmi); f) BSX Lib initialization initParam_t s_input;
s_input.accelspec = (BSX_U8 *)&bsxLibConfAcc;
s_input.magspec = (BSX_U8 *)&bsxLibConfMag;
s_input.gyrospec = (BSX_U8 *)&bsxLibConfGyro;
s_input.usecase = (BSX_U8 *)&bsxLibConf;
bsx_init(&s_input); where bsxLibConfAcc, bsxLibConfGyro, etc. are BSX_U8 arrays required for configuration (as BSX Lib documentation states). g) Turning on BSX Lib ts_workingModes s_workingmodes;
s_workingmodes.opMode = BSX_WORKINGMODE_NDOF_GEORV_FMC_OFF;
bsx_set_workingmode(&s_workingmodes); h) Providing data to BSX Lib libraryInput_ts.acc.data.x = accel_data.x;
libraryInput_ts.acc.data.y = accel_data.y;
libraryInput_ts.acc.data.z = accel_data.z;
libraryInput_ts.acc.time_stamp = accel_data.sensortime*39;
libraryInput_ts.gyro.data.x = gyro_data.x;
libraryInput_ts.gyro.data.y = gyro_data.y;
libraryInput_ts.gyro.data.z = gyro_data.z;
libraryInput_ts.gyro.time_stamp = gyro_data.sensortime*39;
libraryInput_ts.mag.data.x = bmm.data.x;
libraryInput_ts.mag.data.y = bmm.data.y;
libraryInput_ts.mag.data.z = bmm.data.z;
libraryInput_ts.mag.time_stamp = accel_data.sensortime*39; // accelerometer timestamp is used here, could that be the problem?
bsx_dostep(&libraryInput_ts); Multiplying timestamps by 39 is conducted because BMX160 datasheet states that timestamp resolutions is 39us and BSX Lib documentation says that timestamps should be in us format. i) BSX Lib data acquistion ts_dataxyzf32 acc, gyro, mag;
bsx_get_acccordata(&acc);
bsx_get_gyrocordata_rps(&gyro);
bsx_get_magcordata(&mag);
printf("ACC -> x: %f y: %f z: %f \n", acc.x, acc.y, acc.z);
printf("GYRO -> x: %f y: %f z: %f \n", gyro.x, gyro.y, gyro.z);
printf("MAG -> x: %f y: %f z: %f \n", mag.x, mag.y, mag.z); I used this as a reference when configuring the auxiliary sensor (magnetometer). Kind regards, Marko Njirjak
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