2 * Copyright (C) 2014 Intel Corporation.
8 #include <hardware/sensors.h>
11 #include <utils/Log.h>
12 #include "calibration.h"
13 #include "matrix-ops.h"
14 #include "description.h"
17 #define MAX_RAW_DATA_COUNT 2000
18 #define RAW_DATA_FULL_PATH "/data/raw_compass_data_full_%d.txt"
19 #define RAW_DATA_SELECTED_PATH "/data/raw_compass_data_selected_%d.txt"
20 static FILE *raw_data = NULL;
21 static FILE *raw_data_selected = NULL;
22 static int raw_data_count = 0;
27 #define COMPASS_CALIBRATION_PATH "/data/compass.conf"
28 #define EPSILON 0.000000001
30 #define MAGNETIC_LOW 960 /* 31 micro tesla squared */
33 /* We'll have multiple calibration levels
34 * so that we can provide an estimation as fast as possible
36 static const float min_diffs[CAL_STEPS] = {0.2, 0.25, 0.4, 0.6, 1.0 };
37 static const float max_sqr_errs[CAL_STEPS] = {10.0, 10.0, 8.0, 5.0, 3.5 };
38 static const unsigned int lookback_counts[CAL_STEPS] = {2, 3, 4, 5, 6 };
41 /* Reset calibration algorithm */
42 static void reset_sample (compass_cal_t* data)
45 data->sample_count = 0;
46 for (i = 0; i < MAGN_DS_SIZE; i++)
48 data->sample[i][j] = 0;
50 data->average[0] = data->average[1] = data->average[2] = 0;
54 static double calc_square_err (compass_cal_t* data)
57 double raw[3][1], result[3][1], mat_diff[3][1];
59 float stdev[3] = {0,0,0};
61 for (i = 0; i < MAGN_DS_SIZE; i++) {
62 raw[0][0] = data->sample[i][0];
63 raw[1][0] = data->sample[i][1];
64 raw[2][0] = data->sample[i][2];
66 stdev[0] += (raw[0][0] - data->average[0]) * (raw[0][0] - data->average[0]);
67 stdev[1] += (raw[1][0] - data->average[1]) * (raw[1][0] - data->average[1]);
68 stdev[2] += (raw[2][0] - data->average[2]) * (raw[2][0] - data->average[2]);
70 substract (3, 1, raw, data->offset, mat_diff);
71 multiply(3, 3, 1, data->w_invert, mat_diff, result);
73 double diff = sqrt(result[0][0] * result[0][0] + result[1][0] * result[1][0]
74 + result[2][0] * result[2][0]) - data->bfield;
79 stdev[0] = sqrt(stdev[0] / MAGN_DS_SIZE);
80 stdev[1] = sqrt(stdev[1] / MAGN_DS_SIZE);
81 stdev[2] = sqrt(stdev[2] / MAGN_DS_SIZE);
84 * A sanity check - if we have too little variation for an axis
85 * it's best to reject the calibration than risking a wrong calibration.
87 if (stdev[0] <= 1 || stdev[1] <= 1 || stdev[2] <= 1)
88 return max_sqr_errs[0];
95 /* Given an real symmetric 3x3 matrix A, compute the eigenvalues */
96 static void compute_eigenvalues (double mat[3][3], double* eig1, double* eig2, double* eig3)
98 double p = mat[0][1] * mat[0][1] + mat[0][2] * mat[0][2] + mat[1][2] * mat[1][2];
107 double q = (mat[0][0] + mat[1][1] + mat[2][2]) / 3;
108 double temp1 = mat[0][0] - q;
109 double temp2 = mat[1][1] - q;
110 double temp3 = mat[2][2] - q;
112 p = temp1 * temp1 + temp2 * temp2 + temp3 * temp3 + 2 * p;
116 assign(3, 3, mat, mat2);
120 multiply_scalar_inplace(3, 3, mat2, 1/p);
122 double r = (mat2[0][0] * mat2[1][1] * mat2[2][2] + mat2[0][1] * mat2[1][2] * mat2[2][0]
123 + mat2[0][2] * mat2[1][0] * mat2[2][1] - mat2[0][2] * mat2[1][1] * mat2[2][0]
124 - mat2[0][0] * mat2[1][2] * mat2[2][1] - mat2[0][1] * mat2[1][0] * mat2[2][2]) / 2;
134 *eig3 = q + 2 * p * cos(phi);
135 *eig1 = q + 2 * p * cos(phi + 2 * M_PI / 3);
136 *eig2 = 3 * q - *eig1 - *eig3;
140 static void calc_evector (double mat[3][3], double eig, double vec[3][1])
144 assign(3, 3, mat, h);
155 assign(2, 2, x_tmp, x);
157 double temp1 = x[0][0] * (-h[1][0]) + x[0][1] * (-h[2][0]);
158 double temp2 = x[1][0] * (-h[1][0]) + x[1][1] * (-h[2][0]);
159 double norm = sqrt(1 + temp1 * temp1 + temp2 * temp2);
161 vec[0][0] = 1.0 / norm;
162 vec[1][0] = temp1 / norm;
163 vec[2][0] = temp2 / norm;
167 static int ellipsoid_fit (mat_input_t m, double offset[3][1], double w_invert[3][3], double* bfield)
170 double h[MAGN_DS_SIZE][9];
171 double w[MAGN_DS_SIZE][1];
172 double h_trans[9][MAGN_DS_SIZE];
173 double p_temp1[9][9];
174 double p_temp2[9][MAGN_DS_SIZE];
175 double temp1[3][3], temp[3][3];
176 double temp1_inv[3][3];
180 double a[3][3], sqrt_evals[3][3], evecs[3][3], evecs_trans[3][3];
181 double evec1[3][1], evec2[3][1], evec3[3][1];
183 for (i = 0; i < MAGN_DS_SIZE; i++) {
184 w[i][0] = m[i][0] * m[i][0];
188 h[i][3] = -1 * m[i][0] * m[i][1];
189 h[i][4] = -1 * m[i][0] * m[i][2];
190 h[i][5] = -1 * m[i][1] * m[i][2];
191 h[i][6] = -1 * m[i][1] * m[i][1];
192 h[i][7] = -1 * m[i][2] * m[i][2];
195 transpose (MAGN_DS_SIZE, 9, h, h_trans);
196 multiply (9, MAGN_DS_SIZE, 9, h_trans, h, result);
197 invert (9, result, p_temp1);
198 multiply (9, 9, MAGN_DS_SIZE, p_temp1, h_trans, p_temp2);
199 multiply (9, MAGN_DS_SIZE, 1, p_temp2, w, p);
202 temp1[0][1] = p[3][0];
203 temp1[0][2] = p[4][0];
204 temp1[1][0] = p[3][0];
205 temp1[1][1] = 2 * p[6][0];
206 temp1[1][2] = p[5][0];
207 temp1[2][0] = p[4][0];
208 temp1[2][1] = p[5][0];
209 temp1[2][2] = 2 * p[7][0];
211 temp2[0][0] = p[0][0];
212 temp2[1][0] = p[1][0];
213 temp2[2][0] = p[2][0];
215 invert(3, temp1, temp1_inv);
216 multiply(3, 3, 1, temp1_inv, temp2, offset);
217 double off_x = offset[0][0];
218 double off_y = offset[1][0];
219 double off_z = offset[2][0];
222 a[0][0] = 1.0 / (p[8][0] + off_x * off_x + p[6][0] * off_y * off_y
223 + p[7][0] * off_z * off_z + p[3][0] * off_x * off_y
224 + p[4][0] * off_x * off_z + p[5][0] * off_y * off_z);
226 a[0][1] = p[3][0] * a[0][0] / 2;
227 a[0][2] = p[4][0] * a[0][0] / 2;
228 a[1][2] = p[5][0] * a[0][0] / 2;
229 a[1][1] = p[6][0] * a[0][0];
230 a[2][2] = p[7][0] * a[0][0];
235 double eig1 = 0, eig2 = 0, eig3 = 0;
236 compute_eigenvalues(a, &eig1, &eig2, &eig3);
238 if (eig1 <=0 || eig2 <= 0 || eig3 <= 0)
241 sqrt_evals[0][0] = sqrt(eig1);
242 sqrt_evals[1][0] = 0;
243 sqrt_evals[2][0] = 0;
244 sqrt_evals[0][1] = 0;
245 sqrt_evals[1][1] = sqrt(eig2);
246 sqrt_evals[2][1] = 0;
247 sqrt_evals[0][2] = 0;
248 sqrt_evals[1][2] = 0;
249 sqrt_evals[2][2] = sqrt(eig3);
251 calc_evector(a, eig1, evec1);
252 calc_evector(a, eig2, evec2);
253 calc_evector(a, eig3, evec3);
255 evecs[0][0] = evec1[0][0];
256 evecs[1][0] = evec1[1][0];
257 evecs[2][0] = evec1[2][0];
258 evecs[0][1] = evec2[0][0];
259 evecs[1][1] = evec2[1][0];
260 evecs[2][1] = evec2[2][0];
261 evecs[0][2] = evec3[0][0];
262 evecs[1][2] = evec3[1][0];
263 evecs[2][2] = evec3[2][0];
265 multiply (3, 3, 3, evecs, sqrt_evals, temp1);
266 transpose(3, 3, evecs, evecs_trans);
267 multiply (3, 3, 3, temp1, evecs_trans, temp);
268 transpose (3, 3, temp, w_invert);
269 *bfield = pow(sqrt(1/eig1) * sqrt(1/eig2) * sqrt(1/eig3), 1.0/3.0);
274 multiply_scalar_inplace(3, 3, w_invert, *bfield);
280 static void compass_cal_init (FILE* data_file, sensor_info_t* info)
288 if (raw_data_selected) {
289 fclose(raw_data_selected);
290 raw_data_selected = NULL;
294 snprintf(path, 64, RAW_DATA_FULL_PATH, file_no);
295 raw_data = fopen(path,"w+");
296 snprintf(path, 64, RAW_DATA_SELECTED_PATH, file_no);
297 raw_data_selected = fopen(path,"w+");
302 compass_cal_t* cal_data = (compass_cal_t*) info->cal_data;
303 int cal_steps = (info->max_cal_level && info->max_cal_level <= CAL_STEPS) ?
304 info->max_cal_level : CAL_STEPS;
305 if (cal_data == NULL)
309 reset_sample(cal_data);
311 if (!info->cal_level && data_file != NULL) {
312 int ret = fscanf(data_file, "%d %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf",
313 &info->cal_level, &cal_data->offset[0][0], &cal_data->offset[1][0], &cal_data->offset[2][0],
314 &cal_data->w_invert[0][0], &cal_data->w_invert[0][1], &cal_data->w_invert[0][2],
315 &cal_data->w_invert[1][0], &cal_data->w_invert[1][1], &cal_data->w_invert[1][2],
316 &cal_data->w_invert[2][0], &cal_data->w_invert[2][1], &cal_data->w_invert[2][2],
319 if (ret != data_count || info->cal_level >= cal_steps) {
324 if (info->cal_level) {
325 ALOGV("CompassCalibration: load old data, caldata: %f %f %f %f %f %f %f %f %f %f %f %f %f",
326 cal_data->offset[0][0], cal_data->offset[1][0], cal_data->offset[2][0],
327 cal_data->w_invert[0][0], cal_data->w_invert[0][1], cal_data->w_invert[0][2], cal_data->w_invert[1][0],
328 cal_data->w_invert[1][1], cal_data->w_invert[1][2], cal_data->w_invert[2][0], cal_data->w_invert[2][1],
329 cal_data->w_invert[2][2], cal_data->bfield);
332 cal_data->offset[0][0] = 0;
333 cal_data->offset[1][0] = 0;
334 cal_data->offset[2][0] = 0;
336 cal_data->w_invert[0][0] = 1;
337 cal_data->w_invert[1][0] = 0;
338 cal_data->w_invert[2][0] = 0;
339 cal_data->w_invert[0][1] = 0;
340 cal_data->w_invert[1][1] = 1;
341 cal_data->w_invert[2][1] = 0;
342 cal_data->w_invert[0][2] = 0;
343 cal_data->w_invert[1][2] = 0;
344 cal_data->w_invert[2][2] = 1;
346 cal_data->bfield = 0;
351 static void compass_store_result (FILE* data_file, sensor_info_t* info)
353 compass_cal_t* cal_data = (compass_cal_t*) info->cal_data;
355 if (data_file == NULL || cal_data == NULL)
358 int ret = fprintf(data_file, "%d %f %f %f %f %f %f %f %f %f %f %f %f %f\n",
359 info->cal_level, cal_data->offset[0][0], cal_data->offset[1][0], cal_data->offset[2][0],
360 cal_data->w_invert[0][0], cal_data->w_invert[0][1], cal_data->w_invert[0][2],
361 cal_data->w_invert[1][0], cal_data->w_invert[1][1], cal_data->w_invert[1][2],
362 cal_data->w_invert[2][0], cal_data->w_invert[2][1], cal_data->w_invert[2][2],
366 ALOGE ("Compass calibration - store data failed!");
370 static int compass_collect (sensors_event_t* event, sensor_info_t* info)
372 float data[3] = {event->magnetic.x, event->magnetic.y, event->magnetic.z};
373 unsigned int index,j;
374 unsigned int lookback_count;
377 compass_cal_t* cal_data = (compass_cal_t*) info->cal_data;
379 if (cal_data == NULL)
382 /* Discard the point if not valid */
383 if (data[0] == 0 || data[1] == 0 || data[2] == 0)
387 if (raw_data && raw_data_count < MAX_RAW_DATA_COUNT) {
388 fprintf(raw_data, "%f %f %f\n", (double)data[0], (double)data[1],
393 if (raw_data && raw_data_count >= MAX_RAW_DATA_COUNT) {
399 lookback_count = lookback_counts[info->cal_level];
400 min_diff = min_diffs[info->cal_level];
403 * For the current point to be accepted, each x/y/z value must be different
404 * enough to the last several collected points.
406 if (cal_data->sample_count > 0 && cal_data->sample_count < MAGN_DS_SIZE) {
407 unsigned int lookback = lookback_count < cal_data->sample_count ? lookback_count : cal_data->sample_count;
408 for (index = 0; index < lookback; index++)
409 for (j = 0; j < 3; j++)
410 if (fabsf(data[j] - cal_data->sample[cal_data->sample_count-1-index][j]) < min_diff) {
411 ALOGV("CompassCalibration:point reject: [%f,%f,%f], selected_count=%d",
412 data[0], data[1], data[2], cal_data->sample_count);
417 if (cal_data->sample_count < MAGN_DS_SIZE) {
418 memcpy(cal_data->sample[cal_data->sample_count], data, sizeof(float) * 3);
419 cal_data->sample_count++;
420 cal_data->average[0] += data[0];
421 cal_data->average[1] += data[1];
422 cal_data->average[2] += data[2];
423 ALOGV("CompassCalibration:point collected [%f,%f,%f], selected_count=%d",
424 (double)data[0], (double)data[1], (double)data[2], cal_data->sample_count);
426 if (raw_data_selected) {
427 fprintf(raw_data_selected, "%f %f %f\n", (double)data[0], (double)data[1], (double)data[2]);
435 static void scale_event (sensors_event_t* event)
438 float sanity_norm = 0;
441 sqr_norm = (event->magnetic.x * event->magnetic.x +
442 event->magnetic.y * event->magnetic.y +
443 event->magnetic.z * event->magnetic.z);
445 if (sqr_norm < MAGNETIC_LOW)
446 sanity_norm = MAGNETIC_LOW;
448 if (sanity_norm && sqr_norm) {
449 scale = sanity_norm / sqr_norm;
451 event->magnetic.x = event->magnetic.x * scale;
452 event->magnetic.y = event->magnetic.y * scale;
453 event->magnetic.z = event->magnetic.z * scale;
458 static void compass_compute_cal (sensors_event_t* event, sensor_info_t* info)
460 compass_cal_t* cal_data = (compass_cal_t*) info->cal_data;
461 double result[3][1], raw[3][1], diff[3][1];
463 if (!info->cal_level || cal_data == NULL)
466 raw[0][0] = event->magnetic.x;
467 raw[1][0] = event->magnetic.y;
468 raw[2][0] = event->magnetic.z;
470 substract(3, 1, raw, cal_data->offset, diff);
471 multiply (3, 3, 1, cal_data->w_invert, diff, result);
473 event->magnetic.x = event->data[0] = result[0][0];
474 event->magnetic.y = event->data[1] = result[1][0];
475 event->magnetic.z = event->data[2] = result[2][0];
481 static int compass_ready (sensor_info_t* info)
487 compass_cal_t* cal_data = (compass_cal_t*) info->cal_data;
488 compass_cal_t new_cal_data;
491 * Some sensors take unrealistically long to calibrate at higher levels.
492 * We'll use a max_cal_level if we have such a property setup, or go with
493 * the default settings if not.
495 int cal_steps = (info->max_cal_level && info->max_cal_level <= CAL_STEPS) ?
496 info->max_cal_level : CAL_STEPS;
498 if (cal_data->sample_count < MAGN_DS_SIZE)
499 return info->cal_level;
501 max_sqr_err = max_sqr_errs[info->cal_level];
503 /* Enough points have been collected, do the ellipsoid calibration */
505 /* Compute average per axis */
506 cal_data->average[0] /= MAGN_DS_SIZE;
507 cal_data->average[1] /= MAGN_DS_SIZE;
508 cal_data->average[2] /= MAGN_DS_SIZE;
510 for (i = 0; i < MAGN_DS_SIZE; i++) {
511 mat[i][0] = cal_data->sample[i][0];
512 mat[i][1] = cal_data->sample[i][1];
513 mat[i][2] = cal_data->sample[i][2];
516 /* Check if result is good. The sample data must remain the same */
517 new_cal_data = *cal_data;
519 if (ellipsoid_fit(mat, new_cal_data.offset, new_cal_data.w_invert, &new_cal_data.bfield)) {
520 double new_err = calc_square_err (&new_cal_data);
521 ALOGI("new err is %f, max sqr err id %f", new_err,max_sqr_err);
522 if (new_err < max_sqr_err) {
523 double err = calc_square_err(cal_data);
525 /* New cal data is better, so we switch to the new */
526 memcpy(cal_data->offset, new_cal_data.offset, sizeof(cal_data->offset));
527 memcpy(cal_data->w_invert, new_cal_data.w_invert, sizeof(cal_data->w_invert));
528 cal_data->bfield = new_cal_data.bfield;
529 if (info->cal_level < (cal_steps - 1))
531 ALOGV("CompassCalibration: ready check success, caldata: %f %f %f %f %f %f %f %f %f %f %f %f %f, err %f",
532 cal_data->offset[0][0], cal_data->offset[1][0], cal_data->offset[2][0], cal_data->w_invert[0][0],
533 cal_data->w_invert[0][1], cal_data->w_invert[0][2], cal_data->w_invert[1][0], cal_data->w_invert[1][1],
534 cal_data->w_invert[1][2], cal_data->w_invert[2][0], cal_data->w_invert[2][1], cal_data->w_invert[2][2],
535 cal_data->bfield, new_err);
539 reset_sample(cal_data);
540 return info->cal_level;
544 void calibrate_compass (sensors_event_t* event, sensor_info_t* info)
548 /* Calibration is continuous */
549 compass_collect (event, info);
551 cal_level = compass_ready(info);
556 event->magnetic.status = SENSOR_STATUS_UNRELIABLE;
560 compass_compute_cal (event, info);
561 event->magnetic.status = SENSOR_STATUS_ACCURACY_LOW;
565 compass_compute_cal (event, info);
566 event->magnetic.status = SENSOR_STATUS_ACCURACY_MEDIUM;
570 compass_compute_cal (event, info);
571 event->magnetic.status = SENSOR_STATUS_ACCURACY_HIGH;
576 void compass_read_data (sensor_info_t* info)
578 FILE* data_file = fopen (COMPASS_CALIBRATION_PATH, "r");
580 compass_cal_init(data_file, info);
586 void compass_store_data (sensor_info_t* info)
588 FILE* data_file = fopen (COMPASS_CALIBRATION_PATH, "w");
590 compass_store_result(data_file, info);