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 };
40 /* reset calibration algorithm */
41 static void reset_sample (struct compass_cal* data)
44 data->sample_count = 0;
45 for (i = 0; i < MAGN_DS_SIZE; i++)
47 data->sample[i][j] = 0;
49 data->average[0] = data->average[1] = data->average[2] = 0;
52 static double calc_square_err (struct compass_cal* data)
55 double raw[3][1], result[3][1], mat_diff[3][1];
57 float stdev[3] = {0,0,0};
59 for (i = 0; i < MAGN_DS_SIZE; i++) {
60 raw[0][0] = data->sample[i][0];
61 raw[1][0] = data->sample[i][1];
62 raw[2][0] = data->sample[i][2];
64 stdev[0] += (raw[0][0] - data->average[0]) * (raw[0][0] - data->average[0]);
65 stdev[1] += (raw[1][0] - data->average[1]) * (raw[1][0] - data->average[1]);
66 stdev[2] += (raw[2][0] - data->average[2]) * (raw[2][0] - data->average[2]);
68 substract (3, 1, raw, data->offset, mat_diff);
69 multiply(3, 3, 1, data->w_invert, mat_diff, result);
71 double diff = sqrt(result[0][0] * result[0][0] + result[1][0] * result[1][0]
72 + result[2][0] * result[2][0]) - data->bfield;
77 stdev[0] = sqrt(stdev[0] / MAGN_DS_SIZE);
78 stdev[1] = sqrt(stdev[1] / MAGN_DS_SIZE);
79 stdev[2] = sqrt(stdev[2] / MAGN_DS_SIZE);
82 * A sanity check - if we have too little variation for an axis
83 * it's best to reject the calibration than risking a wrong calibration.
85 if (stdev[0] <= 1 || stdev[1] <= 1 || stdev[2] <= 1)
86 return max_sqr_errs[0];
92 /* Given an real symmetric 3x3 matrix A, compute the eigenvalues */
93 static void compute_eigenvalues(double mat[3][3], double* eig1, double* eig2, double* eig3)
95 double p = mat[0][1] * mat[0][1] + mat[0][2] * mat[0][2] + mat[1][2] * mat[1][2];
104 double q = (mat[0][0] + mat[1][1] + mat[2][2]) / 3;
105 double temp1 = mat[0][0] - q;
106 double temp2 = mat[1][1] - q;
107 double temp3 = mat[2][2] - q;
109 p = temp1 * temp1 + temp2 * temp2 + temp3 * temp3 + 2 * p;
113 assign(3, 3, mat, mat2);
117 multiply_scalar_inplace(3, 3, mat2, 1/p);
119 double r = (mat2[0][0] * mat2[1][1] * mat2[2][2] + mat2[0][1] * mat2[1][2] * mat2[2][0]
120 + mat2[0][2] * mat2[1][0] * mat2[2][1] - mat2[0][2] * mat2[1][1] * mat2[2][0]
121 - mat2[0][0] * mat2[1][2] * mat2[2][1] - mat2[0][1] * mat2[1][0] * mat2[2][2]) / 2;
131 *eig3 = q + 2 * p * cos(phi);
132 *eig1 = q + 2 * p * cos(phi + 2 * M_PI / 3);
133 *eig2 = 3 * q - *eig1 - *eig3;
136 static void calc_evector(double mat[3][3], double eig, double vec[3][1])
140 assign(3, 3, mat, h);
151 assign(2, 2, x_tmp, x);
153 double temp1 = x[0][0] * (-h[1][0]) + x[0][1] * (-h[2][0]);
154 double temp2 = x[1][0] * (-h[1][0]) + x[1][1] * (-h[2][0]);
155 double norm = sqrt(1 + temp1 * temp1 + temp2 * temp2);
157 vec[0][0] = 1.0 / norm;
158 vec[1][0] = temp1 / norm;
159 vec[2][0] = temp2 / norm;
162 static int ellipsoid_fit (mat_input_t m, double offset[3][1], double w_invert[3][3], double* bfield)
165 double h[MAGN_DS_SIZE][9];
166 double w[MAGN_DS_SIZE][1];
167 double h_trans[9][MAGN_DS_SIZE];
168 double p_temp1[9][9];
169 double p_temp2[9][MAGN_DS_SIZE];
170 double temp1[3][3], temp[3][3];
171 double temp1_inv[3][3];
175 double a[3][3], sqrt_evals[3][3], evecs[3][3], evecs_trans[3][3];
176 double evec1[3][1], evec2[3][1], evec3[3][1];
178 for (i = 0; i < MAGN_DS_SIZE; i++) {
179 w[i][0] = m[i][0] * m[i][0];
183 h[i][3] = -1 * m[i][0] * m[i][1];
184 h[i][4] = -1 * m[i][0] * m[i][2];
185 h[i][5] = -1 * m[i][1] * m[i][2];
186 h[i][6] = -1 * m[i][1] * m[i][1];
187 h[i][7] = -1 * m[i][2] * m[i][2];
190 transpose (MAGN_DS_SIZE, 9, h, h_trans);
191 multiply (9, MAGN_DS_SIZE, 9, h_trans, h, result);
192 invert (9, result, p_temp1);
193 multiply (9, 9, MAGN_DS_SIZE, p_temp1, h_trans, p_temp2);
194 multiply (9, MAGN_DS_SIZE, 1, p_temp2, w, p);
197 temp1[0][1] = p[3][0];
198 temp1[0][2] = p[4][0];
199 temp1[1][0] = p[3][0];
200 temp1[1][1] = 2 * p[6][0];
201 temp1[1][2] = p[5][0];
202 temp1[2][0] = p[4][0];
203 temp1[2][1] = p[5][0];
204 temp1[2][2] = 2 * p[7][0];
206 temp2[0][0] = p[0][0];
207 temp2[1][0] = p[1][0];
208 temp2[2][0] = p[2][0];
210 invert(3, temp1, temp1_inv);
211 multiply(3, 3, 1, temp1_inv, temp2, offset);
212 double off_x = offset[0][0];
213 double off_y = offset[1][0];
214 double off_z = offset[2][0];
217 a[0][0] = 1.0 / (p[8][0] + off_x * off_x + p[6][0] * off_y * off_y
218 + p[7][0] * off_z * off_z + p[3][0] * off_x * off_y
219 + p[4][0] * off_x * off_z + p[5][0] * off_y * off_z);
221 a[0][1] = p[3][0] * a[0][0] / 2;
222 a[0][2] = p[4][0] * a[0][0] / 2;
223 a[1][2] = p[5][0] * a[0][0] / 2;
224 a[1][1] = p[6][0] * a[0][0];
225 a[2][2] = p[7][0] * a[0][0];
230 double eig1 = 0, eig2 = 0, eig3 = 0;
231 compute_eigenvalues(a, &eig1, &eig2, &eig3);
233 if (eig1 <=0 || eig2 <= 0 || eig3 <= 0)
236 sqrt_evals[0][0] = sqrt(eig1);
237 sqrt_evals[1][0] = 0;
238 sqrt_evals[2][0] = 0;
239 sqrt_evals[0][1] = 0;
240 sqrt_evals[1][1] = sqrt(eig2);
241 sqrt_evals[2][1] = 0;
242 sqrt_evals[0][2] = 0;
243 sqrt_evals[1][2] = 0;
244 sqrt_evals[2][2] = sqrt(eig3);
246 calc_evector(a, eig1, evec1);
247 calc_evector(a, eig2, evec2);
248 calc_evector(a, eig3, evec3);
250 evecs[0][0] = evec1[0][0];
251 evecs[1][0] = evec1[1][0];
252 evecs[2][0] = evec1[2][0];
253 evecs[0][1] = evec2[0][0];
254 evecs[1][1] = evec2[1][0];
255 evecs[2][1] = evec2[2][0];
256 evecs[0][2] = evec3[0][0];
257 evecs[1][2] = evec3[1][0];
258 evecs[2][2] = evec3[2][0];
260 multiply (3, 3, 3, evecs, sqrt_evals, temp1);
261 transpose(3, 3, evecs, evecs_trans);
262 multiply (3, 3, 3, temp1, evecs_trans, temp);
263 transpose (3, 3, temp, w_invert);
264 *bfield = pow(sqrt(1/eig1) * sqrt(1/eig2) * sqrt(1/eig3), 1.0/3.0);
269 multiply_scalar_inplace(3, 3, w_invert, *bfield);
274 static void compass_cal_init (FILE* data_file, struct sensor_info_t* info)
283 if (raw_data_selected) {
284 fclose(raw_data_selected);
285 raw_data_selected = NULL;
289 snprintf(path, 64, RAW_DATA_FULL_PATH, file_no);
290 raw_data = fopen(path,"w+");
291 snprintf(path, 64, RAW_DATA_SELECTED_PATH, file_no);
292 raw_data_selected = fopen(path,"w+");
297 struct compass_cal* cal_data = (struct compass_cal*) info->cal_data;
298 int cal_steps = (info->max_cal_level && info->max_cal_level <= CAL_STEPS) ?
299 info->max_cal_level : CAL_STEPS;
300 if (cal_data == NULL)
304 reset_sample(cal_data);
306 if (!info->cal_level && data_file != NULL) {
307 int ret = fscanf(data_file, "%d %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf",
308 &info->cal_level, &cal_data->offset[0][0], &cal_data->offset[1][0], &cal_data->offset[2][0],
309 &cal_data->w_invert[0][0], &cal_data->w_invert[0][1], &cal_data->w_invert[0][2],
310 &cal_data->w_invert[1][0], &cal_data->w_invert[1][1], &cal_data->w_invert[1][2],
311 &cal_data->w_invert[2][0], &cal_data->w_invert[2][1], &cal_data->w_invert[2][2],
314 if (ret != data_count || info->cal_level >= cal_steps) {
320 if (info->cal_level) {
321 ALOGV("CompassCalibration: load old data, caldata: %f %f %f %f %f %f %f %f %f %f %f %f %f",
322 cal_data->offset[0][0], cal_data->offset[1][0], cal_data->offset[2][0],
323 cal_data->w_invert[0][0], cal_data->w_invert[0][1], cal_data->w_invert[0][2], cal_data->w_invert[1][0],
324 cal_data->w_invert[1][1], cal_data->w_invert[1][2], cal_data->w_invert[2][0], cal_data->w_invert[2][1],
325 cal_data->w_invert[2][2], cal_data->bfield);
328 cal_data->offset[0][0] = 0;
329 cal_data->offset[1][0] = 0;
330 cal_data->offset[2][0] = 0;
332 cal_data->w_invert[0][0] = 1;
333 cal_data->w_invert[1][0] = 0;
334 cal_data->w_invert[2][0] = 0;
335 cal_data->w_invert[0][1] = 0;
336 cal_data->w_invert[1][1] = 1;
337 cal_data->w_invert[2][1] = 0;
338 cal_data->w_invert[0][2] = 0;
339 cal_data->w_invert[1][2] = 0;
340 cal_data->w_invert[2][2] = 1;
342 cal_data->bfield = 0;
347 static void compass_store_result(FILE* data_file, struct sensor_info_t* info)
349 struct compass_cal* cal_data = (struct compass_cal*) info->cal_data;
351 if (data_file == NULL || cal_data == NULL)
354 int ret = fprintf(data_file, "%d %f %f %f %f %f %f %f %f %f %f %f %f %f\n",
355 info->cal_level, cal_data->offset[0][0], cal_data->offset[1][0], cal_data->offset[2][0],
356 cal_data->w_invert[0][0], cal_data->w_invert[0][1], cal_data->w_invert[0][2],
357 cal_data->w_invert[1][0], cal_data->w_invert[1][1], cal_data->w_invert[1][2],
358 cal_data->w_invert[2][0], cal_data->w_invert[2][1], cal_data->w_invert[2][2],
362 ALOGE ("compass calibration - store data failed!");
365 static int compass_collect (struct sensors_event_t* event, struct sensor_info_t* info)
367 float data[3] = {event->magnetic.x, event->magnetic.y, event->magnetic.z};
368 unsigned int index,j;
369 unsigned int lookback_count;
372 struct compass_cal* cal_data = (struct compass_cal*) info->cal_data;
374 if (cal_data == NULL)
377 /* Discard the point if not valid */
378 if (data[0] == 0 || data[1] == 0 || data[2] == 0)
382 if (raw_data && raw_data_count < MAX_RAW_DATA_COUNT) {
383 fprintf(raw_data, "%f %f %f\n", (double)data[0], (double)data[1],
388 if (raw_data && raw_data_count >= MAX_RAW_DATA_COUNT) {
394 lookback_count = lookback_counts[info->cal_level];
395 min_diff = min_diffs[info->cal_level];
398 * For the current point to be accepted, each x/y/z value must be different
399 * enough to the last several collected points.
401 if (cal_data->sample_count > 0 && cal_data->sample_count < MAGN_DS_SIZE) {
402 unsigned int lookback = lookback_count < cal_data->sample_count ? lookback_count :
403 cal_data->sample_count;
404 for (index = 0; index < lookback; index++){
405 for (j = 0; j < 3; j++) {
406 if (fabsf(data[j] - cal_data->sample[cal_data->sample_count-1-index][j]) < min_diff) {
407 ALOGV("CompassCalibration:point reject: [%f,%f,%f], selected_count=%d",
408 data[0], data[1], data[2], cal_data->sample_count);
415 if (cal_data->sample_count < MAGN_DS_SIZE) {
416 memcpy(cal_data->sample[cal_data->sample_count], data, sizeof(float) * 3);
417 cal_data->sample_count++;
418 cal_data->average[0] += data[0];
419 cal_data->average[1] += data[1];
420 cal_data->average[2] += data[2];
421 ALOGV("CompassCalibration:point collected [%f,%f,%f], selected_count=%d",
422 (double)data[0], (double)data[1], (double)data[2], cal_data->sample_count);
424 if (raw_data_selected) {
425 fprintf(raw_data_selected, "%f %f %f\n", (double)data[0], (double)data[1], (double)data[2]);
432 static void scale_event (struct sensors_event_t* event)
435 float sanity_norm = 0;
438 sqr_norm = (event->magnetic.x * event->magnetic.x +
439 event->magnetic.y * event->magnetic.y +
440 event->magnetic.z * event->magnetic.z);
442 if (sqr_norm < MAGNETIC_LOW)
443 sanity_norm = MAGNETIC_LOW;
445 if (sanity_norm && sqr_norm) {
446 scale = sanity_norm / sqr_norm;
448 event->magnetic.x = event->magnetic.x * scale;
449 event->magnetic.y = event->magnetic.y * scale;
450 event->magnetic.z = event->magnetic.z * scale;
455 static void compass_compute_cal (struct sensors_event_t* event, struct sensor_info_t* info)
457 struct compass_cal* cal_data = (struct compass_cal*) info->cal_data;
458 double result[3][1], raw[3][1], diff[3][1];
460 if (!info->cal_level || cal_data == NULL)
463 raw[0][0] = event->magnetic.x;
464 raw[1][0] = event->magnetic.y;
465 raw[2][0] = event->magnetic.z;
467 substract(3, 1, raw, cal_data->offset, diff);
468 multiply (3, 3, 1, cal_data->w_invert, diff, result);
470 event->magnetic.x = event->data[0] = result[0][0];
471 event->magnetic.y = event->data[1] = result[1][0];
472 event->magnetic.z = event->data[2] = result[2][0];
478 static int compass_ready (struct sensor_info_t* info)
484 struct compass_cal* cal_data = (struct compass_cal*) info->cal_data;
487 * Some sensors take unrealistically long to calibrate at higher levels.
488 * We'll use a max_cal_level if we have such a property setup, or go with
489 * the default settings if not.
491 int cal_steps = (info->max_cal_level && info->max_cal_level <= CAL_STEPS) ?
492 info->max_cal_level : CAL_STEPS;
494 if (cal_data->sample_count < MAGN_DS_SIZE)
495 return info->cal_level;
497 max_sqr_err = max_sqr_errs[info->cal_level];
499 /* Enough points have been collected, do the ellipsoid calibration */
501 /* Compute average per axis */
502 cal_data->average[0] /= MAGN_DS_SIZE;
503 cal_data->average[1] /= MAGN_DS_SIZE;
504 cal_data->average[2] /= MAGN_DS_SIZE;
506 for (i = 0; i < MAGN_DS_SIZE; i++) {
507 mat[i][0] = cal_data->sample[i][0];
508 mat[i][1] = cal_data->sample[i][1];
509 mat[i][2] = cal_data->sample[i][2];
512 /* check if result is good */
513 struct compass_cal new_cal_data;
514 /* the sample data must remain the same */
515 new_cal_data = *cal_data;
516 if (ellipsoid_fit(mat, new_cal_data.offset, new_cal_data.w_invert, &new_cal_data.bfield)) {
517 double new_err = calc_square_err (&new_cal_data);
518 ALOGI("new err is %f, max sqr err id %f", new_err,max_sqr_err);
519 if (new_err < max_sqr_err) {
520 double err = calc_square_err(cal_data);
522 /* new cal data is better, so we switch to the new */
523 memcpy(cal_data->offset, new_cal_data.offset, sizeof(cal_data->offset));
524 memcpy(cal_data->w_invert, new_cal_data.w_invert, sizeof(cal_data->w_invert));
525 cal_data->bfield = new_cal_data.bfield;
526 if (info->cal_level < (cal_steps - 1))
528 ALOGV("CompassCalibration: ready check success, caldata: %f %f %f %f %f %f %f %f %f %f %f %f %f, err %f",
529 cal_data->offset[0][0], cal_data->offset[1][0], cal_data->offset[2][0], cal_data->w_invert[0][0],
530 cal_data->w_invert[0][1], cal_data->w_invert[0][2], cal_data->w_invert[1][0], cal_data->w_invert[1][1],
531 cal_data->w_invert[1][2], cal_data->w_invert[2][0], cal_data->w_invert[2][1], cal_data->w_invert[2][2],
532 cal_data->bfield, new_err);
536 reset_sample(cal_data);
537 return info->cal_level;
541 void calibrate_compass (struct sensors_event_t* event, struct sensor_info_t* info)
545 /* Calibration is continuous */
546 compass_collect (event, info);
548 cal_level = compass_ready(info);
554 event->magnetic.status = SENSOR_STATUS_UNRELIABLE;
558 compass_compute_cal (event, info);
559 event->magnetic.status = SENSOR_STATUS_ACCURACY_LOW;
563 compass_compute_cal (event, info);
564 event->magnetic.status = SENSOR_STATUS_ACCURACY_MEDIUM;
568 compass_compute_cal (event, info);
569 event->magnetic.status = SENSOR_STATUS_ACCURACY_HIGH;
574 void compass_read_data (struct sensor_info_t* info)
576 FILE* data_file = fopen (COMPASS_CALIBRATION_PATH, "r");
578 compass_cal_init(data_file, info);
583 void compass_store_data (struct sensor_info_t* info)
585 FILE* data_file = fopen (COMPASS_CALIBRATION_PATH, "w");
587 compass_store_result(data_file, info);