2 // Copyright (c) 2015 Intel Corporation
4 // Licensed under the Apache License, Version 2.0 (the "License");
5 // you may not use this file except in compliance with the License.
6 // You may obtain a copy of the License at
8 // http://www.apache.org/licenses/LICENSE-2.0
10 // Unless required by applicable law or agreed to in writing, software
11 // distributed under the License is distributed on an "AS IS" BASIS,
12 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 // See the License for the specific language governing permissions and
14 // limitations under the License.
18 #include <hardware/sensors.h>
20 #include <utils/Log.h>
21 #include "calibration.h"
22 #include "matrix-ops.h"
23 #include "description.h"
27 #define COMPASS_CALIBRATION_PATH "/data/compass.conf"
28 #define EPSILON 0.000000001
30 #define MAGNETIC_LOW 960 /* 31 micro tesla squared */
32 #define CAL_VERSION 1.0
34 /* We'll have multiple calibration levels so that we can provide an estimation as fast as possible */
35 static const float min_diffs [CAL_STEPS] = {0.2, 0.25, 0.4, 0.6, 1.0};
36 static const float max_sqr_errs [CAL_STEPS] = {10.0, 10.0, 8.0, 5.0, 3.5};
37 static const unsigned int lookback_counts [CAL_STEPS] = {2, 3, 4, 5, 6 };
40 /* Reset calibration algorithm */
41 static void reset_sample (compass_cal_t* 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;
53 static double calc_square_err (compass_cal_t* data)
56 double raw[3][1], result[3][1], mat_diff[3][1];
58 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 diff = sqrt(result[0][0] * result[0][0] + result[1][0] * result[1][0] + result[2][0] * result[2][0]) - data->bfield;
78 stdev[0] = sqrt(stdev[0] / MAGN_DS_SIZE);
79 stdev[1] = sqrt(stdev[1] / MAGN_DS_SIZE);
80 stdev[2] = sqrt(stdev[2] / MAGN_DS_SIZE);
82 /* A sanity check - if we have too little variation for an axis it's best to reject the calibration than risking a wrong calibration */
83 if (stdev[0] <= 1 || stdev[1] <= 1 || stdev[2] <= 1)
84 return max_sqr_errs[0];
91 /* Given an real symmetric 3x3 matrix A, compute the eigenvalues */
92 static void compute_eigenvalues (double mat[3][3], double* eig1, double* eig2, double* eig3)
94 double p = mat[0][1] * mat[0][1] + mat[0][2] * mat[0][2] + mat[1][2] * mat[1][2];
103 double q = (mat[0][0] + mat[1][1] + mat[2][2]) / 3;
104 double temp1 = mat[0][0] - q;
105 double temp2 = mat[1][1] - q;
106 double temp3 = mat[2][2] - q;
108 p = temp1 * temp1 + temp2 * temp2 + temp3 * temp3 + 2 * p;
112 assign(3, 3, mat, mat2);
116 multiply_scalar_inplace(3, 3, mat2, 1/p);
118 double r = (mat2[0][0] * mat2[1][1] * mat2[2][2] + mat2[0][1] * mat2[1][2] * mat2[2][0]
119 + mat2[0][2] * mat2[1][0] * mat2[2][1] - mat2[0][2] * mat2[1][1] * mat2[2][0]
120 - mat2[0][0] * mat2[1][2] * mat2[2][1] - mat2[0][1] * mat2[1][0] * mat2[2][2]) / 2;
130 *eig3 = q + 2 * p * cos(phi);
131 *eig1 = q + 2 * p * cos(phi + 2 * M_PI / 3);
132 *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;
163 static int ellipsoid_fit (mat_input_t m, double offset[3][1], double w_invert[3][3], double* bfield)
166 double h[MAGN_DS_SIZE][9];
167 double w[MAGN_DS_SIZE][1];
168 double h_trans[9][MAGN_DS_SIZE];
169 double p_temp1[9][9];
170 double p_temp2[9][MAGN_DS_SIZE];
171 double temp1[3][3], temp[3][3];
172 double temp1_inv[3][3];
176 double a[3][3], sqrt_evals[3][3], evecs[3][3], evecs_trans[3][3];
177 double evec1[3][1], evec2[3][1], evec3[3][1];
179 for (i = 0; i < MAGN_DS_SIZE; i++) {
180 w[i][0] = m[i][0] * m[i][0];
184 h[i][3] = -1 * m[i][0] * m[i][1];
185 h[i][4] = -1 * m[i][0] * m[i][2];
186 h[i][5] = -1 * m[i][1] * m[i][2];
187 h[i][6] = -1 * m[i][1] * m[i][1];
188 h[i][7] = -1 * m[i][2] * m[i][2];
192 transpose (MAGN_DS_SIZE, 9, h, h_trans);
193 multiply (9, MAGN_DS_SIZE, 9, h_trans, h, result);
194 invert (9, result, p_temp1);
195 multiply (9, 9, MAGN_DS_SIZE, p_temp1, h_trans, p_temp2);
196 multiply (9, MAGN_DS_SIZE, 1, p_temp2, w, p);
199 temp1[0][1] = p[3][0];
200 temp1[0][2] = p[4][0];
201 temp1[1][0] = p[3][0];
202 temp1[1][1] = 2 * p[6][0];
203 temp1[1][2] = p[5][0];
204 temp1[2][0] = p[4][0];
205 temp1[2][1] = p[5][0];
206 temp1[2][2] = 2 * p[7][0];
208 temp2[0][0] = p[0][0];
209 temp2[1][0] = p[1][0];
210 temp2[2][0] = p[2][0];
212 invert(3, temp1, temp1_inv);
213 multiply(3, 3, 1, temp1_inv, temp2, offset);
214 double off_x = offset[0][0];
215 double off_y = offset[1][0];
216 double off_z = offset[2][0];
218 a[0][0] = 1.0 / (p[8][0] + off_x * off_x + p[6][0] * off_y * off_y
219 + p[7][0] * off_z * off_z + p[3][0] * off_x * off_y
220 + p[4][0] * off_x * off_z + p[5][0] * off_y * off_z);
222 a[0][1] = p[3][0] * a[0][0] / 2;
223 a[0][2] = p[4][0] * a[0][0] / 2;
224 a[1][2] = p[5][0] * a[0][0] / 2;
225 a[1][1] = p[6][0] * a[0][0];
226 a[2][2] = p[7][0] * a[0][0];
231 double eig1 = 0, eig2 = 0, eig3 = 0;
232 compute_eigenvalues(a, &eig1, &eig2, &eig3);
234 if (eig1 <=0 || eig2 <= 0 || eig3 <= 0)
237 sqrt_evals[0][0] = sqrt(eig1);
238 sqrt_evals[1][0] = 0;
239 sqrt_evals[2][0] = 0;
240 sqrt_evals[0][1] = 0;
241 sqrt_evals[1][1] = sqrt(eig2);
242 sqrt_evals[2][1] = 0;
243 sqrt_evals[0][2] = 0;
244 sqrt_evals[1][2] = 0;
245 sqrt_evals[2][2] = sqrt(eig3);
247 calc_evector(a, eig1, evec1);
248 calc_evector(a, eig2, evec2);
249 calc_evector(a, eig3, evec3);
251 evecs[0][0] = evec1[0][0];
252 evecs[1][0] = evec1[1][0];
253 evecs[2][0] = evec1[2][0];
254 evecs[0][1] = evec2[0][0];
255 evecs[1][1] = evec2[1][0];
256 evecs[2][1] = evec2[2][0];
257 evecs[0][2] = evec3[0][0];
258 evecs[1][2] = evec3[1][0];
259 evecs[2][2] = evec3[2][0];
261 multiply (3, 3, 3, evecs, sqrt_evals, temp1);
262 transpose(3, 3, evecs, evecs_trans);
263 multiply (3, 3, 3, temp1, evecs_trans, temp);
264 transpose (3, 3, temp, w_invert);
266 *bfield = pow(sqrt(1/eig1) * sqrt(1/eig2) * sqrt(1/eig3), 1.0/3.0);
271 multiply_scalar_inplace(3, 3, w_invert, *bfield);
277 static void compass_cal_init (FILE* data_file, sensor_info_t* info)
279 compass_cal_t* cal_data = (compass_cal_t*) info->cal_data;
280 int cal_steps = (info->max_cal_level && info->max_cal_level <= CAL_STEPS) ? info->max_cal_level : CAL_STEPS;
283 if (cal_data == NULL)
287 reset_sample(cal_data);
289 if (!info->cal_level && data_file != NULL) {
290 int ret = fscanf(data_file, "%f %d %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf",
291 &version, &info->cal_level,
292 &cal_data->offset[0][0], &cal_data->offset[1][0], &cal_data->offset[2][0],
293 &cal_data->w_invert[0][0], &cal_data->w_invert[0][1], &cal_data->w_invert[0][2],
294 &cal_data->w_invert[1][0], &cal_data->w_invert[1][1], &cal_data->w_invert[1][2],
295 &cal_data->w_invert[2][0], &cal_data->w_invert[2][1], &cal_data->w_invert[2][2],
298 if (ret != data_count || info->cal_level >= cal_steps || version != CAL_VERSION)
302 if (info->cal_level) {
303 ALOGV("CompassCalibration: load old data, caldata: %f %f %f %f %f %f %f %f %f %f %f %f %f",
304 cal_data->offset[0][0], cal_data->offset[1][0], cal_data->offset[2][0],
305 cal_data->w_invert[0][0], cal_data->w_invert[0][1], cal_data->w_invert[0][2], cal_data->w_invert[1][0],
306 cal_data->w_invert[1][1], cal_data->w_invert[1][2], cal_data->w_invert[2][0], cal_data->w_invert[2][1],
307 cal_data->w_invert[2][2], cal_data->bfield);
309 cal_data->offset[0][0] = 0;
310 cal_data->offset[1][0] = 0;
311 cal_data->offset[2][0] = 0;
313 cal_data->w_invert[0][0] = 1;
314 cal_data->w_invert[1][0] = 0;
315 cal_data->w_invert[2][0] = 0;
316 cal_data->w_invert[0][1] = 0;
317 cal_data->w_invert[1][1] = 1;
318 cal_data->w_invert[2][1] = 0;
319 cal_data->w_invert[0][2] = 0;
320 cal_data->w_invert[1][2] = 0;
321 cal_data->w_invert[2][2] = 1;
323 cal_data->bfield = 0;
328 static void compass_store_result (FILE* data_file, sensor_info_t* info)
330 compass_cal_t* cal_data = (compass_cal_t*) info->cal_data;
332 if (data_file == NULL || cal_data == NULL)
335 int ret = fprintf(data_file, "%f %d %f %f %f %f %f %f %f %f %f %f %f %f %f\n",
336 CAL_VERSION, info->cal_level,
337 cal_data->offset[0][0], cal_data->offset[1][0], cal_data->offset[2][0],
338 cal_data->w_invert[0][0], cal_data->w_invert[0][1], cal_data->w_invert[0][2],
339 cal_data->w_invert[1][0], cal_data->w_invert[1][1], cal_data->w_invert[1][2],
340 cal_data->w_invert[2][0], cal_data->w_invert[2][1], cal_data->w_invert[2][2],
344 ALOGE ("Compass calibration - store data failed!");
348 static int compass_collect (sensors_event_t* event, sensor_info_t* info)
350 float data[3] = {event->magnetic.x, event->magnetic.y, event->magnetic.z};
351 unsigned int index,j;
352 unsigned int lookback_count;
355 compass_cal_t* cal_data = (compass_cal_t*) info->cal_data;
357 if (cal_data == NULL)
360 /* Discard the point if not valid */
361 if (data[0] == 0 || data[1] == 0 || data[2] == 0)
364 lookback_count = lookback_counts[info->cal_level];
365 min_diff = min_diffs[info->cal_level];
367 /* For the current point to be accepted, each x/y/z value must be different enough to the last several collected points */
368 if (cal_data->sample_count > 0 && cal_data->sample_count < MAGN_DS_SIZE) {
369 unsigned int lookback = lookback_count < cal_data->sample_count ? lookback_count : cal_data->sample_count;
370 for (index = 0; index < lookback; index++)
371 for (j = 0; j < 3; j++)
372 if (fabsf(data[j] - cal_data->sample[cal_data->sample_count-1-index][j]) < min_diff) {
373 ALOGV("CompassCalibration:point reject: [%f,%f,%f], selected_count=%d", data[0], data[1], data[2], cal_data->sample_count);
378 if (cal_data->sample_count < MAGN_DS_SIZE) {
379 memcpy(cal_data->sample[cal_data->sample_count], data, sizeof(float) * 3);
380 cal_data->sample_count++;
381 cal_data->average[0] += data[0];
382 cal_data->average[1] += data[1];
383 cal_data->average[2] += data[2];
384 ALOGV("CompassCalibration:point collected [%f,%f,%f], selected_count=%d", (double)data[0], (double)data[1], (double)data[2], cal_data->sample_count);
390 static void scale_event (sensors_event_t* event)
393 float sanity_norm = 0;
396 sqr_norm = (event->magnetic.x * event->magnetic.x +
397 event->magnetic.y * event->magnetic.y +
398 event->magnetic.z * event->magnetic.z);
400 if (sqr_norm < MAGNETIC_LOW)
401 sanity_norm = MAGNETIC_LOW;
403 if (sanity_norm && sqr_norm) {
404 scale = sanity_norm / sqr_norm;
406 event->magnetic.x = event->magnetic.x * scale;
407 event->magnetic.y = event->magnetic.y * scale;
408 event->magnetic.z = event->magnetic.z * scale;
413 static void compass_compute_cal (sensors_event_t* event, sensor_info_t* info)
415 compass_cal_t* cal_data = (compass_cal_t*) info->cal_data;
416 double result[3][1], raw[3][1], diff[3][1];
418 if (!info->cal_level || cal_data == NULL)
421 raw[0][0] = event->magnetic.x;
422 raw[1][0] = event->magnetic.y;
423 raw[2][0] = event->magnetic.z;
425 substract(3, 1, raw, cal_data->offset, diff);
426 multiply (3, 3, 1, cal_data->w_invert, diff, result);
428 event->magnetic.x = event->data[0] = result[0][0];
429 event->magnetic.y = event->data[1] = result[1][0];
430 event->magnetic.z = event->data[2] = result[2][0];
436 static int compass_ready (sensor_info_t* info)
442 compass_cal_t* cal_data = (compass_cal_t*) info->cal_data;
443 compass_cal_t new_cal_data;
446 * Some sensors take unrealistically long to calibrate at higher levels. We'll use a max_cal_level if we have such a property setup,
447 * or go with the default settings if not.
449 int cal_steps = (info->max_cal_level && info->max_cal_level <= CAL_STEPS) ? info->max_cal_level : CAL_STEPS;
451 if (cal_data->sample_count < MAGN_DS_SIZE)
452 return info->cal_level;
454 max_sqr_err = max_sqr_errs[info->cal_level];
456 /* Enough points have been collected, do the ellipsoid calibration */
458 /* Compute average per axis */
459 cal_data->average[0] /= MAGN_DS_SIZE;
460 cal_data->average[1] /= MAGN_DS_SIZE;
461 cal_data->average[2] /= MAGN_DS_SIZE;
463 for (i = 0; i < MAGN_DS_SIZE; i++) {
464 mat[i][0] = cal_data->sample[i][0];
465 mat[i][1] = cal_data->sample[i][1];
466 mat[i][2] = cal_data->sample[i][2];
469 /* Check if result is good. The sample data must remain the same */
470 new_cal_data = *cal_data;
472 if (ellipsoid_fit(mat, new_cal_data.offset, new_cal_data.w_invert, &new_cal_data.bfield)) {
473 double new_err = calc_square_err (&new_cal_data);
474 ALOGI("new err is %f, max sqr err id %f", new_err,max_sqr_err);
475 if (new_err < max_sqr_err) {
476 double err = calc_square_err(cal_data);
478 /* New cal data is better, so we switch to the new */
479 memcpy(cal_data->offset, new_cal_data.offset, sizeof(cal_data->offset));
480 memcpy(cal_data->w_invert, new_cal_data.w_invert, sizeof(cal_data->w_invert));
481 cal_data->bfield = new_cal_data.bfield;
482 if (info->cal_level < (cal_steps - 1))
484 ALOGV("CompassCalibration: ready check success, caldata: %f %f %f %f %f %f %f %f %f %f %f %f %f, err %f",
485 cal_data->offset[0][0], cal_data->offset[1][0], cal_data->offset[2][0], cal_data->w_invert[0][0],
486 cal_data->w_invert[0][1], cal_data->w_invert[0][2], cal_data->w_invert[1][0], cal_data->w_invert[1][1],
487 cal_data->w_invert[1][2], cal_data->w_invert[2][0], cal_data->w_invert[2][1], cal_data->w_invert[2][2],
488 cal_data->bfield, new_err);
492 reset_sample(cal_data);
493 return info->cal_level;
497 void calibrate_compass (int s, sensors_event_t* event)
501 /* Calibration is continuous */
502 compass_collect (event, &sensor[s]);
504 cal_level = compass_ready(&sensor[s]);
509 event->magnetic.status = SENSOR_STATUS_UNRELIABLE;
513 compass_compute_cal (event, &sensor[s]);
514 event->magnetic.status = SENSOR_STATUS_ACCURACY_LOW;
518 compass_compute_cal (event, &sensor[s]);
519 event->magnetic.status = SENSOR_STATUS_ACCURACY_MEDIUM;
523 compass_compute_cal (event, &sensor[s]);
524 event->magnetic.status = SENSOR_STATUS_ACCURACY_HIGH;
529 void compass_read_data (int s)
531 FILE* data_file = fopen (COMPASS_CALIBRATION_PATH, "r");
533 compass_cal_init(data_file, &sensor[s]);
540 void compass_store_data (int s)
542 FILE* data_file = fopen (COMPASS_CALIBRATION_PATH, "w");
544 compass_store_result(data_file, &sensor[s]);