gyro-calibration.c

   1 /*
   2  * Copyright (C) 2014-2015 Intel Corporation.
   3  */
   4
   5 #include <stdio.h>
   6 #include <math.h>
   7 #include <sys/time.h>
   8 #include <utils/Log.h>
   9 #include <hardware/sensors.h>
  10 #include "common.h"
  11 #include "calibration.h"
  12
  13
  14 /* Gyro defines */
  15 #define GYRO_MAX_ERR 0.05
  16 #define GYRO_DS_SIZE 100
  17 #define GYRO_CALIBRATION_PATH "/data/gyro.conf"
  18
  19
  20 static void reset (gyro_cal_t* cal_data)
  21 {
  22         cal_data->count = 0;
  23
  24         cal_data->bias_x = cal_data->bias_y = cal_data->bias_z = 0;
  25
  26         cal_data->min_x  = cal_data->min_y  = cal_data->min_z  = 1.0;
  27         cal_data->max_x  = cal_data->max_y  = cal_data->max_z  =-1.0;
  28 }
  29
  30
  31 void gyro_cal_init (sensor_info_t* info)
  32 {
  33         int ret;
  34         gyro_cal_t* cal_data = (gyro_cal_t*) info->cal_data;
  35         FILE* data_file;
  36
  37         info->cal_level = 0;
  38
  39         if (cal_data == NULL)
  40                 return;
  41
  42         reset(cal_data);
  43
  44         data_file = fopen (GYRO_CALIBRATION_PATH, "r");
  45         if (data_file == NULL)
  46                 return;
  47
  48         ret = fscanf(data_file, "%f %f %f",
  49                         &cal_data->bias_x, &cal_data->bias_y, &cal_data->bias_z);
  50         if (ret != 3)
  51                 ALOGE("Gyro calibration - init failed!\n");
  52
  53         fclose(data_file);
  54 }
  55
  56
  57 void gyro_store_data (sensor_info_t* info)
  58 {
  59         int ret;
  60         gyro_cal_t* cal_data = (gyro_cal_t*) info->cal_data;
  61         FILE* data_file;
  62
  63         if (cal_data == NULL)
  64                 return;
  65
  66         data_file = fopen (GYRO_CALIBRATION_PATH, "w");
  67
  68         if (data_file == NULL)
  69                 return;
  70
  71         ret = fprintf(data_file, "%f %f %f",
  72                 cal_data->bias_x, cal_data->bias_y, cal_data->bias_z);
  73
  74         if (ret < 0)
  75                 ALOGE ("Gyro calibration - store data failed!");
  76
  77         fclose(data_file);
  78 }
  79
  80
  81 static int gyro_collect (float x, float y, float z, gyro_cal_t* cal_data)
  82 {
  83         /* Analyze gyroscope data */
  84
  85         if (fabs(x) >= 1 || fabs(y) >= 1 || fabs(z) >= 1) {
  86
  87                 /* We're supposed to be standing still ; start over */
  88                 reset(cal_data);
  89
  90                 return 0; /* Uncalibrated */
  91         }
  92
  93         if (cal_data->count < GYRO_DS_SIZE) {
  94
  95                 if (x < cal_data->min_x)
  96                         cal_data->min_x = x;
  97
  98                 if (y < cal_data->min_y)
  99                         cal_data->min_y = y;
 100
 101                 if (z < cal_data->min_z)
 102                         cal_data->min_z = z;
 103
 104                 if (x > cal_data->max_x)
 105                         cal_data->max_x = x;
 106
 107                 if (y > cal_data->max_y)
 108                         cal_data->max_y = y;
 109
 110                 if (z > cal_data->max_z)
 111                         cal_data->max_z = z;
 112
 113                 if (fabs(cal_data->max_x - cal_data->min_x) <= GYRO_MAX_ERR &&
 114                     fabs(cal_data->max_y - cal_data->min_y) <= GYRO_MAX_ERR &&
 115                     fabs(cal_data->max_z - cal_data->min_z) <= GYRO_MAX_ERR)
 116                         cal_data->count++; /* One more conformant sample */
 117                 else
 118                         reset(cal_data); /* Out of spec sample ; start over */
 119
 120                 return 0; /* Still uncalibrated */
 121         }
 122
 123         /* We got enough stable samples to estimate gyroscope bias */
 124         cal_data->bias_x = (cal_data->max_x + cal_data->min_x) / 2;
 125         cal_data->bias_y = (cal_data->max_y + cal_data->min_y) / 2;
 126         cal_data->bias_z = (cal_data->max_z + cal_data->min_z) / 2;
 127
 128         return 1; /* Calibrated! */
 129 }
 130
 131
 132 void calibrate_gyro (sensors_event_t* event, sensor_info_t* info)
 133 {
 134         gyro_cal_t* cal_data = (gyro_cal_t*) info->cal_data;
 135
 136         if (cal_data == NULL)
 137                 return;
 138
 139         /* Attempt gyroscope calibration if we have not reached this state */
 140         if (info->cal_level == 0)
 141                 info->cal_level = gyro_collect(event->data[0], event->data[1],
 142                                                event->data[2], cal_data);
 143
 144
 145         event->data[0] = event->data[0] - cal_data->bias_x;
 146         event->data[1] = event->data[1] - cal_data->bias_y;
 147         event->data[2] = event->data[2] - cal_data->bias_z;
 148
 149         if (info->cal_level)
 150                event->gyro.status = SENSOR_STATUS_ACCURACY_HIGH;
 151 }