gyro-calibration.c

   1 /*
   2  * Copyright (C) 2014 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         fclose(data_file);
  51 }
  52
  53
  54 void gyro_store_data (sensor_info_t* info)
  55 {
  56         int ret;
  57         gyro_cal_t* cal_data = (gyro_cal_t*) info->cal_data;
  58         FILE* data_file;
  59
  60         if (cal_data == NULL)
  61                 return;
  62
  63         data_file = fopen (GYRO_CALIBRATION_PATH, "w");
  64
  65         if (data_file == NULL)
  66                 return;
  67
  68         ret = fprintf(data_file, "%f %f %f",
  69                 cal_data->bias_x, cal_data->bias_y, cal_data->bias_z);
  70
  71         if (ret < 0)
  72                 ALOGE ("Gyro calibration - store data failed!");
  73
  74         fclose(data_file);
  75 }
  76
  77
  78 static int gyro_collect (float x, float y, float z, gyro_cal_t* cal_data)
  79 {
  80         /* Analyze gyroscope data */
  81
  82         if (fabs(x) >= 1 || fabs(y) >= 1 || fabs(z) >= 1) {
  83
  84                 /* We're supposed to be standing still ; start over */
  85                 reset(cal_data);
  86
  87                 return 0; /* Uncalibrated */
  88         }
  89
  90         if (cal_data->count < GYRO_DS_SIZE) {
  91
  92                 if (x < cal_data->min_x)
  93                         cal_data->min_x = x;
  94
  95                 if (y < cal_data->min_y)
  96                         cal_data->min_y = y;
  97
  98                 if (z < cal_data->min_z)
  99                         cal_data->min_z = z;
 100
 101                 if (x > cal_data->max_x)
 102                         cal_data->max_x = x;
 103
 104                 if (y > cal_data->max_y)
 105                         cal_data->max_y = y;
 106
 107                 if (z > cal_data->max_z)
 108                         cal_data->max_z = z;
 109
 110                 if (fabs(cal_data->max_x - cal_data->min_x) <= GYRO_MAX_ERR &&
 111                     fabs(cal_data->max_y - cal_data->min_y) <= GYRO_MAX_ERR &&
 112                     fabs(cal_data->max_z - cal_data->min_z) <= GYRO_MAX_ERR)
 113                         cal_data->count++; /* One more conformant sample */
 114                 else
 115                         reset(cal_data); /* Out of spec sample ; start over */
 116
 117                 return 0; /* Still uncalibrated */
 118         }
 119
 120         /* We got enough stable samples to estimate gyroscope bias */
 121         cal_data->bias_x = (cal_data->max_x + cal_data->min_x) / 2;
 122         cal_data->bias_y = (cal_data->max_y + cal_data->min_y) / 2;
 123         cal_data->bias_z = (cal_data->max_z + cal_data->min_z) / 2;
 124
 125         return 1; /* Calibrated! */
 126 }
 127
 128
 129 void calibrate_gyro (sensors_event_t* event, sensor_info_t* info)
 130 {
 131         gyro_cal_t* cal_data = (gyro_cal_t*) info->cal_data;
 132
 133         if (cal_data == NULL)
 134                 return;
 135
 136         /* Attempt gyroscope calibration if we have not reached this state */
 137         if (info->cal_level == 0)
 138                 info->cal_level = gyro_collect(event->data[0], event->data[1],
 139                                                event->data[2], cal_data);
 140
 141
 142         event->data[0] = event->data[0] - cal_data->bias_x;
 143         event->data[1] = event->data[1] - cal_data->bias_y;
 144         event->data[2] = event->data[2] - cal_data->bias_z;
 145
 146         if (info->cal_level)
 147                event->gyro.status = SENSOR_STATUS_ACCURACY_HIGH;
 148 }