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ardupilot/libraries/AP_IMU/AP_IMU_Oilpan.cpp

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// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
//
//
// AP_IMU.cpp - IMU Sensor Library for Ardupilot Mega
// Code by Michael Smith, Doug Weibel, Jordi Muñoz and Jose Julio. DIYDrones.com
//
// This library works with the ArduPilot Mega and "Oilpan"
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
/// @file AP_IMU.h
/// @brief IMU driver for the APM oilpan
#include <FastSerial.h>
#include <AP_Common.h>
#include <avr/eeprom.h>
#include "AP_IMU_Oilpan.h"
// XXX secret knowledge about the APM/oilpan wiring
//
#define A_LED_PIN 37
#define C_LED_PIN 35
// Sensors: GYROX, GYROY, GYROZ, ACCELX, ACCELY, ACCELZ
const uint8_t AP_IMU_Oilpan::_sensors[6] = { 1, 2, 0, 4, 5, 6}; // Channel assignments on the APM oilpan
const int8_t AP_IMU_Oilpan::_sensor_signs[6] = { 1,-1,-1, 1,-1,-1}; // Channel orientation vs. normal
// Temp compensation curve constants
// These must be produced by measuring data and curve fitting
// [X/Y/Z gyro][A/B/C or 0 order/1st order/2nd order constants]
//
const float AP_IMU_Oilpan::_gyro_temp_curve[3][3] = {
{1658,0,0}, // Values to use if no temp compensation data available
{1658,0,0}, // Based on average values for 20 sample boards
{1658,0,0}
};
void
AP_IMU_Oilpan::init(Start_style style, void (*callback)(unsigned long t))
{
// if we are warm-starting, load the calibration data from EEPROM and go
//
if (WARM_START == style) {
_sensor_cal.load();
} else {
// do cold-start calibration for both accel and gyro
_init_gyro(callback);
_init_accel(callback);
// save calibration
_sensor_cal.save();
}
}
/**************************************************/
void
AP_IMU_Oilpan::init_gyro(void (*callback)(unsigned long t))
{
_init_gyro(callback);
_sensor_cal.save();
}
void
AP_IMU_Oilpan::_init_gyro(void (*callback)(unsigned long t))
{
int flashcount = 0;
int tc_temp;
float adc_in;
float prev[3] = {0,0,0};
float total_change;
float max_offset;
uint16_t adc_values[6];
// cold start
tc_temp = _adc->Ch(_gyro_temp_ch);
callback(500);
Serial.printf_P(PSTR("Init Gyro"));
for(int c = 0; c < 25; c++){ // Mostly we are just flashing the LED's here to tell the user to keep the IMU still
digitalWrite(A_LED_PIN, LOW);
digitalWrite(C_LED_PIN, HIGH);
callback(20);
_adc->Ch6(_sensors, adc_values);
digitalWrite(A_LED_PIN, HIGH);
digitalWrite(C_LED_PIN, LOW);
callback(20);
}
for (int j = 0; j <= 2; j++)
_sensor_cal[j] = 500; // Just a large value to load prev[j] the first time
do {
// get 6 sensor values
_adc->Ch6(_sensors, adc_values);
for (int j = 0; j <= 2; j++){
prev[j] = _sensor_cal[j];
adc_in = adc_values[j];
adc_in -= _sensor_compensation(j, tc_temp);
_sensor_cal[j] = adc_in;
}
for(int i = 0; i < 50; i++){
// get 6 sensor values
_adc->Ch6(_sensors, adc_values);
for (int j = 0; j < 3; j++){
adc_in = adc_values[j];
// Subtract temp compensated typical gyro bias
adc_in -= _sensor_compensation(j, tc_temp);
// filter
_sensor_cal[j] = _sensor_cal[j] * 0.9 + adc_in * 0.1;
}
callback(20);
if(flashcount == 5) {
Serial.printf_P(PSTR("*"));
digitalWrite(A_LED_PIN, LOW);
digitalWrite(C_LED_PIN, HIGH);
}
if(flashcount >= 10) {
flashcount = 0;
digitalWrite(C_LED_PIN, LOW);
digitalWrite(A_LED_PIN, HIGH);
}
flashcount++;
}
total_change = fabs(prev[0] - _sensor_cal[0]) + fabs(prev[1] - _sensor_cal[1]) +fabs(prev[2] - _sensor_cal[2]);
max_offset = (_sensor_cal[0] > _sensor_cal[1]) ? _sensor_cal[0] : _sensor_cal[1];
max_offset = (max_offset > _sensor_cal[2]) ? max_offset : _sensor_cal[2];
callback(500);
} while ( total_change > _gyro_total_cal_change || max_offset > _gyro_max_cal_offset);
}
void
AP_IMU_Oilpan::save()
{
_sensor_cal.save();
}
void
AP_IMU_Oilpan::init_accel(void (*callback)(unsigned long t))
{
_init_accel(callback);
_sensor_cal.save();
}
void
AP_IMU_Oilpan::_init_accel(void (*callback)(unsigned long t))
{
int flashcount = 0;
float adc_in;
float prev[6] = {0,0,0};
float total_change;
float max_offset;
uint16_t adc_values[6];
// cold start
callback(500);
Serial.printf_P(PSTR("Init Accel"));
for (int j=3; j<=5; j++) _sensor_cal[j] = 500; // Just a large value to load prev[j] the first time
do {
_adc->Ch6(_sensors, adc_values);
for (int j = 3; j <= 5; j++){
prev[j] = _sensor_cal[j];
adc_in = adc_values[j];
adc_in -= _sensor_compensation(j, 0); // temperature ignored
_sensor_cal[j] = adc_in;
}
for(int i = 0; i < 50; i++){ // We take some readings...
callback(20);
_adc->Ch6(_sensors, adc_values);
for (int j = 3; j < 6; j++){
adc_in = adc_values[j];
adc_in -= _sensor_compensation(j, 0); // temperature ignored
_sensor_cal[j] = _sensor_cal[j] * 0.9 + adc_in * 0.1;
}
if(flashcount == 5) {
Serial.printf_P(PSTR("*"));
digitalWrite(A_LED_PIN, LOW);
digitalWrite(C_LED_PIN, HIGH);
}
if(flashcount >= 10) {
flashcount = 0;
digitalWrite(C_LED_PIN, LOW);
digitalWrite(A_LED_PIN, HIGH);
}
flashcount++;
}
// null gravity from the Z accel
_sensor_cal[5] += _gravity * _sensor_signs[5];
total_change = fabs(prev[3] - _sensor_cal[3]) + fabs(prev[4] - _sensor_cal[4]) +fabs(prev[5] - _sensor_cal[5]);
max_offset = (_sensor_cal[3] > _sensor_cal[4]) ? _sensor_cal[3] : _sensor_cal[4];
max_offset = (max_offset > _sensor_cal[5]) ? max_offset : _sensor_cal[5];
callback(500);
} while ( total_change > _accel_total_cal_change || max_offset > _accel_max_cal_offset);
Serial.printf_P(PSTR(" "));
}
/**************************************************/
// Returns the temperature compensated raw gyro value
//---------------------------------------------------
float
AP_IMU_Oilpan::_sensor_compensation(uint8_t channel, int temperature) const
{
// do gyro temperature compensation
if (channel < 3) {
return 1658.0;
/*
return _gyro_temp_curve[channel][0] +
_gyro_temp_curve[channel][1] * temperature +
_gyro_temp_curve[channel][2] * temperature * temperature;
//*/
}
// do fixed-offset accelerometer compensation
return 2041.0; // Average raw value from a 20 board sample
}
float
AP_IMU_Oilpan::_sensor_in(uint8_t channel, uint16_t adc_value, int temperature)
{
float adc_in;
// get the compensated sensor value
//
adc_in = adc_value - _sensor_compensation(channel, temperature);
// adjust for sensor sign and apply calibration offset
//
if (_sensor_signs[channel] < 0) {
adc_in = _sensor_cal[channel] - adc_in;
} else {
adc_in = adc_in - _sensor_cal[channel];
}
// constrain sensor readings to the sensible range
//
if (fabs(adc_in) > _adc_constraint) {
adc_constraints++; // We keep track of the number of times
adc_in = constrain(adc_in, -_adc_constraint, _adc_constraint); // Throw out nonsensical values
}
return adc_in;
}
bool
AP_IMU_Oilpan::update(void)
{
int tc_temp = _adc->Ch(_gyro_temp_ch);
uint16_t adc_values[6];
_sample_time = _adc->Ch6(_sensors, adc_values);
// convert corrected gyro readings to delta acceleration
//
_gyro.x = _gyro_gain_x * _sensor_in(0, adc_values[0], tc_temp);
_gyro.y = _gyro_gain_y * _sensor_in(1, adc_values[1], tc_temp);
_gyro.z = _gyro_gain_z * _sensor_in(2, adc_values[2], tc_temp);
// convert corrected accelerometer readings to acceleration
//
_accel.x = _accel_scale * _sensor_in(3, adc_values[3], tc_temp);
_accel.y = _accel_scale * _sensor_in(4, adc_values[4], tc_temp);
_accel.z = _accel_scale * _sensor_in(5, adc_values[5], tc_temp);
_accel_filtered.x = _accel_filtered.x * .98 + _accel.x * .02;
_accel_filtered.y = _accel_filtered.y * .98 + _accel.y * .02;
_accel_filtered.z = _accel_filtered.z * .98 + _accel.z * .02;
// always updated
return true;
}
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