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333 lines
8.3 KiB
333 lines
8.3 KiB
/* |
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AP_IMU.cpp - IMU Sensor Library for Ardupilot Mega |
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Code by Doug Weibel, Jordi Muñoz and Jose Julio. DIYDrones.com |
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This library works with the ArduPilot Mega and "Oilpan" |
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This library is free software; you can redistribute it and/or |
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modify it under the terms of the GNU Lesser General Public |
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License as published by the Free Software Foundation; either |
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version 2.1 of the License, or (at your option) any later version. |
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Methods: |
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quick_init() : For air restart |
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init() : Calibration |
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gyro_init() : For ground start using saved accel offsets |
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get_gyro() : Returns gyro vector. Elements in radians/second |
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get_accel() : Returns acceleration vector. Elements in meters/seconds squared |
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*/ |
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#include <AP_IMU.h> |
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#define A_LED_PIN 37 //37 = A, 35 = C |
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#define C_LED_PIN 35 |
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// ADC : Voltage reference 3.3v / 12bits(4096 steps) => 0.8mV/ADC step |
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// ADXL335 Sensitivity(from datasheet) => 330mV/g, 0.8mV/ADC step => 330/0.8 = 412 |
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// Tested value : 418 |
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#define GRAVITY 418 //this equivalent to 1G in the raw data coming from the accelerometer |
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#define accel_scale(x) (x*9.80665/GRAVITY)//Scaling the raw data of the accel to actual acceleration in meters per second squared |
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#define ToRad(x) (x*0.01745329252) // *pi/180 |
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#define ToDeg(x) (x*57.2957795131) // *180/pi |
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// IDG500 Sensitivity (from datasheet) => 2.0mV/º/s, 0.8mV/ADC step => 0.8/3.33 = 0.4 |
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// Tested values : 0.4026, ?, 0.4192 |
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#define _gyro_gain_x 0.4 //X axis Gyro gain |
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#define _gyro_gain_y 0.41 //Y axis Gyro gain |
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#define _gyro_gain_z 0.41 //Z axis Gyro |
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#define ADC_CONSTRAINT 900 |
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// Sensor: GYROX, GYROY, GYROZ, ACCELX, ACCELY, ACCELZ |
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const uint8_t AP_IMU::_sensors[6] = {1,2,0,4,5,6}; // For ArduPilot Mega Sensor Shield Hardware |
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const int AP_IMU::_sensor_signs[] = { 1, -1, -1, |
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1, -1, -1}; |
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// Temp compensation curve constants |
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// These must be produced by measuring data and curve fitting |
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// [X/Y/Z gyro][A/B/C or 0 order/1st order/2nd order constants] |
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const float AP_IMU::_gyro_temp_curve[3][3] = { |
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{1665,0,0}, |
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{1665,0,0}, |
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{1665,0,0} |
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}; // To Do - make additional constructors to pass this in. |
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void |
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AP_IMU::init(void) |
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{ |
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init_gyro(); |
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init_accel(); |
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} |
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/**************************************************/ |
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void |
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AP_IMU::init_gyro(void) |
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{ |
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float temp; |
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int flashcount = 0; |
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int tc_temp = _adc->Ch(_gyro_temp_ch); |
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delay(500); |
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Serial.println("Init Gyro"); |
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for(int c = 0; c < 200; c++){ |
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digitalWrite(A_LED_PIN, LOW); |
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digitalWrite(C_LED_PIN, HIGH); |
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delay(20); |
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for (int i = 0; i < 6; i++) |
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_adc_in[i] = _adc->Ch(_sensors[i]); |
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digitalWrite(A_LED_PIN, HIGH); |
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digitalWrite(C_LED_PIN, LOW); |
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delay(20); |
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} |
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for(int i = 0; i < 200; i++){ |
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for (int j = 0; j <= 2; j++){ |
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_adc_in[j] = _adc->Ch(_sensors[j]); |
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// Subtract temp compensated typical gyro bias |
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_adc_in[j] -= gyro_temp_comp(j, tc_temp); |
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// filter |
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_adc_offset[j] = _adc_offset[j] * 0.9 + _adc_in[j] * 0.1; |
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//Serial.print(_adc_offset[j], 1); |
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//Serial.print(", "); |
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} |
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//Serial.println(" "); |
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delay(20); |
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if(flashcount == 5) { |
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Serial.print("*"); |
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digitalWrite(A_LED_PIN, LOW); |
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digitalWrite(C_LED_PIN, HIGH); |
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} |
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if(flashcount >= 10) { |
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flashcount = 0; |
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digitalWrite(C_LED_PIN, LOW); |
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digitalWrite(A_LED_PIN, HIGH); |
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} |
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flashcount++; |
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} |
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Serial.println(" "); |
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save_gyro_eeprom(); |
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} |
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void |
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AP_IMU::init_accel(void) // 3, 4, 5 |
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{ |
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float temp; |
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int flashcount = 0; |
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delay(500); |
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Serial.println("Init Accel"); |
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for (int j = 3; j <= 5; j++){ |
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_adc_in[j] = _adc->Ch(_sensors[j]); |
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_adc_in[j] -= 2025; |
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_adc_offset[j] = _adc_in[j]; |
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} |
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for(int i = 0; i < 200; i++){ // We take some readings... |
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delay(20); |
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for (int j = 3; j <= 5; j++){ |
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_adc_in[j] = _adc->Ch(_sensors[j]); |
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_adc_in[j] -= 2025; |
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_adc_offset[j] = _adc_offset[j] * 0.9 + _adc_in[j] * 0.1; |
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//Serial.print(j); |
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//Serial.print(": "); |
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//Serial.print(_adc_in[j], 1); |
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//Serial.print(" | "); |
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//Serial.print(_adc_offset[j], 1); |
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//Serial.print(", "); |
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} |
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//Serial.println(" "); |
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if(flashcount == 5) { |
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Serial.print("*"); |
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digitalWrite(A_LED_PIN, LOW); |
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digitalWrite(C_LED_PIN, HIGH); |
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} |
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if(flashcount >= 10) { |
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flashcount = 0; |
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digitalWrite(C_LED_PIN, LOW); |
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digitalWrite(A_LED_PIN, HIGH); |
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} |
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flashcount++; |
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} |
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Serial.println(" "); |
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_adc_offset[5] += GRAVITY * _sensor_signs[5]; |
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save_accel_eeprom(); |
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} |
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void |
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AP_IMU::zero_accel(void) // 3, 4, 5 |
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{ |
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_adc_offset[3] = 0; |
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_adc_offset[4] = 0; |
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_adc_offset[5] = 0; |
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save_accel_eeprom(); |
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} |
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/**************************************************/ |
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// Returns the temperature compensated raw gyro value |
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//--------------------------------------------------- |
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float |
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AP_IMU::gyro_temp_comp(int i, int temp) const |
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{ |
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// We use a 2nd order curve of the form Gtc = A + B * Graw + C * (Graw)**2 |
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//------------------------------------------------------------------------ |
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return _gyro_temp_curve[i][0] + _gyro_temp_curve[i][1] * temp + _gyro_temp_curve[i][2] * temp * temp; |
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} |
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/**************************************************/ |
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Vector3f |
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AP_IMU::get_gyro(void) |
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{ |
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int tc_temp = _adc->Ch(_gyro_temp_ch); |
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for (int i = 0; i < 3; i++) { |
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_adc_in[i] = _adc->Ch(_sensors[i]); |
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_adc_in[i] -= gyro_temp_comp(i,tc_temp); // Subtract temp compensated typical gyro bias |
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if (_sensor_signs[i] < 0) |
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_adc_in[i] = (_adc_offset[i] - _adc_in[i]); |
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else |
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_adc_in[i] = (_adc_in[i] - _adc_offset[i]); |
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if (fabs(_adc_in[i]) > ADC_CONSTRAINT) { |
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adc_constraints++; // We keep track of the number of times |
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_adc_in[i] = constrain(_adc_in[i], -ADC_CONSTRAINT, ADC_CONSTRAINT); // Throw out nonsensical values |
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} |
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} |
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_gyro_vector.x = ToRad(_gyro_gain_x) * _adc_in[0]; |
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_gyro_vector.y = ToRad(_gyro_gain_y) * _adc_in[1]; |
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_gyro_vector.z = ToRad(_gyro_gain_z) * _adc_in[2]; |
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return _gyro_vector; |
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} |
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/**************************************************/ |
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Vector3f |
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AP_IMU::get_accel(void) |
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{ |
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for (int i = 3; i < 6; i++) { |
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_adc_in[i] = _adc->Ch(_sensors[i]); |
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_adc_in[i] -= 2025; // Subtract typical accel bias |
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if (_sensor_signs[i] < 0) |
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_adc_in[i] = _adc_offset[i] - _adc_in[i]; |
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else |
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_adc_in[i] = _adc_in[i] - _adc_offset[i]; |
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if (fabs(_adc_in[i]) > ADC_CONSTRAINT) { |
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adc_constraints++; // We keep track of the number of times |
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_adc_in[i] = constrain(_adc_in[i], -ADC_CONSTRAINT, ADC_CONSTRAINT); // Throw out nonsensical values |
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} |
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} |
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_accel_vector.x = accel_scale(_adc_in[3]); |
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_accel_vector.y = accel_scale(_adc_in[4]); |
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_accel_vector.z = accel_scale(_adc_in[5]); |
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return _accel_vector; |
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} |
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/********************************************************************************/ |
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void |
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AP_IMU::load_gyro_eeprom(void) |
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{ |
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_adc_offset[0] = read_EE_float(_address ); |
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_adc_offset[1] = read_EE_float(_address + 4); |
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_adc_offset[2] = read_EE_float(_address + 8); |
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} |
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void |
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AP_IMU::save_gyro_eeprom(void) |
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{ |
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write_EE_float(_adc_offset[0], _address); |
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write_EE_float(_adc_offset[1], _address + 4); |
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write_EE_float(_adc_offset[2], _address + 8); |
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} |
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/********************************************************************************/ |
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void |
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AP_IMU::load_accel_eeprom(void) |
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{ |
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_adc_offset[3] = read_EE_float(_address + 12); |
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_adc_offset[4] = read_EE_float(_address + 16); |
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_adc_offset[5] = read_EE_float(_address + 20); |
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} |
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void |
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AP_IMU::save_accel_eeprom(void) |
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{ |
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write_EE_float(_adc_offset[3], _address + 12); |
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write_EE_float(_adc_offset[4], _address + 16); |
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write_EE_float(_adc_offset[5], _address + 20); |
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} |
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void |
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AP_IMU::print_accel_offsets(void) |
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{ |
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Serial.print("Accel offsets: "); |
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Serial.print(_adc_offset[3], 2); |
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Serial.print(", "); |
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Serial.print(_adc_offset[4], 2); |
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Serial.print(", "); |
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Serial.println(_adc_offset[5], 2); |
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} |
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void |
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AP_IMU::print_gyro_offsets(void) |
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{ |
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Serial.print("Gyro offsets: "); |
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Serial.print(_adc_offset[0], 2); |
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Serial.print(", "); |
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Serial.print(_adc_offset[1], 2); |
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Serial.print(", "); |
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Serial.println(_adc_offset[2], 2); |
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} |
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/********************************************************************************/ |
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float |
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AP_IMU::read_EE_float(int address) |
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{ |
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union { |
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byte bytes[4]; |
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float value; |
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} _floatOut; |
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for (int i = 0; i < 4; i++) |
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_floatOut.bytes[i] = eeprom_read_byte((uint8_t *) (address + i)); |
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return _floatOut.value; |
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} |
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void |
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AP_IMU::write_EE_float(float value, int address) |
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{ |
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union { |
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byte bytes[4]; |
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float value; |
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} _floatIn; |
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_floatIn.value = value; |
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for (int i = 0; i < 4; i++) |
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eeprom_write_byte((uint8_t *) (address + i), _floatIn.bytes[i]); |
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} |
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