Diff: FreeIMU.cpp

Revision:

0:c7a5b6fa0171

Child:

2:a79ea2f610a1

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/FreeIMU.cpp	Wed Feb 20 15:53:00 2013 +0000
@@ -0,0 +1,496 @@
+/*
+FreeIMU.cpp - A libre and easy to use orientation sensing library for Arduino
+Copyright (C) 2011-2012 Fabio Varesano <fabio at varesano dot net>
+
+Development of this code has been supported by the Department of Computer Science,
+Universita' degli Studi di Torino, Italy within the Piemonte Project
+http://www.piemonte.di.unito.it/
+
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the version 3 GNU General Public License as
+published by the Free Software Foundation.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+//#include <inttypes.h>
+//#include <stdint.h>
+//#define DEBUG
+#include "FreeIMU.h"
+#define     M_PI 3.1415926535897932384626433832795
+
+#ifdef DEBUG
+ #define DEBUG_PRINT(x) Serial.println(x)
+ #else
+ #define DEBUG_PRINT(x)
+ #endif
+// #include "WireUtils.h"
+//#include "DebugUtils.h"
+
+//#include "vector_math.h"
+
+FreeIMU::FreeIMU() {
+
+    accgyro = MPU6050(0x69); // I2C
+
+  // initialize quaternion
+  q0 = 1.0f;
+  q1 = 0.0f;
+  q2 = 0.0f;
+  q3 = 0.0f;
+  exInt = 0.0;
+  eyInt = 0.0;
+  ezInt = 0.0;
+  twoKp = twoKpDef;
+  twoKi = twoKiDef;
+  integralFBx = 0.0f,  integralFBy = 0.0f, integralFBz = 0.0f;
+  
+  
+  update.start();
+  int dt_us=0;
+  /*
+  lastUpdate = 0;
+  now = 0;
+  */
+  #ifndef CALIBRATION_H
+  // initialize scale factors to neutral values
+  acc_scale_x = 1;
+  acc_scale_y = 1;
+  acc_scale_z = 1;
+  magn_scale_x = 1;
+  magn_scale_y = 1;
+  magn_scale_z = 1;
+  #else
+  // get values from global variables of same name defined in calibration.h
+  acc_off_x = ::acc_off_x;
+  acc_off_y = ::acc_off_y;
+  acc_off_z = ::acc_off_z;
+  acc_scale_x = ::acc_scale_x;
+  acc_scale_y = ::acc_scale_y;
+  acc_scale_z = ::acc_scale_z;
+  magn_off_x = ::magn_off_x;
+  magn_off_y = ::magn_off_y;
+  magn_off_z = ::magn_off_z;
+  magn_scale_x = ::magn_scale_x;
+  magn_scale_y = ::magn_scale_y;
+  magn_scale_z = ::magn_scale_z;
+  #endif
+}
+
+void FreeIMU::init() {
+
+  init(FIMU_ACCGYRO_ADDR, false);
+
+}
+
+void FreeIMU::init(bool fastmode) {
+ 
+  init(FIMU_ACCGYRO_ADDR, fastmode);
+ 
+}
+
+
+/**
+ * Initialize the FreeIMU I2C bus, sensors and performs gyro offsets calibration
+*/
+
+void FreeIMU::init(int accgyro_addr, bool fastmode) {
+
+  wait_ms(5);
+  /*
+  // disable internal pullups of the ATMEGA which Wire enable by default
+  #if defined(__AVR_ATmega168__) || defined(__AVR_ATmega8__) || defined(__AVR_ATmega328P__)
+    // deactivate internal pull-ups for twi
+    // as per note from atmega8 manual pg167
+    cbi(PORTC, 4);
+    cbi(PORTC, 5);
+  #else
+    // deactivate internal pull-ups for twi
+    // as per note from atmega128 manual pg204
+    cbi(PORTD, 0);
+    cbi(PORTD, 1);
+  #endif
+  */
+  
+  /*
+  if(fastmode) { // switch to 400KHz I2C - eheheh
+    TWBR = ((F_CPU / 400000L) - 16) / 2; // see twi_init in Wire/utility/twi.c
+  }
+*/
+  //accgyro = MPU6050(false, accgyro_addr);
+  accgyro = MPU6050(0x69);
+  accgyro.initialize();
+  accgyro.setI2CMasterModeEnabled(0);
+  accgyro.setI2CBypassEnabled(1);
+  accgyro.setFullScaleGyroRange(MPU6050_GYRO_FS_2000);
+  wait_ms(5);
+
+  
+  // zero gyro
+  zeroGyro();
+  
+  #ifndef CALIBRATION_H
+  // load calibration from eeprom
+  calLoad();
+  #endif
+}
+/*
+#ifndef CALIBRATION_H
+
+static uint8_t location; // assuming ordered reads
+
+void eeprom_read_var(uint8_t size, byte * var) {
+  for(uint8_t i = 0; i<size; i++) {
+    var[i] = EEPROM.read(location + i);
+  }
+  location += size;
+}
+*/
+void FreeIMU::calLoad() {
+/*
+  if(EEPROM.read(FREEIMU_EEPROM_BASE) == FREEIMU_EEPROM_SIGNATURE) { // check if signature is ok so we have good data
+    location = FREEIMU_EEPROM_BASE + 1; // reset location
+    
+    eeprom_read_var(sizeof(acc_off_x), (byte *) &acc_off_x);
+    eeprom_read_var(sizeof(acc_off_y), (byte *) &acc_off_y);
+    eeprom_read_var(sizeof(acc_off_z), (byte *) &acc_off_z);
+    
+    eeprom_read_var(sizeof(magn_off_x), (byte *) &magn_off_x);
+    eeprom_read_var(sizeof(magn_off_y), (byte *) &magn_off_y);
+    eeprom_read_var(sizeof(magn_off_z), (byte *) &magn_off_z);
+    
+    eeprom_read_var(sizeof(acc_scale_x), (byte *) &acc_scale_x);
+    eeprom_read_var(sizeof(acc_scale_y), (byte *) &acc_scale_y);
+    eeprom_read_var(sizeof(acc_scale_z), (byte *) &acc_scale_z);
+    
+    eeprom_read_var(sizeof(magn_scale_x), (byte *) &magn_scale_x);
+    eeprom_read_var(sizeof(magn_scale_y), (byte *) &magn_scale_y);
+    eeprom_read_var(sizeof(magn_scale_z), (byte *) &magn_scale_z);
+  }
+  else {
+  */
+    acc_off_x = 0;
+    acc_off_y = 0;
+    acc_off_z = 0;
+    acc_scale_x = 1;
+    acc_scale_y = 1;
+    acc_scale_z = 1;
+
+    magn_off_x = 0;
+    magn_off_y = 0;
+    magn_off_z = 0;
+    magn_scale_x = 1;
+    magn_scale_y = 1;
+    magn_scale_z = 1;
+ // }
+}
+//#endif
+
+/**
+ * Populates raw_values with the raw_values from the sensors
+*/
+void FreeIMU::getRawValues(int16_t * raw_values) {
+
+    accgyro.getMotion6(&raw_values[0], &raw_values[1], &raw_values[2], &raw_values[3], &raw_values[4], &raw_values[5]);
+
+}
+
+
+/**
+ * Populates values with calibrated readings from the sensors
+*/
+void FreeIMU::getValues(float * values) {  
+
+// MPU6050
+    int16_t accgyroval[6];
+    accgyro.getMotion6(&accgyroval[0], &accgyroval[1], &accgyroval[2], &accgyroval[3], &accgyroval[4], &accgyroval[5]);
+    
+    // remove offsets from the gyroscope
+    accgyroval[3] = accgyroval[3] - gyro_off_x;
+    accgyroval[4] = accgyroval[4] - gyro_off_y;
+    accgyroval[5] = accgyroval[5] - gyro_off_z;
+
+    for(int i = 0; i<6; i++) {
+      if(i < 3) {
+        values[i] = (float) accgyroval[i];
+      }
+      else {
+        values[i] = ((float) accgyroval[i]) / 16.4f; // NOTE: this depends on the sensitivity chosen
+      }
+    }
+
+  
+  
+  #warning Accelerometer calibration active: have you calibrated your device?
+  // remove offsets and scale accelerometer (calibration)
+  values[0] = (values[0] - acc_off_x) / acc_scale_x;
+  values[1] = (values[1] - acc_off_y) / acc_scale_y;
+  values[2] = (values[2] - acc_off_z) / acc_scale_z;
+  
+  
+ 
+}
+
+
+/**
+ * Computes gyro offsets
+*/
+void FreeIMU::zeroGyro() {
+  const int totSamples = 3;
+  int16_t raw[11];
+  float tmpOffsets[] = {0,0,0};
+  
+  for (int i = 0; i < totSamples; i++){
+    getRawValues(raw);
+    tmpOffsets[0] += raw[3];
+    tmpOffsets[1] += raw[4];
+    tmpOffsets[2] += raw[5];
+  }
+  
+  gyro_off_x = tmpOffsets[0] / totSamples;
+  gyro_off_y = tmpOffsets[1] / totSamples;
+  gyro_off_z = tmpOffsets[2] / totSamples;
+}
+
+
+/**
+ * Quaternion implementation of the 'DCM filter' [Mayhony et al].  Incorporates the magnetic distortion
+ * compensation algorithms from Sebastian Madgwick's filter which eliminates the need for a reference
+ * direction of flux (bx bz) to be predefined and limits the effect of magnetic distortions to yaw
+ * axis only.
+ * 
+ * @see: http://www.x-io.co.uk/node/8#open_source_ahrs_and_imu_algorithms
+*/
+
+void  FreeIMU::AHRSupdate(float gx, float gy, float gz, float ax, float ay, float az) {
+
+  float recipNorm;
+  float q0q0, q0q1, q0q2, q0q3, q1q1, q1q2, q1q3, q2q2, q2q3, q3q3;
+  float halfex = 0.0f, halfey = 0.0f, halfez = 0.0f;
+  float qa, qb, qc;
+
+  // Auxiliary variables to avoid repeated arithmetic
+  q0q0 = q0 * q0;
+  q0q1 = q0 * q1;
+  q0q2 = q0 * q2;
+  q0q3 = q0 * q3;
+  q1q1 = q1 * q1;
+  q1q2 = q1 * q2;
+  q1q3 = q1 * q3;
+  q2q2 = q2 * q2;
+  q2q3 = q2 * q3;
+  q3q3 = q3 * q3;
+  
+  
+
+  // Compute feedback only if accelerometer measurement valid (avoids NaN in accelerometer normalisation)
+  if((ax != 0.0f) && (ay != 0.0f) && (az != 0.0f)) {
+    float halfvx, halfvy, halfvz;
+    
+    // Normalise accelerometer measurement
+    recipNorm = invSqrt(ax * ax + ay * ay + az * az);
+    ax *= recipNorm;
+    ay *= recipNorm;
+    az *= recipNorm;
+    
+    // Estimated direction of gravity
+    halfvx = q1q3 - q0q2;
+    halfvy = q0q1 + q2q3;
+    halfvz = q0q0 - 0.5f + q3q3;
+  
+    // Error is sum of cross product between estimated direction and measured direction of field vectors
+    halfex += (ay * halfvz - az * halfvy);
+    halfey += (az * halfvx - ax * halfvz);
+    halfez += (ax * halfvy - ay * halfvx);
+  }
+
+  // Apply feedback only when valid data has been gathered from the accelerometer or magnetometer
+  if(halfex != 0.0f && halfey != 0.0f && halfez != 0.0f) {
+    // Compute and apply integral feedback if enabled
+    if(twoKi > 0.0f) {
+      integralFBx += twoKi * halfex * (1.0f / sampleFreq);  // integral error scaled by Ki
+      integralFBy += twoKi * halfey * (1.0f / sampleFreq);
+      integralFBz += twoKi * halfez * (1.0f / sampleFreq);
+      gx += integralFBx;  // apply integral feedback
+      gy += integralFBy;
+      gz += integralFBz;
+    }
+    else {
+      integralFBx = 0.0f; // prevent integral windup
+      integralFBy = 0.0f;
+      integralFBz = 0.0f;
+    }
+
+    // Apply proportional feedback
+    gx += twoKp * halfex;
+    gy += twoKp * halfey;
+    gz += twoKp * halfez;
+  }
+  
+  // Integrate rate of change of quaternion
+  gx *= (0.5f * (1.0f / sampleFreq));   // pre-multiply common factors
+  gy *= (0.5f * (1.0f / sampleFreq));
+  gz *= (0.5f * (1.0f / sampleFreq));
+  qa = q0;
+  qb = q1;
+  qc = q2;
+  q0 += (-qb * gx - qc * gy - q3 * gz);
+  q1 += (qa * gx + qc * gz - q3 * gy);
+  q2 += (qa * gy - qb * gz + q3 * gx);
+  q3 += (qa * gz + qb * gy - qc * gx);
+  
+  // Normalise quaternion
+  recipNorm = invSqrt(q0 * q0 + q1 * q1 + q2 * q2 + q3 * q3);
+  q0 *= recipNorm;
+  q1 *= recipNorm;
+  q2 *= recipNorm;
+  q3 *= recipNorm;
+}
+
+
+/**
+ * Populates array q with a quaternion representing the IMU orientation with respect to the Earth
+ * 
+ * @param q the quaternion to populate
+*/
+void FreeIMU::getQ(float * q) {
+  float val[9];
+  getValues(val);
+  
+  DEBUG_PRINT(val[3] * M_PI/180);
+  DEBUG_PRINT(val[4] * M_PI/180);
+  DEBUG_PRINT(val[5] * M_PI/180);
+  DEBUG_PRINT(val[0]);
+  DEBUG_PRINT(val[1]);
+  DEBUG_PRINT(val[2]);
+  DEBUG_PRINT(val[6]);
+  DEBUG_PRINT(val[7]);
+  DEBUG_PRINT(val[8]);
+  
+  //now = micros();
+  dt_us=update.read_us();
+  sampleFreq = 1.0 / ((dt_us) / 1000000.0);
+  update.reset();
+ // lastUpdate = now;
+  // gyro values are expressed in deg/sec, the * M_PI/180 will convert it to radians/sec
+
+    AHRSupdate(val[3] * M_PI/180, val[4] * M_PI/180, val[5] * M_PI/180, val[0], val[1], val[2]);
+
+  
+  q[0] = q0;
+  q[1] = q1;
+  q[2] = q2;
+  q[3] = q3;
+}
+
+
+
+/**
+ * Returns the Euler angles in radians defined in the Aerospace sequence.
+ * See Sebastian O.H. Madwick report "An efficient orientation filter for 
+ * inertial and intertial/magnetic sensor arrays" Chapter 2 Quaternion representation
+ * 
+ * @param angles three floats array which will be populated by the Euler angles in radians
+*/
+void FreeIMU::getEulerRad(float * angles) {
+  float q[4]; // quaternion
+  getQ(q);
+  angles[0] = atan2(2 * q[1] * q[2] - 2 * q[0] * q[3], 2 * q[0]*q[0] + 2 * q[1] * q[1] - 1); // psi
+  angles[1] = -asin(2 * q[1] * q[3] + 2 * q[0] * q[2]); // theta
+  angles[2] = atan2(2 * q[2] * q[3] - 2 * q[0] * q[1], 2 * q[0] * q[0] + 2 * q[3] * q[3] - 1); // phi
+}
+
+
+/**
+ * Returns the Euler angles in degrees defined with the Aerospace sequence.
+ * See Sebastian O.H. Madwick report "An efficient orientation filter for 
+ * inertial and intertial/magnetic sensor arrays" Chapter 2 Quaternion representation
+ * 
+ * @param angles three floats array which will be populated by the Euler angles in degrees
+*/
+void FreeIMU::getEuler(float * angles) {
+  getEulerRad(angles);
+  arr3_rad_to_deg(angles);
+}
+
+
+/**
+ * Returns the yaw pitch and roll angles, respectively defined as the angles in radians between
+ * the Earth North and the IMU X axis (yaw), the Earth ground plane and the IMU X axis (pitch)
+ * and the Earth ground plane and the IMU Y axis.
+ * 
+ * @note This is not an Euler representation: the rotations aren't consecutive rotations but only
+ * angles from Earth and the IMU. For Euler representation Yaw, Pitch and Roll see FreeIMU::getEuler
+ * 
+ * @param ypr three floats array which will be populated by Yaw, Pitch and Roll angles in radians
+*/
+void FreeIMU::getYawPitchRollRad(float * ypr) {
+  float q[4]; // quaternion
+  float gx, gy, gz; // estimated gravity direction
+  getQ(q);
+  
+  gx = 2 * (q[1]*q[3] - q[0]*q[2]);
+  gy = 2 * (q[0]*q[1] + q[2]*q[3]);
+  gz = q[0]*q[0] - q[1]*q[1] - q[2]*q[2] + q[3]*q[3];
+  
+  ypr[0] = atan2(2 * q[1] * q[2] - 2 * q[0] * q[3], 2 * q[0]*q[0] + 2 * q[1] * q[1] - 1);
+  ypr[1] = atan(gx / sqrt(gy*gy + gz*gz));
+  ypr[2] = atan(gy / sqrt(gx*gx + gz*gz));
+}
+
+
+/**
+ * Returns the yaw pitch and roll angles, respectively defined as the angles in degrees between
+ * the Earth North and the IMU X axis (yaw), the Earth ground plane and the IMU X axis (pitch)
+ * and the Earth ground plane and the IMU Y axis.
+ * 
+ * @note This is not an Euler representation: the rotations aren't consecutive rotations but only
+ * angles from Earth and the IMU. For Euler representation Yaw, Pitch and Roll see FreeIMU::getEuler
+ * 
+ * @param ypr three floats array which will be populated by Yaw, Pitch and Roll angles in degrees
+*/
+void FreeIMU::getYawPitchRoll(float * ypr) {
+  getYawPitchRollRad(ypr);
+  arr3_rad_to_deg(ypr);
+}
+
+
+/**
+ * Converts a 3 elements array arr of angles expressed in radians into degrees
+*/
+void arr3_rad_to_deg(float * arr) {
+  arr[0] *= 180/M_PI;
+  arr[1] *= 180/M_PI;
+  arr[2] *= 180/M_PI;
+}
+
+
+/**
+ * Fast inverse square root implementation
+ * @see http://en.wikipedia.org/wiki/Fast_inverse_square_root
+*/
+float invSqrt(float number) {
+  volatile long i;
+  volatile float x, y;
+  volatile const float f = 1.5F;
+
+  x = number * 0.5F;
+  y = number;
+  i = * ( long * ) &y;
+  i = 0x5f375a86 - ( i >> 1 );
+  y = * ( float * ) &i;
+  y = y * ( f - ( x * y * y ) );
+  return y;
+}
+
+
+
+