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/*
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  AeroQuad v2.1 - October 2010
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  www.AeroQuad.com
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  Copyright (c) 2010 Ted Carancho.  All rights reserved.
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  An Open Source Arduino based multicopter.
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  This program is free software: you can redistribute it and/or modify 
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  it under the terms of the GNU General Public License as published by 
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  the Free Software Foundation, either version 3 of the License, or 
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  (at your option) any later version. 
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  This program is distributed in the hope that it will be useful, 
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  but WITHOUT ANY WARRANTY; without even the implied warranty of 
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  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 
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  GNU General Public License for more details. 
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  You should have received a copy of the GNU General Public License 
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  along with this program. If not, see <http://www.gnu.org/licenses/>. 
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*/
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// Sensors.pde is responsible for taking on board sensor measuremens of the AeroQuad
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void readSensors(void) {
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  // *********************** Read Critical Sensors **********************
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  // Apply low pass filter to sensor values and center around zero
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  gyro.measure(); // defined in Gyro.h
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  accel.measure(); // defined in Accel.h
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 // ********************* Read Slower Sensors *******************
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 #if defined(HeadingMagHold)
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   if (currentTime > (compassTime + COMPASSLOOPTIME)) { // 10Hz
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     compass.measure(); // defined in compass.h
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     compassTime = currentTime;
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   }
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 #endif
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 #if defined(AltitudeHold)
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   if (currentTime > (altitudeTime + ALTITUDELOOPTIME)) { // 37Hz
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     altitude.measure(); // defined in altitude.h
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     altitudeTime = currentTime;
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   }
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 #endif
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  #if defined(SonarHold)
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   if (currentTime > (sonarTime + SONARLOOPTIME)) { // ~14Hz
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     sonar.measure(); // defined in sonar.h
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     sonarTime = currentTime;
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   }
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 #endif
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 // ****************** Calculate Absolute Angle *****************
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 flightAngle.calculate(); // defined in FlightAngle.h
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}
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// Alternate method to calculate arctangent from: http://www.dspguru.com/comp.dsp/tricks/alg/fxdatan2.htm
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float arctan2(float y, float x) {
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  float coeff_1 = PI/4;
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  float coeff_2 = 3*coeff_1;
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  float abs_y = abs(y)+1e-10;      // kludge to prevent 0/0 condition
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  float r, angle;
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  if (x >= 0) {
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    r = (x - abs_y) / (x + abs_y);
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    angle = coeff_1 - coeff_1 * r;
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  }
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  else {
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    r = (x + abs_y) / (abs_y - x);
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    angle = coeff_2 - coeff_1 * r;
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  }
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  if (y < 0)
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    return(-angle);     // negate if in quad III or IV
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  else
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    return(angle);
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}
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// Used for sensor calibration
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// The mode of a set of numbers returns the value that occurs most frequently
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int findMode(int *data, int arraySize) {
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  boolean done = 0;
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  byte i;
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  int temp, maxData, frequency, maxFrequency;
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  // Sorts numbers from lowest to highest
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  while (done != 1) {        
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    done = 1;
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    for (i=0; i<(arraySize-1); i++) {
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      if (data[i] > data[i+1]) {     // numbers are out of order - swap
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        temp = data[i+1];
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        data[i+1] = data[i];
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        data[i] = temp;
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        done = 0;
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      }
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    }
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  }
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  temp = -32768;
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  frequency = 0;
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  maxFrequency = 0;
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  // Count number of times a value occurs in sorted array
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  for (i=0; i<arraySize; i++) {
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    if (data[i] > temp) {
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      frequency = 0;
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      temp = data[i];
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      frequency++;
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    } else if (data[i] == temp) frequency++;
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    if (frequency > maxFrequency) {
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      maxFrequency = frequency;
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      maxData = data[i];
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    }
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  }
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  return maxData;
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}