Subversion Repositories FlightCtrl

// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

// + Copyright (c) 04.2007 Holger Buss

// + Nur für den privaten Gebrauch

// + www.MikroKopter.com

// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

// + Es gilt für das gesamte Projekt (Hardware, Software, Binärfiles, Sourcecode und Dokumentation),

// + dass eine Nutzung (auch auszugsweise) nur f�r den privaten und nicht-kommerziellen Gebrauch zulässig ist.

// + Sollten direkte oder indirekte kommerzielle Absichten verfolgt werden, ist mit uns (info@mikrokopter.de) Kontakt

// + bzgl. der Nutzungsbedingungen aufzunehmen.

// + Eine kommerzielle Nutzung ist z.B.Verkauf von MikroKoptern, Bestückung und Verkauf von Platinen oder Bausätzen,

// + Verkauf von Luftbildaufnahmen, usw.

// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

// + Werden Teile des Quellcodes (mit oder ohne Modifikation) weiterverwendet oder veröffentlicht,

// + unterliegen sie auch diesen Nutzungsbedingungen und diese Nutzungsbedingungen incl. Copyright müssen dann beiliegen

// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

// + Sollte die Software (auch auszugesweise) oder sonstige Informationen des MikroKopter-Projekts

// + auf anderen Webseiten oder Medien veröffentlicht werden, muss unsere Webseite "http://www.mikrokopter.de"

// + eindeutig als Ursprung verlinkt und genannt werden

// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

// + Keine Gewähr auf Fehlerfreiheit, Vollständigkeit oder Funktion

// + Benutzung auf eigene Gefahr

// + Wir übernehmen keinerlei Haftung für direkte oder indirekte Personen- oder Sachschäden

// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

// + Die Portierung der Software (oder Teile davon) auf andere Systeme (ausser der Hardware von www.mikrokopter.de) ist nur

// + mit unserer Zustimmung zulässig

// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

// + Die Funktion printf_P() unterliegt ihrer eigenen Lizenz und ist hiervon nicht betroffen

// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

// + Redistributions of source code (with or without modifications) must retain the above copyright notice,

// + this list of conditions and the following disclaimer.

// +   * Neither the name of the copyright holders nor the names of contributors may be used to endorse or promote products derived

// +     from this software without specific prior written permission.

// +   * The use of this project (hardware, software, binary files, sources and documentation) is only permittet

// +     for non-commercial use (directly or indirectly)

// +     Commercial use (for example: selling of MikroKopters, selling of PCBs, assembly, ...) is only permitted

// +     with our written permission

// +   * If sources or documentations are redistributet on other webpages, out webpage (http://www.MikroKopter.de) must be

// +     clearly linked as origin

// +   * porting to systems other than hardware from www.mikrokopter.de is not allowed

// +  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

// +  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

// +  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

// +  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE

// +  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

// +  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

// +  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

// +  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

// +  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

// +  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

// +  POSSIBILITY OF SUCH DAMAGE.

// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

#include <avr/io.h>

#include <avr/interrupt.h>

#include <avr/pgmspace.h>

#include "analog.h"

#include "attitude.h"

#include "sensors.h"

#include "printf_P.h"

// for Delay functions

#include "timer0.h"

// For debugOut

#include "uart0.h"

// For reading and writing acc. meter offsets.

#include "eeprom.h"

// For debugOut.digital

#include "output.h"

// set ADC enable & ADC Start Conversion & ADC Interrupt Enable bit

#define startADC() (ADCSRA |= (1<<ADEN)|(1<<ADSC)|(1<<ADIE))

/*

 * For each A/D conversion cycle, each analog channel is sampled a number of times

 * (see array channelsForStates), and the results for each channel are summed.

 * Here are those for the gyros and the acc. meters. They are not zero-offset.

 * They are exported in the analog.h file - but please do not use them! The only

 * reason for the export is that the ENC-03_FC1.3 modules needs them for calibrating

 * the offsets with the DAC.

 */

volatile uint16_t sensorInputs[8];

volatile int16_t rawGyroSum[3];

volatile int16_t acc[3];

volatile int16_t filteredAcc[2] = { 0,0 };

// volatile int32_t stronglyFilteredAcc[3] = { 0,0,0 };

/*

 * These 4 exported variables are zero-offset. The "PID" ones are used

 * in the attitude control as rotation rates. The "ATT" ones are for

 * integration to angles.

 */

volatile int16_t gyro_PID[2];

volatile int16_t gyro_ATT[2];

volatile int16_t gyroD[2];

volatile int16_t yawGyro;

/*

 * Offset values. These are the raw gyro and acc. meter sums when the copter is

 * standing still. They are used for adjusting the gyro and acc. meter values

 * to be centered on zero.

 */

volatile sensorOffset_t gyroOffset;

volatile sensorOffset_t accOffset;

volatile sensorOffset_t gyroAmplifierOffset;

/*

 * This allows some experimentation with the gyro filters.

 * Should be replaced by #define's later on...

 */

/*

 * Air pressure

 */

volatile uint8_t rangewidth = 106;

// Direct from sensor, irrespective of range.

// volatile uint16_t rawAirPressure;

// Value of 2 samples, with range.

volatile uint16_t simpleAirPressure;

// Value of AIRPRESSURE_SUMMATION_FACTOR samples, with range, filtered.

volatile int32_t filteredAirPressure;

// Partial sum of AIRPRESSURE_SUMMATION_FACTOR samples.

volatile int32_t airPressureSum;

// The number of samples summed into airPressureSum so far.

volatile uint8_t pressureMeasurementCount;

/*

 * Battery voltage, in units of: 1k/11k / 3V * 1024 = 31.03 per volt.

 * That is divided by 3 below, for a final 10.34 per volt.

 * So the initial value of 100 is for 9.7 volts.

 */

volatile int16_t UBat = 100;

/*

 * Control and status.

 */

volatile uint16_t ADCycleCount = 0;

volatile uint8_t analogDataReady = 1;

/*

 * Experiment: Measuring vibration-induced sensor noise.

 */

volatile uint16_t gyroNoisePeak[2];

volatile uint16_t accNoisePeak[2];

// ADC channels

#define AD_GYRO_YAW       0

#define AD_GYRO_ROLL      1

#define AD_GYRO_PITCH     2

#define AD_AIRPRESSURE    3

#define AD_UBAT           4

#define AD_ACC_Z          5

#define AD_ACC_ROLL       6

#define AD_ACC_PITCH      7

/*

 * Table of AD converter inputs for each state.

 * The number of samples summed for each channel is equal to

 * the number of times the channel appears in the array.

 * The max. number of samples that can be taken in 2 ms is:

 * 20e6 / 128 / 13 / (1/2e-3) = 24. Since the main control

 * loop needs a little time between reading AD values and

 * re-enabling ADC, the real limit is (how much?) lower.

 * The acc. sensor is sampled even if not used - or installed

 * at all. The cost is not significant.

 */

const uint8_t channelsForStates[] PROGMEM = {

  AD_GYRO_PITCH, AD_GYRO_ROLL, AD_GYRO_YAW,

  AD_ACC_PITCH, AD_ACC_ROLL, AD_AIRPRESSURE,

  AD_GYRO_PITCH, AD_GYRO_ROLL, AD_ACC_Z, // at 8, measure Z acc.

  AD_GYRO_PITCH, AD_GYRO_ROLL, AD_GYRO_YAW, // at 11, finish yaw gyro

  AD_ACC_PITCH,   // at 12, finish pitch axis acc.

  AD_ACC_ROLL,    // at 13, finish roll axis acc.

  AD_AIRPRESSURE, // at 14, finish air pressure.

  AD_GYRO_PITCH,  // at 15, finish pitch gyro

  AD_GYRO_ROLL,   // at 16, finish roll gyro

  AD_UBAT         // at 17, measure battery.

};

// Feature removed. Could be reintroduced later - but should work for all gyro types then.

// uint8_t GyroDefectPitch = 0, GyroDefectRoll = 0, GyroDefectYaw = 0;

void analog_init(void) {

        uint8_t sreg = SREG;

        // disable all interrupts before reconfiguration

        cli();

        //ADC0 ... ADC7 is connected to PortA pin 0 ... 7

        DDRA = 0x00;

        PORTA = 0x00;

        // Digital Input Disable Register 0

        // Disable digital input buffer for analog adc_channel pins

        DIDR0 = 0xFF;

        // external reference, adjust data to the right

        ADMUX &= ~((1<<REFS1)|(1<<REFS0)|(1<<ADLAR));

        // set muxer to ADC adc_channel 0 (0 to 7 is a valid choice)

        ADMUX = (ADMUX & 0xE0) | channelsForStates[0];

        //Set ADC Control and Status Register A

        //Auto Trigger Enable, Prescaler Select Bits to Division Factor 128, i.e. ADC clock = SYSCKL/128 = 156.25 kHz

        ADCSRA = (1<<ADPS2)|(1<<ADPS1)|(1<<ADPS0);

        //Set ADC Control and Status Register B

        //Trigger Source to Free Running Mode

        ADCSRB &= ~((1<<ADTS2)|(1<<ADTS1)|(1<<ADTS0));

        startAnalogConversionCycle();

        // restore global interrupt flags

        SREG = sreg;

}

void measureNoise(const int16_t sensor,

                volatile uint16_t* const noiseMeasurement, const uint8_t damping) {

        if (sensor > (int16_t) (*noiseMeasurement)) {

                *noiseMeasurement = sensor;

        } else if (-sensor > (int16_t) (*noiseMeasurement)) {

                *noiseMeasurement = -sensor;

        } else if (*noiseMeasurement > damping) {

                *noiseMeasurement -= damping;

        } else {

                *noiseMeasurement = 0;

        }

}

/*

 * Min.: 0

 * Max: About 106 * 240 + 2047 = 27487; it is OK with just a 16 bit type.

 */

uint16_t getSimplePressure(int advalue) {

        return (uint16_t) OCR0A * (uint16_t) rangewidth + advalue;

}

void startAnalogConversionCycle(void) {

  analogDataReady = 0;

  // Stop the sampling. Cycle is over.

  for (uint8_t i = 0; i < 8; i++) {

    sensorInputs[i] = 0;

  }

  ADMUX = (ADMUX & 0xE0) | channelsForStates[0];

  startADC();

}

/*****************************************************

 * Interrupt Service Routine for ADC

 * Runs at 312.5 kHz or 3.2 �s. When all states are

 * processed further conversions are stopped.

 *****************************************************/

ISR(ADC_vect) {

  static uint8_t ad_channel = AD_GYRO_PITCH, state = 0;

  sensorInputs[ad_channel] += ADC;

  // set up for next state.

  state++;

  if (state < 18) {

    ad_channel = pgm_read_byte(&channelsForStates[state]);

    // set adc muxer to next ad_channel

    ADMUX = (ADMUX & 0xE0) | ad_channel;

    // after full cycle stop further interrupts

    startADC();

  } else {

    state = 0;

    ADCycleCount++;

    analogDataReady = 1;

    // do not restart ADC converter. 

  }

}

void analog_updateGyros(void) {

  // for various filters...

  int16_t tempOffsetGyro, tempGyro;

  for (uint8_t axis=0; axis<2; axis++) {

    tempGyro = rawGyroSum[axis] = sensorInputs[AD_GYRO_PITCH-axis];

    /*

     * Process the gyro data for the PID controller.

     */

    // 1) Extrapolate: Near the ends of the range, we boost the input significantly. This simulates a

    //    gyro with a wider range, and helps counter saturation at full control.

    if (staticParams.bitConfig & CFG_GYRO_SATURATION_PREVENTION) {

      if (tempGyro < SENSOR_MIN_PITCHROLL) {

        debugOut.digital[0] |= DEBUG_SENSORLIMIT;

        tempGyro = tempGyro * EXTRAPOLATION_SLOPE - EXTRAPOLATION_LIMIT;

      } else if (tempGyro > SENSOR_MAX_PITCHROLL) {

        debugOut.digital[0] |= DEBUG_SENSORLIMIT;

        tempGyro = (tempGyro - SENSOR_MAX_PITCHROLL) * EXTRAPOLATION_SLOPE

          + SENSOR_MAX_PITCHROLL;

      } else {

        debugOut.digital[0] &= ~DEBUG_SENSORLIMIT;

      }

    }

    // 2) Apply sign and offset, scale before filtering.

    if (GYRO_REVERSED[axis]) {

      tempOffsetGyro = (gyroOffset.offsets[axis] - tempGyro) * GYRO_FACTOR_PITCHROLL;

    } else {

      tempOffsetGyro = (tempGyro - gyroOffset.offsets[axis]) * GYRO_FACTOR_PITCHROLL;

    }

    // 3) Scale and filter.

    tempOffsetGyro = (gyro_PID[axis] * (staticParams.gyroPIDFilterConstant - 1) + tempOffsetGyro) / staticParams.gyroPIDFilterConstant;

    // 4) Measure noise.

    measureNoise(tempOffsetGyro, &gyroNoisePeak[axis], GYRO_NOISE_MEASUREMENT_DAMPING);

    // 5) Differential measurement.

    gyroD[axis] = (gyroD[axis] * (staticParams.gyroDFilterConstant - 1) + (tempOffsetGyro - gyro_PID[axis])) / staticParams.gyroDFilterConstant;

    // 6) Done.

    gyro_PID[axis] = tempOffsetGyro;

    /*

     * Now process the data for attitude angles.

     */

    tempGyro = rawGyroSum[axis];

    // 1) Apply sign and offset, scale before filtering.

    if (GYRO_REVERSED[axis]) {

      tempOffsetGyro = (gyroOffset.offsets[axis] - tempGyro) * GYRO_FACTOR_PITCHROLL;

    } else {

      tempOffsetGyro = (tempGyro - gyroOffset.offsets[axis]) * GYRO_FACTOR_PITCHROLL;

    }

    // 2) Filter.

    gyro_ATT[axis] = (gyro_ATT[axis] * (staticParams.gyroATTFilterConstant - 1) + tempOffsetGyro) / staticParams.gyroATTFilterConstant;

  }

  // Yaw gyro.

  rawGyroSum[YAW] = sensorInputs[AD_GYRO_YAW];

  if (GYRO_REVERSED[YAW])

    yawGyro = gyroOffset.offsets[YAW] - sensorInputs[AD_GYRO_YAW];

  else

    yawGyro = sensorInputs[AD_GYRO_YAW] - gyroOffset.offsets[YAW];

  debugOut.analog[3] = rawGyroSum[0];

  debugOut.analog[4] = rawGyroSum[1];

  debugOut.analog[5] = rawGyroSum[2];

}

void analog_updateAccelerometers(void) {

  // Pitch and roll axis accelerations.

  for (uint8_t axis=0; axis<2; axis++) {

    if (ACC_REVERSED[axis])

      acc[axis] = accOffset.offsets[axis] - sensorInputs[AD_ACC_PITCH-axis];

    else

      acc[axis] = sensorInputs[AD_ACC_PITCH-axis] - accOffset.offsets[axis];

    filteredAcc[axis] = (filteredAcc[axis] * (staticParams.accFilterConstant - 1) + acc[axis]) / staticParams.accFilterConstant;

    /*

      stronglyFilteredAcc[PITCH] =

      (stronglyFilteredAcc[PITCH] * 99 + acc[PITCH] * 10) / 100;

    */

    measureNoise(acc[axis], &accNoisePeak[axis], 1);

  }

  // Z acc.

  if (ACC_REVERSED[Z])

    acc[Z] = accOffset.offsets[Z] - sensorInputs[AD_ACC_Z];

  else

    acc[Z] = sensorInputs[AD_ACC_Z] - accOffset.offsets[Z];

  /*

    stronglyFilteredAcc[Z] =

    (stronglyFilteredAcc[Z] * 99 + acc[Z] * 10) / 100;

  */

}

void analog_updateAirPressure(void) {

  static uint16_t pressureAutorangingWait = 25;

  uint16_t rawAirPressure;

  int16_t newrange;

  // air pressure

  if (pressureAutorangingWait) {

    //A range switch was done recently. Wait for steadying.

    pressureAutorangingWait--;

    debugOut.analog[27] = (uint16_t) OCR0A;

    debugOut.analog[31] = simpleAirPressure;

  } else {

    rawAirPressure = sensorInputs[AD_AIRPRESSURE];

    if (rawAirPressure < MIN_RAWPRESSURE) {

      // value is too low, so decrease voltage on the op amp minus input, making the value higher.

      newrange = OCR0A - (MAX_RAWPRESSURE - MIN_RAWPRESSURE) / (rangewidth * 4); // 4; // (MAX_RAWPRESSURE - rawAirPressure) / (rangewidth * 2) + 1;

      if (newrange > MIN_RANGES_EXTRAPOLATION) {

        pressureAutorangingWait = (OCR0A - newrange) * AUTORANGE_WAIT_FACTOR; // = OCRA0 - OCRA0 +

        OCR0A = newrange;

      } else {

        if (OCR0A) {

          OCR0A--;

          pressureAutorangingWait = AUTORANGE_WAIT_FACTOR;

        }

      }

    } else if (rawAirPressure > MAX_RAWPRESSURE) {

      // value is too high, so increase voltage on the op amp minus input, making the value lower.

      // If near the end, make a limited increase

      newrange = OCR0A + (MAX_RAWPRESSURE - MIN_RAWPRESSURE) / (rangewidth * 4); // 4;  // (rawAirPressure - MIN_RAWPRESSURE) / (rangewidth * 2) - 1;

      if (newrange < MAX_RANGES_EXTRAPOLATION) {

        pressureAutorangingWait = (newrange - OCR0A) * AUTORANGE_WAIT_FACTOR;

        OCR0A = newrange;

      } else {

        if (OCR0A < 254) {

          OCR0A++;

          pressureAutorangingWait = AUTORANGE_WAIT_FACTOR;

        }

      }

    }

    // Even if the sample is off-range, use it.

    simpleAirPressure = getSimplePressure(rawAirPressure);

    debugOut.analog[27] = (uint16_t) OCR0A;

    debugOut.analog[31] = simpleAirPressure;

    if (simpleAirPressure < MIN_RANGES_EXTRAPOLATION * rangewidth) {

      // Danger: pressure near lower end of range. If the measurement saturates, the

      // copter may climb uncontrolledly... Simulate a drastic reduction in pressure.

      debugOut.digital[1] |= DEBUG_SENSORLIMIT;

      airPressureSum += (int16_t) MIN_RANGES_EXTRAPOLATION * rangewidth

        + (simpleAirPressure - (int16_t) MIN_RANGES_EXTRAPOLATION

           * rangewidth) * PRESSURE_EXTRAPOLATION_COEFF;

    } else if (simpleAirPressure > MAX_RANGES_EXTRAPOLATION * rangewidth) {

      // Danger: pressure near upper end of range. If the measurement saturates, the

      // copter may descend uncontrolledly... Simulate a drastic increase in pressure.

      debugOut.digital[1] |= DEBUG_SENSORLIMIT;

      airPressureSum += (int16_t) MAX_RANGES_EXTRAPOLATION * rangewidth

        + (simpleAirPressure - (int16_t) MAX_RANGES_EXTRAPOLATION

           * rangewidth) * PRESSURE_EXTRAPOLATION_COEFF;

    } else {

      // normal case.

      // If AIRPRESSURE_SUMMATION_FACTOR is an odd number we only want to add half the double sample.

      // The 2 cases above (end of range) are ignored for this.

      debugOut.digital[1] &= ~DEBUG_SENSORLIMIT;

      if (pressureMeasurementCount == AIRPRESSURE_SUMMATION_FACTOR - 1)

        airPressureSum += simpleAirPressure / 2;

      else

        airPressureSum += simpleAirPressure;

    }

    // 2 samples were added.

    pressureMeasurementCount += 2;

    if (pressureMeasurementCount >= AIRPRESSURE_SUMMATION_FACTOR) {

      filteredAirPressure = (filteredAirPressure * (AIRPRESSURE_FILTER - 1)

                             + airPressureSum + AIRPRESSURE_FILTER / 2) / AIRPRESSURE_FILTER;

      pressureMeasurementCount = airPressureSum = 0;

    }

  }

}

void analog_updateBatteryVoltage(void) {

  // Battery. The measured value is: (V * 1k/11k)/3v * 1024 = 31.03 counts per volt (max. measurable is 33v).

  // This is divided by 3 --> 10.34 counts per volt.

  UBat = (3 * UBat + sensorInputs[AD_UBAT] / 3) / 4;

  debugOut.analog[11] = UBat;

}

void analog_update(void) {

  analog_updateGyros();

  analog_updateAccelerometers();

  analog_updateAirPressure();

  analog_updateBatteryVoltage();

}

void analog_setNeutral() {

  if (gyroAmplifierOffset_readFromEEProm()) {

    printf("gyro amp invalid, you must recalibrate.");

    gyro_loadOffsets(1);

  }

  if (gyroOffset_readFromEEProm()) {

    printf("gyro offsets invalid, you must recalibrate.");

    gyroOffset.offsets[PITCH] = gyroOffset.offsets[ROLL] = 512 * GYRO_SUMMATION_FACTOR_PITCHROLL;

    gyroOffset.offsets[YAW] = 512 * GYRO_SUMMATION_FACTOR_YAW;

  }

  debugOut.analog[6] = gyroOffset.offsets[PITCH];

  debugOut.analog[7] = gyroOffset.offsets[ROLL];

  if (accOffset_readFromEEProm()) {

    printf("acc. meter offsets invalid, you must recalibrate.");

    accOffset.offsets[PITCH] = accOffset.offsets[ROLL] = 512 * ACC_SUMMATION_FACTOR_PITCHROLL;

    accOffset.offsets[Z] = 512 * ACC_SUMMATION_FACTOR_Z;

  }

  // Noise is relative to offset. So, reset noise measurements when changing offsets.

  gyroNoisePeak[PITCH] = gyroNoisePeak[ROLL] = 0;

  accNoisePeak[PITCH] = accNoisePeak[ROLL] = 0;

  // Setting offset values has an influence in the analog.c ISR

  // Therefore run measurement for 100ms to achive stable readings

  delay_ms_with_adc_measurement(100);

  // Rough estimate. Hmm no nothing happens at calibration anyway.

  // airPressureSum = simpleAirPressure * (AIRPRESSURE_SUMMATION_FACTOR/2);

  // pressureMeasurementCount = 0;

}

void analog_calibrateGyros(void) {

#define GYRO_OFFSET_CYCLES 32

  uint8_t i, axis;

  int32_t offsets[3] = { 0, 0, 0 };

  gyro_calibrate();

  // determine gyro bias by averaging (requires that the copter does not rotate around any axis!)

  for (i = 0; i < GYRO_OFFSET_CYCLES; i++) {

    delay_ms_with_adc_measurement(20);

    for (axis = PITCH; axis <= YAW; axis++) {

      offsets[axis] += rawGyroSum[axis];

    }

  }

  for (axis = PITCH; axis <= YAW; axis++) {

    gyroOffset.offsets[axis] = (offsets[axis] + GYRO_OFFSET_CYCLES / 2) / GYRO_OFFSET_CYCLES;

  }

  gyroOffset_writeToEEProm();  

}

/*

 * Find acc. offsets for a neutral reading, and write them to EEPROM.

 * Does not (!} update the local variables. This must be done with a

 * call to analog_calibrate() - this always (?) is done by the caller

 * anyway. There would be nothing wrong with updating the variables

 * directly from here, though.

 */

void analog_calibrateAcc(void) {

#define ACC_OFFSET_CYCLES 10

  uint8_t i, axis;

  int32_t deltaOffset[3] = { 0, 0, 0 };

  int16_t filteredDelta;

  for (i = 0; i < ACC_OFFSET_CYCLES; i++) {

    delay_ms_with_adc_measurement(10);

    for (axis = PITCH; axis <= YAW; axis++) {

      deltaOffset[axis] += acc[axis];

    }

  }

  for (axis = PITCH; axis <= YAW; axis++) {

    filteredDelta = (deltaOffset[axis] + ACC_OFFSET_CYCLES / 2)

      / ACC_OFFSET_CYCLES;

    accOffset.offsets[axis] += ACC_REVERSED[axis] ? -filteredDelta : filteredDelta;

  }

  accOffset_writeToEEProm();  

}