Subversion Repositories FlightCtrl

#include <avr/io.h>

#include <avr/interrupt.h>

#include "eeprom.h"

#include "output.h"

#include "flight.h"

#include "attitude.h"

#include "timer2.h"

// #define COARSERESOLUTION 1

#ifdef COARSERESOLUTION

#define NEUTRAL_PULSELENGTH 938

#define STABILIZATION_LOG_DIVIDER 6

#define SERVOLIMIT 500

#define SCALE_FACTOR 4

#define CS2 ((1<<CS21)|(1<<CS20))

#else

#define NEUTRAL_PULSELENGTH 3750

#define STABILIZATION_LOG_DIVIDER 4

#define SERVOLIMIT 2000

#define SCALE_FACTOR 16

#define CS2 (1<<CS21)

#endif

#define FRAMELEN ((NEUTRAL_PULSELENGTH + SERVOLIMIT) * staticParams.servoCount + 128)

#define MIN_PULSELENGTH (NEUTRAL_PULSELENGTH - SERVOLIMIT)

#define MAX_PULSELENGTH (NEUTRAL_PULSELENGTH + SERVOLIMIT)

volatile uint8_t recalculateServoTimes = 0;

volatile uint16_t servoValues[MAX_SERVOS];

volatile uint16_t previousManualValues[2];

#define HEF4017R_ON     PORTD |=  (1<<PORTD4)

#define HEF4017R_OFF    PORTD &= ~(1<<PORTD4)

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

 *              Initialize Timer 2

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

void timer2_init(void) {

    uint8_t sreg = SREG;

    // disable all interrupts before reconfiguration

    cli();

    // set PD7 as output of the PWM for pitch servo

    DDRD |= (1 << DDD3);

    PORTD &= ~(1 << PORTD3); // set PD7 to low

    DDRD |= (1 << DDD4); // set PC6 as output (Reset for HEF4017)

    HEF4017R_ON; // enable reset

    // Timer/Counter 2 Control Register A

    // Timer Mode is CTC (Bits: WGM22 = 0, WGM21 = 1, WGM20 = 0)

    // PD3: Output OCR2 match, (Bits: COM2B1 = 1, COM2B0 = 0)

    // PB3: Normal port operation, OC2A disconnected, (Bits: COM2A1 = 0, COM2A0 = 0)

    TCCR2A &= ~((1 << COM2B0) | (1 << COM2A1) | (1 << COM2A0) | (1 << WGM20) | (1 << WGM22));

    TCCR2A |= (1 << COM2B1) | (1 << WGM21);

    // Timer/Counter 2 Control Register B

    // Set clock divider for timer 2 to 20MHz / 8 = 2.5 MHz

    // The timer increments from 0x00 to 0xFF with an update rate of 2.5 kHz or 0.4 us

    // hence the timer overflow interrupt frequency is 625 kHz / 256 = 9.765 kHz or 0.1024ms

    TCCR2B &= ~((1 << FOC2A) | (1 << FOC2B) | (1 << CS20) | (1 << CS21) | (1 << CS22));

    TCCR2B |= CS2;

    // Initialize the Timer/Counter 2 Register

    TCNT2 = 0;

    // Initialize the Output Compare Register A used for signal generation on port PD7.

    OCR2A = 255;

    // Timer/Counter 2 Interrupt Mask Register

    // Enable timer output compare match A Interrupt only

    TIMSK2 &= ~((1 << OCIE2B) | (1 << TOIE2));

    TIMSK2 |= (1 << OCIE2A);

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

      previousManualValues[axis] = dynamicParams.servoManualControl[axis] * SCALE_FACTOR;

    SREG = sreg;

}

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

 * Control (camera gimbal etc.) servos

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

int16_t calculateStabilizedServoAxis(uint8_t axis) {

  int32_t value = attitude[axis] >> STABILIZATION_LOG_DIVIDER; // between -500000 to 500000 extreme limits. Just about

  // With full blast on stabilization gain (255) we want to convert a delta of, say, 125000 to 2000.

  // That is a divisor of about 1<<14. Same conclusion as H&I.

  value *= staticParams.servoConfigurations[axis].stabilizationFactor;

  value = value >> 8;

  if (staticParams.servoConfigurations[axis].flags & SERVO_STABILIZATION_REVERSE)

    return -value;

  return value;

}

// With constant-speed limitation.

uint16_t calculateManualServoAxis(uint8_t axis, uint16_t manualValue) {

  int16_t diff = manualValue - previousManualValues[axis];

  uint8_t maxSpeed = staticParams.servoManualMaxSpeed;

  if (diff > maxSpeed) diff = maxSpeed;

  else if (diff < -maxSpeed) diff = -maxSpeed;

  manualValue = previousManualValues[axis] + diff;

  previousManualValues[axis] = manualValue;

  return manualValue;

}

// add stabilization and manual, apply soft position limits.

// All in a [0..255*SCALE_FACTOR] space (despite signed types used internally)

int16_t featuredServoValue(uint8_t axis) {

  int16_t value = calculateManualServoAxis(axis, dynamicParams.servoManualControl[axis] * SCALE_FACTOR);

  value += calculateStabilizedServoAxis(axis);

  int16_t limit = staticParams.servoConfigurations[axis].minValue * SCALE_FACTOR;

  if (value < limit) value = limit;

  limit = staticParams.servoConfigurations[axis].maxValue * SCALE_FACTOR;

  if (value > limit) value = limit;

  value -= (128 * SCALE_FACTOR);

  if (value < -SERVOLIMIT) value = -SERVOLIMIT;

  else if (value > SERVOLIMIT) value = SERVOLIMIT;

  // Shift into the [NEUTRAL_PULSELENGTH-SERVOLIMIT..NEUTRAL_PULSELENGTH+SERVOLIMIT] space.

  return value + NEUTRAL_PULSELENGTH;

}

void calculateControlServoValues(void) {

  int16_t value;

  for (uint8_t axis=0; axis<4; axis++) {

        value = controlServos[axis];

        value *= 2;

        servoValues[axis] = value + NEUTRAL_PULSELENGTH;

  }

  debugOut.analog[24] = servoValues[0];

  debugOut.analog[25] = servoValues[1];

  debugOut.analog[26] = servoValues[2];

  debugOut.analog[27] = servoValues[3];

}

void calculateFeaturedServoValues(void) {

  int16_t value;

  uint8_t axis;

  // Save the computation cost of computing a new value before the old one is used.

  if (!recalculateServoTimes) return;

  for (axis= MAX_CONTROL_SERVOS; axis<MAX_CONTROL_SERVOS+2; axis++) {

        value = featuredServoValue(axis-MAX_CONTROL_SERVOS);

        servoValues[axis] = value;

  }

  for (axis=MAX_CONTROL_SERVOS+2; axis<MAX_SERVOS; axis++) {

        value = 128 * SCALE_FACTOR;

        servoValues[axis] = value;

  }

  recalculateServoTimes = 0;

}

ISR(TIMER2_COMPA_vect) {

  static uint16_t remainingPulseTime;

  static uint8_t servoIndex = 0;

  static uint16_t sumOfPulseTimes = 0;

  if (!remainingPulseTime) {

    // Pulse is over, and the next pulse has already just started. Calculate length of next pulse.

    if (servoIndex < staticParams.servoCount) {

      // There are more signals to output.

      sumOfPulseTimes += (remainingPulseTime = servoValues[servoIndex]);

      servoIndex++;

    } else {

      // There are no more signals. Reset the counter and make this pulse cover the missing frame time.

      remainingPulseTime = FRAMELEN - sumOfPulseTimes;

      sumOfPulseTimes = servoIndex = 0;

      recalculateServoTimes = 1;

      HEF4017R_ON;

    }

  }

  // Schedule the next OCR2A event. The counter is already reset at this time.

  if (remainingPulseTime > 256+128) {

    // Set output to reset to zero at next OCR match. It does not really matter when the output is set low again,

    // as long as it happens once per pulse. This will, because all pulses are > 255+128 long.

    OCR2A = 255;

    TCCR2A &= ~(1<<COM2A0);

    remainingPulseTime-=256;

  } else if (remainingPulseTime > 256) {

    // Remaining pulse lengths in the range [256..256+128] might cause trouble if handled the standard

    // way, which is in chunks of 256. The remainder would be very small, possibly causing an interrupt on interrupt

    // condition. Instead we now make a chunk of 128. The remaining chunk will then be in [128..255] which is OK.

    remainingPulseTime-=128;

    OCR2A=127;

  } else {

    // Set output to high at next OCR match. This is when the 4017 counter will advance by one. Also set reset low

    TCCR2A |= (1<<COM2A0);

    OCR2A = remainingPulseTime-1;

    remainingPulseTime=0;

    HEF4017R_OFF; // implement servo-disable here, by only removing the reset signal if ServoEnabled!=0.

  }

}