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     PORTC |=  (1<<PORTC6)
#define HEF4017R_OFF    PORTC &= ~(1<<PORTC6)

/*****************************************************
 *              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 << DDD7);
    PORTD &= ~(1 << PORTD7); // set PD7 to low

    DDRC |= (1 << DDC6); // 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)
    // PD7: Output OCR2 match, (Bits: COM2A1 = 1, COM2A0 = 0)
    // PD6: Normal port operation, OC2B disconnected, (Bits: COM2B1 = 0, COM2B0 = 0)
    TCCR2A &= ~((1 << COM2A0) | (1 << COM2B1) | (1 << COM2B0) | (1 << WGM20) | (1 << WGM22));
    TCCR2A |= (1 << COM2A1) | (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.
  }
}