Subversion Repositories FlightCtrl

#include <stdlib.h>

#include <avr/io.h>

#include <avr/interrupt.h>

#include "main.h"

volatile int16_t PPM_in[15]; //PPM24 supports 12 channels per frame

volatile uint8_t NewPpmData = 1;

void RC_Init (void)

{

        uint8_t sreg = SREG;

        // disable all interrupts before reconfiguration

        cli();

        // PPM-signal is connected to the Input Capture Pin (PD6) of timer 1

        DDRD &= ~(1<<DDD6);

        PORTD |= (1<<PORTD6);

        // Channel 5,6,7 is decoded to servo signals at pin PD5 (J3), PD4(J4), PD3(J5)

        // set as output

        DDRD |= (1<<DDD5)|(1<<DDD4);

        // low level

        PORTD &= ~((1<<PORTD5)|(1<<PORTD4));

        // PD3 can't be used in FC 1.1 if 2nd UART is activated

        // because TXD1 is at that port

        if(BoardRelease == 10)

        {

                DDRD |= (1<<PORTD3);

                PORTD &= ~(1<<PORTD3);

        }

        // Timer/Counter1 Control Register A, B, C

        // Normal Mode (bits: WGM13=0, WGM12=0, WGM11=0, WGM10=0)

        // Compare output pin A & B is disabled (bits: COM1A1=0, COM1A0=0, COM1B1=0, COM1B0=0)

        // Set clock source to SYSCLK/64 (bit: CS12=0, CS11=1, CS10=1)

        // Enable input capture noise cancler (bit: ICNC1=1)

        // Trigger on positive edge of the input capture pin (bit: ICES1=1),

    // The longest period is 0xFFFF / 312.5 kHz = 0.209712 s.

        TCCR1A &= ~((1<<COM1A1)|(1<<COM1A0)|(1<<COM1B1)|(1<<COM1B0)|(1<<WGM11)|(1<<WGM10));

        TCCR1B &= ~((1<<WGM13)|(1<<WGM12)|(1<<CS12));

        TCCR1B |= (1<<CS11)|(1<<CS10)|(1<<ICES1)|(1<<ICNC1);

        TCCR1C &= ~((1<<FOC1A)|(1<<FOC1B));

        // Timer/Counter1 Interrupt Mask Register

        // Enable Input Capture Interrupt (bit: ICIE1=1)

        // Disable Output Compare A & B Match Interrupts (bit: OCIE1B=0, OICIE1A=0)

        // Enable Overflow Interrupt (bit: TOIE1=0)

    SREG = sreg;

}

// happens every 0.209712 s.

// check for at least one new frame per timer overflow (timeout)

ISR(TIMER1_OVF_vect)

{

        if (NewRCFrames == 0) RC_Quality -= RC_Quality/8;

        NewRCFrames = 0;

}

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

/*         Every time a positive edge is detected at PD6            */

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

/*                               t-Frame

       <----------------------------------------------------------------------->

         ____   ______   _____   ________                ______    sync gap      ____

        |    | |      | |     | |        |              |      |                |

     ___|    |_|      |_|     |_|        |_.............|      |________________|

        <-----><-------><------><-------->              <------>                <---

          t0       t1      t2       t4                     tn                     t0

The PPM-Frame length is 22.5 ms.

Channel high pulse width range is 0.7 ms to 1.7 ms completed by an 0.3 ms low pulse.

The mininimum time delay of two events coding a channel is ( 0.7 + 0.3) ms = 1 ms.

The maximum time delay of two events coding a chanel is ( 1.7 + 0.3) ms = 2 ms.

The minimum duration of all channels at minimum value is  8 * 1 ms = 8 ms.

The maximum duration of all channels at maximum value is  8 * 2 ms = 16 ms.

*/

ISR(TIMER1_CAPT_vect) // typical rate of 1 ms to 2 ms

{

    int16_t signal = 0, tmp;

        static uint16_t oldICR1 = 0;

        // 16bit Input Capture Register ICR1 contains the timer value TCNT1

        // calculate the time delay to the previous event time which is stored in oldICR1

        signal = (uint16_t) ICR1 - oldICR1;

        if((signal > 1100) && (signal < 8000))

                // if a sync gap happens and there where at least 4 channels decoded before

                // then the NewPpmData flag is reset indicating valid data in the PPM_in[] array.

                if(index >= 4)

                        NewRCFrames++;

                // synchronize channel index

        }

        else // within the PPM frame

                        // check for valid signal length (0.8 ms < signal < 2.1984 ms)

                signal -= 466; // offset of 1.4912 ms ??? (469 * 3.2µs = 1.5008 ms)

                                }

                if(RC_Quality >= 195)  PPM_diff[index] = ((tmp - PPM_in[index]) / 3) * 3; // cut off lower 3 bit for nois reduction

            }

            index++; // next channel

                if(index == 5) PORTD |= (1<<PORTD5); else PORTD &= ~(1<<PORTD5);

                {