Rev 886 | Go to most recent revision | Details | Compare with Previous | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 886 | killagreg | 1 | #include <avr/io.h> |
| 2 | #include <avr/interrupt.h> |
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| 3 | #include "fc.h" |
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| 4 | #include "eeprom.h" |
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| 5 | |||
| 6 | volatile int16_t ServoValue = 0; |
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| 7 | |||
| 8 | |||
| 9 | /*****************************************************/ |
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| 10 | /* Initialize Timer 2 */ |
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| 11 | /*****************************************************/ |
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| 12 | // The timer 2 is used to generate the PWM at PD7 (J7) |
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| 13 | // to control a camera servo for pitch compensation. |
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| 14 | void TIMER2_Init(void) |
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| 15 | { |
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| 16 | uint8_t sreg = SREG; |
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| 17 | |||
| 18 | // disable all interrupts before reconfiguration |
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| 19 | cli(); |
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| 20 | |||
| 21 | // set PD7 as output of the PWM for pitch servo |
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| 22 | DDRD |=(1<<DDD7); |
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| 23 | PORTD |= (1<<PORTD7); |
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| 24 | |||
| 25 | |||
| 26 | // Timer/Counter 2 Control Register A |
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| 27 | |||
| 28 | // Waveform Generation Mode is Fast PWM (Bits: WGM22 = 0, WGM21 = 1, WGM20 = 1) |
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| 29 | // PD7: Clear OC2B on Compare Match, set OC2B at BOTTOM, non inverting PWM (Bits: COM2A1 = 1, COM2A0 = 0) |
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| 30 | // PD6: Normal port operation, OC2B disconnected, (Bits: COM2B1 = 0, COM2B0 = 0) |
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| 31 | TCCR2A &= ~((1<<COM2B1)|(1<<COM2B0)|(1<<COM2A0)); |
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| 32 | TCCR2A |= (1<<COM2A1)|(1<<WGM21)|(1<<WGM20); |
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| 33 | |||
| 34 | // Timer/Counter 2 Control Register B |
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| 35 | |||
| 36 | // Set clock divider for timer 2 to SYSKLOCK/256 = 20MHz / 256 = 78.128 kHz |
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| 37 | // The timer increments from 0x00 to 0xFF with an update rate of 78.128 kHz or 12.8 us |
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| 38 | // hence the timer overflow interrupt frequency is 78.128 kHz / 256 = 305.176 Hz or 3.276 ms |
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| 39 | |||
| 40 | // divider 256 (Bits: CS022 = 1, CS21 = 1, CS20 = 0) |
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| 41 | TCCR2B &= ~((1<<FOC2A)|(1<<FOC2B)|(1<<CS20)|(1<<WGM22)); |
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| 42 | TCCR2B |= (1<<CS22)|(1<<CS21); |
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| 43 | |||
| 44 | // Initialize the Output Compare Register A used for PWM generation on port PD7. |
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| 45 | OCR2A = 10; //10 * 12.8us = 1.28 ms high time |
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| 46 | |||
| 47 | // Initialize the Timer/Counter 2 Register |
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| 48 | TCNT2 = 0; |
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| 49 | |||
| 50 | // Timer/Counter 2 Interrupt Mask Register |
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| 51 | // Enable timer output compare match A Interrupt only |
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| 52 | TIMSK2 &= ~((1<<OCIE2B)|(1<<TOIE2)); |
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| 53 | TIMSK2 |= (1<<OCIE2A); |
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| 54 | |||
| 55 | SREG = sreg; |
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| 56 | } |
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| 57 | |||
| 58 | |||
| 59 | /*****************************************************/ |
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| 60 | /* Control Servo Position */ |
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| 61 | /*****************************************************/ |
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| 62 | ISR(TIMER2_COMPA_vect) // every OCR2A * 12.8 us (compare match) |
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| 63 | { |
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| 64 | static uint8_t timer = 10; |
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| 65 | |||
| 66 | if(!timer--) |
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| 67 | { |
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| 68 | // enable PWM on PD7 in non inverting mode |
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| 69 | TCCR2A &= ~(0<<COM2A0); |
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| 70 | TCCR2A |= (1<<COM2A1); |
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| 71 | |||
| 72 | ServoValue = FCParam.ServoPitchControl; |
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| 73 | // inverting movment of servo |
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| 74 | if(ParamSet.ServoPitchCompInvert & 0x01) |
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| 75 | { |
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| 76 | ServoValue += ((int32_t) ParamSet.ServoPitchComp * (IntegralPitch / 128)) / 512; |
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| 77 | } |
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| 78 | else // non inverting movement of servo |
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| 79 | { |
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| 80 | ServoValue -= ((int32_t) ParamSet.ServoPitchComp * (IntegralPitch / 128)) / 512; |
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| 81 | } |
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| 82 | |||
| 83 | // limit servo value to its parameter range definition |
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| 84 | if(ServoValue < ParamSet.ServoPitchMin) |
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| 85 | { |
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| 86 | ServoValue = ParamSet.ServoPitchMin; |
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| 87 | } |
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| 88 | else if(ServoValue > ParamSet.ServoPitchMax) |
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| 89 | { |
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| 90 | ServoValue = ParamSet.ServoPitchMax; |
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| 91 | } |
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| 92 | |||
| 93 | // update PWM |
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| 94 | OCR2A = ServoValue; |
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| 95 | timer = ParamSet.ServoPitchRefresh; |
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| 96 | } |
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| 97 | else |
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| 98 | { |
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| 99 | // disable PWM at PD7 |
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| 100 | TCCR2A &= ~((1<<COM2A1)|(1<<COM2A0)); |
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| 101 | // set PD7 to low |
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| 102 | PORTD &= ~(1<<PORTD7); |
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| 103 | } |
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| 104 | } |