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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 1 | ingob | 1 | /*####################################################################################### |
| 886 | killagreg | 2 | Decodieren eines RC Summen Signals |
| 1 | ingob | 3 | #######################################################################################*/ |
| 4 | // ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
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| 5 | // + Copyright (c) 04.2007 Holger Buss |
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| 6 | // + only for non-profit use |
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| 7 | // + www.MikroKopter.com |
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| 8 | // + see the File "License.txt" for further Informations |
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| 9 | // ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
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| 10 | |||
| 886 | killagreg | 11 | #include <stdlib.h> |
| 12 | #include <avr/io.h> |
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| 13 | #include <avr/interrupt.h> |
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| 14 | |||
| 1 | ingob | 15 | #include "rc.h" |
| 16 | #include "main.h" |
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| 17 | |||
| 886 | killagreg | 18 | volatile int16_t PPM_in[15]; //PPM24 supports 12 channels per frame |
| 19 | volatile int16_t PPM_diff[15]; |
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| 20 | volatile uint8_t NewPpmData = 1; |
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| 21 | volatile int16_t RC_Quality = 0; |
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| 1 | ingob | 22 | |
| 886 | killagreg | 23 | volatile uint8_t NewRCFrames = 0; |
| 24 | |||
| 25 | |||
| 26 | /***************************************************************/ |
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| 27 | /* 16bit timer 1 is used to decode the PPM-Signal */ |
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| 28 | /***************************************************************/ |
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| 29 | void RC_Init (void) |
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| 1 | ingob | 30 | { |
| 886 | killagreg | 31 | uint8_t sreg = SREG; |
| 1 | ingob | 32 | |
| 886 | killagreg | 33 | // disable all interrupts before reconfiguration |
| 34 | cli(); |
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| 35 | |||
| 36 | // PPM-signal is connected to the Input Capture Pin (PD6) of timer 1 |
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| 37 | DDRD &= ~(1<<DDD6); |
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| 38 | PORTD |= (1<<PORTD6); |
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| 39 | |||
| 40 | // Channel 5,6,7 is decoded to servo signals at pin PD5 (J3), PD4(J4), PD3(J5) |
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| 41 | // set as output |
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| 42 | DDRD |= (1<<DDD5)|(1<<DDD4); |
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| 43 | // low level |
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| 44 | PORTD &= ~((1<<PORTD5)|(1<<PORTD4)); |
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| 45 | |||
| 46 | // PD3 can't be used in FC 1.1 if 2nd UART is activated |
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| 47 | // because TXD1 is at that port |
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| 48 | if(BoardRelease == 10) |
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| 49 | { |
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| 50 | DDRD |= (1<<PORTD3); |
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| 51 | PORTD &= ~(1<<PORTD3); |
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| 52 | } |
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| 53 | |||
| 54 | // Timer/Counter1 Control Register A, B, C |
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| 55 | |||
| 56 | // Normal Mode (bits: WGM13=0, WGM12=0, WGM11=0, WGM10=0) |
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| 57 | // Compare output pin A & B is disabled (bits: COM1A1=0, COM1A0=0, COM1B1=0, COM1B0=0) |
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| 58 | // Set clock source to SYSCLK/64 (bit: CS12=0, CS11=1, CS10=1) |
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| 59 | // Enable input capture noise cancler (bit: ICNC1=1) |
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| 60 | // Trigger on positive edge of the input capture pin (bit: ICES1=1), |
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| 61 | // Therefore the counter incremets at a clock of 20 MHz/64 = 312.5 kHz or 3.2µs |
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| 62 | // The longest period is 0xFFFF / 312.5 kHz = 0.209712 s. |
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| 63 | TCCR1A &= ~((1<<COM1A1)|(1<<COM1A0)|(1<<COM1B1)|(1<<COM1B0)|(1<<WGM11)|(1<<WGM10)); |
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| 64 | TCCR1B &= ~((1<<WGM13)|(1<<WGM12)|(1<<CS12)); |
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| 65 | TCCR1B |= (1<<CS11)|(1<<CS10)|(1<<ICES1)|(1<<ICNC1); |
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| 66 | TCCR1C &= ~((1<<FOC1A)|(1<<FOC1B)); |
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| 67 | |||
| 68 | // Timer/Counter1 Interrupt Mask Register |
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| 69 | |||
| 70 | // Enable Input Capture Interrupt (bit: ICIE1=1) |
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| 71 | // Disable Output Compare A & B Match Interrupts (bit: OCIE1B=0, OICIE1A=0) |
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| 72 | // Enable Overflow Interrupt (bit: TOIE1=0) |
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| 73 | TIMSK1 &= ~((1<<OCIE1B)|(1<<OCIE1A)); |
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| 74 | TIMSK1 |= (1<<ICIE1)|(1<<TOIE1); |
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| 75 | |||
| 76 | RC_Quality = 0; |
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| 77 | |||
| 78 | SREG = sreg; |
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| 1 | ingob | 79 | } |
| 80 | |||
| 81 | |||
| 886 | killagreg | 82 | // happens every 0.209712 s. |
| 83 | // check for at least one new frame per timer overflow (timeout) |
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| 84 | ISR(TIMER1_OVF_vect) |
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| 1 | ingob | 85 | { |
| 886 | killagreg | 86 | if (NewRCFrames == 0) RC_Quality -= RC_Quality/8; |
| 87 | NewRCFrames = 0; |
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| 88 | } |
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| 89 | |||
| 90 | |||
| 91 | /********************************************************************/ |
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| 92 | /* Every time a positive edge is detected at PD6 */ |
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| 93 | /********************************************************************/ |
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| 94 | /* t-Frame |
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| 95 | <-----------------------------------------------------------------------> |
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| 96 | ____ ______ _____ ________ ______ sync gap ____ |
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| 97 | | | | | | | | | | | | |
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| 98 | | | | | | | | | | | | |
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| 99 | ___| |_| |_| |_| |_.............| |________________| |
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| 100 | <-----><-------><------><--------> <------> <--- |
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| 101 | t0 t1 t2 t4 tn t0 |
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| 102 | |||
| 103 | The PPM-Frame length is 22.5 ms. |
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| 104 | Channel high pulse width range is 0.7 ms to 1.7 ms completed by an 0.3 ms low pulse. |
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| 105 | The mininimum time delay of two events coding a channel is ( 0.7 + 0.3) ms = 1 ms. |
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| 106 | The maximum time delay of two events coding a chanel is ( 1.7 + 0.3) ms = 2 ms. |
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| 107 | The minimum duration of all channels at minimum value is 8 * 1 ms = 8 ms. |
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| 108 | The maximum duration of all channels at maximum value is 8 * 2 ms = 16 ms. |
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| 109 | The remaining time of (22.5 - 8 ms) ms = 14.5 ms to (22.5 - 16 ms) ms = 6.5 ms is |
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| 110 | the syncronization gap. |
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| 111 | */ |
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| 112 | ISR(TIMER1_CAPT_vect) // typical rate of 1 ms to 2 ms |
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| 113 | { |
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| 114 | int16_t signal = 0, tmp; |
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| 115 | static int16_t index; |
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| 116 | static uint16_t oldICR1 = 0; |
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| 117 | |||
| 118 | // 16bit Input Capture Register ICR1 contains the timer value TCNT1 |
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| 119 | // at the time the edge was detected |
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| 120 | |||
| 121 | // calculate the time delay to the previous event time which is stored in oldICR1 |
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| 122 | // calculatiing the difference of the two uint16_t and converting the result to an int16_t |
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| 123 | // implicit handles a timer overflow 65535 -> 0 the right way. |
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| 124 | signal = (uint16_t) ICR1 - oldICR1; |
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| 125 | oldICR1 = ICR1; |
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| 126 | |||
| 127 | //sync gap? (3.52 ms < signal < 25.6 ms) |
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| 128 | if((signal > 1100) && (signal < 8000)) |
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| 129 | { |
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| 130 | // if a sync gap happens and there where at least 4 channels decoded before |
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| 131 | // then the NewPpmData flag is reset indicating valid data in the PPM_in[] array. |
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| 132 | if(index >= 4) |
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| 133 | { |
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| 134 | NewPpmData = 0; // Null means NewData for the first 4 channels |
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| 135 | NewRCFrames++; |
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| 136 | } |
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| 137 | // synchronize channel index |
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| 138 | index = 1; |
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| 139 | } |
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| 140 | else // within the PPM frame |
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| 141 | { |
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| 142 | if(index < 14) // PPM24 supports 12 channels |
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| 1 | ingob | 143 | { |
| 886 | killagreg | 144 | // check for valid signal length (0.8 ms < signal < 2.1984 ms) |
| 145 | // signal range is from 1.0ms/3.2us = 312 to 2.0ms/3.2us = 625 |
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| 146 | if((signal > 250) && (signal < 687)) |
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| 1 | ingob | 147 | { |
| 886 | killagreg | 148 | // shift signal to zero symmetric range -154 to 159 |
| 149 | signal -= 466; // offset of 1.4912 ms ??? (469 * 3.2µs = 1.5008 ms) |
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| 150 | // check for stable signal |
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| 151 | if(abs(signal-PPM_in[index]) < 6) |
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| 152 | { |
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| 153 | if(RC_Quality < 200) RC_Quality +=10; |
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| 154 | } |
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| 155 | // calculate exponential history for signal |
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| 156 | tmp = (3 * (PPM_in[index]) + signal) / 4; |
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| 604 | hbuss | 157 | if(tmp > signal+1) tmp--; else |
| 886 | killagreg | 158 | if(tmp < signal-1) tmp++; |
| 159 | // calculate signal difference on good signal level |
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| 160 | if(RC_Quality >= 195) PPM_diff[index] = ((tmp - PPM_in[index]) / 3) * 3; // cut off lower 3 bit for nois reduction |
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| 604 | hbuss | 161 | else PPM_diff[index] = 0; |
| 886 | killagreg | 162 | PPM_in[index] = tmp; // update channel value |
| 163 | } |
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| 164 | index++; // next channel |
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| 165 | // demux sum signal for channels 5 to 7 to J3, J4, J5 |
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| 166 | if(index == 5) PORTD |= (1<<PORTD5); else PORTD &= ~(1<<PORTD5); |
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| 167 | if(index == 6) PORTD |= (1<<PORTD4); else PORTD &= ~(1<<PORTD4); |
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| 168 | if(BoardRelease == 10) |
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| 169 | { |
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| 170 | if(index == 7) PORTD |= (1<<PORTD3); else PORTD &= ~(1<<PORTD3); |
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| 171 | } |
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| 1 | ingob | 172 | } |
| 173 | } |
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| 886 | killagreg | 174 | if(RC_Quality) RC_Quality--; |
| 1 | ingob | 175 | } |
| 176 | |||
| 177 | |||
| 178 | |||
| 179 | |||
| 180 |