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1 | ingob | 1 | /*####################################################################################### |
685 | 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 | |||
687 | killagreg | 11 | #include <stdlib.h> |
685 | killagreg | 12 | #include <avr/io.h> |
13 | #include <avr/interrupt.h> |
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14 | |||
1 | ingob | 15 | #include "rc.h" |
685 | killagreg | 16 | #include "fc.h" |
1 | ingob | 17 | |
687 | killagreg | 18 | volatile int16_t PPM_in[11]; |
688 | killagreg | 19 | volatile int16_t PPM_diff[11]; |
687 | killagreg | 20 | volatile uint8_t NewPpmData = 1; |
688 | killagreg | 21 | volatile uint8_t SenderOkay = 0; |
1 | ingob | 22 | |
687 | killagreg | 23 | /***************************************************************/ |
688 | killagreg | 24 | /* 16bit timer 1 is used to decode the PPM-Signal */ |
687 | killagreg | 25 | /***************************************************************/ |
1 | ingob | 26 | void rc_sum_init (void) |
27 | { |
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688 | killagreg | 28 | uint8_t sreg = SREG; |
1 | ingob | 29 | |
688 | killagreg | 30 | // disable all interrupts before reconfiguration |
31 | cli(); |
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685 | killagreg | 32 | |
688 | killagreg | 33 | // PPM-signal is connected to the Input Capture Pin (PD6) of timer 1 |
34 | DDRD &= ~(1<<DDD6); |
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35 | PORTD |= (1<<PORTD6); |
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36 | |||
37 | // Timer/Counter1 Control Register A, B, C |
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38 | |||
39 | // Normal Mode (bits: WGM13=0, WGM12=0, WGM11=0, WGM10=0) |
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40 | // Compare output pin A & B is disabled (bits: COM1A1=0, COM1A0=0, COM1B1=0, COM1B0=0) |
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41 | // Set clock source to SYSCLK/64 (bit: CS12=0, CS11=1, CS10=1) |
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42 | // Enable input capture noise cancler (bit: ICNC1=1) |
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43 | // Trigger on positive edge of the input capture pin (bit: ICES1=1), |
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44 | // Therefore the counter incremets at a clock of 20 MHz/64 = 312.5 kHz or 3.2µs |
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45 | // The longest period is 0xFFFF / 312.5 kHz = 0.209712 s. |
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46 | TCCR1A &= ~((1<<COM1A1)|(1<<COM1A0)|(1<<COM1B1)|(1<<COM1B0)|(1<<WGM11)|(1<<WGM10)); |
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47 | TCCR1B &= ~((1<<WGM13)|(1<<WGM12)|(1<<CS12)); |
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48 | TCCR1B |= (1<<CS11)|(1<<CS10)|(1<<ICES1)|(1<<ICNC1); |
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49 | TCCR1C &= ~((1<<FOC1A)|(1<<FOC1B)); |
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50 | |||
51 | // Timer/Counter1 Interrupt Mask Register |
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52 | |||
53 | // Enable Input Capture Interrupt (bit: ICIE1=1) |
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54 | // Disable Output Compare A & B Match Interrupts (bit: OCIE1B=0, OICIE1A=0) |
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55 | // Disable Overflow Interrupt (bit: TOIE1=0) |
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56 | TIMSK1 &= ~((1<<OCIE1B)|(1<<OCIE1A)|(1<<TOIE1)); |
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57 | TIMSK1 |= (1<<ICIE1); |
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58 | |||
1 | ingob | 59 | AdNeutralGier = 0; |
60 | AdNeutralRoll = 0; |
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61 | AdNeutralNick = 0; |
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688 | killagreg | 62 | |
63 | SREG = sreg; |
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1 | ingob | 64 | } |
65 | |||
66 | |||
688 | killagreg | 67 | /********************************************************************/ |
68 | /* Every time a positive edge is detected at PD6 */ |
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69 | /********************************************************************/ |
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70 | /* |
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71 | The PPM-Frame length is 22.5 ms. |
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72 | 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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73 | The mininimum time delay of two events coding a channel is ( 0.7 + 0.3) ms = 1 ms. |
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74 | The maximum time delay of two events coding a chanel is ( 1.7 + 0.3) ms = 2 ms. |
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75 | The minimum duration of all channels at minimum value is 8 * 1 ms = 8 ms. |
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76 | The maximum duration of all channels at maximum value is 8 * 2 ms = 16 ms. |
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77 | 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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78 | the syncronization gap. |
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79 | */ |
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80 | ISR(TIMER1_CAPT_vect) // typical rate of 1 ms to 2 ms |
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1 | ingob | 81 | { |
688 | killagreg | 82 | static uint16_t oldICR1 = 0; |
83 | int16_t signal = 0, tmp; |
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84 | static int16_t index; |
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685 | killagreg | 85 | |
688 | killagreg | 86 | // 16bit Input Capture Register ICR1 contains the timer value TCNT1 |
87 | // at the time the edge was detected |
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685 | killagreg | 88 | |
688 | killagreg | 89 | // calculate the time delay to the previous event time which is stored in oldICR1 |
90 | signal = (uint16_t) ICR1 - oldICR1; |
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91 | oldICR1 = ICR1; |
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92 | |||
93 | |||
94 | //sync gap? (3.52 ms < signal < 25.6 ms) |
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685 | killagreg | 95 | if((signal > 1100) && (signal < 8000)) |
688 | killagreg | 96 | { |
97 | // if a sync gap happens and there where at least 4 channels decoded before |
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98 | // then the NewPpmData flag is reset indicating valid data in the PPM_in[] array. |
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99 | if(index >= 4) NewPpmData = 0; // Null means NewData |
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100 | // synchronize channel index |
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101 | index = 1; |
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102 | } |
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103 | else // within the PPM frame |
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1 | ingob | 104 | { |
688 | killagreg | 105 | if(index < 10) // channel limit is 9 because of the frame length of 22.5 ms |
1 | ingob | 106 | { |
688 | killagreg | 107 | // check for valid signal length (0.8 ms < signal < 2.1984 ms) |
108 | if((signal > 250) && (signal < 687)) |
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1 | ingob | 109 | { |
688 | killagreg | 110 | signal -= 466; // offset of 1.4912 ms ??? (469 * 3.2µs = 1.5008 ms) |
111 | // check for stable signal |
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112 | // the deviation of the current signal level from the average must be less than 6 (aprox. 1%) |
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113 | if(abs(signal - PPM_in[index]) < 6) |
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685 | killagreg | 114 | { |
688 | killagreg | 115 | // a good signal condition increases SenderOkay by 10 |
116 | // SignalOkay is decremented every 2 ms in timer0.c |
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117 | // this variable is a level for the average rate of noiseless signal |
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118 | if(SenderOkay < 200) SenderOkay += 10; |
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119 | } |
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120 | // calculate exponential history for signal |
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685 | killagreg | 121 | tmp = (3 * (PPM_in[index]) + signal) / 4; |
604 | hbuss | 122 | if(tmp > signal+1) tmp--; else |
685 | killagreg | 123 | if(tmp < signal-1) tmp++; |
688 | killagreg | 124 | // calculate signal difference on good signal level |
125 | if(SenderOkay >= 195) PPM_diff[index] = ((tmp - PPM_in[index]) / 3) * 3; // cut off lower 3 bit for nois reduction |
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604 | hbuss | 126 | else PPM_diff[index] = 0; |
688 | killagreg | 127 | PPM_in[index] = tmp; // update channel value |
128 | } |
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129 | index++; // next channel |
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130 | // demux sum signal fpr channels 5 to 7 |
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131 | if(index == 5) PORTD |= 0x20; else PORTD &= ~0x20; // Servosignal an J3 anlegen |
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132 | if(index == 6) PORTD |= 0x10; else PORTD &= ~0x10; // Servosignal an J4 anlegen |
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133 | if(index == 7) PORTD |= 0x08; else PORTD &= ~0x08; // Servosignal an J5 anlegen |
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1 | ingob | 134 | } |
135 | } |
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136 | } |
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137 | |||
138 | |||
139 | |||
140 | |||
141 |