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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" |
16 | |||
687 | killagreg | 17 | volatile int16_t PPM_in[11]; |
688 | killagreg | 18 | volatile int16_t PPM_diff[11]; |
687 | killagreg | 19 | volatile uint8_t NewPpmData = 1; |
688 | killagreg | 20 | volatile uint8_t SenderOkay = 0; |
1 | ingob | 21 | |
687 | killagreg | 22 | /***************************************************************/ |
688 | killagreg | 23 | /* 16bit timer 1 is used to decode the PPM-Signal */ |
687 | killagreg | 24 | /***************************************************************/ |
1 | ingob | 25 | void rc_sum_init (void) |
26 | { |
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688 | killagreg | 27 | uint8_t sreg = SREG; |
1 | ingob | 28 | |
688 | killagreg | 29 | // disable all interrupts before reconfiguration |
30 | cli(); |
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685 | killagreg | 31 | |
688 | killagreg | 32 | // PPM-signal is connected to the Input Capture Pin (PD6) of timer 1 |
33 | DDRD &= ~(1<<DDD6); |
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34 | PORTD |= (1<<PORTD6); |
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35 | |||
689 | killagreg | 36 | // Channel 5,6,7 is decoded to servo signals at pin PD5 (J3), PD4(J4), PD3(J5) |
37 | // set as output |
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38 | DDRD |= (1<<DDD5)|(1<<DDD4)|(1<<DDD3); |
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39 | // low level |
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40 | PORTD &= ~((1<<PORTD5)|(1<<PORTD4)|(1<<PORTD3)); |
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41 | |||
688 | killagreg | 42 | // Timer/Counter1 Control Register A, B, C |
43 | |||
44 | // Normal Mode (bits: WGM13=0, WGM12=0, WGM11=0, WGM10=0) |
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45 | // Compare output pin A & B is disabled (bits: COM1A1=0, COM1A0=0, COM1B1=0, COM1B0=0) |
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46 | // Set clock source to SYSCLK/64 (bit: CS12=0, CS11=1, CS10=1) |
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47 | // Enable input capture noise cancler (bit: ICNC1=1) |
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48 | // Trigger on positive edge of the input capture pin (bit: ICES1=1), |
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49 | // Therefore the counter incremets at a clock of 20 MHz/64 = 312.5 kHz or 3.2µs |
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50 | // The longest period is 0xFFFF / 312.5 kHz = 0.209712 s. |
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51 | TCCR1A &= ~((1<<COM1A1)|(1<<COM1A0)|(1<<COM1B1)|(1<<COM1B0)|(1<<WGM11)|(1<<WGM10)); |
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52 | TCCR1B &= ~((1<<WGM13)|(1<<WGM12)|(1<<CS12)); |
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53 | TCCR1B |= (1<<CS11)|(1<<CS10)|(1<<ICES1)|(1<<ICNC1); |
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54 | TCCR1C &= ~((1<<FOC1A)|(1<<FOC1B)); |
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55 | |||
56 | // Timer/Counter1 Interrupt Mask Register |
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57 | |||
58 | // Enable Input Capture Interrupt (bit: ICIE1=1) |
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59 | // Disable Output Compare A & B Match Interrupts (bit: OCIE1B=0, OICIE1A=0) |
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60 | // Disable Overflow Interrupt (bit: TOIE1=0) |
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61 | TIMSK1 &= ~((1<<OCIE1B)|(1<<OCIE1A)|(1<<TOIE1)); |
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62 | TIMSK1 |= (1<<ICIE1); |
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63 | |||
64 | SREG = sreg; |
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1 | ingob | 65 | } |
66 | |||
67 | |||
688 | killagreg | 68 | /********************************************************************/ |
69 | /* Every time a positive edge is detected at PD6 */ |
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70 | /********************************************************************/ |
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71 | /* |
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72 | The PPM-Frame length is 22.5 ms. |
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73 | 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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74 | The mininimum time delay of two events coding a channel is ( 0.7 + 0.3) ms = 1 ms. |
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75 | The maximum time delay of two events coding a chanel is ( 1.7 + 0.3) ms = 2 ms. |
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76 | The minimum duration of all channels at minimum value is 8 * 1 ms = 8 ms. |
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77 | The maximum duration of all channels at maximum value is 8 * 2 ms = 16 ms. |
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78 | 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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79 | the syncronization gap. |
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80 | */ |
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81 | ISR(TIMER1_CAPT_vect) // typical rate of 1 ms to 2 ms |
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1 | ingob | 82 | { |
688 | killagreg | 83 | static uint16_t oldICR1 = 0; |
84 | int16_t signal = 0, tmp; |
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85 | static int16_t index; |
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685 | killagreg | 86 | |
688 | killagreg | 87 | // 16bit Input Capture Register ICR1 contains the timer value TCNT1 |
88 | // at the time the edge was detected |
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685 | killagreg | 89 | |
688 | killagreg | 90 | // calculate the time delay to the previous event time which is stored in oldICR1 |
91 | signal = (uint16_t) ICR1 - oldICR1; |
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92 | oldICR1 = ICR1; |
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93 | |||
94 | |||
95 | //sync gap? (3.52 ms < signal < 25.6 ms) |
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685 | killagreg | 96 | if((signal > 1100) && (signal < 8000)) |
688 | killagreg | 97 | { |
98 | // if a sync gap happens and there where at least 4 channels decoded before |
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99 | // then the NewPpmData flag is reset indicating valid data in the PPM_in[] array. |
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100 | if(index >= 4) NewPpmData = 0; // Null means NewData |
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101 | // synchronize channel index |
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102 | index = 1; |
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103 | } |
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104 | else // within the PPM frame |
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1 | ingob | 105 | { |
688 | killagreg | 106 | if(index < 10) // channel limit is 9 because of the frame length of 22.5 ms |
1 | ingob | 107 | { |
688 | killagreg | 108 | // check for valid signal length (0.8 ms < signal < 2.1984 ms) |
109 | if((signal > 250) && (signal < 687)) |
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1 | ingob | 110 | { |
688 | killagreg | 111 | signal -= 466; // offset of 1.4912 ms ??? (469 * 3.2µs = 1.5008 ms) |
112 | // check for stable signal |
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113 | // the deviation of the current signal level from the average must be less than 6 (aprox. 1%) |
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114 | if(abs(signal - PPM_in[index]) < 6) |
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685 | killagreg | 115 | { |
688 | killagreg | 116 | // a good signal condition increases SenderOkay by 10 |
117 | // SignalOkay is decremented every 2 ms in timer0.c |
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118 | // this variable is a level for the average rate of noiseless signal |
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119 | if(SenderOkay < 200) SenderOkay += 10; |
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120 | } |
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121 | // calculate exponential history for signal |
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685 | killagreg | 122 | tmp = (3 * (PPM_in[index]) + signal) / 4; |
604 | hbuss | 123 | if(tmp > signal+1) tmp--; else |
685 | killagreg | 124 | if(tmp < signal-1) tmp++; |
688 | killagreg | 125 | // calculate signal difference on good signal level |
126 | 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 | 127 | else PPM_diff[index] = 0; |
688 | killagreg | 128 | PPM_in[index] = tmp; // update channel value |
129 | } |
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130 | index++; // next channel |
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689 | killagreg | 131 | // demux sum signal for channels 5 to 7 to J3, J4, J5 |
132 | if(index == 5) PORTD |= (1<<PORTD5); else PORTD &= ~(1<<PORTD5); |
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133 | if(index == 6) PORTD |= (1<<PORTD4); else PORTD &= ~(1<<PORTD4); |
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134 | if(index == 7) PORTD |= (1<<PORTD3); else PORTD &= ~(1<<PORTD3); |
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1 | ingob | 135 | } |
136 | } |
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137 | } |
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138 | |||
139 | |||
140 | |||
141 | |||
142 |