0,0 → 1,198 |
/*####################################################################################### |
Decodieren eines RC Summen Signals |
#######################################################################################*/ |
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
// + Copyright (c) 04.2007 Holger Buss |
// + only for non-profit use |
// + www.MikroKopter.com |
// + see the File "License.txt" for further Informations |
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
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#include <stdlib.h> |
#include <avr/io.h> |
#include <avr/interrupt.h> |
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#include "rc.h" |
#include "main.h" |
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volatile int16_t PPM_in[15]; //PPM24 supports 12 channels per frame |
volatile int16_t PPM_diff[15]; |
volatile uint8_t NewPpmData = 1; |
volatile int16_t RC_Quality = 0; |
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/***************************************************************/ |
/* 16bit timer 1 is used to decode the PPM-Signal */ |
/***************************************************************/ |
void RC_Init (void) |
{ |
uint8_t sreg = SREG; |
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// disable all interrupts before reconfiguration |
cli(); |
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// PPM-signal is connected to the Input Capture Pin (PD6) of timer 1 |
DDRD &= ~(1<<DDD6); |
PORTD |= (1<<PORTD6); |
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// 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)); |
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// 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); |
} |
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// Timer/Counter1 Control Register A, B, C |
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// 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), |
// Therefore the counter incremets at a clock of 20 MHz/64 = 312.5 kHz or 3.2µs |
// 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)); |
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// Timer/Counter1 Interrupt Mask Register |
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// 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) |
TIMSK1 &= ~((1<<OCIE1B)|(1<<OCIE1A)); |
TIMSK1 |= (1<<ICIE1)|(1<<TOIE1); |
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RC_Quality = 0; |
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SREG = sreg; |
} |
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// happens every 0.209712 s. |
// check for at least one input capture event per timer overflow (timeout) |
ISR(TIMER1_OVF_vect) |
{ |
int16_t signal = 0; |
static uint16_t lastICR1 = 0; |
// if ICR1 has not changed |
// then no new input capture event has occured since last timer overflow |
if (lastICR1 == ICR1) RC_Quality = 0; |
lastICR1 = ICR1; // store last ICR1 |
} |
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/********************************************************************/ |
/* Every time a positive edge is detected at PD6 */ |
/********************************************************************/ |
/* t-Frame |
<-----------------------------------------------------------------------> |
____ ______ _____ ________ ______ sync gap ____ |
| | | | | | | | | | | |
| | | | | | | | | | | |
___| |_| |_| |_| |_.............| |________________| |
<-----><-------><------><--------> <------> <--- |
t0 t1 t2 t4 tn t0 |
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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. |
The remaining time of (22.5 - 8 ms) ms = 14.5 ms to (22.5 - 16 ms) ms = 6.5 ms is |
the syncronization gap. |
*/ |
ISR(TIMER1_CAPT_vect) // typical rate of 1 ms to 2 ms |
{ |
int16_t signal = 0, tmp; |
static int16_t index; |
static int16_t Sum_RC_Quality = 0; |
static uint16_t oldICR1 = 0; |
int16_t Noise; |
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// 16bit Input Capture Register ICR1 contains the timer value TCNT1 |
// at the time the edge was detected |
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// calculate the time delay to the previous event time which is stored in oldICR1 |
// calculatiing the difference of the two uint16_t and converting the result to an int16_t |
// implicit handles a timer overflow 65535 -> 0 the right way. |
signal = (uint16_t) ICR1 - oldICR1; |
oldICR1 = ICR1; |
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// lost frame? |
if(signal > 8000) |
{ |
Sum_RC_Quality -= Sum_RC_Quality/2; |
} |
else |
//sync gap? (3.52 ms < signal < 25.6 ms) |
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) NewPpmData = 0; // Null means NewData for the first 4 channels |
// synchronize channel index |
index = 1; |
} |
else // within the PPM frame |
{ |
if(index < 14) // PPM24 supports 12 channels |
{ |
// check for valid signal length (0.8 ms < signal < 2.1984 ms) |
// signal range is from 1.0ms/3.2us = 312 to 2.0ms/3.2us = 625 |
if((signal > 250) && (signal < 687)) |
{ |
// shift signal to zero symmetric range -154 to 159 |
signal -= 466; // offset of 1.4912 ms ??? (469 * 3.2µs = 1.5008 ms) |
// check for stable signal |
Noise = abs(signal - PPM_in[index]); |
if((Noise/16) > (200-RC_Quality)) // spike detector |
{ |
Sum_RC_Quality -= 3*RC_Quality; |
Sum_RC_Quality += 3*(200 - Noise); |
} |
else |
{ |
Sum_RC_Quality -= RC_Quality; |
Sum_RC_Quality += 200 - Noise; |
} |
// calculate exponential history for signal |
tmp = (3 * (PPM_in[index]) + signal) / 4; |
if(tmp > signal+1) tmp--; else |
if(tmp < signal-1) tmp++; |
// calculate signal difference on good signal level |
if(RC_Quality >= 170) PPM_diff[index] = ((tmp - PPM_in[index]) / 3) * 3; // cut off lower 3 bit for nois reduction |
else PPM_diff[index] = 0; |
PPM_in[index] = tmp; // update channel value |
} |
else |
{ // invalid PPM time |
Sum_RC_Quality /= 8; |
} |
index++; // next channel |
// demux sum signal for channels 5 to 7 to J3, J4, J5 |
if(index == 5) PORTD |= (1<<PORTD5); else PORTD &= ~(1<<PORTD5); |
if(index == 6) PORTD |= (1<<PORTD4); else PORTD &= ~(1<<PORTD4); |
if(BoardRelease == 10) |
{ |
if(index == 7) PORTD |= (1<<PORTD3); else PORTD &= ~(1<<PORTD3); |
} |
} |
} |
if(Sum_RC_Quality < 0) Sum_RC_Quality = 0; |
RC_Quality = Sum_RC_Quality/128; |
} |
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