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@ -32,27 +32,23 @@ along with VP-Digi. If not, see <http://www.gnu.org/licenses/>. |
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* DCD_MAXPULSE and DCD_THRES difference sets the DCD "inertia" so that the DCD state won't change rapidly when a valid signal is present |
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* DCD_DEC is the DCD pulse counter decrementation value when symbol changes too far from PLL counter zero |
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* DCD_INC is the DCD pulse counter incrementation value when symbol changes near the PLL counter zero |
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* DCD_PLLTUNE is the DCD timing coefficient when symbol changes, pll_counter = pll_counter * DCD_PLLTUNE |
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* The DCD mechanism is described in afsk_demod(). |
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* The DCD mechanism is described in demodulate(). |
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* All values were selected by trial and error |
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*/ |
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#define DCD1200_MAXPULSE 100 |
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#define DCD1200_THRES 30 |
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#define DCD1200_DEC 1 |
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#define DCD1200_INC 7 |
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#define DCD1200_PLLTUNE 0 |
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#define DCD9600_MAXPULSE 200 |
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#define DCD9600_THRES 80 |
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#define DCD9600_DEC 3 |
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#define DCD9600_INC 6 |
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#define DCD9600_PLLTUNE 0 |
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#define DCD300_MAXPULSE 50 |
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#define DCD300_THRES 6 |
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#define DCD300_DEC 1 |
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#define DCD1200_DEC 2 |
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#define DCD1200_INC 1 |
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#define DCD9600_MAXPULSE 70 |
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#define DCD9600_THRES 50 |
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#define DCD9600_DEC 5 |
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#define DCD9600_INC 1 |
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#define DCD300_MAXPULSE 140 |
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#define DCD300_THRES 120 |
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#define DCD300_DEC 3 |
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#define DCD300_INC 5 |
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#define DCD300_PLLTUNE 0 |
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#define N1200 8 //samples per symbol @ fs=9600, oversampling = 38400 Hz |
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#define N9600 4 //fs=38400, oversampling = 153600 Hz |
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@ -84,7 +80,7 @@ static enum ModemTxTestMode txTestState; //current TX test mode |
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static uint8_t demodCount; //actual number of parallel demodulators |
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static uint16_t dacSine[DAC_SINE_SIZE]; //sine samples for DAC |
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static uint8_t dacSineIdx; //current sine sample index |
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static uint16_t samples[4]; //very raw received samples, filled directly by DMA |
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static volatile uint16_t samples[4]; //very raw received samples, filled directly by DMA |
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static uint8_t currentSymbol; //current symbol for NRZI encoding |
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static uint8_t scrambledSymbol; //current symbol after scrambling |
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static float markFreq; //mark frequency |
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@ -198,12 +194,11 @@ struct DemodState |
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int32_t dcdPll; //DCD PLL main counter |
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uint8_t dcdLastSymbol; //last symbol for DCD |
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uint8_t dcdCounter; //DCD "pulse" counter (incremented when RX signal is correct) |
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int32_t dcdMax; |
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int32_t dcdThres; |
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int32_t dcdInc; |
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int32_t dcdDec; |
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float dcdAdjust; |
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uint16_t dcdCounter; //DCD "pulse" counter (incremented when RX signal is correct) |
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uint16_t dcdMax; |
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uint16_t dcdThres; |
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uint16_t dcdInc; |
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uint16_t dcdDec; |
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int16_t peak; |
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int16_t valley; |
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@ -314,7 +309,7 @@ void DMA1_Channel2_IRQHandler(void) |
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DMA1->IFCR |= DMA_IFCR_CTCIF2; |
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//each sample is 12 bits, output sample is 13 bits |
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int16_t sample = ((samples[0] + samples[1] + samples[2] + samples[3]) >> 1) - 4095; //calculate input sample (decimation) |
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int32_t sample = ((samples[0] + samples[1] + samples[2] + samples[3]) >> 1) - 4095; //calculate input sample (decimation) |
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bool partialDcd = false; |
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@ -352,21 +347,17 @@ void DMA1_Channel2_IRQHandler(void) |
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if(ModemConfig.modem == MODEM_9600) |
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{ |
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if(ModemConfig.usePWM) |
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sample = scrambledSymbol ? 89 : 0; |
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sample = scrambledSymbol ? 99 : 0; |
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else |
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sample = scrambledSymbol ? 15 : 0; |
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sample = filter(&demodState[0].lpf, sample); |
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if(sample < 0) |
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sample = 0; |
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else if(sample > 15) |
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sample = 15; |
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} |
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else |
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{ |
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sample = dacSine[dacSineIdx]; |
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dacSineIdx++; |
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dacSineIdx &= (DAC_SINE_SIZE - 1); |
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dacSineIdx %= DAC_SINE_SIZE; |
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} |
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if(ModemConfig.usePWM) |
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@ -381,17 +372,6 @@ void DMA1_Channel2_IRQHandler(void) |
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} |
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void txBit() |
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{ |
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if(Ax25GetTxBit() == 0) //get next bit and check if it's 0 |
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{ |
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currentSymbol ^= 1; //change symbol - NRZI encoding |
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} |
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//if 1, no symbol change |
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scrambledSymbol = scramble(currentSymbol); |
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} |
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/** |
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* @brief ISR for baudrate generator timer. NRZI encoding is done here. |
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@ -411,17 +391,21 @@ void txBit() |
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} |
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else //transmit test mode |
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{ |
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if(ModemConfig.modem == MODEM_9600) |
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{ |
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scrambledSymbol ^= 1; |
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return; |
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} |
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currentSymbol ^= 1; //change symbol |
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} |
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TIM1->CNT = 0; |
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if(ModemConfig.modem == MODEM_9600) |
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{ |
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scrambledSymbol = scramble(currentSymbol); |
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} |
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else |
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{ |
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TIM1->CNT = 0; |
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if(currentSymbol) //current symbol is space |
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TIM1->ARR = spaceStep; |
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else //mark |
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@ -503,18 +487,19 @@ static int32_t demodulate(int16_t sample, struct DemodState *dem) |
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//when configured properly, it's generally immune to noise, as the detected tone changes much faster than 1200 baud |
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//it's also important to set some maximum value for DCD counter, otherwise the DCD is "sticky" |
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dem->dcdPll = (signed)((unsigned)(dem->dcdPll) + (unsigned)(dem->pllStep)); //keep PLL ticking at the frequency equal to baudrate |
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dem->dcdPll = (int32_t)((uint32_t)(dem->dcdPll) + (uint32_t)(dem->pllStep)); //keep PLL ticking at the frequency equal to baudrate |
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if((sample > 0) != dem->dcdLastSymbol) //tone changed |
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{ |
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if(abs(dem->dcdPll) < dem->pllStep) //tone change occurred near zero |
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if(abs(dem->dcdPll) <= (uint32_t)(dem->pllStep)) //tone change occurred near zero |
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dem->dcdCounter += dem->dcdInc; //increase DCD counter |
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else //tone change occurred far from zero |
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{ |
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if(dem->dcdCounter >= dem->dcdDec) //avoid overflow |
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dem->dcdCounter -= dem->dcdDec; //decrease DCD counter |
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} |
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dem->dcdPll = (int)(dem->dcdPll * dem->dcdAdjust); //adjust PLL |
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dem->dcdPll = 0; |
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} |
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dem->dcdLastSymbol = sample > 0; //store last symbol for symbol change detection |
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@ -544,7 +529,7 @@ static void decode(uint8_t symbol, uint8_t demod) |
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//Current symbol is sampled at PLL counter overflow, so symbol transition should occur at PLL counter zero |
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int32_t previous = dem->pll; //store last clock state |
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dem->pll = (signed)((unsigned)(dem->pll) + (unsigned)(dem->pllStep)); //keep PLL running |
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dem->pll = (int32_t)((uint32_t)(dem->pll) + (uint32_t)(dem->pllStep)); //keep PLL running |
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dem->rawSymbols <<= 1; //store received unsynchronized symbol |
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dem->rawSymbols |= (symbol & 1); |
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@ -606,6 +591,15 @@ void ModemTxTestStart(enum ModemTxTestMode type) |
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NVIC_DisableIRQ(DMA1_Channel2_IRQn); //disable RX DMA interrupt |
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NVIC_EnableIRQ(TIM1_UP_IRQn); //enable DAC interrupt |
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if(ModemConfig.modem == MODEM_9600) |
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{ |
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TIM1->ARR = 103; |
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//enable baudrate generator |
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TIM3->CR1 = TIM_CR1_CEN; //enable timer |
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NVIC_EnableIRQ(TIM3_IRQn); //enable interrupt in NVIC |
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return; |
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} |
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if(type == TEST_MARK) |
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{ |
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TIM1->ARR = markStep; |
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@ -642,6 +636,8 @@ void ModemTxTestStop(void) |
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void ModemTransmitStart(void) |
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{ |
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setPtt(1); //PTT on |
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if(ModemConfig.modem == MODEM_9600) |
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TIM1->ARR = 103; |
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TIM3->CR1 = TIM_CR1_CEN; |
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TIM1->CR1 = TIM_CR1_CEN; |
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@ -813,7 +809,6 @@ void ModemInit(void) |
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demodState[0].dcdThres = DCD1200_THRES; |
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demodState[0].dcdInc = DCD1200_INC; |
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demodState[0].dcdDec = DCD1200_DEC; |
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demodState[0].dcdAdjust = DCD1200_PLLTUNE; |
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demodState[1].pllStep = PLL1200_STEP; |
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demodState[1].pllLockedAdjust = PLL1200_LOCKED_TUNE; |
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@ -822,7 +817,6 @@ void ModemInit(void) |
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demodState[1].dcdThres = DCD1200_THRES; |
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demodState[1].dcdInc = DCD1200_INC; |
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demodState[1].dcdDec = DCD1200_DEC; |
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demodState[1].dcdAdjust = DCD1200_PLLTUNE; |
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demodState[1].prefilter = PREFILTER_NONE; |
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demodState[1].lpf.coeffs = (int16_t*)lpf1200; |
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@ -895,7 +889,6 @@ void ModemInit(void) |
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demodState[0].dcdThres = DCD300_THRES; |
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demodState[0].dcdInc = DCD300_INC; |
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demodState[0].dcdDec = DCD300_DEC; |
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demodState[0].dcdAdjust = DCD300_PLLTUNE; |
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demodState[0].prefilter = PREFILTER_FLAT; |
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demodState[0].bpf.coeffs = (int16_t*)bpf300; |
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@ -920,7 +913,6 @@ void ModemInit(void) |
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demodState[0].dcdThres = DCD9600_THRES; |
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demodState[0].dcdInc = DCD9600_INC; |
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demodState[0].dcdDec = DCD9600_DEC; |
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demodState[0].dcdAdjust = DCD9600_PLLTUNE; |
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demodState[0].prefilter = PREFILTER_NONE; |
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//this filter will be used for RX and TX |
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Piotr Wilkon
2 years ago