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MMDVM
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MMDVM/YSFRX.cpp

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/*
* Copyright (C) 2009-2017 by Jonathan Naylor G4KLX
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#define WANT_DEBUG
#include "Config.h"
#include "Globals.h"
#include "DMRIdleRX.h"
#include "Utils.h"
const q15_t SCALING_FACTOR = 18750; // Q15(0.55)
const uint8_t MAX_SYNC_SYMBOLS_ERRS = 2U;
const uint8_t MAX_SYNC_BYTES_ERRS = 3U;
const uint8_t BIT_MASK_TABLE[] = {0x80U, 0x40U, 0x20U, 0x10U, 0x08U, 0x04U, 0x02U, 0x01U};
#define WRITE_BIT1(p,i,b) p[(i)>>3] = (b) ? (p[(i)>>3] | BIT_MASK_TABLE[(i)&7]) : (p[(i)>>3] & ~BIT_MASK_TABLE[(i)&7])
const uint16_t NOENDPTR = 9999U;
const unsigned int MAX_SYNC_FRAMES = 4U + 1U;
CYSFRX::CYSFRX() :
m_state(YSFRXS_NONE),
m_bitBuffer(),
m_buffer(),
m_bitPtr(0U),
m_dataPtr(0U),
m_endPtr(NOENDPTR),
m_syncPtr(NOENDPTR),
m_syncStartPtr(NOENDPTR),
m_syncEndPtr(NOENDPTR),
m_syncCheck(false),
m_maxCorr(0),
m_lostCount(0U),
m_centre(),
m_centreVal(0),
m_centreBest(0),
m_threshold(),
m_thresholdVal(0),
m_thresholdBest(0),
m_averagePtr(0u),
m_rssiAccum(0U),
m_rssiCount(0U)
{
}
void CYSFRX::reset()
{
m_state = YSFRXS_NONE;
m_dataPtr = 0U;
m_bitPtr = 0U;
m_maxCorr = 0;
m_averagePtr = 0U;
m_endPtr = NOENDPTR;
m_syncPtr = NOENDPTR;
m_syncStartPtr = NOENDPTR;
m_syncEndPtr = NOENDPTR;
m_centreVal = 0;
m_thresholdVal = 0;
m_syncCheck = false;
m_lostCount = 0U;
m_rssiAccum = 0U;
m_rssiCount = 0U;
}
void CYSFRX::samples(const q15_t* samples, uint16_t* rssi, uint8_t length)
{
for (uint8_t i = 0U; i < length; i++) {
m_rssiAccum += rssi[i];
m_rssiCount++;
if (m_state == YSFRXS_NONE)
processNone(samples[i]);
else
processData(samples[i]);
}
}
void CYSFRX::processNone(q15_t sample)
{
m_bitBuffer[m_bitPtr] <<= 1;
if (sample < 0)
m_bitBuffer[m_bitPtr] |= 0x01U;
m_buffer[m_dataPtr] = sample;
if (countBits32((m_bitBuffer[m_bitPtr] & YSF_SYNC_SYMBOLS_MASK) ^ YSF_SYNC_SYMBOLS) <= MAX_SYNC_SYMBOLS_ERRS) {
uint16_t ptr = m_dataPtr + YSF_FRAME_LENGTH_SAMPLES - YSF_SYNC_LENGTH_SAMPLES + YSF_RADIO_SYMBOL_LENGTH;
if (ptr >= YSF_FRAME_LENGTH_SAMPLES)
ptr -= YSF_FRAME_LENGTH_SAMPLES;
q31_t corr = 0;
q15_t max = -16000;
q15_t min = 16000;
uint32_t mask = 0x00080000U;
for (uint8_t i = 0U; i < YSF_SYNC_LENGTH_SYMBOLS; i++, mask >>= 1) {
bool b = (YSF_SYNC_SYMBOLS & mask) == mask;
if (m_buffer[ptr] > max)
max = m_buffer[ptr];
if (m_buffer[ptr] < min)
min = m_buffer[ptr];
corr += b ? -m_buffer[ptr] : m_buffer[ptr];
ptr += YSF_RADIO_SYMBOL_LENGTH;
if (ptr >= YSF_FRAME_LENGTH_SAMPLES)
ptr -= YSF_FRAME_LENGTH_SAMPLES;
}
if (corr > m_maxCorr) {
q15_t centre = (max + min) >> 1;
q31_t v1 = (max - centre) * SCALING_FACTOR;
q15_t threshold = q15_t(v1 >> 15);
uint8_t sync[YSF_SYNC_BYTES_LENGTH];
uint16_t ptr = m_dataPtr + YSF_FRAME_LENGTH_SAMPLES - YSF_SYNC_LENGTH_SAMPLES + YSF_RADIO_SYMBOL_LENGTH;
if (ptr >= YSF_FRAME_LENGTH_SAMPLES)
ptr -= YSF_FRAME_LENGTH_SAMPLES;
samplesToBits(ptr, YSF_SYNC_LENGTH_SYMBOLS, sync, 0U, centre, threshold);
uint8_t errs = 0U;
for (uint8_t i = 0U; i < YSF_SYNC_BYTES_LENGTH; i++)
errs += countBits8(sync[i] ^ YSF_SYNC_BYTES[i]);
if (errs <= MAX_SYNC_BYTES_ERRS) {
DEBUG4("YSFRX: sync found in None pos/centre/threshold", m_dataPtr, centre, threshold);
m_maxCorr = corr;
m_thresholdBest = m_thresholdVal = m_threshold[0U] = m_threshold[1U] = m_threshold[2U] = m_threshold[3U] = threshold;
m_centreBest = m_centreVal = m_centre[0U] = m_centre[1U] = m_centre[2U] = m_centre[3U] = centre;
m_averagePtr = 0U;
m_rssiAccum = 0U;
m_rssiCount = 0U;
m_lostCount = MAX_SYNC_FRAMES;
m_syncPtr = m_dataPtr;
io.setDecode(true);
io.setADCDetection(true);
m_endPtr = m_dataPtr + YSF_FRAME_LENGTH_SAMPLES - YSF_SYNC_LENGTH_SAMPLES - 1U;
if (m_endPtr >= YSF_FRAME_LENGTH_SAMPLES)
m_endPtr -= YSF_FRAME_LENGTH_SAMPLES;
}
}
}
if (m_dataPtr == m_endPtr) {
uint16_t ptr = m_endPtr + YSF_RADIO_SYMBOL_LENGTH + 1U;
if (ptr >= YSF_FRAME_LENGTH_SAMPLES)
ptr -= YSF_FRAME_LENGTH_SAMPLES;
uint8_t frame[YSF_FRAME_LENGTH_BYTES + 3U];
samplesToBits(ptr, YSF_FRAME_LENGTH_SYMBOLS, frame, 8U, m_centreVal, m_thresholdVal);
frame[0U] = 0x01U;
writeRSSIData(frame);
// Start the next frame
::memset(frame, 0x00U, YSF_FRAME_LENGTH_BYTES + 3U);
m_syncStartPtr = m_syncPtr + YSF_FRAME_LENGTH_SAMPLES - 2U;
if (m_syncStartPtr >= YSF_FRAME_LENGTH_SAMPLES)
m_syncStartPtr -= YSF_FRAME_LENGTH_SAMPLES;
m_syncEndPtr = m_syncPtr + 2U;
if (m_syncEndPtr >= YSF_FRAME_LENGTH_SAMPLES)
m_syncEndPtr -= YSF_FRAME_LENGTH_SAMPLES;
m_syncCheck = false;
m_state = YSFRXS_DATA;
m_maxCorr = 0U;
}
m_dataPtr++;
if (m_dataPtr >= YSF_FRAME_LENGTH_SAMPLES)
m_dataPtr = 0U;
m_bitPtr++;
if (m_bitPtr >= YSF_RADIO_SYMBOL_LENGTH)
m_bitPtr = 0U;
}
void CYSFRX::processData(q15_t sample)
{
m_bitBuffer[m_bitPtr] <<= 1;
if (sample < 0)
m_bitBuffer[m_bitPtr] |= 0x01U;
m_buffer[m_dataPtr] = sample;
if (m_dataPtr == m_syncStartPtr) m_syncCheck = true;
if (m_dataPtr == m_syncEndPtr) m_syncCheck = false;
if (m_syncCheck) {
if (countBits32((m_bitBuffer[m_bitPtr] & YSF_SYNC_SYMBOLS_MASK) ^ YSF_SYNC_SYMBOLS) <= MAX_SYNC_SYMBOLS_ERRS) {
uint16_t ptr = m_dataPtr + YSF_FRAME_LENGTH_SAMPLES - YSF_SYNC_LENGTH_SAMPLES + YSF_RADIO_SYMBOL_LENGTH;
if (ptr >= YSF_FRAME_LENGTH_SAMPLES)
ptr -= YSF_FRAME_LENGTH_SAMPLES;
q31_t corr = 0;
q15_t max = -16000;
q15_t min = 16000;
uint32_t mask = 0x00080000U;
for (uint8_t i = 0U; i < YSF_SYNC_LENGTH_SYMBOLS; i++, mask >>= 1) {
bool b = (YSF_SYNC_SYMBOLS & mask) == mask;
if (m_buffer[ptr] > max)
max = m_buffer[ptr];
if (m_buffer[ptr] < min)
min = m_buffer[ptr];
corr += b ? -m_buffer[ptr] : m_buffer[ptr];
ptr += YSF_RADIO_SYMBOL_LENGTH;
if (ptr >= YSF_FRAME_LENGTH_SAMPLES)
ptr -= YSF_FRAME_LENGTH_SAMPLES;
}
if (corr > m_maxCorr) {
q15_t centre = (max + min) >> 1;
q31_t v1 = (max - centre) * SCALING_FACTOR;
q15_t threshold = q15_t(v1 >> 15);
uint16_t ptr = m_dataPtr + YSF_FRAME_LENGTH_SAMPLES - YSF_SYNC_LENGTH_SAMPLES + YSF_RADIO_SYMBOL_LENGTH;
if (ptr >= YSF_FRAME_LENGTH_SAMPLES)
ptr -= YSF_FRAME_LENGTH_SAMPLES;
uint8_t sync[YSF_SYNC_BYTES_LENGTH];
samplesToBits(ptr, YSF_SYNC_LENGTH_SYMBOLS, sync, 0U, m_centreVal, m_thresholdVal);
uint8_t errs = 0U;
for (uint8_t i = 0U; i < YSF_SYNC_BYTES_LENGTH; i++)
errs += countBits8(sync[i] ^ YSF_SYNC_BYTES[i]);
if (errs <= MAX_SYNC_BYTES_ERRS) {
DEBUG4("YSFRX: sync found in Data pos/centre/threshold", m_dataPtr, centre, threshold);
m_maxCorr = corr;
m_lostCount = MAX_SYNC_FRAMES;
m_syncPtr = m_dataPtr;
m_centreBest = centre;
m_thresholdBest = threshold;
m_endPtr = m_dataPtr + YSF_FRAME_LENGTH_SAMPLES - YSF_SYNC_LENGTH_SAMPLES - 1U;
if (m_endPtr >= YSF_FRAME_LENGTH_SAMPLES)
m_endPtr -= YSF_FRAME_LENGTH_SAMPLES;
}
}
}
}
if (m_dataPtr == m_endPtr) {
uint16_t ptr = m_endPtr + YSF_RADIO_SYMBOL_LENGTH + 1U;
if (ptr >= YSF_FRAME_LENGTH_SAMPLES)
ptr -= YSF_FRAME_LENGTH_SAMPLES;
// Only update the centre and threshold if they are from a good sync
if (m_lostCount == MAX_SYNC_FRAMES) {
m_threshold[m_averagePtr] = m_thresholdBest;
m_centre[m_averagePtr] = m_centreBest;
m_averagePtr++;
if (m_averagePtr >= 4U)
m_averagePtr = 0U;
// Find the average centre and threshold values
m_centreVal = (m_centre[0U] + m_centre[1U] + m_centre[2U] + m_centre[3U]) >> 2;
m_thresholdVal = (m_threshold[0U] + m_threshold[1U] + m_threshold[2U] + m_threshold[3U]) >> 2;
}
uint8_t frame[YSF_FRAME_LENGTH_BYTES + 3U];
samplesToBits(ptr, YSF_FRAME_LENGTH_SYMBOLS, frame, 8U, m_centreVal, m_thresholdVal);
// We've not seen a data sync for too long, signal RXLOST and change to RX_NONE
m_lostCount--;
if (m_lostCount == 0U) {
DEBUG1("YSFRX: sync timed out, lost lock");
io.setDecode(false);
io.setADCDetection(false);
serial.writeYSFLost();
m_state = YSFRXS_NONE;
m_endPtr = NOENDPTR;
} else {
frame[0U] = m_lostCount == (MAX_SYNC_FRAMES - 1U) ? 0x01U : 0x00U;
writeRSSIData(frame);
m_syncStartPtr = m_syncPtr + YSF_FRAME_LENGTH_SAMPLES - 2U;
if (m_syncStartPtr >= YSF_FRAME_LENGTH_SAMPLES)
m_syncStartPtr -= YSF_FRAME_LENGTH_SAMPLES;
m_syncEndPtr = m_syncPtr + 2U;
if (m_syncEndPtr >= YSF_FRAME_LENGTH_SAMPLES)
m_syncEndPtr -= YSF_FRAME_LENGTH_SAMPLES;
// Start the next frame
::memset(frame, 0x00U, YSF_FRAME_LENGTH_BYTES + 3U);
}
m_syncCheck = false;
m_maxCorr = 0U;
m_centreBest = 0;
m_thresholdBest = 0;
}
m_dataPtr++;
if (m_dataPtr >= YSF_FRAME_LENGTH_SAMPLES)
m_dataPtr = 0U;
m_bitPtr++;
if (m_bitPtr >= YSF_RADIO_SYMBOL_LENGTH)
m_bitPtr = 0U;
}
void CYSFRX::samplesToBits(uint16_t start, uint16_t count, uint8_t* buffer, uint16_t offset, q15_t centre, q15_t threshold)
{
for (uint16_t i = 0U; i < count; i++) {
q15_t sample = m_buffer[start] - centre;
if (sample < -threshold) {
WRITE_BIT1(buffer, offset, false);
offset++;
WRITE_BIT1(buffer, offset, true);
offset++;
} else if (sample < 0) {
WRITE_BIT1(buffer, offset, false);
offset++;
WRITE_BIT1(buffer, offset, false);
offset++;
} else if (sample < threshold) {
WRITE_BIT1(buffer, offset, true);
offset++;
WRITE_BIT1(buffer, offset, false);
offset++;
} else {
WRITE_BIT1(buffer, offset, true);
offset++;
WRITE_BIT1(buffer, offset, true);
offset++;
}
start += YSF_RADIO_SYMBOL_LENGTH;
if (start >= YSF_FRAME_LENGTH_SAMPLES)
start -= YSF_FRAME_LENGTH_SAMPLES;
}
}
void CYSFRX::writeRSSIData(uint8_t* data)
{
#if defined(SEND_RSSI_DATA)
if (m_rssiCount > 0U) {
uint16_t rssi = m_rssiAccum / m_rssiCount;
data[120U] = (rssi >> 8) & 0xFFU;
data[121U] = (rssi >> 0) & 0xFFU;
serial.writeYSFData(data, YSF_FRAME_LENGTH_BYTES + 3U);
} else {
serial.writeYSFData(data, YSF_FRAME_LENGTH_BYTES + 1U);
}
#else
serial.writeYSFData(data, YSF_FRAME_LENGTH_BYTES + 1U);
#endif
m_rssiAccum = 0U;
m_rssiCount = 0U;
}
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