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MMDVM/P25RX.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
#define DUMP_SAMPLES
#include "Config.h"
#include "Globals.h"
#include "P25RX.h"
#include "Utils.h"
const q15_t SCALING_FACTOR = 18750; // Q15(0.55)
const uint8_t MAX_SYNC_BIT_START_ERRS = 2U;
const uint8_t MAX_SYNC_BIT_RUN_ERRS = 4U;
const uint8_t MAX_SYNC_SYMBOLS_ERRS = 2U;
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;
CP25RX::CP25RX() :
m_state(P25RXS_NONE),
m_bitBuffer(),
m_buffer(),
m_bitPtr(0U),
m_dataPtr(0U),
m_hdrStartPtr(NOENDPTR),
m_lduStartPtr(NOENDPTR),
m_lduEndPtr(NOENDPTR),
m_minSyncPtr(NOENDPTR),
m_maxSyncPtr(NOENDPTR),
m_hdrSyncPtr(NOENDPTR),
m_lduSyncPtr(NOENDPTR),
m_maxCorr(0),
m_lostCount(0U),
m_countdown(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 CP25RX::reset()
{
m_state = P25RXS_NONE;
m_dataPtr = 0U;
m_bitPtr = 0U;
m_maxCorr = 0;
m_averagePtr = 0U;
m_hdrStartPtr = NOENDPTR;
m_lduStartPtr = NOENDPTR;
m_lduEndPtr = NOENDPTR;
m_hdrSyncPtr = NOENDPTR;
m_lduSyncPtr = NOENDPTR;
m_minSyncPtr = NOENDPTR;
m_maxSyncPtr = NOENDPTR;
m_centreVal = 0;
m_thresholdVal = 0;
m_lostCount = 0U;
m_countdown = 0U;
m_rssiAccum = 0U;
m_rssiCount = 0U;
}
void CP25RX::samples(const q15_t* samples, uint16_t* rssi, uint8_t length)
{
for (uint8_t i = 0U; i < length; i++) {
q15_t sample = samples[i];
m_rssiAccum += rssi[i];
m_rssiCount++;
m_bitBuffer[m_bitPtr] <<= 1;
if (sample < 0)
m_bitBuffer[m_bitPtr] |= 0x01U;
m_buffer[m_dataPtr] = sample;
switch (m_state) {
case P25RXS_HDR:
processHdr(sample);
break;
case P25RXS_LDU:
processLdu(sample);
break;
default:
processNone(sample);
break;
}
m_dataPtr++;
if (m_dataPtr >= P25_LDU_FRAME_LENGTH_SAMPLES)
m_dataPtr = 0U;
m_bitPtr++;
if (m_bitPtr >= P25_RADIO_SYMBOL_LENGTH)
m_bitPtr = 0U;
}
}
void CP25RX::processNone(q15_t sample)
{
bool ret = correlateSync();
if (ret) {
// On the first sync, start the countdown to the state change
if (m_countdown == 0U) {
m_rssiAccum = 0U;
m_rssiCount = 0U;
io.setDecode(true);
io.setADCDetection(true);
m_countdown = 5U;
}
}
if (m_countdown > 0U)
m_countdown--;
if (m_countdown == 1U) {
for (uint8_t i = 0U; i < 16U; i++) {
m_centre[i] = m_centreBest;
m_threshold[i] = m_thresholdBest;
}
m_centreVal = m_centreBest;
m_thresholdVal = m_thresholdBest;
m_averagePtr = 0U;
// These are the sync positions for the following LDU after a HDR
m_minSyncPtr = m_hdrSyncPtr + P25_HDR_FRAME_LENGTH_SAMPLES - 1U;
if (m_minSyncPtr >= P25_LDU_FRAME_LENGTH_SAMPLES)
m_minSyncPtr -= P25_LDU_FRAME_LENGTH_SAMPLES;
m_maxSyncPtr = m_hdrSyncPtr + P25_HDR_FRAME_LENGTH_SAMPLES + 1U;
if (m_maxSyncPtr >= P25_LDU_FRAME_LENGTH_SAMPLES)
m_maxSyncPtr -= P25_LDU_FRAME_LENGTH_SAMPLES;
m_state = P25RXS_HDR;
m_countdown = 0U;
}
}
void CP25RX::processHdr(q15_t sample)
{
if (m_minSyncPtr < m_maxSyncPtr) {
if (m_dataPtr >= m_minSyncPtr && m_dataPtr <= m_maxSyncPtr)
correlateSync();
} else {
if (m_dataPtr >= m_minSyncPtr || m_dataPtr <= m_maxSyncPtr)
correlateSync();
}
if (m_dataPtr == m_maxSyncPtr) {
bool isSync = false;
if (m_minSyncPtr < m_maxSyncPtr) {
if (m_lduSyncPtr >= m_minSyncPtr && m_lduSyncPtr <= m_maxSyncPtr)
isSync = true;
} else {
if (m_lduSyncPtr >= m_minSyncPtr || m_lduSyncPtr <= m_maxSyncPtr)
isSync = true;
}
if (isSync) {
m_threshold[m_averagePtr] = m_thresholdBest;
m_centre[m_averagePtr] = m_centreBest;
m_averagePtr++;
if (m_averagePtr >= 16U)
m_averagePtr = 0U;
// Find the average centre and threshold values
m_centreVal = 0;
m_thresholdVal = 0;
for (uint8_t i = 0U; i < 16U; i++) {
m_centreVal += m_centre[i];
m_thresholdVal += m_threshold[i];
}
m_centreVal >>= 4;
m_thresholdVal >>= 4;
DEBUG4("P25RX: sync found in Hdr (best) pos/centre/threshold", m_hdrSyncPtr, m_centreBest, m_thresholdBest);
DEBUG4("P25RX: sync found in Hdr pos/centre/threshold", m_hdrSyncPtr, m_centreVal, m_thresholdVal);
uint8_t frame[P25_HDR_FRAME_LENGTH_BYTES + 1U];
samplesToBits(m_hdrStartPtr, P25_HDR_FRAME_LENGTH_SYMBOLS, frame, 8U, m_centreVal, m_thresholdVal);
#if defined(DUMP_SAMPLES)
writeSync(m_hdrStartPtr);
#endif
frame[0U] = 0x01U;
serial.writeP25Hdr(frame, P25_HDR_FRAME_LENGTH_BYTES + 1U);
}
m_minSyncPtr = m_lduSyncPtr + P25_LDU_FRAME_LENGTH_SAMPLES - 1U;
if (m_minSyncPtr >= P25_LDU_FRAME_LENGTH_SAMPLES)
m_minSyncPtr -= P25_LDU_FRAME_LENGTH_SAMPLES;
m_maxSyncPtr = m_lduSyncPtr + 1U;
if (m_maxSyncPtr >= P25_LDU_FRAME_LENGTH_SAMPLES)
m_maxSyncPtr -= P25_LDU_FRAME_LENGTH_SAMPLES;
m_state = P25RXS_LDU;
m_maxCorr = 0;
}
}
void CP25RX::processLdu(q15_t sample)
{
if (m_minSyncPtr < m_maxSyncPtr) {
if (m_dataPtr >= m_minSyncPtr && m_dataPtr <= m_maxSyncPtr)
correlateSync();
} else {
if (m_dataPtr >= m_minSyncPtr || m_dataPtr <= m_maxSyncPtr)
correlateSync();
}
if (m_dataPtr == m_lduEndPtr) {
// 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 >= 16U)
m_averagePtr = 0U;
// Find the average centre and threshold values
m_centreVal = 0;
m_thresholdVal = 0;
for (uint8_t i = 0U; i < 16U; i++) {
m_centreVal += m_centre[i];
m_thresholdVal += m_threshold[i];
}
m_centreVal >>= 4;
m_thresholdVal >>= 4;
DEBUG4("P25RX: sync found in Ldu (best) pos/centre/threshold", m_lduSyncPtr, m_centreBest, m_thresholdBest);
DEBUG4("P25RX: sync found in Ldu pos/centre/threshold", m_lduSyncPtr, m_centreVal, m_thresholdVal);
m_minSyncPtr = m_lduSyncPtr + P25_LDU_FRAME_LENGTH_SAMPLES - 1U;
if (m_minSyncPtr >= P25_LDU_FRAME_LENGTH_SAMPLES)
m_minSyncPtr -= P25_LDU_FRAME_LENGTH_SAMPLES;
m_maxSyncPtr = m_lduSyncPtr + 1U;
if (m_maxSyncPtr >= P25_LDU_FRAME_LENGTH_SAMPLES)
m_maxSyncPtr -= P25_LDU_FRAME_LENGTH_SAMPLES;
}
uint8_t frame[P25_LDU_FRAME_LENGTH_BYTES + 3U];
samplesToBits(m_lduStartPtr, P25_LDU_FRAME_LENGTH_SYMBOLS, frame, 8U, m_centreVal, m_thresholdVal);
#if defined(DUMP_SAMPLES)
writeSync(m_lduStartPtr);
#endif
// We've not seen a data sync for too long, signal RXLOST and change to RX_NONE
m_lostCount--;
if (m_lostCount == 0U) {
DEBUG1("P25RX: sync timed out, lost lock");
io.setDecode(false);
io.setADCDetection(false);
serial.writeP25Lost();
m_state = P25RXS_NONE;
m_lduEndPtr = NOENDPTR;
m_maxCorr = 0;
} else {
frame[0U] = m_lostCount == (MAX_SYNC_FRAMES - 1U) ? 0x01U : 0x00U;
writeRSSILdu(frame);
m_maxCorr = 0;
}
}
}
bool CP25RX::correlateSync()
{
if (countBits32((m_bitBuffer[m_bitPtr] & P25_SYNC_SYMBOLS_MASK) ^ P25_SYNC_SYMBOLS) <= MAX_SYNC_SYMBOLS_ERRS) {
uint16_t ptr = m_dataPtr + P25_LDU_FRAME_LENGTH_SAMPLES - P25_SYNC_LENGTH_SAMPLES + P25_RADIO_SYMBOL_LENGTH;
if (ptr >= P25_LDU_FRAME_LENGTH_SAMPLES)
ptr -= P25_LDU_FRAME_LENGTH_SAMPLES;
q31_t corr = 0;
q15_t max = -16000;
q15_t min = 16000;
for (uint8_t i = 0U; i < P25_SYNC_LENGTH_SYMBOLS; i++) {
q15_t val = m_buffer[ptr];
if (val > max)
max = val;
if (val < min)
min = val;
switch (P25_SYNC_SYMBOLS_VALUES[i]) {
case +3:
corr -= (val + val + val);
break;
case +1:
corr -= val;
break;
case -1:
corr += val;
break;
default: // -3
corr += (val + val + val);
break;
}
ptr += P25_RADIO_SYMBOL_LENGTH;
if (ptr >= P25_LDU_FRAME_LENGTH_SAMPLES)
ptr -= P25_LDU_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[P25_SYNC_BYTES_LENGTH];
uint16_t startPtr = m_dataPtr + P25_LDU_FRAME_LENGTH_SAMPLES - P25_SYNC_LENGTH_SAMPLES + P25_RADIO_SYMBOL_LENGTH;
if (startPtr >= P25_LDU_FRAME_LENGTH_SAMPLES)
startPtr -= P25_LDU_FRAME_LENGTH_SAMPLES;
uint8_t maxErrs;
if (m_state == P25RXS_NONE) {
samplesToBits(startPtr, P25_SYNC_LENGTH_SYMBOLS, sync, 0U, centre, threshold);
maxErrs = MAX_SYNC_BIT_START_ERRS;
} else {
samplesToBits(startPtr, P25_SYNC_LENGTH_SYMBOLS, sync, 0U, m_centreVal, m_thresholdVal);
maxErrs = MAX_SYNC_BIT_RUN_ERRS;
}
uint8_t errs = 0U;
for (uint8_t i = 0U; i < P25_SYNC_BYTES_LENGTH; i++)
errs += countBits8(sync[i] ^ P25_SYNC_BYTES[i]);
if (errs <= maxErrs) {
m_maxCorr = corr;
m_thresholdBest = threshold;
m_centreBest = centre;
m_lostCount = MAX_SYNC_FRAMES;
m_lduSyncPtr = m_dataPtr;
// These are the positions of the start and end of an LDU
m_lduStartPtr = startPtr;
m_lduEndPtr = m_dataPtr + P25_LDU_FRAME_LENGTH_SAMPLES - P25_SYNC_LENGTH_SAMPLES - 1U;
if (m_lduEndPtr >= P25_LDU_FRAME_LENGTH_SAMPLES)
m_lduEndPtr -= P25_LDU_FRAME_LENGTH_SAMPLES;
if (m_state == P25RXS_NONE) {
m_hdrSyncPtr = m_dataPtr;
// This is the position of the start of a HDR
m_hdrStartPtr = startPtr;
// These are the range of positions for a sync for an LDU following a HDR
m_minSyncPtr = m_dataPtr + P25_HDR_FRAME_LENGTH_SAMPLES - 1U;
if (m_minSyncPtr >= P25_LDU_FRAME_LENGTH_SAMPLES)
m_minSyncPtr -= P25_LDU_FRAME_LENGTH_SAMPLES;
m_maxSyncPtr = m_dataPtr + P25_HDR_FRAME_LENGTH_SAMPLES + 1U;
if (m_maxSyncPtr >= P25_LDU_FRAME_LENGTH_SAMPLES)
m_maxSyncPtr -= P25_LDU_FRAME_LENGTH_SAMPLES;
}
return true;
}
}
}
return false;
}
void CP25RX::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 += P25_RADIO_SYMBOL_LENGTH;
if (start >= P25_LDU_FRAME_LENGTH_SAMPLES)
start -= P25_LDU_FRAME_LENGTH_SAMPLES;
}
}
void CP25RX::writeRSSILdu(uint8_t* ldu)
{
#if defined(SEND_RSSI_DATA)
if (m_rssiCount > 0U) {
uint16_t rssi = m_rssiAccum / m_rssiCount;
ldu[216U] = (rssi >> 8) & 0xFFU;
ldu[217U] = (rssi >> 0) & 0xFFU;
serial.writeP25Ldu(ldu, P25_LDU_FRAME_LENGTH_BYTES + 3U);
} else {
serial.writeP25Ldu(ldu, P25_LDU_FRAME_LENGTH_BYTES + 1U);
}
#else
serial.writeP25Ldu(ldu, P25_LDU_FRAME_LENGTH_BYTES + 1U);
#endif
m_rssiAccum = 0U;
m_rssiCount = 0U;
}
#if defined(DUMP_SAMPLES)
void CP25RX::writeSync(uint16_t start)
{
q15_t sync[P25_SYNC_LENGTH_SYMBOLS];
for (uint16_t i = 0U; i < P25_SYNC_LENGTH_SYMBOLS; i++) {
if (i == (P25_SYNC_LENGTH_SYMBOLS - 1U))
DEBUG4("P25RX: sync1/sync2/start", m_hdrSyncPtr, m_lduSyncPtr, start);
sync[i] = m_buffer[start];
start += P25_RADIO_SYMBOL_LENGTH;
if (start >= P25_LDU_FRAME_LENGTH_SAMPLES)
start -= P25_LDU_FRAME_LENGTH_SAMPLES;
}
serial.writeSamples(STATE_P25, sync, P25_SYNC_LENGTH_SYMBOLS);
}
#endif
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