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MMDVM/DMRSlotRX.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 "DMRSlotRX.h"
#include "DMRSlotType.h"
#include "Utils.h"
const uint16_t SCAN_START = 400U;
const uint16_t SCAN_END = 490U;
const q15_t SCALING_FACTOR = 19505; // Q15(0.60)
const uint8_t MAX_SYNC_SYMBOLS_ERRS = 2U;
const uint8_t MAX_SYNC_BYTES_ERRS = 3U;
const uint8_t MAX_SYNC_LOST_FRAMES = 13U;
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 uint8_t CONTROL_NONE = 0x00U;
const uint8_t CONTROL_VOICE = 0x20U;
const uint8_t CONTROL_DATA = 0x40U;
CDMRSlotRX::CDMRSlotRX(bool slot) :
m_slot(slot),
m_bitBuffer(),
m_buffer(),
m_bitPtr(0U),
m_dataPtr(0U),
m_syncPtr(0U),
m_startPtr(0U),
m_endPtr(NOENDPTR),
m_delayPtr(0U),
m_maxCorr(0),
m_centre(),
m_threshold(),
m_averagePtr(0U),
m_control(CONTROL_NONE),
m_syncCount(0U),
m_colorCode(0U),
m_delay(0U),
m_state(DMRRXS_NONE),
m_n(0U),
m_type(0U),
m_rssi()
{
}
void CDMRSlotRX::start()
{
m_dataPtr = 0U;
m_delayPtr = 0U;
m_bitPtr = 0U;
m_maxCorr = 0;
m_control = CONTROL_NONE;
}
void CDMRSlotRX::reset()
{
m_syncPtr = 0U;
m_dataPtr = 0U;
m_delayPtr = 0U;
m_bitPtr = 0U;
m_maxCorr = 0;
m_control = CONTROL_NONE;
m_syncCount = 0U;
m_state = DMRRXS_NONE;
m_startPtr = 0U;
m_endPtr = NOENDPTR;
}
bool CDMRSlotRX::processSample(q15_t sample, uint16_t rssi)
{
m_delayPtr++;
if (m_delayPtr < m_delay)
return m_state != DMRRXS_NONE;
// Ensure that the buffer doesn't overflow
if (m_dataPtr > m_endPtr || m_dataPtr >= 900U)
return m_state != DMRRXS_NONE;
m_buffer[m_dataPtr] = sample;
m_rssi[m_dataPtr] = rssi;
m_bitBuffer[m_bitPtr] <<= 1;
if (sample < 0)
m_bitBuffer[m_bitPtr] |= 0x01U;
if (m_state == DMRRXS_NONE) {
if (m_dataPtr >= SCAN_START && m_dataPtr <= SCAN_END)
correlateSync(true);
} else {
uint16_t min = m_syncPtr - 1U;
uint16_t max = m_syncPtr + 1U;
if (m_dataPtr >= min && m_dataPtr <= max)
correlateSync(false);
}
if (m_dataPtr == m_endPtr) {
// Find the average centre and threshold values
q15_t centre = (m_centre[0U] + m_centre[1U] + m_centre[2U] + m_centre[3U]) >> 2;
q15_t threshold = (m_threshold[0U] + m_threshold[1U] + m_threshold[2U] + m_threshold[3U]) >> 2;
uint8_t frame[DMR_FRAME_LENGTH_BYTES + 3U];
frame[0U] = m_control;
uint16_t ptr = m_endPtr - DMR_FRAME_LENGTH_SAMPLES + DMR_RADIO_SYMBOL_LENGTH + 1U;
samplesToBits(ptr, DMR_FRAME_LENGTH_SYMBOLS, frame, 8U, centre, threshold);
if (m_control == CONTROL_DATA) {
// Data sync
uint8_t colorCode;
uint8_t dataType;
CDMRSlotType slotType;
slotType.decode(frame + 1U, colorCode, dataType);
if (colorCode == m_colorCode) {
m_syncCount = 0U;
m_n = 0U;
frame[0U] |= dataType;
switch (dataType) {
case DT_DATA_HEADER:
DEBUG5("DMRSlotRX: data header found slot/pos/centre/threshold", m_slot ? 2U : 1U, m_syncPtr, centre, threshold);
writeRSSIData(frame);
m_state = DMRRXS_DATA;
m_type = 0x00U;
break;
case DT_RATE_12_DATA:
case DT_RATE_34_DATA:
case DT_RATE_1_DATA:
if (m_state == DMRRXS_DATA) {
DEBUG5("DMRSlotRX: data payload found slot/pos/centre/threshold", m_slot ? 2U : 1U, m_syncPtr, centre, threshold);
writeRSSIData(frame);
m_type = dataType;
}
break;
case DT_VOICE_LC_HEADER:
DEBUG5("DMRSlotRX: voice header found slot/pos/centre/threshold", m_slot ? 2U : 1U, m_syncPtr, centre, threshold);
writeRSSIData(frame);
m_state = DMRRXS_VOICE;
break;
case DT_VOICE_PI_HEADER:
if (m_state == DMRRXS_VOICE) {
DEBUG5("DMRSlotRX: voice pi header found slot/pos/centre/threshold", m_slot ? 2U : 1U, m_syncPtr, centre, threshold);
writeRSSIData(frame);
}
m_state = DMRRXS_VOICE;
break;
case DT_TERMINATOR_WITH_LC:
if (m_state == DMRRXS_VOICE) {
DEBUG5("DMRSlotRX: voice terminator found slot/pos/centre/threshold", m_slot ? 2U : 1U, m_syncPtr, centre, threshold);
writeRSSIData(frame);
m_state = DMRRXS_NONE;
m_endPtr = NOENDPTR;
}
break;
default: // DT_CSBK
DEBUG5("DMRSlotRX: csbk found slot/pos/centre/threshold", m_slot ? 2U : 1U, m_syncPtr, centre, threshold);
writeRSSIData(frame);
m_state = DMRRXS_NONE;
m_endPtr = NOENDPTR;
break;
}
}
} else if (m_control == CONTROL_VOICE) {
// Voice sync
DEBUG5("DMRSlotRX: voice sync found slot/pos/centre/threshold", m_slot ? 2U : 1U, m_syncPtr, centre, threshold);
writeRSSIData(frame);
m_state = DMRRXS_VOICE;
m_syncCount = 0U;
m_n = 0U;
} else {
if (m_state != DMRRXS_NONE) {
m_syncCount++;
if (m_syncCount >= MAX_SYNC_LOST_FRAMES) {
serial.writeDMRLost(m_slot);
m_state = DMRRXS_NONE;
m_endPtr = NOENDPTR;
}
}
if (m_state == DMRRXS_VOICE) {
if (m_n >= 5U) {
frame[0U] = CONTROL_VOICE;
m_n = 0U;
} else {
frame[0U] = ++m_n;
}
serial.writeDMRData(m_slot, frame, DMR_FRAME_LENGTH_BYTES + 1U);
} else if (m_state == DMRRXS_DATA) {
if (m_type != 0x00U) {
frame[0U] = CONTROL_DATA | m_type;
writeRSSIData(frame);
}
}
}
}
m_dataPtr++;
m_bitPtr++;
if (m_bitPtr >= DMR_RADIO_SYMBOL_LENGTH)
m_bitPtr = 0U;
return m_state != DMRRXS_NONE;
}
void CDMRSlotRX::correlateSync(bool first)
{
uint8_t errs = countBits32((m_bitBuffer[m_bitPtr] & DMR_SYNC_SYMBOLS_MASK) ^ DMR_MS_DATA_SYNC_SYMBOLS);
// The voice sync is the complement of the data sync
bool data = (errs <= MAX_SYNC_SYMBOLS_ERRS);
bool voice = (errs >= (DMR_SYNC_LENGTH_SYMBOLS - MAX_SYNC_SYMBOLS_ERRS));
if (data || voice) {
uint16_t ptr = m_dataPtr - DMR_SYNC_LENGTH_SAMPLES + DMR_RADIO_SYMBOL_LENGTH;
q31_t corr = 0;
q15_t min = 16000;
q15_t max = -16000;
for (uint8_t i = 0U; i < DMR_SYNC_LENGTH_SYMBOLS; i++) {
q15_t val = m_buffer[ptr];
if (val > max)
max = val;
if (val < min)
min = val;
int8_t corrVal;
if (data)
corrVal = DMR_MS_DATA_SYNC_SYMBOLS_VALUES[i];
else
corrVal = DMR_MS_VOICE_SYNC_SYMBOLS_VALUES[i];
switch (corrVal) {
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 += DMR_RADIO_SYMBOL_LENGTH;
}
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[DMR_SYNC_BYTES_LENGTH];
uint16_t ptr = m_dataPtr - DMR_SYNC_LENGTH_SAMPLES + DMR_RADIO_SYMBOL_LENGTH;
samplesToBits(ptr, DMR_SYNC_LENGTH_SYMBOLS, sync, 4U, centre, threshold);
if (data) {
uint8_t errs = 0U;
for (uint8_t i = 0U; i < DMR_SYNC_BYTES_LENGTH; i++)
errs += countBits8((sync[i] & DMR_SYNC_BYTES_MASK[i]) ^ DMR_MS_DATA_SYNC_BYTES[i]);
if (errs <= MAX_SYNC_BYTES_ERRS) {
if (first) {
m_threshold[0U] = m_threshold[1U] = m_threshold[2U] = m_threshold[3U] = threshold;
m_centre[0U] = m_centre[1U] = m_centre[2U] = m_centre[3U] = centre;
m_averagePtr = 0U;
} else {
m_threshold[m_averagePtr] = threshold;
m_centre[m_averagePtr] = centre;
m_averagePtr++;
if (m_averagePtr >= 4U)
m_averagePtr = 0U;
}
m_maxCorr = corr;
m_control = CONTROL_DATA;
m_syncPtr = m_dataPtr;
m_startPtr = m_dataPtr - DMR_SLOT_TYPE_LENGTH_SAMPLES / 2U - DMR_INFO_LENGTH_SAMPLES / 2U - DMR_SYNC_LENGTH_SAMPLES;
m_endPtr = m_dataPtr + DMR_SLOT_TYPE_LENGTH_SAMPLES / 2U + DMR_INFO_LENGTH_SAMPLES / 2U - 1U;
}
} else { // if (voice)
uint8_t errs = 0U;
for (uint8_t i = 0U; i < DMR_SYNC_BYTES_LENGTH; i++)
errs += countBits8((sync[i] & DMR_SYNC_BYTES_MASK[i]) ^ DMR_MS_VOICE_SYNC_BYTES[i]);
if (errs <= MAX_SYNC_BYTES_ERRS) {
if (first) {
m_threshold[0U] = m_threshold[1U] = m_threshold[2U] = m_threshold[3U] = threshold;
m_centre[0U] = m_centre[1U] = m_centre[2U] = m_centre[3U] = centre;
m_averagePtr = 0U;
} else {
m_threshold[m_averagePtr] = threshold;
m_centre[m_averagePtr] = centre;
m_averagePtr++;
if (m_averagePtr >= 4U)
m_averagePtr = 0U;
}
m_maxCorr = corr;
m_control = CONTROL_VOICE;
m_syncPtr = m_dataPtr;
m_startPtr = m_dataPtr - DMR_SLOT_TYPE_LENGTH_SAMPLES / 2U - DMR_INFO_LENGTH_SAMPLES / 2U - DMR_SYNC_LENGTH_SAMPLES;
m_endPtr = m_dataPtr + DMR_SLOT_TYPE_LENGTH_SAMPLES / 2U + DMR_INFO_LENGTH_SAMPLES / 2U - 1U;
}
}
}
}
}
void CDMRSlotRX::samplesToBits(uint16_t start, uint8_t count, uint8_t* buffer, uint16_t offset, q15_t centre, q15_t threshold)
{
for (uint8_t i = 0U; i < count; i++, start += DMR_RADIO_SYMBOL_LENGTH) {
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++;
}
}
}
void CDMRSlotRX::setColorCode(uint8_t colorCode)
{
m_colorCode = colorCode;
}
void CDMRSlotRX::setDelay(uint8_t delay)
{
m_delay = delay;
}
void CDMRSlotRX::writeRSSIData(uint8_t* frame)
{
#if defined(SEND_RSSI_DATA)
// Calculate RSSI average over a burst period. We don't take into account 2.5 ms at the beginning and 2.5 ms at the end
uint16_t start = m_startPtr + DMR_SYNC_LENGTH_SAMPLES / 2U;
uint32_t accum = 0U;
for (uint16_t i = 0U; i < (DMR_FRAME_LENGTH_SAMPLES - DMR_SYNC_LENGTH_SAMPLES); i++)
accum += m_rssi[start++];
uint16_t avg = accum / (DMR_FRAME_LENGTH_SAMPLES - DMR_SYNC_LENGTH_SAMPLES);
frame[34U] = (avg >> 8) & 0xFFU;
frame[35U] = (avg >> 0) & 0xFFU;
serial.writeDMRData(m_slot, frame, DMR_FRAME_LENGTH_BYTES + 3U);
#else
serial.writeDMRData(m_slot, frame, DMR_FRAME_LENGTH_BYTES + 1U);
#endif
}
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