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DMRIdleRX.cpp
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DMRIdleRX.cpp
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/*
* Copyright (C) 2009-2017,2020 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.
*/
#include "Config.h"
#if defined(MODE_DMR)
#include "Globals.h"
#include "DMRIdleRX.h"
#include "DMRSlotType.h"
#include "Utils.h"
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 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_IDLE = 0x80U;
const uint8_t CONTROL_DATA = 0x40U;
CDMRIdleRX::CDMRIdleRX() :
m_bitBuffer(),
m_buffer(),
m_bitPtr(0U),
m_dataPtr(0U),
m_endPtr(NOENDPTR),
m_maxCorr(0),
m_centre(0),
m_threshold(0),
m_colorCode(0U)
{
}
void CDMRIdleRX::reset()
{
m_dataPtr = 0U;
m_bitPtr = 0U;
m_maxCorr = 0;
m_threshold = 0;
m_centre = 0;
m_endPtr = NOENDPTR;
}
void CDMRIdleRX::samples(const q15_t* samples, uint8_t length)
{
for (uint8_t i = 0U; i < length; i++)
processSample(samples[i]);
}
void CDMRIdleRX::processSample(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] & DMR_SYNC_SYMBOLS_MASK) ^ DMR_MS_DATA_SYNC_SYMBOLS) <= MAX_SYNC_SYMBOLS_ERRS) {
uint16_t ptr = m_dataPtr + DMR_FRAME_LENGTH_SAMPLES - DMR_SYNC_LENGTH_SAMPLES + DMR_RADIO_SYMBOL_LENGTH;
if (ptr >= DMR_FRAME_LENGTH_SAMPLES)
ptr -= DMR_FRAME_LENGTH_SAMPLES;
q31_t corr = 0;
q15_t max = -16000;
q15_t min = 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;
switch (DMR_MS_DATA_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 += DMR_RADIO_SYMBOL_LENGTH;
if (ptr >= DMR_FRAME_LENGTH_SAMPLES)
ptr -= DMR_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[DMR_SYNC_BYTES_LENGTH];
uint16_t ptr = m_dataPtr + DMR_FRAME_LENGTH_SAMPLES - DMR_SYNC_LENGTH_SAMPLES + DMR_RADIO_SYMBOL_LENGTH;
if (ptr >= DMR_FRAME_LENGTH_SAMPLES)
ptr -= DMR_FRAME_LENGTH_SAMPLES;
samplesToBits(ptr, DMR_SYNC_LENGTH_SYMBOLS, sync, 4U, centre, threshold);
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) {
DEBUG3("DMRIdleRX: data sync found centre/threshold", centre, threshold);
m_maxCorr = corr;
m_centre = centre;
m_threshold = threshold;
m_endPtr = m_dataPtr + DMR_SLOT_TYPE_LENGTH_SAMPLES / 2U + DMR_INFO_LENGTH_SAMPLES / 2U - 1U;
if (m_endPtr >= DMR_FRAME_LENGTH_SAMPLES)
m_endPtr -= DMR_FRAME_LENGTH_SAMPLES;
}
}
}
if (m_dataPtr == m_endPtr) {
uint16_t ptr = m_endPtr + DMR_RADIO_SYMBOL_LENGTH + 1U;
if (ptr >= DMR_FRAME_LENGTH_SAMPLES)
ptr -= DMR_FRAME_LENGTH_SAMPLES;
uint8_t frame[DMR_FRAME_LENGTH_BYTES + 1U];
samplesToBits(ptr, DMR_FRAME_LENGTH_SYMBOLS, frame, 8U, m_centre, m_threshold);
uint8_t colorCode;
uint8_t dataType;
CDMRSlotType slotType;
slotType.decode(frame + 1U, colorCode, dataType);
if (colorCode == m_colorCode && dataType == DT_CSBK) {
frame[0U] = CONTROL_IDLE | CONTROL_DATA | DT_CSBK;
DEBUG1("CSBK Received");
serial.writeDMRData(false, frame, DMR_FRAME_LENGTH_BYTES + 1U);
}
m_endPtr = NOENDPTR;
m_maxCorr = 0;
}
m_dataPtr++;
if (m_dataPtr >= DMR_FRAME_LENGTH_SAMPLES)
m_dataPtr = 0U;
m_bitPtr++;
if (m_bitPtr >= DMR_RADIO_SYMBOL_LENGTH)
m_bitPtr = 0U;
}
void CDMRIdleRX::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++) {
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 += DMR_RADIO_SYMBOL_LENGTH;
if (start >= DMR_FRAME_LENGTH_SAMPLES)
start -= DMR_FRAME_LENGTH_SAMPLES;
}
}
void CDMRIdleRX::setColorCode(uint8_t colorCode)
{
m_colorCode = colorCode;
}
#endif