mirror of https://github.com/f4exb/sdrangel.git
280 lines
10 KiB
C++
280 lines
10 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
|
|
// Copyright (C) 2019 Edouard Griffiths, F4EXB //
|
|
// Copyright (C) 2020 Jon Beniston, M7RCE //
|
|
// //
|
|
// 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 as version 3 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 V3 for more details. //
|
|
// //
|
|
// You should have received a copy of the GNU General Public License //
|
|
// along with this program. If not, see <http://www.gnu.org/licenses/>. //
|
|
///////////////////////////////////////////////////////////////////////////////////
|
|
|
|
#include <stdio.h>
|
|
#include <complex.h>
|
|
#include <cmath>
|
|
|
|
#include <QTime>
|
|
#include <QDebug>
|
|
|
|
#include "util/stepfunctions.h"
|
|
#include "util/db.h"
|
|
#include "util/crc.h"
|
|
#include "audio/audiooutput.h"
|
|
#include "dsp/dspengine.h"
|
|
#include "dsp/dspcommands.h"
|
|
#include "dsp/devicesamplemimo.h"
|
|
#include "device/deviceapi.h"
|
|
|
|
#include "adsbdemodreport.h"
|
|
#include "adsbdemodsink.h"
|
|
#include "adsb.h"
|
|
|
|
ADSBDemodSink::ADSBDemodSink() :
|
|
m_channelSampleRate(6000000),
|
|
m_channelFrequencyOffset(0),
|
|
m_sampleIdx(0),
|
|
m_sampleCount(0),
|
|
m_skipCount(0),
|
|
m_magsq(0.0f),
|
|
m_magsqSum(0.0f),
|
|
m_magsqPeak(0.0f),
|
|
m_magsqCount(0),
|
|
m_messageQueueToGUI(nullptr),
|
|
m_sampleBuffer(nullptr),
|
|
m_preamble(nullptr)
|
|
{
|
|
applySettings(m_settings, true);
|
|
applyChannelSettings(m_channelSampleRate, m_channelFrequencyOffset, true);
|
|
}
|
|
|
|
ADSBDemodSink::~ADSBDemodSink()
|
|
{
|
|
delete m_sampleBuffer;
|
|
delete m_preamble;
|
|
}
|
|
|
|
void ADSBDemodSink::feed(const SampleVector::const_iterator& begin, const SampleVector::const_iterator& end)
|
|
{
|
|
Complex ci;
|
|
|
|
for (SampleVector::const_iterator it = begin; it != end; ++it)
|
|
{
|
|
Complex c(it->real(), it->imag());
|
|
c *= m_nco.nextIQ();
|
|
|
|
if (m_interpolatorDistance == 1.0f)
|
|
{
|
|
processOneSample(c);
|
|
}
|
|
else if (m_interpolatorDistance < 1.0f) // interpolate
|
|
{
|
|
while (!m_interpolator.interpolate(&m_interpolatorDistanceRemain, c, &ci))
|
|
{
|
|
processOneSample(ci);
|
|
m_interpolatorDistanceRemain += m_interpolatorDistance;
|
|
}
|
|
}
|
|
else // decimate
|
|
{
|
|
if (m_interpolator.decimate(&m_interpolatorDistanceRemain, c, &ci))
|
|
{
|
|
processOneSample(ci);
|
|
m_interpolatorDistanceRemain += m_interpolatorDistance;
|
|
}
|
|
}
|
|
}
|
|
|
|
}
|
|
|
|
void ADSBDemodSink::processOneSample(Complex &ci)
|
|
{
|
|
Real sample;
|
|
|
|
double magsqRaw = ci.real()*ci.real() + ci.imag()*ci.imag();
|
|
Real magsq = magsqRaw / (SDR_RX_SCALED*SDR_RX_SCALED);
|
|
m_movingAverage(magsq);
|
|
m_magsqSum += magsq;
|
|
|
|
if (magsq > m_magsqPeak)
|
|
{
|
|
m_magsqPeak = magsq;
|
|
}
|
|
m_magsqCount++;
|
|
|
|
sample = sqrtf(magsq);
|
|
m_sampleBuffer[m_sampleCount] = sample;
|
|
m_sampleCount++;
|
|
|
|
// Do we have enough data for a frame
|
|
if ((m_sampleCount >= m_totalSamples) && (m_skipCount == 0))
|
|
{
|
|
int startIdx = m_sampleCount - m_totalSamples;
|
|
|
|
// Correlate received signal with expected preamble
|
|
Real preambleCorrelation = 0.0f;
|
|
for (int i = 0; i < ADS_B_PREAMBLE_CHIPS*m_samplesPerChip; i++)
|
|
preambleCorrelation += m_preamble[i] * m_sampleBuffer[startIdx+i];
|
|
|
|
// If the correlation is exactly 0, it's probably no signal
|
|
if ((preambleCorrelation > m_settings.m_correlationThreshold) && (preambleCorrelation != 0.0f))
|
|
{
|
|
// Skip over preamble
|
|
startIdx += m_settings.m_samplesPerBit*ADS_B_PREAMBLE_BITS;
|
|
|
|
// Demodulate waveform to bytes
|
|
unsigned char data[ADS_B_ES_BYTES];
|
|
int byteIdx = 0;
|
|
int currentBit;
|
|
unsigned char currentByte = 0;
|
|
bool adsbOnly = true;
|
|
int df;
|
|
|
|
for (int bit = 0; bit < ADS_B_ES_BITS; bit++)
|
|
{
|
|
// PPM (Pulse position modulation) - Each bit spreads to two chips, 1->10, 0->01
|
|
// Determine if bit is 1 or 0, by seeing which chip has largest combined energy over the sampling period
|
|
Real oneSum = 0.0f;
|
|
Real zeroSum = 0.0f;
|
|
for (int i = 0; i < m_samplesPerChip; i++)
|
|
{
|
|
oneSum += m_sampleBuffer[startIdx+i];
|
|
zeroSum += m_sampleBuffer[startIdx+m_samplesPerChip+i];
|
|
}
|
|
currentBit = oneSum > zeroSum;
|
|
startIdx += m_settings.m_samplesPerBit;
|
|
// Convert bit to bytes - MSB first
|
|
currentByte |= currentBit << (7-(bit & 0x7));
|
|
if ((bit & 0x7) == 0x7)
|
|
{
|
|
data[byteIdx++] = currentByte;
|
|
currentByte = 0;
|
|
// Don't try to demodulate any further, if this isn't an ADS-B frame
|
|
// to help reduce processing overhead
|
|
if (adsbOnly && (bit == 7))
|
|
{
|
|
df = ((data[0] >> 3) & ADS_B_DF_MASK);
|
|
if ((df != 17) && (df != 18))
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Is ADS-B?
|
|
df = ((data[0] >> 3) & ADS_B_DF_MASK);
|
|
if ((df == 17) || (df == 18))
|
|
{
|
|
crcadsb crc;
|
|
//int icao = (data[1] << 16) | (data[2] << 8) | data[3]; // ICAO aircraft address
|
|
int parity = (data[11] << 16) | (data[12] << 8) | data[13]; // Parity / CRC
|
|
|
|
crc.calculate(data, ADS_B_ES_BYTES-3);
|
|
if (parity == crc.get())
|
|
{
|
|
// Got a valid frame
|
|
// Don't try to re-demodulate the same frame
|
|
m_skipCount = (ADS_B_ES_BITS+ADS_B_PREAMBLE_BITS)*ADS_B_CHIPS_PER_BIT*m_samplesPerChip;
|
|
// Pass to GUI
|
|
if (getMessageQueueToGUI())
|
|
{
|
|
ADSBDemodReport::MsgReportADSB *msg = ADSBDemodReport::MsgReportADSB::create(QByteArray((char*)data, sizeof(data)), preambleCorrelation);
|
|
getMessageQueueToGUI()->push(msg);
|
|
}
|
|
// Pass to worker
|
|
if (getMessageQueueToWorker())
|
|
{
|
|
ADSBDemodReport::MsgReportADSB *msg = ADSBDemodReport::MsgReportADSB::create(QByteArray((char*)data, sizeof(data)), preambleCorrelation);
|
|
getMessageQueueToWorker()->push(msg);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
if (m_skipCount > 0)
|
|
m_skipCount--;
|
|
if (m_sampleCount >= 2*m_totalSamples)
|
|
{
|
|
// Copy second half of buffer to first
|
|
memcpy(&m_sampleBuffer[0], &m_sampleBuffer[m_totalSamples], m_totalSamples*sizeof(Real));
|
|
m_sampleCount = m_totalSamples;
|
|
}
|
|
m_sampleIdx++;
|
|
|
|
}
|
|
|
|
void ADSBDemodSink::init(int samplesPerBit)
|
|
{
|
|
if (m_sampleBuffer)
|
|
delete m_sampleBuffer;
|
|
if (m_preamble)
|
|
delete m_preamble;
|
|
|
|
m_totalSamples = samplesPerBit*(ADS_B_PREAMBLE_BITS+ADS_B_ES_BITS);
|
|
m_samplesPerChip = samplesPerBit/ADS_B_CHIPS_PER_BIT;
|
|
|
|
m_sampleBuffer = new Real[2*m_totalSamples];
|
|
m_preamble = new Real[ADS_B_PREAMBLE_CHIPS*m_samplesPerChip];
|
|
// Possibly don't look for first chip
|
|
const int preambleChips[] = {1, -1, 1, -1, -1, -1, -1, 1, -1, 1, -1, -1, -1, -1, -1, -1};
|
|
for (int i = 0; i < ADS_B_PREAMBLE_CHIPS; i++)
|
|
{
|
|
for (int j = 0; j < m_samplesPerChip; j++)
|
|
{
|
|
m_preamble[i*m_samplesPerChip+j] = preambleChips[i];
|
|
}
|
|
}
|
|
}
|
|
|
|
void ADSBDemodSink::applyChannelSettings(int channelSampleRate, int channelFrequencyOffset, bool force)
|
|
{
|
|
qDebug() << "ADSBDemodSink::applyChannelSettings:"
|
|
<< " channelSampleRate: " << channelSampleRate
|
|
<< " channelFrequencyOffset: " << channelFrequencyOffset;
|
|
|
|
if ((channelFrequencyOffset != m_channelFrequencyOffset) ||
|
|
(channelSampleRate != m_channelSampleRate) || force)
|
|
{
|
|
m_nco.setFreq(-channelFrequencyOffset, channelSampleRate);
|
|
}
|
|
|
|
if ((channelSampleRate != m_channelSampleRate) || force)
|
|
{
|
|
m_interpolator.create(16, channelSampleRate, m_settings.m_rfBandwidth / 2.2);
|
|
m_interpolatorDistanceRemain = 0;
|
|
m_interpolatorDistance = (Real) channelSampleRate / (Real) (ADS_B_BITS_PER_SECOND * m_settings.m_samplesPerBit);
|
|
}
|
|
|
|
m_channelSampleRate = channelSampleRate;
|
|
m_channelFrequencyOffset = channelFrequencyOffset;
|
|
}
|
|
|
|
void ADSBDemodSink::applySettings(const ADSBDemodSettings& settings, bool force)
|
|
{
|
|
qDebug() << "ADSBDemodSink::applySettings:"
|
|
<< " m_inputFrequencyOffset: " << settings.m_inputFrequencyOffset
|
|
<< " m_rfBandwidth: " << settings.m_rfBandwidth
|
|
<< " m_correlationThreshold: " << settings.m_correlationThreshold
|
|
<< " m_samplesPerBit: " << settings.m_samplesPerBit
|
|
<< " force: " << force;
|
|
|
|
if ((settings.m_rfBandwidth != m_settings.m_rfBandwidth)
|
|
|| (settings.m_samplesPerBit != m_settings.m_samplesPerBit) || force)
|
|
{
|
|
m_interpolator.create(16, m_channelSampleRate, settings.m_rfBandwidth / 2.2);
|
|
m_interpolatorDistanceRemain = 0;
|
|
m_interpolatorDistance = (Real) m_channelSampleRate / (Real) (ADS_B_BITS_PER_SECOND * settings.m_samplesPerBit);
|
|
}
|
|
if ((settings.m_samplesPerBit != m_settings.m_samplesPerBit) || force)
|
|
{
|
|
init(settings.m_samplesPerBit);
|
|
}
|
|
|
|
m_settings = settings;
|
|
}
|