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Add 9600 FSK modem with scrambler and raised-cosine pulse-shaping. Add baseband BPF for AFSK.

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This commit is contained in:
Jon Beniston
2020-09-23 13:42:29 +01:00
committed by f4exb
parent 5211f4a25b
commit 9187cda3c2
27 changed files with 1529 additions and 219 deletions
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plugins/channeltx/modpacket/packetmodsource.cpp
+113 -25
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@@ -25,11 +25,12 @@
PacketModSource::PacketModSource() :
m_channelSampleRate(48000),
m_spectrumRate(0),
m_preemphasisFilter(48000, FMPREEMPHASIS_TAU_US),
m_channelFrequencyOffset(0),
m_magsq(0.0),
m_audioPhase(0.0f),
m_fmPhase(0.0f),
m_fmPhase(0.0),
m_levelCalcCount(0),
m_peakLevel(0.0f),
m_levelSum(0.0f),
@@ -37,9 +38,13 @@ PacketModSource::PacketModSource() :
m_byteIdx(0),
m_bitIdx(0),
m_last5Bits(0),
m_state(idle)
m_state(idle),
m_scrambler(0x10800, 0x0)
{
m_lowpass.create(301, m_channelSampleRate, 22000.0 / 2.0);
qDebug() << "PacketModSource::PacketModSource creating BPF : " << m_channelSampleRate;
m_bandpass.create(301, m_channelSampleRate, 800.0, 2600.0);
m_pulseShape.create(0.5, 6, m_channelSampleRate/9600);
applySettings(m_settings, true);
applyChannelSettings(m_channelSampleRate, m_channelFrequencyOffset, true);
}
@@ -111,9 +116,6 @@ void PacketModSource::sampleToSpectrum(Real sample)
void PacketModSource::modulateSample()
{
Real audioMod;
Real theta;
Real f_delta;
Real linearGain;
Real linearRampGain;
Real emphasis;
@@ -133,14 +135,19 @@ void PacketModSource::modulateSample()
}
else
{
// Bell 202 AFSK
if (m_sampleIdx == 0)
{
if (bitsValid())
{
// NRZI encoding - encode 0 as change of freq, 1 no change
if (getBit() == 0)
m_f = m_f == m_settings.m_markFrequency ? m_settings.m_spaceFrequency : m_settings.m_markFrequency;
m_nrziBit = m_nrziBit == 1 ? 0 : 1;
// Scramble to ensure lots of transitions
if (m_settings.m_scramble)
m_scrambledBit = m_scrambler.scramble(m_nrziBit);
else
m_scrambledBit = m_nrziBit;
}
// Should we start ramping down power?
if ((m_bitCount < m_settings.m_rampDownBits) || ((m_bitCount == 0) && !m_settings.m_rampDownBits))
@@ -151,17 +158,40 @@ void PacketModSource::modulateSample()
}
}
m_sampleIdx++;
if (m_sampleIdx > m_samplesPerSymbol)
if (m_sampleIdx >= m_samplesPerSymbol)
m_sampleIdx = 0;
if (!m_settings.m_bbNoise)
audioMod = sin(m_audioPhase);
{
if (m_settings.m_modulation == PacketModSettings::AFSK)
{
// Bell 202 AFSK
audioMod = sin(m_audioPhase);
if ((m_state == tx) || m_settings.m_modulateWhileRamping)
m_audioPhase += (M_PI * 2.0f * (m_scrambledBit ? m_settings.m_markFrequency : m_settings.m_spaceFrequency)) / (m_channelSampleRate);
if (m_audioPhase > M_PI)
m_audioPhase -= (2.0f * M_PI);
}
else
{
// FSK
if (m_settings.m_pulseShaping)
{
if ((m_sampleIdx == 1) && (m_state != ramp_down))
audioMod = m_pulseShape.filter(m_scrambledBit ? 1.0f : -1.0f);
else
audioMod = m_pulseShape.filter(0.0f);
}
else
audioMod = m_scrambledBit ? 1.0f : -1.0f;
}
}
else
audioMod = (Real)rand()/((Real)RAND_MAX)-0.5; // Noise to test filter frequency response
if ((m_state == tx) || m_settings.m_modulateWhileRamping)
m_audioPhase += (M_PI * 2.0f * m_f) / (m_channelSampleRate);
if (m_audioPhase > M_PI)
m_audioPhase -= (2.0f * M_PI);
// Baseband bandpass filter
if (m_settings.m_bpf)
audioMod = m_bandpass.filter(audioMod);
// Preemphasis filter
if (m_settings.m_preEmphasis)
@@ -174,25 +204,25 @@ void PacketModSource::modulateSample()
sampleToSpectrum(audioMod);
// FM
m_fmPhase += audioMod;
m_fmPhase += m_phaseSensitivity * audioMod;
// Keep phase in range -pi,pi
if (m_fmPhase > M_PI)
m_fmPhase -= (2.0f * M_PI);
f_delta = m_settings.m_fmDeviation / m_channelSampleRate;
theta = 2.0f * M_PI * f_delta * m_fmPhase;
m_fmPhase -= 2.0f * M_PI;
else if (m_fmPhase < -M_PI)
m_fmPhase += 2.0f * M_PI;
linearRampGain = powf(10.0f, m_pow/20.0f);
linearGain = powf(10.0f, m_settings.m_gain/20.0f);
if (!m_settings.m_rfNoise)
{
m_modSample.real(linearGain * linearRampGain * cos(theta));
m_modSample.imag(linearGain * linearRampGain * sin(theta));
m_modSample.real(m_linearGain * linearRampGain * cos(m_fmPhase));
m_modSample.imag(m_linearGain * linearRampGain * sin(m_fmPhase));
}
else
{
// Noise to test filter frequency response
m_modSample.real(linearGain * ((Real)rand()/((Real)RAND_MAX)-0.5f));
m_modSample.imag(linearGain * ((Real)rand()/((Real)RAND_MAX)-0.5f));
m_modSample.real(m_linearGain * ((Real)rand()/((Real)RAND_MAX)-0.5f));
m_modSample.imag(m_linearGain * ((Real)rand()/((Real)RAND_MAX)-0.5f));
}
// Apply low pass filter to limit RF BW
@@ -262,6 +292,7 @@ void PacketModSource::calculateLevel(Real& sample)
void PacketModSource::applySettings(const PacketModSettings& settings, bool force)
{
// Only recreate filters if settings have changed
if ((settings.m_lpfTaps != m_settings.m_lpfTaps) || (settings.m_rfBandwidth != m_settings.m_rfBandwidth) || force)
{
qDebug() << "PacketModSource::applySettings: Creating new lpf with taps " << settings.m_lpfTaps << " rfBW " << settings.m_rfBandwidth;
@@ -272,8 +303,40 @@ void PacketModSource::applySettings(const PacketModSettings& settings, bool forc
qDebug() << "PacketModSource::applySettings: Creating new preemphasis filter with tau " << settings.m_preEmphasisTau << " highFreq " << settings.m_preEmphasisHighFreq << " sampleRate " << m_channelSampleRate;
m_preemphasisFilter.configure(m_channelSampleRate, settings.m_preEmphasisTau, settings.m_preEmphasisHighFreq);
}
if ((settings.m_bpfLowCutoff != m_settings.m_bpfLowCutoff) || (settings.m_bpfHighCutoff != m_settings.m_bpfHighCutoff)
|| (settings.m_bpfTaps != m_settings.m_bpfTaps)|| force)
{
qDebug() << "PacketModSource::applySettings: Recreating bandpass filter: "
<< " m_bpfTaps: " << settings.m_bpfTaps
<< " m_channelSampleRate:" << m_channelSampleRate
<< " m_bpfLowCutoff: " << settings.m_bpfLowCutoff
<< " m_bpfHighCutoff: " << settings.m_bpfHighCutoff;
m_bandpass.create(settings.m_bpfTaps, m_channelSampleRate, settings.m_bpfLowCutoff, settings.m_bpfHighCutoff);
}
if ((settings.m_beta != m_settings.m_beta) || (settings.m_symbolSpan != m_settings.m_symbolSpan) || (settings.m_baud != m_settings.m_baud) || force)
{
qDebug() << "PacketModSource::applySettings: Recreating pulse shaping filter: "
<< " beta: " << settings.m_beta
<< " symbolSpan: " << settings.m_symbolSpan
<< " channelSampleRate:" << m_channelSampleRate
<< " baud:" << settings.m_baud;
m_pulseShape.create(settings.m_beta, m_settings.m_symbolSpan, m_channelSampleRate/settings.m_baud);
}
if ((settings.m_polynomial != m_settings.m_polynomial) || force)
m_scrambler.setPolynomial(settings.m_polynomial);
if ((settings.m_spectrumRate != m_settings.m_spectrumRate) || force)
{
m_interpolatorDistanceRemain = 0;
m_interpolatorConsumed = false;
m_interpolatorDistance = (Real) m_channelSampleRate / (Real) settings.m_spectrumRate;
m_interpolator.create(48, settings.m_spectrumRate, settings.m_spectrumRate / 2.2, 3.0);
}
m_settings = settings;
// Precalculate FM sensensity and linear gain to save doing it in the loop
m_phaseSensitivity = 2.0f * M_PI * m_settings.m_fmDeviation / (double)m_channelSampleRate;
m_linearGain = powf(10.0f, m_settings.m_gain/20.0f);
}
void PacketModSource::applyChannelSettings(int channelSampleRate, int channelFrequencyOffset, bool force)
@@ -292,8 +355,25 @@ void PacketModSource::applyChannelSettings(int channelSampleRate, int channelFre
if ((m_channelSampleRate != channelSampleRate) || force)
{
m_preemphasisFilter.configure(channelSampleRate, m_settings.m_preEmphasisTau);
qDebug() << "PacketModSource::applyChannelSettings: Recreating filters";
m_lowpass.create(m_settings.m_lpfTaps, channelSampleRate, m_settings.m_rfBandwidth / 2.0);
qDebug() << "PacketModSource::applyChannelSettings: Recreating bandpass filter: "
<< " bpfTaps: " << m_settings.m_bpfTaps
<< " channelSampleRate:" << channelSampleRate
<< " bpfLowCutoff: " << m_settings.m_bpfLowCutoff
<< " bpfHighCutoff: " << m_settings.m_bpfHighCutoff;
m_bandpass.create(m_settings.m_bpfTaps, channelSampleRate, m_settings.m_bpfLowCutoff, m_settings.m_bpfHighCutoff);
m_preemphasisFilter.configure(channelSampleRate, m_settings.m_preEmphasisTau);
qDebug() << "PacketModSource::applyChannelSettings: Recreating pulse shaping filter: "
<< " beta: " << m_settings.m_beta
<< " symbolSpan: " << m_settings.m_symbolSpan
<< " channelSampleRate:" << m_channelSampleRate
<< " baud:" << m_settings.m_baud;
m_pulseShape.create(m_settings.m_beta, m_settings.m_symbolSpan, channelSampleRate/m_settings.m_baud);
}
if ((m_channelSampleRate != channelSampleRate) || (m_spectrumRate != m_settings.m_spectrumRate) || force)
{
m_interpolatorDistanceRemain = 0;
m_interpolatorConsumed = false;
m_interpolatorDistance = (Real) channelSampleRate / (Real) m_settings.m_spectrumRate;
@@ -302,6 +382,11 @@ void PacketModSource::applyChannelSettings(int channelSampleRate, int channelFre
m_channelSampleRate = channelSampleRate;
m_channelFrequencyOffset = channelFrequencyOffset;
m_spectrumRate = m_settings.m_spectrumRate;
m_samplesPerSymbol = m_channelSampleRate / m_settings.m_baud;
qDebug() << "m_samplesPerSymbol: " << m_samplesPerSymbol << " (" << m_channelSampleRate << "/" << m_settings.m_baud << ")";
// Precalculate FM sensensity to save doing it in the loop
m_phaseSensitivity = 2.0f * M_PI * m_settings.m_fmDeviation / (double)m_channelSampleRate;
}
static uint8_t *ax25_address(uint8_t *p, QString address, uint8_t crrl)
@@ -395,7 +480,7 @@ void PacketModSource::initTX()
m_byteIdx = 0;
m_bitIdx = 0;
m_bitCount = m_bitCountTotal; // Reset to allow retransmission
m_f = m_settings.m_spaceFrequency;
m_nrziBit = 0;
if (m_settings.m_rampUpBits == 0)
{
m_state = tx;
@@ -407,6 +492,7 @@ void PacketModSource::initTX()
m_pow = -(Real)m_settings.m_rampRange;
m_powRamp = m_settings.m_rampRange/(m_settings.m_rampUpBits * (Real)m_samplesPerSymbol);
}
m_scrambler.init();
}
void PacketModSource::addTXPacket(QString callsign, QString to, QString via, QString data)
@@ -475,8 +561,10 @@ void PacketModSource::addTXPacket(QString callsign, QString to, QString via, QSt
// single tone
m_sampleIdx = 0;
m_audioPhase = 0.0f;
m_fmPhase = 0.0f;
m_fmPhase = 0.0;
if (m_settings.m_writeToFile)
m_audioFile.open("packetmod.csv", std::ofstream::out);
else if (m_audioFile.is_open())
m_audioFile.close();
}