lorademod.cpp

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// Copyright (C) 2012 maintech GmbH, Otto-Hahn-Str. 15, 97204 Hoechberg, Germany //
// written by Christian Daniel                                                   //
// (c) 2015 John Greb
//                                                                               //
// 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 <QTime>
#include <QDebug>
#include <stdio.h>

#include "dsp/downchannelizer.h"
#include "dsp/threadedbasebandsamplesink.h"
#include "dsp/dspcommands.h"
#include "device/deviceapi.h"

#include "lorademod.h"
#include "lorabits.h"

MESSAGE_CLASS_DEFINITION(LoRaDemod::MsgConfigureLoRaDemod, Message)
MESSAGE_CLASS_DEFINITION(LoRaDemod::MsgConfigureChannelizer, Message)

const QString LoRaDemod::m_channelIdURI = "sdrangel.channel.lorademod";
const QString LoRaDemod::m_channelId = "LoRaDemod";

LoRaDemod::LoRaDemod(DeviceAPI* deviceAPI) :
        ChannelAPI(m_channelIdURI, ChannelAPI::StreamSingleSink),
        m_deviceAPI(deviceAPI),
        m_sampleSink(0),
        m_settingsMutex(QMutex::Recursive)
{
    setObjectName(m_channelId);

    m_Bandwidth = LoRaDemodSettings::bandwidths[0];
    m_sampleRate = 96000;
    m_frequency = 0;
    m_nco.setFreq(m_frequency, m_sampleRate);
    m_interpolator.create(16, m_sampleRate, m_Bandwidth/1.9);
    m_sampleDistanceRemain = (Real)m_sampleRate / m_Bandwidth;

    m_chirp = 0;
    m_angle = 0;
    m_bin = 0;
    m_result = 0;
    m_count = 0;
    m_header = 0;
    m_time = 0;
    m_tune = 0;

    loraFilter = new sfft(LORA_SFFT_LEN);
    negaFilter = new sfft(LORA_SFFT_LEN);

    mov = new float[4*LORA_SFFT_LEN];
    history = new short[1024];
    finetune = new short[16];

    m_channelizer = new DownChannelizer(this);
    m_threadedChannelizer = new ThreadedBasebandSampleSink(m_channelizer);
    m_deviceAPI->addChannelSink(m_threadedChannelizer);
    m_deviceAPI->addChannelSinkAPI(this);
}

LoRaDemod::~LoRaDemod()
{
    if (loraFilter)
        delete loraFilter;
    if (negaFilter)
        delete negaFilter;
    if (mov)
        delete [] mov;
    if (history)
        delete [] history;
    if (finetune)
        delete [] finetune;

    m_deviceAPI->removeChannelSinkAPI(this);
    m_deviceAPI->removeChannelSink(m_threadedChannelizer);
    delete m_threadedChannelizer;
    delete m_channelizer;
}

void LoRaDemod::dumpRaw()
{
    short bin, j, max;
    char text[256];

    max = m_time / 4 - 3;

    if (max > 140)
    {
        max = 140; // about 2 symbols to each char
    }

    for ( j=0; j < max; j++)
    {
        bin = (history[(j + 1)  * 4] + m_tune ) & (LORA_SFFT_LEN - 1);
        text[j] = toGray(bin >> 1);
    }

    prng6(text, max);
    // First block is always 8 symbols
    interleave6(text, 6);
    interleave6(&text[8], max);
    hamming6(text, 6);
    hamming6(&text[8], max);

    for ( j=0; j < max / 2; j++)
    {
        text[j] = (text[j * 2 + 1] << 4) | (0xf & text[j * 2 + 0]);

        if ((text[j] < 32 )||( text[j] > 126))
        {
            text[j] = 0x5f;
        }
    }

    text[3] = text[2];
    text[2] = text[1];
    text[1] = text[0];
    text[j] = 0;

    printf("%s\n", &text[1]);
}

short LoRaDemod::synch(short bin)
{
    short i, j;

    if (bin < 0)
    {
        if (m_time > 70)
        {
            dumpRaw();
        }

        m_time = 0;
        return -1;
    }

    history[m_time] = bin;

    if (m_time > 12)
    {
        if (bin == history[m_time - 6])
        {
            if (bin == history[m_time - 12])
            {
                m_tune = LORA_SFFT_LEN - bin;
                j = 0;

                for (i=0; i<12; i++)
                {
                    j += finetune[15 & (m_time - i)];
                }

                if (j < 0)
                {
                    m_tune += 1;
                }

                m_tune &= (LORA_SFFT_LEN - 1);
                m_time = 0;
                return -1;
            }
        }
    }

    m_time++;
    m_time &= 1023;

    if (m_time & 3)
    {
        return -1;
    }

    return (bin + m_tune) & (LORA_SFFT_LEN - 1);
}

int LoRaDemod::detect(Complex c, Complex a)
{
    int p, q;
    short i, result, negresult, movpoint;
    float peak, negpeak, tfloat;
    float mag[LORA_SFFT_LEN];
    float rev[LORA_SFFT_LEN];

    loraFilter->run(c * a);
    negaFilter->run(c * conj(a));

    // process spectrum twice in FFTLEN
    if (++m_count & ((1 << DATA_BITS) - 1))
    {
        return m_result;
    }

    movpoint = 3 & (m_count >> DATA_BITS);

    loraFilter->fetch(mag);
    negaFilter->fetch(rev);
    peak = negpeak = 0.0f;
    result = negresult = 0;

    for (i = 0; i < LORA_SFFT_LEN; i++)
    {
        if (rev[i] > negpeak)
        {
            negpeak = rev[i];
            negresult = i;
        }

        tfloat = mov[i] + mov[LORA_SFFT_LEN + i] +mov[2 * LORA_SFFT_LEN + i]
                + mov[3 * LORA_SFFT_LEN + i] + mag[i];

        if (tfloat > peak)
        {
            peak = tfloat;
            result = i;
        }

        mov[movpoint * LORA_SFFT_LEN + i] = mag[i];
    }

    p = (result - 1 + LORA_SFFT_LEN) & (LORA_SFFT_LEN -1);
    q = (result + 1) & (LORA_SFFT_LEN -1);
    finetune[15 & m_time] = (mag[p] > mag[q]) ? -1 : 1;

    if (peak < negpeak * LORA_SQUELCH)
    {
        result = -1;
    }

    result = synch(result);

    if (result >= 0)
    {
        m_result = result;
    }

    return m_result;
}

void LoRaDemod::feed(const SampleVector::const_iterator& begin, const SampleVector::const_iterator& end, bool pO)
{
    (void) pO;
    int newangle;
    Complex ci;

    m_sampleBuffer.clear();

    m_settingsMutex.lock();

    for(SampleVector::const_iterator it = begin; it < end; ++it)
    {
        Complex c(it->real() / SDR_RX_SCALEF, it->imag() / SDR_RX_SCALEF);
        c *= m_nco.nextIQ();

        if(m_interpolator.decimate(&m_sampleDistanceRemain, c, &ci))
        {
            m_chirp = (m_chirp + 1) & (SPREADFACTOR - 1);
                        m_angle = (m_angle + m_chirp) & (SPREADFACTOR - 1);
            Complex cangle(cos(M_PI*2*m_angle/SPREADFACTOR),-sin(M_PI*2*m_angle/SPREADFACTOR));
            newangle = detect(ci, cangle);

            m_bin = (m_bin + newangle) & (LORA_SFFT_LEN - 1);
            Complex nangle(cos(M_PI*2*m_bin/LORA_SFFT_LEN),sin(M_PI*2*m_bin/LORA_SFFT_LEN));
            m_sampleBuffer.push_back(Sample(nangle.real() * 100, nangle.imag() * 100));
            m_sampleDistanceRemain += (Real)m_sampleRate / m_Bandwidth;
        }
    }

    if(m_sampleSink != 0)
    {
        m_sampleSink->feed(m_sampleBuffer.begin(), m_sampleBuffer.end(), false);
    }

    m_settingsMutex.unlock();
}

void LoRaDemod::start()
{
}

void LoRaDemod::stop()
{
}

bool LoRaDemod::handleMessage(const Message& cmd)
{
    qDebug() << "LoRaDemod::handleMessage";

    if (DownChannelizer::MsgChannelizerNotification::match(cmd))
    {
        DownChannelizer::MsgChannelizerNotification& notif = (DownChannelizer::MsgChannelizerNotification&) cmd;

        m_settingsMutex.lock();

        m_sampleRate = notif.getSampleRate();
        m_nco.setFreq(-notif.getFrequencyOffset(), m_sampleRate);
        m_interpolator.create(16, m_sampleRate, m_Bandwidth/1.9);
        m_sampleDistanceRemain = m_sampleRate / m_Bandwidth;

        m_settingsMutex.unlock();

        qDebug() << "LoRaDemod::handleMessage: MsgChannelizerNotification: m_sampleRate: " << m_sampleRate
                << " frequencyOffset: " << notif.getFrequencyOffset();

        return true;
    }
    else if (MsgConfigureChannelizer::match(cmd))
    {
        MsgConfigureChannelizer& cfg = (MsgConfigureChannelizer&) cmd;

        m_channelizer->configure(m_channelizer->getInputMessageQueue(),
            cfg.getSampleRate(),
            cfg.getCenterFrequency());

        qDebug() << "LoRaDemod::handleMessage: MsgConfigureChannelizer: sampleRate: " << cfg.getSampleRate()
                << " centerFrequency: " << cfg.getCenterFrequency();

        return true;
    }
    else if (MsgConfigureLoRaDemod::match(cmd))
    {
        MsgConfigureLoRaDemod& cfg = (MsgConfigureLoRaDemod&) cmd;

        m_settingsMutex.lock();

        LoRaDemodSettings settings = cfg.getSettings();

        m_Bandwidth = LoRaDemodSettings::bandwidths[settings.m_bandwidthIndex];
        m_interpolator.create(16, m_sampleRate, m_Bandwidth/1.9);

        m_settingsMutex.unlock();

        m_settings = settings;
        qDebug() << "LoRaDemod::handleMessage: MsgConfigureLoRaDemod: m_Bandwidth: " << m_Bandwidth;

        return true;
    }
    else if (DSPSignalNotification::match(cmd))
    {
        return true;
    }
    else
    {
        if(m_sampleSink != 0)
        {
             return m_sampleSink->handleMessage(cmd);
        }
        else
        {
            return false;
        }
    }
}

QByteArray LoRaDemod::serialize() const
{
    return m_settings.serialize();
}

bool LoRaDemod::deserialize(const QByteArray& data)
{
    if (m_settings.deserialize(data))
    {
        MsgConfigureLoRaDemod *msg = MsgConfigureLoRaDemod::create(m_settings, true);
        m_inputMessageQueue.push(msg);
        return true;
    }
    else
    {
        m_settings.resetToDefaults();
        MsgConfigureLoRaDemod *msg = MsgConfigureLoRaDemod::create(m_settings, true);
        m_inputMessageQueue.push(msg);
        return false;
    }
}