193 lines
6.3 KiB
C++
193 lines
6.3 KiB
C++
/*
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* Copyright (C) 2020,2021 by Jonathan Naylor G4KLX
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include "FMControl.h"
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#include <string>
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#if defined(DUMP_RF_AUDIO)
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#include <cstdio>
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#endif
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#define SWAP_BYTES_16(a) (((a >> 8) & 0x00FFU) | ((a << 8) & 0xFF00U))
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const float DEEMPHASIS_GAIN_DB = 8.0F; // Audio gain adjustment
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const float PREEMPHASIS_GAIN_DB = 0.0F; // Audio gain adjustment
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const float FILTER_GAIN_DB = 2.0F; // Audio gain adjustment
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const unsigned int FM_MASK = 0x00000FFFU;
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CFMControl::CFMControl(CFMNetwork* network, float txAudioGain, float rxAudioGain, bool preEmphasisOn, bool deEmphasisOn) :
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m_network(network),
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m_txAudioGain(txAudioGain),
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m_rxAudioGain(rxAudioGain),
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m_preEmphasisOn(preEmphasisOn),
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m_deEmphasisOn(deEmphasisOn),
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m_enabled(false),
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m_incomingRFAudio(1600U, "Incoming RF FM Audio"),
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m_preEmphasis(NULL),
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m_deEmphasis(NULL),
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m_filterStage1(NULL),
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m_filterStage2(NULL),
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m_filterStage3(NULL)
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{
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assert(txAudioGain > 0.0F);
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assert(rxAudioGain > 0.0F);
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m_preEmphasis = new CIIRDirectForm1Filter(8.315375384336983F, -7.03334621603483F,0.0F,1.0F, 0.282029168302153F,0.0F, PREEMPHASIS_GAIN_DB);
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m_deEmphasis = new CIIRDirectForm1Filter(0.07708787090460224F, 0.07708787090460224F,0.0F, 1.0F, -0.8458242581907955F,0.0F, DEEMPHASIS_GAIN_DB);
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// Chebyshev type 1 0.2dB cheby type 1 3rd order 300-2700Hz fs=8000
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m_filterStage1 = new CIIRDirectForm1Filter(0.29495028f, 0.0f, -0.29495028f, 1.0f, -0.61384624f, -0.057158668f, FILTER_GAIN_DB);
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m_filterStage2 = new CIIRDirectForm1Filter(1.0f, 2.0f, 1.0f, 1.0f, 0.9946123f, 0.6050482f, FILTER_GAIN_DB);
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m_filterStage3 = new CIIRDirectForm1Filter(1.0f, -2.0f, 1.0f, 1.0f, -1.8414584f, 0.8804949f, FILTER_GAIN_DB);
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}
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CFMControl::~CFMControl()
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{
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delete m_preEmphasis;
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delete m_deEmphasis;
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delete m_filterStage1;
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delete m_filterStage2;
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delete m_filterStage3;
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}
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bool CFMControl::writeModem(const unsigned char* data, unsigned int length)
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{
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assert(data != NULL);
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assert(length > 0U);
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if (m_network == NULL)
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return true;
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if (data[0U] == TAG_HEADER)
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return true;
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if (data[0U] == TAG_EOT)
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return m_network->writeEnd();
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if (data[0U] != TAG_DATA)
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return false;
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m_incomingRFAudio.addData(data + 1U, length - 1U);
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unsigned int bufferLength = m_incomingRFAudio.dataSize();
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if (bufferLength > 240U) // 160 samples 12-bit
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bufferLength = 240U; // 160 samples 12-bit
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if (bufferLength >= 3U) {
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bufferLength = bufferLength - bufferLength % 3U; // Round down to nearest multiple of 3
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unsigned char bufferData[240U]; // 160 samples 12-bit
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m_incomingRFAudio.getData(bufferData, bufferLength);
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unsigned int pack = 0U;
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unsigned char* packPointer = (unsigned char*)&pack;
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float out[160U]; // 160 samples 12-bit
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unsigned int nOut = 0U;
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short unpackedSamples[2U];
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for (unsigned int i = 0U; i < bufferLength; i += 3U) {
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// Extract unsigned 12 bit unsigned sample pairs packed into 3 bytes to 16 bit signed
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packPointer[0U] = bufferData[i + 0U];
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packPointer[1U] = bufferData[i + 1U];
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packPointer[2U] = bufferData[i + 2U];
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unpackedSamples[1U] = short(int(pack & FM_MASK) - 2048);
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unpackedSamples[0U] = short(int(pack >> 12 & FM_MASK) - 2048); //
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// Process unpacked sample pair
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for (unsigned char j = 0U; j < 2U; j++) {
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// Convert to float (-1.0 to +1.0)
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float sampleFloat = (float(unpackedSamples[j]) * m_rxAudioGain) / 2048.0F;
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// De-emphasise and remove CTCSS
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if (m_deEmphasisOn)
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sampleFloat = m_deEmphasis->filter(sampleFloat);
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out[nOut++] = m_filterStage3->filter(m_filterStage2->filter(m_filterStage1->filter(sampleFloat)));
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}
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}
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#if defined(DUMP_RF_AUDIO)
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FILE * audiofile = fopen("./audiodump.bin", "ab");
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if (audiofile != NULL) {
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fwrite(out, sizeof(float), nOut, audiofile);
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fclose(audiofile);
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}
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#endif
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return m_network->writeData(out, nOut);
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}
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return true;
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}
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unsigned int CFMControl::readModem(unsigned char* data, unsigned int space)
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{
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assert(data != NULL);
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assert(space > 0U);
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if (m_network == NULL)
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return 0U;
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if (space > 240U) // 160 samples 12-bit
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space = 240U; // 160 samples 12-bit
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float netData[160U]; // Modem can handle up to 160 samples at a time
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unsigned int length = m_network->read(netData, 160U); // 160 samples 12-bit
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if (length == 0U)
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return 0U;
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unsigned int pack = 0U;
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unsigned char* packPointer = (unsigned char*)&pack;
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unsigned int nData = 0U;
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for (unsigned int i = 0; i < length; i++) {
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float sampleFloat = netData[i] * m_txAudioGain;
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// Pre-emphasis
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if (m_preEmphasisOn)
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sampleFloat = m_preEmphasis->filter(sampleFloat);
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// Convert float to 12-bit samples (0 to 4095)
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unsigned int sample12bit = (unsigned int)((sampleFloat + 1.0F) * 2048.0F + 0.5F);
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// Pack 2 samples into 3 bytes
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if ((i & 1U) == 0) {
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pack = 0U;
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pack = sample12bit << 12;
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} else {
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pack |= sample12bit;
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data[nData++] = packPointer[0U];
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data[nData++] = packPointer[1U];
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data[nData++] = packPointer[2U];
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}
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}
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return nData;
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}
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void CFMControl::clock(unsigned int ms)
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{
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// May not be needed
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}
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void CFMControl::enable(bool enabled)
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{
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// May not be needed
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}
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