MMDVMHost-Private/FMControl.cpp

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/*
* Copyright (C) 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 "FMControl.h"
#include <string>
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const float EMPHASIS_GAIN_DB = 0.0F; //Gain needs to be the same for pre an deeemphasis
const unsigned int FM_MASK = 0x00000FFFU;
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CFMControl::CFMControl(CFMNetwork* network) :
m_network(network),
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m_enabled(false),
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m_incomingRFAudio(1600U, "Incoming RF FM Audio"),
m_preemphasis(0.3889703155F, -0.32900055326F, 0.0F, 1.0F, 0.2820291817F, 0.0F, EMPHASIS_GAIN_DB),
m_deemphasis(1.0F, 0.2820291817F, 0.0F, 0.3889703155F, -0.32900055326F, 0.0F, EMPHASIS_GAIN_DB)
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{
}
CFMControl::~CFMControl()
{
}
bool CFMControl::writeModem(const unsigned char* data, unsigned int length)
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{
assert(data != NULL);
assert(length > 0U);
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if (data[0U] == TAG_HEADER)
return true;
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if (data[0U] == TAG_EOT)
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return m_network->writeEOT();
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if (data[0U] != TAG_DATA)
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return false;
if (m_network == NULL)
return true;
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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 > 255U)
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bufferLength = 255U;
if (bufferLength >= 3U) {
bufferLength = bufferLength - bufferLength % 3U; //round down to nearest multiple of 3
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unsigned char bufferData[255U];
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m_incomingRFAudio.getData(bufferData, bufferLength);
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unsigned int nSamples = 0;
float samples[85U]; // 255 / 3;
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// Unpack the serial data into float values.
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for (unsigned int i = 0U; i < bufferLength; i += 3U) {
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unsigned short sample1 = 0U;
unsigned short sample2 = 0U;
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unsigned int pack = 0U;
unsigned char* packPointer = (unsigned char*)&pack;
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packPointer[1U] = bufferData[i];
packPointer[2U] = bufferData[i + 1U];
packPointer[3U] = bufferData[i + 2U];
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sample2 = short(pack & FM_MASK);
sample1 = short(pack >> 12);
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// Convert from unsigned short (0 - +4095) to float (-1.0 - +1.0)
samples[nSamples++] = (float(sample1) - 2048.0F) / 2048.0F;
samples[nSamples++] = (float(sample2) - 2048.0F) / 2048.0F;
}
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//De-emphasise the data and any other processing needed (maybe a low-pass filter to remove the CTCSS)
for (unsigned int i = 0U; i < nSamples; i++)
samples[i] = m_deemphasis.filter(samples[i]);
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unsigned short out[170U]; // 85 * 2
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unsigned int nOut = 0U;
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// Repack the data (8-bit unsigned values containing unsigned 16-bit data)
for (unsigned int i = 0U; i < nSamples; i++) {
unsigned short sample = (unsigned short)((samples[i] + 1.0F) * 32767.0F + 0.5F);
out[nOut++] = (sample >> 8) & 0xFFU;
out[nOut++] = (sample >> 0) & 0xFFU;
}
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return m_network->writeData((unsigned char*)out, nOut);
}
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return true;
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}
unsigned int CFMControl::readModem(unsigned char* data, unsigned int space)
{
assert(data != NULL);
assert(space > 0U);
if (m_network == NULL)
return 0U;
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if(space > 252U)
space = 252U;
unsigned char netData[168U];//84 * 2 modem can handle up to 84 samples (252 bytes) at a time
unsigned int length = m_network->read(netData, 168U);
if (length == 0U)
return 0U;
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float samples[84U];
unsigned int nSamples = 0U;
// Convert the unsigned 16-bit data (+65535 - 0) to float (+1.0 - -1.0)
for (unsigned int i = 0U; i < length; i += 2U) {
unsigned short sample = (netData[i + 0U] << 8) | netData[i + 1U];
samples[nSamples++] = (float(sample) / 32767.0F) - 1.0F;
}
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//Pre-emphasise the data and other stuff.
for (unsigned int i = 0U; i < nSamples; i++)
samples[i] = m_preemphasis.filter(samples[i]);
// Pack the floating point data (+1.0 to -1.0) to packed 12-bit samples (+2047 - -2048)
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unsigned int pack = 0U;
unsigned char* packPointer = (unsigned char*)&pack;
unsigned int j = 0U;
unsigned int i = 0U;
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for (; i < nSamples && j < space; i += 2U, j += 3U) {
unsigned short sample1 = (unsigned short)((samples[i] + 1.0F) * 2048.0F + 0.5F);
unsigned short sample2 = (unsigned short)((samples[i + 1] + 1.0F) * 2048.0F + 0.5F);
pack = 0;
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pack = ((unsigned int)sample1) << 12;
pack |= sample2;
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data[j] = packPointer[1U];
data[j + 1U] = packPointer[2U];
data[j + 2U] = packPointer[3U];
}
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return j;//return the number of bytes written
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}
void CFMControl::clock(unsigned int ms)
{
// May not be needed
}
void CFMControl::enable(bool enabled)
{
// May not be needed
}