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// fskmod.cpp: implementation of the CFskMod class.
//
// This class creates a DSC FSK signal
//
// History:
// 2012-10-23 Initial creation MSW
// 2012-10-23
//////////////////////////////////////////////////////////////////////
#include "fskmod.h"
#include "gui/testbench.h"
#include "dsp/datatypes.h"
#define SHIFT_FREQ 170.0
#define SYMB_FREQ 100.0
#define MSG_SPACING 5.333 //seconds between msgs
const quint16 SYMBTBL[129] = {
0x0380, 0x0181, 0x0182, 0x0283, 0x0184, 0x0285, 0x0286, 0x0087, 0x0188, 0x0289, // 0 to 9
0x028A, 0x008B, 0x028C, 0x008D, 0x008E, 0x030F, 0x0190, 0x0291, 0x0292, 0x0093, // 10 to 19
0x0294, 0x0095, 0x0096, 0x0317, 0x0298, 0x0099, 0x009A, 0x031B, 0x009C, 0x031D, // 20 to 29
0x031E, 0x011F, 0x01A0, 0x02A1, 0x02A2, 0x00A3, 0x02A4, 0x00A5, 0x00A6, 0x0327, // 30 to 39
0x02A8, 0x00A9, 0x00AA, 0x032B, 0x00AC, 0x032D, 0x032E, 0x012F, 0x02B0, 0x00B1, // 40 to 49
0x00B2, 0x0333, 0x00B4, 0x0335, 0x0336, 0x0137, 0x00B8, 0x0339, 0x033A, 0x013B, // 50 to 59
0x033C, 0x013D, 0x013E, 0x023F, 0x01C0, 0x02C1, 0x02C2, 0x00C3, 0x02C4, 0x00C5, // 60 to 69
0x00C6, 0x0347, 0x02C8, 0x00C9, 0x00CA, 0x034B, 0x00CC, 0x034D, 0x034E, 0x014F, // 70 to 79
0x02D0, 0x00D1, 0x00D2, 0x0353, 0x00D4, 0x0355, 0x0356, 0x0157, 0x00D8, 0x0359, // 80 to 89
0x035A, 0x015B, 0x035C, 0x015D, 0x015E, 0x025F, 0x02E0, 0x00E1, 0x00E2, 0x0363, // 90 to 99
0x00E4, 0x0365, 0x0366, 0x0167, 0x00E8, 0x0369, 0x036A, 0x016B, 0x036C, 0x016D, //100 to 109
0x016E, 0x026F, 0x00F0, 0x0371, 0x0372, 0x0173, 0x0374, 0x0175, 0x0176, 0x0277, //110 to 119
0x0378, 0x0179, 0x017A, 0x027B, 0x017C, 0x027D, 0x027E, 0x007F, 0x0155
};
const quint8 DSC_MSG[] =
{
128,128, //sync dots
125,111,125,110,125,109,125,108,125,107,125,106,
120,105,120,104,
0,120,36,120,60,0,0,36,30,60,108,0,30,30,96,108,
82,30,0,96,0,82,118,0,126,0,126,118,
126,126,126,126,126,126,126,126,126,126,
117,126,67,126,117,117,117,67,
255
};
/////////////////////////////////////////////////////////////////////////////////
// Construct FSK mod object
/////////////////////////////////////////////////////////////////////////////////
CFskMod::CFskMod()
{
SetSampleRate(12500.0, 0.0);
}
/////////////////////////////////////////////////////////////////////////////////
// Initialize variables with given SampleRate
/////////////////////////////////////////////////////////////////////////////////
void CFskMod::SetSampleRate(TYPEREAL SampleRate, TYPEREAL FreqOffset)
{
m_SampleRate = SampleRate;
m_FskAcc = 0.0;
m_SymbTime = 0.0;
m_SymbPeriod = 1.0/SYMB_FREQ;
m_SymbInc = 1.0/SampleRate;
m_MarkInc = -K_2PI*(SHIFT_FREQ/2.0 - FreqOffset)/SampleRate;
m_SpaceInc = K_2PI*(SHIFT_FREQ/2.0 + FreqOffset)/SampleRate;
m_FskState = false;
m_MsgDelay = (int)(SYMB_FREQ*MSG_SPACING);
m_MsgTimer = m_MsgDelay;
m_BitPos = 0;
m_TxShiftReg = 0;
m_MsgPos = 0;
}
/////////////////////////////////////////////////////////////////////////////////
// Create FSK Modulation Signal
/////////////////////////////////////////////////////////////////////////////////
void CFskMod::GenerateData(int Length, TYPEREAL SigAmplitude, TYPECPX* pOutData)
{
int i;
double rad;
double r;
double u1;
double u2;
for( i=0; i<Length; i++)
{
if(m_FskState != 0)
{
pOutData[i].re = SigAmplitude*cos(m_FskAcc);
pOutData[i].im = SigAmplitude*sin(m_FskAcc);
if(1 == m_FskState)
m_FskAcc += m_MarkInc;
else
m_FskAcc += m_SpaceInc;
}
else
{
pOutData[i].re = 0.0;
pOutData[i].im = 0.0;
}
m_SymbTime += m_SymbInc;
if( m_SymbTime >= m_SymbPeriod)
{
m_SymbTime -= m_SymbPeriod;
m_FskState = CreateDSCData();
}
}
m_FskAcc = (double)fmod((double)m_FskAcc, K_2PI); //keep radian counter bounded
}
/////////////////////////////////////////////////////////////////////////////////
// Create DSC Data Signal
// returns -1 for space, +1 for Mark, and 0 for no signal
/////////////////////////////////////////////////////////////////////////////////
int CFskMod::CreateDSCData()
{
if(m_MsgTimer)
{ //here if during intermsg time
m_MsgTimer--;
m_BitPos = 0;
m_MsgPos = 0;
return 0;
}
//here to generate DSC bit stream
if(0==m_BitPos)
{
quint8 ch = DSC_MSG[m_MsgPos++];
if(255 == ch )
m_MsgTimer = m_MsgDelay;
else
m_TxShiftReg = SYMBTBL[ch];
}
else
m_TxShiftReg >>= 1;
//inc current Bit position modulo 10
if( ++m_BitPos >= 10)
m_BitPos = 0;
if(m_TxShiftReg&1)
return 1;
else
return -1;
}
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