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BFM demod: RDS demod completed

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This commit is contained in:
Edouard Griffiths 2015-12-10 13:39:15 +01:00
parent 0705461d8a
commit 3cdab34fb7
3 changed files with 103 additions and 0 deletions
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2
plugins/channel/bfm/CMakeLists.txt
View File

@ -4,12 +4,14 @@ set(bfm_SOURCES
bfmdemod.cpp
bfmdemodgui.cpp
bfmplugin.cpp
rdsdemod.cpp
)
set(bfm_HEADERS
bfmdemod.h
bfmdemodgui.h
bfmplugin.h
rdsdemod.h
)
set(bfm_FORMS

85
plugins/channel/bfm/rdsdemod.cpp
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@ -16,6 +16,9 @@
///////////////////////////////////////////////////////////////////////////////////
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include "rdsdemod.h"
RDSDemod::RDSDemod()
@ -25,6 +28,15 @@ RDSDemod::RDSDemod()
m_rdsClockPhase = 0.0;
m_rdsClockOffset = 0.0;
m_rdsClockLO = 0.0;
m_rdsClockLO_1 = 0.0;
m_numSamples = 0;
m_acc = 0.0;
m_acc_1 = 0.0;
m_counter = 0;
m_readingFrame = 0;
m_totErrors[0] = 0;
m_totErrors[1] = 0;
m_dbit = 0;
}
RDSDemod::~RDSDemod()
@ -38,6 +50,34 @@ void RDSDemod::process(Real rdsSample, Real pilotSample)
// 1187.5 Hz clock
m_rdsClockPhase = (pilotSample / 48.0) + m_rdsClockOffset;
m_rdsClockLO = (fmod(m_rdsClockPhase, 2 * M_PI) < M_PI ? 1 : -1);
// Clock phase recovery
if (sign(m_rdsBB_1) != sign(m_rdsBB))
{
Real d_cphi = fmod(m_rdsClockPhase, M_PI);
if (d_cphi >= M_PI_2)
{
d_cphi -= M_PI;
}
m_rdsClockOffset -= 0.005 * d_cphi;
}
// Decimate band-limited signal
if (m_numSamples % 8 == 0)
{
/* biphase symbol integrate & dump */
m_acc += m_rdsBB * m_rdsClockLO;
if (sign(m_rdsClockLO) != sign(m_rdsClockLO_1))
{
biphase(m_acc);
m_acc = 0;
}
m_rdsClockLO_1 = m_rdsClockLO;
}
}
Real RDSDemod::filter_lp_2400_iq(Real input, int iqIndex)
@ -55,3 +95,48 @@ Real RDSDemod::filter_lp_2400_iq(Real input, int iqIndex)
return m_yv[iqIndex][2];
}
int RDSDemod::sign(Real a)
{
return (a >= 0 ? 1 : 0);
}
void RDSDemod::biphase(Real acc)
{
static int reading_frame = 0;
if (sign(acc) != sign(m_acc_1)) // two successive of different sign: error detected
{
m_totErrors[m_counter % 2]++;
}
if (m_counter % 2 == reading_frame) // two successive of the same sing: OK
{
print_delta(sign(acc + m_acc_1));
}
if (m_counter == 0)
{
if (m_totErrors[1 - reading_frame] < m_totErrors[reading_frame])
{
reading_frame = 1 - reading_frame;
}
m_totErrors[0] = 0;
m_totErrors[1] = 0;
}
m_acc_1 = acc; // memorize (z^-1)
m_counter = (m_counter + 1) % 800;
}
void RDSDemod::print_delta(char b)
{
output_bit(b ^ m_dbit);
m_dbit = b;
}
void RDSDemod::output_bit(char b)
{
printf("%d", b);
}

16
plugins/channel/bfm/rdsdemod.h
View File

@ -19,6 +19,8 @@
#ifndef PLUGINS_CHANNEL_BFM_RDSDEMOD_H_
#define PLUGINS_CHANNEL_BFM_RDSDEMOD_H_
#include "dsp/dsptypes.h"
class RDSDemod
{
public:
@ -26,7 +28,13 @@ public:
~RDSDemod();
void process(Real rdsSample, Real pilotSample);
protected:
Real filter_lp_2400_iq(Real in, int iqIndex);
int sign(Real a);
void biphase(Real acc);
void print_delta(char b);
void output_bit(char b);
private:
Real m_xv[2][2+1];
@ -36,6 +44,14 @@ private:
Real m_rdsClockPhase;
Real m_rdsClockOffset;
Real m_rdsClockLO;
Real m_rdsClockLO_1;
int m_numSamples;
Real m_acc;
Real m_acc_1;
int m_counter;
int m_readingFrame;
int m_totErrors[2];
int m_dbit;
};
#endif /* PLUGINS_CHANNEL_BFM_RDSDEMOD_H_ */