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Add FM filtering

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This commit is contained in:
Geoffrey Merck 2020-04-24 09:10:50 +02:00
parent 4f9d5a8c70
commit 5c2659deaa
4 changed files with 170 additions and 9 deletions
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14
FM.cpp
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@ -23,9 +23,9 @@
// 3 stage IIR Butterworth filter generated (if you change the order change the size of m_filterState). Also change the ordre in init call below
// 0.2db band pass ripple
// 300 - 2700Hz
q15_t FILTER_COEFFS[] = { 362, 724, 362,16384,-18947,10676, 14,//1st stage
16384, 0, -16384,16384,-25170, 9526, 14,//2nd stage
16384,-32768, 16384,16384,-32037,15730,14};//3rd stage
q15_t FILTER_COEFFS[] = {362,724,362,16384,-18947,10676,
16384,0,-16384,16384,-25170,9526,
16384,-32768,16384,16384,-32037,15730};
CFM::CFM() :
@ -44,14 +44,14 @@ m_kerchunkTimer(),
m_ackMinTimer(),
m_ackDelayTimer(),
m_hangTimer(),
m_filter()
m_filterStage1( 724, 1448, 724, 32768, -37895, 21352),
m_filterStage2(32768, 0,-32768, 32768, -50339, 19052),
m_filterStage3(32768, -65536, 32768, 32768, -64075, 31460)
{
arm_biquad_cascade_df1_init_q15(&m_filter, 3, FILTER_COEFFS, m_filterState, 0);
}
void CFM::samples(q15_t* samples, uint8_t length)
{
arm_biquad_casd_df1_inst_q15* filterPtr = &m_filter;
uint8_t i = 0;
for (; i < length; i++) {
q15_t currentSample = samples[i];//save to a local variable to avoid indirection on every access
@ -97,7 +97,7 @@ void CFM::samples(q15_t* samples, uint8_t length)
if (!m_callsign.isRunning() && !m_rfAck.isRunning())
currentSample += m_timeoutTone.getAudio();
arm_biquad_cascade_df1_fast_q15(filterPtr, samples +i, &currentSample, 1);
currentSample = q15_t(m_filterStage3.filter(m_filterStage2.filter(m_filterStage1.filter(currentSample))));
currentSample += m_ctcssTX.getAudio();