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MMDVM
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3rd order IIR

This commit is contained in:
Geoffrey Merck 2020-04-23 22:37:29 +02:00
parent ce0aebce48
commit 507a4bf64c
2 changed files with 9 additions and 6 deletions
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13
FM.cpp
View File

@ -20,9 +20,13 @@
#include "Globals.h" #include "Globals.h"
#include "FM.h" #include "FM.h"
// 2 stage IIR Butterworth filter generated using https://github.com/F4FXL/iir_fixed_point/blob/4f1e580a7dad9f8742d24a06edd14b62110ba6e4/gen_coeff.py // 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
q15_t FILTER_COEFFS[] = {1105, 2210, 1105, 16384,-19003,7512, 14,//1st stage // 0.2db band pass ripple
16384,-32768,16384,16384,-31020,14751,14};//2nd stage // 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
CFM::CFM() : CFM::CFM() :
m_callsign(), m_callsign(),
@ -42,7 +46,7 @@ m_ackDelayTimer(),
m_hangTimer(), m_hangTimer(),
m_filter() m_filter()
{ {
arm_biquad_cascade_df1_init_q15(&m_filter, 2, FILTER_COEFFS, m_filterState, 0); arm_biquad_cascade_df1_init_q15(&m_filter, 3, FILTER_COEFFS, m_filterState, 0);
} }
void CFM::samples(q15_t* samples, uint8_t length) void CFM::samples(q15_t* samples, uint8_t length)
@ -93,7 +97,6 @@ void CFM::samples(q15_t* samples, uint8_t length)
if (!m_callsign.isRunning() && !m_rfAck.isRunning()) if (!m_callsign.isRunning() && !m_rfAck.isRunning())
currentSample += m_timeoutTone.getAudio(); currentSample += m_timeoutTone.getAudio();
//currentSample = filter(currentSample);
arm_biquad_cascade_df1_fast_q15(filterPtr, samples +i, &currentSample, 1); arm_biquad_cascade_df1_fast_q15(filterPtr, samples +i, &currentSample, 1);
currentSample += m_ctcssTX.getAudio(); currentSample += m_ctcssTX.getAudio();

2
FM.h
View File

@ -71,7 +71,7 @@ private:
CFMTimer m_ackDelayTimer; CFMTimer m_ackDelayTimer;
CFMTimer m_hangTimer; CFMTimer m_hangTimer;
arm_biquad_casd_df1_inst_q15 m_filter; arm_biquad_casd_df1_inst_q15 m_filter;
q15_t m_filterState[8];//must be filterOrder * 4 long q15_t m_filterState[12];//must be filterOrder * 4 long
void stateMachine(bool validSignal, uint8_t length); void stateMachine(bool validSignal, uint8_t length);
void listeningState(bool validSignal); void listeningState(bool validSignal);