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MMDVM
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Move division to CTCSSRX, change sample unscaling to 1/rxLevel

This commit is contained in:
Geoffrey Merck 2020-04-27 11:16:06 +02:00
parent f9530ee82a
commit 4ffaa62855
4 changed files with 31 additions and 27 deletions
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17
FM.cpp
View File

@ -55,7 +55,7 @@ void CFM::samples(bool cos, q15_t* samples, uint8_t length)
for (; i < length; i++) {
q15_t currentSample = samples[i];//save to a local variable to avoid indirection on every access
CTCSSState ctcssState = m_ctcssRX.process(getUnscaledSample(currentSample));
CTCSSState ctcssState = m_ctcssRX.process(currentSample);
if (CTCSS_NOT_READY(ctcssState) && m_modemState != STATE_FM) {
//Not enough samples to determine if you have CTCSS, just carry on
@ -158,7 +158,7 @@ uint8_t CFM::setMisc(uint16_t timeout, uint8_t timeoutLevel, uint8_t ctcssFreque
m_timeoutTone.setParams(timeoutLevel);
m_blanking.setParams(maxDev, timeoutLevel);
uint8_t ret = m_ctcssRX.setParams(ctcssFrequency, ctcssThreshold);
uint8_t ret = m_ctcssRX.setParams(ctcssFrequency, ctcssThreshold, m_rxLevel);
if (ret != 0U)
return ret;
@ -400,17 +400,4 @@ void CFM::beginRelaying()
m_ackMinTimer.start();
}
q15_t CFM::getUnscaledSample(q15_t sample)
{
// sample / rxLevel
q31_t sample31 = q31_t(sample) << 16;
if (((sample31 >> 31) & 1) == ((m_rxLevel >> 15) & 1))
sample31 += m_rxLevel >> 1;
else
sample31 -= m_rxLevel >> 1;
sample31 /= m_rxLevel;
return q15_t(sample31);
}

2
FM.h
View File

@ -91,8 +91,6 @@ private:
void sendCallsign();
void beginRelaying();
q15_t getUnscaledSample(q15_t sample);
};
#endif

12
FMCTCSSRX.cpp
View File

@ -86,12 +86,16 @@ m_threshold(0),
m_count(0U),
m_q0(0),
m_q1(0),
m_result(CTS_NONE)
m_result(CTS_NONE),
m_rxLevelInverse(1)
{
}
uint8_t CFMCTCSSRX::setParams(uint8_t frequency, uint8_t threshold)
uint8_t CFMCTCSSRX::setParams(uint8_t frequency, uint8_t threshold, q15_t rxLevel)
{
// Calculate 1/rxLevel
m_rxLevelInverse = q31_t(q15Division(65535 /* This value should be 32767 (q15 1). But this does not work.*/, rxLevel));
m_coeffDivTwo = 0;
for (uint8_t i = 0U; i < CTCSS_TABLE_DATA_LEN; i++) {
@ -111,6 +115,8 @@ uint8_t CFMCTCSSRX::setParams(uint8_t frequency, uint8_t threshold)
CTCSSState CFMCTCSSRX::process(q15_t sample)
{
q63_t sample31 = q31_t(sample) * m_rxLevelInverse;
m_result = m_result & (~CTS_READY);
q31_t q2 = m_q1;
@ -122,7 +128,7 @@ CTCSSState CFMCTCSSRX::process(q15_t sample)
q31_t t3 = t2 * 2;
// m_q0 = m_coeffDivTwo * m_q1 * 2 - q2 + sample
m_q0 = t3 - q2 + q31_t(sample);
m_q0 = t3 - q2 + sample31;
m_count++;
if (m_count == N) {

27
FMCTCSSRX.h
View File

@ -53,7 +53,7 @@ class CFMCTCSSRX {
public:
CFMCTCSSRX();
uint8_t setParams(uint8_t frequency, uint8_t threshold);
uint8_t setParams(uint8_t frequency, uint8_t threshold, q15_t rxLevel);
CTCSSState process(q15_t sample);
@ -62,12 +62,25 @@ public:
void reset();
private:
q63_t m_coeffDivTwo;
q31_t m_threshold;
uint16_t m_count;
q31_t m_q0;
q31_t m_q1;
CTCSSState m_result;
static inline q15_t q15Division(q15_t a, q15_t divisor)
{
q31_t a31 = q31_t(a) << 16;
if (((a >> 31) & 1) == ((divisor >> 15) & 1))
a31 += divisor >> 1;
else
a31 -= divisor >> 1;
return a31 / divisor;
}
q63_t m_coeffDivTwo;
q31_t m_threshold;
uint16_t m_count;
q31_t m_q0;
q31_t m_q1;
CTCSSState m_result;
q31_t m_rxLevelInverse;
};
#endif