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Make whole FM chain RX level independant

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This commit is contained in:
Geoffrey Merck 2020-05-08 09:01:00 +02:00
parent eb9c0dfd93
commit 77e0deee76
4 changed files with 14 additions and 26 deletions
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23
FMCTCSSRX.cpp
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@ -86,15 +86,12 @@ m_threshold(0),
m_count(0U),
m_q0(0),
m_q1(0),
m_result(CTS_NONE),
m_rxLevelInverse(1)
m_result(CTS_NONE)
{
}
uint8_t CFMCTCSSRX::setParams(uint8_t frequency, uint8_t threshold, uint8_t level)
uint8_t CFMCTCSSRX::setParams(uint8_t frequency, uint8_t threshold)
{
m_rxLevelInverse = q15Division(65535, q15_t(level * 128));
m_coeffDivTwo = 0;
for (uint8_t i = 0U; i < CTCSS_TABLE_DATA_LEN; i++) {
@ -114,7 +111,8 @@ uint8_t CFMCTCSSRX::setParams(uint8_t frequency, uint8_t threshold, uint8_t leve
uint8_t CFMCTCSSRX::process(q15_t sample)
{
q31_t sample31 = q31_t(sample) * m_rxLevelInverse;
//get more dynamic into the decoder by multiplying the sample by 1.5
q31_t sample31 = q31_t(sample) + (q31_t(sample) >> 1);
m_result &= ~CTS_READY;
@ -174,16 +172,3 @@ void CFMCTCSSRX::reset()
m_result = CTS_NONE;
m_count = 0U;
}
//Taken from https://en.wikipedia.org/wiki/Q_(number_format)#Division
q15_t CFMCTCSSRX::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;
}