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Use fixed point for the Goertzel algorithm.

This commit is contained in:
Jonathan Naylor 2020-04-22 17:40:01 +01:00
parent 57730d7f81
commit 526a53cd8c
2 changed files with 96 additions and 71 deletions
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157
FMCTCSSRX.cpp
View File

@ -21,59 +21,59 @@
#include "FMCTCSSRX.h"
const struct CTCSS_TABLE {
uint8_t frequency;
float32_t coeff;
uint8_t frequency;
q31_t coeffDivTwo;
} CTCSS_TABLE_DATA[] = {
{ 67U, 1.999692F},
{ 69U, 1.999671F},
{ 71U, 1.999646F},
{ 74U, 1.999621F},
{ 77U, 1.999594F},
{ 79U, 1.999565F},
{ 82U, 1.999534F},
{ 85U, 1.999500F},
{ 88U, 1.999463F},
{ 91U, 1.999426F},
{ 94U, 1.999384F},
{ 97U, 1.999350F},
{100U, 1.999315F},
{103U, 1.999266F},
{107U, 1.999212F},
{110U, 1.999157F},
{114U, 1.999097F},
{118U, 1.999033F},
{123U, 1.998963F},
{127U, 1.998889F},
{131U, 1.998810F},
{136U, 1.998723F},
{141U, 1.998632F},
{146U, 1.998535F},
{151U, 1.998429F},
{156U, 1.998317F},
{159U, 1.998250F},
{162U, 1.998197F},
{165U, 1.998123F},
{167U, 1.998068F},
{171U, 1.997989F},
{173U, 1.997930F},
{177U, 1.997846F},
{179U, 1.997782F},
{183U, 1.997693F},
{186U, 1.997624F},
{189U, 1.997529F},
{192U, 1.997453F},
{196U, 1.997351F},
{199U, 1.997273F},
{203U, 1.997162F},
{206U, 1.997078F},
{210U, 1.996958F},
{218U, 1.996741F},
{225U, 1.996510F},
{229U, 1.996404F},
{233U, 1.996261F},
{241U, 1.995994F},
{250U, 1.995708F},
{254U, 1.995576F}};
{ 67U, 2147153298},
{ 69U, 2147130228},
{ 71U, 2147103212},
{ 74U, 2147076297},
{ 77U, 2147047330},
{ 79U, 2147016195},
{ 82U, 2146982775},
{ 85U, 2146946945},
{ 88U, 2146907275},
{ 91U, 2146867538},
{ 94U, 2146822298},
{ 97U, 2146785526},
{100U, 2146747759},
{103U, 2146695349},
{107U, 2146637984},
{110U, 2146578604},
{114U, 2146513835},
{118U, 2146445080},
{123U, 2146370355},
{127U, 2146291161},
{131U, 2146205372},
{136U, 2146112589},
{141U, 2146014479},
{146U, 2145910829},
{151U, 2145796971},
{156U, 2145676831},
{159U, 2145604646},
{162U, 2145547790},
{165U, 2145468230},
{167U, 2145409363},
{171U, 2145324517},
{173U, 2145261046},
{177U, 2145170643},
{179U, 2145102321},
{183U, 2145006080},
{186U, 2144932648},
{189U, 2144830280},
{192U, 2144748638},
{196U, 2144639788},
{199U, 2144555290},
{203U, 2144436713},
{206U, 2144346237},
{210U, 2144217348},
{218U, 2143983951},
{225U, 2143735870},
{229U, 2143622139},
{233U, 2143469001},
{241U, 2143182299},
{250U, 2142874683},
{254U, 2142733729}};
const uint8_t CTCSS_TABLE_DATA_LEN = 50U;
@ -81,11 +81,11 @@ const uint8_t CTCSS_TABLE_DATA_LEN = 50U;
const uint16_t N = 24000U / 4U;
CFMCTCSSRX::CFMCTCSSRX() :
m_coeff(0.0F),
m_threshold(0.0F),
m_coeffDivTwo(0),
m_threshold(0),
m_count(0U),
m_q0(0.0F),
m_q1(0.0F),
m_q0(0),
m_q1(0),
m_result(CTS_NONE)
{
}
@ -94,15 +94,15 @@ uint8_t CFMCTCSSRX::setParams(uint8_t frequency, uint8_t threshold)
{
for (uint8_t i = 0U; i < CTCSS_TABLE_DATA_LEN; i++) {
if (CTCSS_TABLE_DATA[i].frequency == frequency) {
m_coeff = CTCSS_TABLE_DATA[i].coeff;
m_coeffDivTwo = CTCSS_TABLE_DATA[i].coeffDivTwo;
break;
}
}
if (m_coeff == 0.0F)
if (m_coeffDivTwo == 0)
return 4U;
m_threshold = float32_t(threshold);
m_threshold = q31_t(threshold);
return 0U;
}
@ -110,13 +110,38 @@ uint8_t CFMCTCSSRX::setParams(uint8_t frequency, uint8_t threshold)
CTCSSState CFMCTCSSRX::process(q15_t sample)
{
m_result = m_result & (~CTS_READY);
float32_t q2 = m_q1;
q31_t q2 = m_q1;
m_q1 = m_q0;
m_q0 = m_coeff * m_q1 - q2 + float32_t(sample) / 32768.0F;
// Q31 multiplication, t3 = m_coeffDivTwo * 2 * m_q1
q63_t t1 = m_coeffDivTwo * m_q1;
q31_t t2 = __SSAT((t1 >> 32), 31);
q31_t t3 = t2 * 2;
// m_q0 = m_coeffDivTwo * m_q1 * 2 - q2 + sample
m_q0 = t3 - q2 + q31_t(sample);
m_count++;
if (m_count == N) {
float32_t value = m_q0 * m_q0 + m_q1 * m_q1 - m_q0 * m_q1 * m_coeff;
// Q31 multiplication, t2 = m_q0 * m_q0
q63_t t1 = m_q0 * m_q0;
q31_t t2 = __SSAT((t1 >> 32), 31);
// Q31 multiplication, t4 = m_q0 * m_q0
q63_t t3 = m_q1 * m_q1;
q31_t t4 = __SSAT((t3 >> 32), 31);
// Q31 multiplication, t9 = m_q0 * m_q1 * m_coeffDivTwo * 2
q63_t t5 = m_q0 * m_q1;
q31_t t6 = __SSAT((t5 >> 32), 31);
q63_t t7 = t6 * m_coeffDivTwo;
q31_t t8 = __SSAT((t7 >> 32), 31);
q31_t t9 = t8 * 2;
// value = m_q0 * m_q0 + m_q1 * m_q1 - m_q0 * m_q1 * m_coeffDivTwo * 2
q31_t value = t2 + t4 - t9;
m_result = m_result | CTS_READY;
if (value >= m_threshold)
m_result = m_result | CTS_VALID;
@ -124,8 +149,8 @@ CTCSSState CFMCTCSSRX::process(q15_t sample)
m_result = m_result & ~CTS_VALID;
m_count = 0U;
m_q0 = 0.0F;
m_q1 = 0.0F;
m_q0 = 0;
m_q1 = 0;
}
return m_result;
@ -138,8 +163,8 @@ CTCSSState CFMCTCSSRX::getState()
void CFMCTCSSRX::reset()
{
m_q0 = 0.0F;
m_q1 = 0.0F;
m_q0 = 0;
m_q1 = 0;
m_result = CTS_NONE;
m_count = 0U;
}

10
FMCTCSSRX.h
View File

@ -62,11 +62,11 @@ public:
void reset();
private:
float32_t m_coeff;
float32_t m_threshold;
uint16_t m_count;
float32_t m_q0;
float32_t m_q1;
q31_t m_coeffDivTwo;
q31_t m_threshold;
uint16_t m_count;
q31_t m_q0;
q31_t m_q1;
CTCSSState m_result;
};