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Improving DC filter for D-Star

This commit is contained in:
Andy CA6JAU 2017-04-10 00:30:45 -03:00
parent 4f516a827f
commit 5d1a54eee5
2 changed files with 12 additions and 10 deletions
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18
DStarRX.cpp
View File

@ -35,9 +35,9 @@ const unsigned int SYNC_POS = 21U * DSTAR_DATA_LENGTH_BITS;
const unsigned int SYNC_SCAN_START = SYNC_POS - 3U; const unsigned int SYNC_SCAN_START = SYNC_POS - 3U;
const unsigned int SYNC_SCAN_END = SYNC_POS + 3U; const unsigned int SYNC_SCAN_END = SYNC_POS + 3U;
// Generated using [b, a] = butter(1, 0.002) in MATLAB // Generated using [b, a] = butter(1, 0.001) in MATLAB
static q15_t DC_FILTER[] = {103, 0, 103, 0, 32563, 0}; // {b0, 0, b1, b2, -a1, -a2} static q31_t DC_FILTER[] = {3367972, 0, 3367972, 0, 2140747704, 0}; // {b0, 0, b1, b2, -a1, -a2}
const uint16_t DC_FILTER_STAGES = 1U; // One Biquad stage const uint32_t DC_FILTER_STAGES = 1U; // One Biquad stage
// D-Star bit order version of 0x55 0x55 0x6E 0x0A // D-Star bit order version of 0x55 0x55 0x6E 0x0A
const uint32_t FRAME_SYNC_DATA = 0x00557650U; const uint32_t FRAME_SYNC_DATA = 0x00557650U;
@ -266,7 +266,7 @@ m_rssiCount(0U),
m_dcFilter(), m_dcFilter(),
m_dcState() m_dcState()
{ {
::memset(m_dcState, 0x00U, 4U * sizeof(q15_t)); ::memset(m_dcState, 0x00U, 4U * sizeof(q31_t));
m_dcFilter.numStages = DC_FILTER_STAGES; m_dcFilter.numStages = DC_FILTER_STAGES;
m_dcFilter.pState = m_dcState; m_dcFilter.pState = m_dcState;
@ -289,12 +289,14 @@ void CDStarRX::reset()
void CDStarRX::samples(const q15_t* samples, const uint16_t* rssi, uint8_t length) void CDStarRX::samples(const q15_t* samples, const uint16_t* rssi, uint8_t length)
{ {
q31_t dc_level = 0; q31_t dc_level = 0;
q15_t dcVals[20]; q31_t dcVals[20];
q31_t intSamp[20];
::arm_biquad_cascade_df1_q15(&m_dcFilter, (q15_t*)samples, dcVals, length); ::arm_q15_to_q31((q15_t*)samples, intSamp, length);
::arm_biquad_cascade_df1_q31(&m_dcFilter, intSamp, dcVals, length);
for (uint8_t i = 0U; i < length; i++) for (uint8_t i = 0U; i < length; i++)
dc_level += q31_t(dcVals[i]); dc_level += dcVals[i];
dc_level /= length; dc_level /= length;
@ -302,7 +304,7 @@ void CDStarRX::samples(const q15_t* samples, const uint16_t* rssi, uint8_t lengt
m_rssiAccum += rssi[i]; m_rssiAccum += rssi[i];
m_rssiCount++; m_rssiCount++;
bool bit = samples[i] < q15_t(dc_level); bool bit = samples[i] < (q15_t) (dc_level >> 16);
if (bit != m_prev) { if (bit != m_prev) {
if (m_pll < (PLLMAX / 2U)) if (m_pll < (PLLMAX / 2U))

4
DStarRX.h
View File

@ -53,8 +53,8 @@ private:
uint8_t m_fecOutput[42U]; uint8_t m_fecOutput[42U];
uint32_t m_rssiAccum; uint32_t m_rssiAccum;
uint16_t m_rssiCount; uint16_t m_rssiCount;
arm_biquad_casd_df1_inst_q15 m_dcFilter; arm_biquad_casd_df1_inst_q31 m_dcFilter;
q15_t m_dcState[4]; q31_t m_dcState[4];
void processNone(bool bit); void processNone(bool bit);
void processHeader(bool bit); void processHeader(bool bit);