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Optimise the DC offset code.

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This commit is contained in:
Jonathan Naylor 2017-08-18 10:27:23 +01:00
parent 04ca97e5f8
commit 74682e7ac0
8 changed files with 44 additions and 90 deletions
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29
YSFRX.cpp
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@ -38,10 +38,6 @@ const uint16_t NOENDPTR = 9999U;
const unsigned int MAX_SYNC_FRAMES = 4U + 1U;
// Generated using [b, a] = butter(1, 0.001) in MATLAB
static q31_t DC_FILTER[] = {3367972, 0, 3367972, 0, 2140747704, 0}; // {b0, 0, b1, b2, -a1, -a2}
const uint32_t DC_FILTER_STAGES = 1U; // One Biquad stage
CYSFRX::CYSFRX() :
m_state(YSFRXS_NONE),
m_bitBuffer(),
@ -62,16 +58,8 @@ m_threshold(),
m_thresholdVal(0),
m_averagePtr(NOAVEPTR),
m_rssiAccum(0U),
m_rssiCount(0U),
m_dcFilter(),
m_dcState()
m_rssiCount(0U)
{
::memset(m_dcState, 0x00U, 4U * sizeof(q31_t));
m_dcFilter.numStages = DC_FILTER_STAGES;
m_dcFilter.pState = m_dcState;
m_dcFilter.pCoeffs = DC_FILTER;
m_dcFilter.postShift = 0;
}
void CYSFRX::reset()
@ -96,21 +84,8 @@ void CYSFRX::reset()
void CYSFRX::samples(q15_t* samples, uint16_t* rssi, uint8_t length)
{
q31_t dcLevel = 0;
q31_t dcVals[20U];
q31_t q31Samples[20U];
::arm_q15_to_q31(samples, q31Samples, length);
::arm_biquad_cascade_df1_q31(&m_dcFilter, q31Samples, dcVals, length);
for (uint8_t i = 0U; i < length; i++)
dcLevel += dcVals[i];
dcLevel /= length;
q15_t offset = q15_t(__SSAT((dcLevel >> 16), 16));;
for (uint8_t i = 0U; i < length; i++) {
q15_t sample = samples[i] - offset;
q15_t sample = samples[i];
m_rssiAccum += rssi[i];
m_rssiCount++;