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@ -33,7 +33,7 @@ |
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* frequency of the input sine wave frequency, i.e., an it is an FM detector. |
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* The input needs to be band limited below the lower frequency side of the |
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* input, typically 10 kHz. This is not part of this block. |
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*
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* |
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* NOTE: Due to the sample frequencies we are working with, like 44.1 kHz, this |
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* detector cannot handle full FM broadcast bandwidths. It is suitable for |
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* NBFM as used in communications, marine radio, ham radio, etc. |
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@ -51,17 +51,17 @@ |
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* be removed before the atan2. A pair of FIR filters, using FIR_IQ_Coeffs |
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* are used. These are again programmable and default to a 29-tap LPF with |
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* a 5 kHz cutoff. |
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*
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* |
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* Status: Tested static, tested with FM modulated Fluke 6061B. |
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* An input of about 60 microvolts to the SGTL5000 gave 12 dB SINAD. |
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* The output sounded good. Tested T3.6 and T4.0. No known bugs |
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*
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* |
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* Output: Float, sensitivity is 2*pi*(f - fCenter)*sample_rate_Hz |
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* For 44117Hz samplerate, this is 0.000142421 per Hz |
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*
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* |
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* Accuracy: The function used is precise. However, the approximations, such |
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* fastAtan2, slightly limit the accuracy. A 200 point sample of a |
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* 14 kHz input had an average error of 0.03 Hz
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* 14 kHz input had an average error of 0.03 Hz |
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* and a standard deviation of 0.81 Hz. |
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* The largest errors in this sample were about +/- 1.7 Hz. This is |
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* with the default filters. |
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@ -80,24 +80,24 @@ |
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* filterIQ(float *fir_IQ_Coeffs, uint nFIR_IQ) sets output filtering where: |
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* float32_t* fir_IQ_Coeffs is an array of coefficients |
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* uint nFIR_IQ is the number of coefficients, max 60 |
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*
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* |
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* setSampleRate_Hz(float32_t _sampleRate_Hz) allows dynamic changing of |
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* the sample rate (experimental as of May 2020). |
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*
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* |
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* returnInitializeFMError() Returns the initialization errors. |
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* B0001 (value 1) is an error in the IQ FIR Coefficients or quantity. |
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* B0010 (value 2) is an error in the Output FIR Coefficients or quantity. |
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* B0100 (value 4) is an error in the de-emphasis constant |
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* B1000 (value 8) is center frequency above half-sample frequency. |
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* All for debug. |
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*
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* |
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* showError(uint16_t e) Turns error printing in the update function on (e=1) |
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* or off (e=0). For debug only. |
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* |
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* Time: For T3.6, an update of a 128 sample block, 370 microseconds, or |
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* 2.9 microseconds per data point. |
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* For T4.0, 87 microseconds, or 0.68 microseconds per data point. |
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*
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* |
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* Error checking: See functions setSampleRate_Hz() and returnInitializeFMError() |
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* above. |
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*/ |
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@ -115,7 +115,7 @@ |
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#define TEST_TIME_FM 0 |
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class RadioFMDetector_F32 : public AudioStream_F32 { |
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//GUI: inputs:1, outputs:1 //this line used for automatic generation of GUI node
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//GUI: inputs:1, outputs:2 //this line used for automatic generation of GUI node
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//GUI: shortName: FMDetector
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public: |
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// Default block size and sample rate:
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@ -163,26 +163,53 @@ public: |
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initializeFM(); |
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} |
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void setSampleRate_Hz(float32_t _sampleRate_Hz) { |
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if (fCenter > _sampleRate_Hz/2.0f) { // Check freq range
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// Provide for changing to user supplied BiQuad for Squelch input.
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void setSquelchFilter(float* _sqCoeffs) { |
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if( _sqCoeffs==NULL) |
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pCfSq = coeffSqIn; // Default filter
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else |
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pCfSq = _sqCoeffs; |
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initializeFM(); |
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} |
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// The squelch level reads nominally 0.0 to 1.0 where
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float getSquelchLevel (void) { |
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return squelchLevel; |
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} |
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// The squelch threshold is nominally 0.7 where
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// 0.0 always lets audio through.
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void setSquelchThreshold (float _sqTh) { |
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squelchThreshold = _sqTh; |
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} |
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void setSquelchDecay (float _sqDcy) { |
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gamma = _sqDcy; |
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alpha = 0.5f*(1.0f - gamma); |
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} |
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/* void setSampleRate_Hz(float32_t _sampleRate_Hz) {
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if (fCenter > _sampleRate_Hz/2.0f) { // Check freq range
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initializeFMErrors |= 8; |
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return; |
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} |
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} |
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sampleRate_Hz = _sampleRate_Hz; |
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// update phase increment for new frequency
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phaseIncrement = 512.0f * fCenter / sampleRate_Hz; |
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} |
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} // NOT SUPPORTED - No Dynamic changes
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*/ |
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void showError(uint16_t e) { |
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errorPrintFM = e; |
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} |
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} |
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uint16_t returnInitializeFMError(void) { |
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return initializeFMErrors; |
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} |
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return initializeFMErrors; |
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} |
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void update(void); |
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private: |
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// One input data pointer
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audio_block_f32_t *inputQueueArray_f32[1]; |
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@ -207,6 +234,25 @@ private: |
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float32_t* fir_IQ_Coeffs = fir_IQ29; |
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uint16_t nFIR_Out = 39; |
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float32_t* fir_Out_Coeffs = fir_Out39; |
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/* Info - The structure from arm_biquad_casd_df1_inst_f32 consists of
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* uint32_t numStages; |
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* const float32_t *pCoeffs; //Points to the array of coefficients, length 5*numStages.
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* float32_t *pState; //Points to the array of state variables, length 4*numStages. */
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arm_biquad_casd_df1_inst_f32 iirSqIn_inst; |
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// Default 2 stage Squelch input BiQuad filter, 3000 Hz, 4000 Hz both Q=5
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// The -6 dB points are 2680 and 4420 Hz
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// The -20 dB points are 2300 and 5300 Hz
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float coeffSqIn[10] = { |
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0.0398031529f, 0.0f, -0.0398031529f, 1.74762569f, -0.92039369f, |
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0.0511929547f, 0.0f, -0.0511929547f, 1.59770204f, -0.89761409f}; |
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float* pCfSq = coeffSqIn; |
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float stateSqIn[8]; |
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float squelchThreshold = 0.7f; |
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float squelchLevel = 1.0f; |
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float gamma = 0.99; |
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float alpha = 0.5f*(1.0f - gamma); |
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#if TEST_TIME_FM |
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elapsedMicros tElapse; |
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int32_t iitt = 999000; // count up to a million during startup
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@ -220,29 +266,33 @@ int32_t iitt = 999000; // count up to a million during startup |
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arm_fir_instance_f32 FMDet_Out_inst; |
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float32_t State_Out_F32[AUDIO_BLOCK_SAMPLES + MAX_FIR_OUT_COEFFS]; |
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// Initialize the FM Detector, part of setting up and changing parameters
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void initializeFM(void) { |
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if (fir_IQ_Coeffs && nFIR_IQ <= MAX_FIR_IQ_COEFFS) { |
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if (fir_IQ_Coeffs && nFIR_IQ <= MAX_FIR_IQ_COEFFS) { |
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/* the instance setup call
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* void arm_fir_init_f32(
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* void arm_fir_init_f32( |
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* arm_fir_instance_f32* S, points to instance of floating-point FIR filter structure. |
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* uint16_t numTaps, Number of filter coefficients in the filter. |
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* float32_t* pCoeffs, points to the filter coefficients buffer. |
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* float32_t* pState, points to the state buffer. |
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* uint32_t blockSize) Number of samples that are processed per call. |
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*/ |
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arm_fir_init_f32(&FMDet_I_inst, nFIR_IQ, (float32_t*)fir_IQ_Coeffs, &State_I_F32[0], (uint32_t)block_size);
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arm_fir_init_f32(&FMDet_Q_inst, nFIR_IQ, (float32_t*)fir_IQ_Coeffs, &State_Q_F32[0], (uint32_t)block_size);
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} |
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else initializeFMErrors |= B0001;
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arm_fir_init_f32(&FMDet_I_inst, nFIR_IQ, (float32_t*)fir_IQ_Coeffs, &State_I_F32[0], (uint32_t)block_size); |
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arm_fir_init_f32(&FMDet_Q_inst, nFIR_IQ, (float32_t*)fir_IQ_Coeffs, &State_Q_F32[0], (uint32_t)block_size); |
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} |
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else initializeFMErrors |= B0001; |
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if (fir_Out_Coeffs && nFIR_Out <= MAX_FIR_OUT_COEFFS) { |
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arm_fir_init_f32(&FMDet_Out_inst, nFIR_Out, (float32_t*)fir_Out_Coeffs, &State_Out_F32[0], (uint32_t)block_size); |
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} |
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} |
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else initializeFMErrors |= B0010; |
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dLast = 0.0; |
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} |
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// Initialize squelch Input BPF BiQuad instance (ARM DSP Math Library)
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// https://www.keil.com/pack/doc/CMSIS/DSP/html/group__BiquadCascadeDF1.html
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arm_biquad_cascade_df1_init_f32(&iirSqIn_inst, 2, pCfSq, &stateSqIn[0]); |
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} |
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/* FIR filter designed with http://t-filter.appspot.com
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* fs = 44100 Hz, < 5kHz ripple 0.29 dB, >9 kHz, -62 dB, 29 taps |
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@ -259,19 +309,19 @@ int32_t iitt = 999000; // count up to a million during startup |
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/* FIR filter designed with http://t-filter.appspot.com
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* fs = 44100 Hz, < 3kHz ripple 0.36 dB, >6 kHz, -60 dB, 39 taps |
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* Corrected to give DC gain = 1.00
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* Corrected to give DC gain = 1.00 |
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*/ |
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float32_t fir_Out39[39] = { |
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-0.0008908477f, -0.0008401274f, -0.0001837353f, 0.0017556005f,
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0.0049353322f, 0.0084952916f, 0.0107668722f, 0.0097441685f,
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0.0039877576f, -0.0063455016f, -0.0188069300f, -0.0287453055f,
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-0.0303831521f, -0.0186809770f, 0.0085931270f, 0.0493875744f,
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0.0971742012f, 0.1423015880f, 0.1745838382f, 0.1863024485f,
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0.1745838382f, 0.1423015880f, 0.0971742012f, 0.0493875744f,
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0.0085931270f, -0.0186809770f, -0.0303831521f, -0.0287453055f,
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-0.0188069300f, -0.0063455016f, 0.0039877576f, 0.0097441685f,
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0.0107668722f, 0.0084952916f, 0.0049353322f, 0.0017556005f,
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-0.0008908477f, -0.0008401274f, -0.0001837353f, 0.0017556005f, |
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0.0049353322f, 0.0084952916f, 0.0107668722f, 0.0097441685f, |
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0.0039877576f, -0.0063455016f, -0.0188069300f, -0.0287453055f, |
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-0.0303831521f, -0.0186809770f, 0.0085931270f, 0.0493875744f, |
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0.0971742012f, 0.1423015880f, 0.1745838382f, 0.1863024485f, |
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0.1745838382f, 0.1423015880f, 0.0971742012f, 0.0493875744f, |
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0.0085931270f, -0.0186809770f, -0.0303831521f, -0.0287453055f, |
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-0.0188069300f, -0.0063455016f, 0.0039877576f, 0.0097441685f, |
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0.0107668722f, 0.0084952916f, 0.0049353322f, 0.0017556005f, |
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-0.0001837353f, -0.0008401274f, -0.0008908477f }; |
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}; |
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#endif |
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}; |
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#endif |
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