Jared Baxter
/
Impedance_Fast_Circuitry
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DSP_200kHz
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Jareds_DSP/demodulate.cpp@84:5b4466dd2326, 2018-02-21 (annotated)
- Committer:
- baxterja
- Date:
- Wed Feb 21 23:23:17 2018 +0000
- Revision:
- 84:5b4466dd2326
- Parent:
- 78:10b2916b8f5c
- Child:
- 85:f1be018aacac
Pre_mavrik Version
Who changed what in which revision?
| User | Revision | Line number | New contents of line |
|---|---|---|---|
| baxterja | 75:8bb94685c80b | 1 | #include "demodulate.h" |
| baxterja | 75:8bb94685c80b | 2 | |
| baxterja | 84:5b4466dd2326 | 3 | #define MAX_NUMBER_DEMOD_FREQ 1 |
| baxterja | 75:8bb94685c80b | 4 | |
| baxterja | 75:8bb94685c80b | 5 | #define DEMOD_EXTRA_TABLE_LENGTH 16 |
| baxterja | 75:8bb94685c80b | 6 | #define TWOPI 6.28318530717959 |
| baxterja | 75:8bb94685c80b | 7 | |
| baxterja | 75:8bb94685c80b | 8 | float *imod[MAX_NUMBER_DEMOD_FREQ]; |
| baxterja | 75:8bb94685c80b | 9 | float *qmod[MAX_NUMBER_DEMOD_FREQ]; |
| baxterja | 84:5b4466dd2326 | 10 | float demod_Carrier_Frequency[MAX_NUMBER_DEMOD_FREQ] = {100000/208}; |
| baxterja | 84:5b4466dd2326 | 11 | float demod_Table_Length[MAX_NUMBER_DEMOD_FREQ] = {208/8}; |
| baxterja | 84:5b4466dd2326 | 12 | float demod_Sample_Frequency[MAX_NUMBER_DEMOD_FREQ] = {12500}; |
| baxterja | 75:8bb94685c80b | 13 | |
| baxterja | 75:8bb94685c80b | 14 | void precompute_tables() |
| baxterja | 75:8bb94685c80b | 15 | { |
| baxterja | 75:8bb94685c80b | 16 | static bool precomputed = false; |
| baxterja | 75:8bb94685c80b | 17 | if (precomputed) |
| baxterja | 75:8bb94685c80b | 18 | { |
| baxterja | 75:8bb94685c80b | 19 | printf("TABLES HAVE ALREADY BEEN PRECOMPUTED"); |
| baxterja | 75:8bb94685c80b | 20 | return; |
| baxterja | 75:8bb94685c80b | 21 | } |
| baxterja | 75:8bb94685c80b | 22 | precomputed = true; |
| baxterja | 75:8bb94685c80b | 23 | for (int i = 0; i<MAX_NUMBER_DEMOD_FREQ; i++) |
| baxterja | 75:8bb94685c80b | 24 | { |
| baxterja | 75:8bb94685c80b | 25 | int table_size = demod_Table_Length[i]+DEMOD_EXTRA_TABLE_LENGTH; |
| baxterja | 75:8bb94685c80b | 26 | imod[i] = new float[table_size]; |
| baxterja | 75:8bb94685c80b | 27 | qmod[i] = new float[table_size]; |
| baxterja | 75:8bb94685c80b | 28 | for(int precompute_counter = 0; precompute_counter < demod_Table_Length[i]+DEMOD_EXTRA_TABLE_LENGTH; precompute_counter++) |
| baxterja | 75:8bb94685c80b | 29 | { |
| baxterja | 75:8bb94685c80b | 30 | imod[i][precompute_counter] = ( cos(TWOPI * demod_Carrier_Frequency[i] / demod_Sample_Frequency[i] * precompute_counter)); |
| baxterja | 75:8bb94685c80b | 31 | qmod[i][precompute_counter] = (-sin(TWOPI * demod_Carrier_Frequency[i] / demod_Sample_Frequency[i] * precompute_counter)); |
| baxterja | 75:8bb94685c80b | 32 | } |
| baxterja | 75:8bb94685c80b | 33 | } |
| baxterja | 75:8bb94685c80b | 34 | |
| baxterja | 75:8bb94685c80b | 35 | } |
| baxterja | 75:8bb94685c80b | 36 | void demodulate(float *samples[MAX_NUMBER_OF_FILTERS], int num_filters, int sample_length, int demodulation_frequency) |
| baxterja | 75:8bb94685c80b | 37 | { |
| baxterja | 84:5b4466dd2326 | 38 | static int demod_counters[MAX_NUMBER_DEMOD_FREQ] = {0}; |
| baxterja | 75:8bb94685c80b | 39 | |
| baxterja | 75:8bb94685c80b | 40 | if (demod_counters[demodulation_frequency]>=demod_Table_Length[demodulation_frequency]) |
| baxterja | 75:8bb94685c80b | 41 | { |
| baxterja | 75:8bb94685c80b | 42 | demod_counters[demodulation_frequency]-=demod_Table_Length[demodulation_frequency]; |
| baxterja | 75:8bb94685c80b | 43 | } |
| baxterja | 75:8bb94685c80b | 44 | for(int i = num_filters-1; i>=0; i--) |
| baxterja | 75:8bb94685c80b | 45 | { |
| baxterja | 75:8bb94685c80b | 46 | //important keep in this order or filter 0 will be odd |
| baxterja | 75:8bb94685c80b | 47 | //multiply by -sin |
| baxterja | 75:8bb94685c80b | 48 | arm_mult_f32(qmod[demodulation_frequency]+demod_counters[demodulation_frequency], samples[i], samples[2*i+1], sample_length); |
| baxterja | 75:8bb94685c80b | 49 | //multiply by cos |
| baxterja | 75:8bb94685c80b | 50 | arm_mult_f32(imod[demodulation_frequency]+demod_counters[demodulation_frequency], samples[i], samples[2*i], sample_length); |
| baxterja | 75:8bb94685c80b | 51 | } |
| baxterja | 75:8bb94685c80b | 52 | demod_counters[demodulation_frequency] +=sample_length;//increment counter |
| baxterja | 75:8bb94685c80b | 53 | } |
