
Affichage de la FFT d'un signal analogique sur 256 points
main.cpp@2:47d90ce030a3, 2021-02-09 (annotated)
- Committer:
- villemejane
- Date:
- Tue Feb 09 14:34:53 2021 +0000
- Revision:
- 2:47d90ce030a3
- Parent:
- 0:96c89b4dc711
FFT Calculation
Who changed what in which revision?
User | Revision | Line number | New contents of line |
---|---|---|---|
villemejane | 2:47d90ce030a3 | 1 | /****************************************************************************/ |
villemejane | 2:47d90ce030a3 | 2 | /* FFT d'un signal - Nucleo */ |
villemejane | 2:47d90ce030a3 | 3 | /****************************************************************************/ |
villemejane | 2:47d90ce030a3 | 4 | /* LEnsE / Julien VILLEMEJANE / Institut d'Optique Graduate School */ |
villemejane | 2:47d90ce030a3 | 5 | /****************************************************************************/ |
villemejane | 2:47d90ce030a3 | 6 | /* Brochage */ |
villemejane | 2:47d90ce030a3 | 7 | /* TO COMPLETE */ |
villemejane | 2:47d90ce030a3 | 8 | /****************************************************************************/ |
villemejane | 2:47d90ce030a3 | 9 | /* Test réalisé sur Nucléo-L476RG */ |
villemejane | 2:47d90ce030a3 | 10 | /****************************************************************************/ |
villemejane | 2:47d90ce030a3 | 11 | |
villemejane | 0:96c89b4dc711 | 12 | #include "mbed.h" |
villemejane | 0:96c89b4dc711 | 13 | #include "arm_math.h" |
villemejane | 0:96c89b4dc711 | 14 | /* Include mbed-dsp libraries */ |
villemejane | 0:96c89b4dc711 | 15 | #include "dsp.h" |
villemejane | 0:96c89b4dc711 | 16 | #include "arm_common_tables.h" |
villemejane | 0:96c89b4dc711 | 17 | #include "arm_const_structs.h" |
villemejane | 0:96c89b4dc711 | 18 | |
villemejane | 0:96c89b4dc711 | 19 | #define SAMPLES 512 /* 256 real party and 256 imaginary parts */ |
villemejane | 0:96c89b4dc711 | 20 | #define FFT_SIZE SAMPLES / 2 /* FFT size is always the same size as we have samples, so 256 in our case */ |
villemejane | 0:96c89b4dc711 | 21 | |
villemejane | 0:96c89b4dc711 | 22 | float32_t Input[SAMPLES]; |
villemejane | 0:96c89b4dc711 | 23 | float32_t Output[FFT_SIZE]; |
villemejane | 0:96c89b4dc711 | 24 | bool trig=0; |
villemejane | 0:96c89b4dc711 | 25 | int indice = 0; |
villemejane | 0:96c89b4dc711 | 26 | |
villemejane | 0:96c89b4dc711 | 27 | DigitalOut myled(LED1); |
villemejane | 0:96c89b4dc711 | 28 | AnalogIn myADC(A0); |
villemejane | 0:96c89b4dc711 | 29 | AnalogOut myDAC(A2); |
villemejane | 0:96c89b4dc711 | 30 | Serial pc(USBTX, USBRX); |
villemejane | 0:96c89b4dc711 | 31 | Ticker timer; |
villemejane | 0:96c89b4dc711 | 32 | |
villemejane | 0:96c89b4dc711 | 33 | void sample(){ |
villemejane | 0:96c89b4dc711 | 34 | myled = 1; |
villemejane | 0:96c89b4dc711 | 35 | if(indice < SAMPLES){ |
villemejane | 0:96c89b4dc711 | 36 | Input[indice] = myADC.read() - 0.5f; //Real part NB removing DC offset |
villemejane | 0:96c89b4dc711 | 37 | Input[indice + 1] = 0; //Imaginary Part set to zero |
villemejane | 0:96c89b4dc711 | 38 | indice += 2; |
villemejane | 0:96c89b4dc711 | 39 | } |
villemejane | 0:96c89b4dc711 | 40 | else{ trig = 0; } |
villemejane | 0:96c89b4dc711 | 41 | myled = 0; |
villemejane | 0:96c89b4dc711 | 42 | } |
villemejane | 0:96c89b4dc711 | 43 | |
villemejane | 0:96c89b4dc711 | 44 | int main() { |
villemejane | 0:96c89b4dc711 | 45 | float maxValue; // Max FFT value is stored here |
villemejane | 0:96c89b4dc711 | 46 | uint32_t maxIndex; // Index in Output array where max value is |
villemejane | 0:96c89b4dc711 | 47 | |
villemejane | 0:96c89b4dc711 | 48 | while(1) { |
villemejane | 0:96c89b4dc711 | 49 | if(trig == 0){ |
villemejane | 0:96c89b4dc711 | 50 | timer.detach(); |
villemejane | 0:96c89b4dc711 | 51 | // Init the Complex FFT module, intFlag = 0, doBitReverse = 1 |
villemejane | 0:96c89b4dc711 | 52 | //NB using predefined arm_cfft_sR_f32_lenXXX, in this case XXX is 256 |
villemejane | 0:96c89b4dc711 | 53 | arm_cfft_f32(&arm_cfft_sR_f32_len256, Input, 0, 1); |
villemejane | 0:96c89b4dc711 | 54 | |
villemejane | 0:96c89b4dc711 | 55 | // Complex Magniture Module put results into Output(Half size of the Input) |
villemejane | 0:96c89b4dc711 | 56 | arm_cmplx_mag_f32(Input, Output, FFT_SIZE); |
villemejane | 0:96c89b4dc711 | 57 | Output[0] = 0; |
villemejane | 0:96c89b4dc711 | 58 | //Calculates maxValue and returns corresponding value |
villemejane | 0:96c89b4dc711 | 59 | arm_max_f32(Output, FFT_SIZE/2, &maxValue, &maxIndex); |
villemejane | 0:96c89b4dc711 | 60 | |
villemejane | 0:96c89b4dc711 | 61 | myDAC=1.0; //SYNC Pulse to DAC Output |
villemejane | 0:96c89b4dc711 | 62 | wait_us(20); //Used on Oscilliscope set trigger level to the highest |
villemejane | 0:96c89b4dc711 | 63 | myDAC=0.0; //point on this pulse |
villemejane | 0:96c89b4dc711 | 64 | |
villemejane | 0:96c89b4dc711 | 65 | for(int i=0; i < FFT_SIZE / 2; i++){ |
villemejane | 0:96c89b4dc711 | 66 | myDAC=(Output[i]) * 0.9; // Scale to Max Value and scale to 90 / 100 |
villemejane | 0:96c89b4dc711 | 67 | wait_us(10); //Each pulse of 10us is 50KHz/256 = 195Hz resolution |
villemejane | 0:96c89b4dc711 | 68 | } |
villemejane | 0:96c89b4dc711 | 69 | myDAC=0.0; |
villemejane | 0:96c89b4dc711 | 70 | pc.printf("MAX = %lf, %d \r\n", maxValue, maxIndex); |
villemejane | 0:96c89b4dc711 | 71 | wait(0.2); |
villemejane | 0:96c89b4dc711 | 72 | trig = 1; |
villemejane | 0:96c89b4dc711 | 73 | indice = 0; |
villemejane | 0:96c89b4dc711 | 74 | timer.attach_us(&sample,40); //20us 50KHz sampling rate |
villemejane | 0:96c89b4dc711 | 75 | } |
villemejane | 0:96c89b4dc711 | 76 | } |
villemejane | 0:96c89b4dc711 | 77 | } |