main.cpp

00001 /****************************************************************************/
00002 /*  FFT d'un signal   - Nucleo                                              */
00003 /****************************************************************************/
00004 /*  LEnsE / Julien VILLEMEJANE       /   Institut d'Optique Graduate School */
00005 /****************************************************************************/
00006 /*  Brochage                                                                */
00007 /*      TO COMPLETE                                                         */
00008 /****************************************************************************/
00009 /*  Test réalisé sur Nucléo-L476RG                                          */
00010 /****************************************************************************/
00011 
00012 #include "mbed.h"
00013 #include "arm_math.h"
00014 /* Include mbed-dsp libraries */
00015 #include "dsp.h"
00016 #include "arm_common_tables.h"
00017 #include "arm_const_structs.h"
00018 
00019 #define SAMPLES                 512             /* 256 real party and 256 imaginary parts */
00020 #define FFT_SIZE                SAMPLES / 2     /* FFT size is always the same size as we have samples, so 256 in our case */
00021  
00022 float32_t Input[SAMPLES];
00023 float32_t Output[FFT_SIZE];
00024 bool      trig=0;
00025 int       indice = 0;
00026 
00027 DigitalOut myled(LED1);
00028 AnalogIn   myADC(A0);
00029 AnalogOut  myDAC(A2);
00030 Serial     pc(USBTX, USBRX);
00031 Ticker     timer;
00032  
00033 void sample(){
00034     myled = 1;
00035     if(indice < SAMPLES){
00036         Input[indice] = myADC.read() - 0.5f;    //Real part NB removing DC offset
00037         Input[indice + 1] = 0;                  //Imaginary Part set to zero
00038         indice += 2;
00039     }
00040     else{ trig = 0; }
00041     myled = 0;
00042 }
00043  
00044 int main() {
00045     float maxValue;            // Max FFT value is stored here
00046     uint32_t maxIndex;         // Index in Output array where max value is
00047 
00048     while(1) {
00049         if(trig == 0){
00050             timer.detach();
00051             // Init the Complex FFT module, intFlag = 0, doBitReverse = 1
00052             //NB using predefined arm_cfft_sR_f32_lenXXX, in this case XXX is 256
00053             arm_cfft_f32(&arm_cfft_sR_f32_len256, Input, 0, 1);
00054  
00055             // Complex Magniture Module put results into Output(Half size of the Input)
00056             arm_cmplx_mag_f32(Input, Output, FFT_SIZE);
00057             Output[0] = 0;
00058             //Calculates maxValue and returns corresponding value
00059             arm_max_f32(Output, FFT_SIZE/2, &maxValue, &maxIndex);
00060         
00061             myDAC=1.0;     //SYNC Pulse to DAC Output
00062             wait_us(20);    //Used on Oscilliscope set trigger level to the highest
00063             myDAC=0.0;     //point on this pulse 
00064     
00065             for(int i=0; i < FFT_SIZE / 2; i++){
00066                 myDAC=(Output[i]) * 0.9;   // Scale to Max Value and scale to 90 / 100
00067                 wait_us(10);                //Each pulse of 10us is 50KHz/256 = 195Hz resolution
00068             }
00069             myDAC=0.0;
00070             pc.printf("MAX = %lf, %d \r\n", maxValue, maxIndex);
00071             wait(0.2);
00072             trig = 1;
00073             indice = 0;
00074             timer.attach_us(&sample,40);      //20us 50KHz sampling rate
00075         }
00076     }
00077 }