不韋 呂 / Mbed 2 deprecated F746_SpectralAnalysis_Example

Spectrum analyzer using DISCO-F746NG. Spectrum is calculated by FFT or linear prediction. The vowel data is in "vowel_data.hpp"

Dependencies:   BSP_DISCO_F746NG LCD_DISCO_F746NG TS_DISCO_F746NG UIT_FFT_Real mbed BUTTON_GROUP

SpactrumAnalysisClasses/FFT_Analysis.cpp@0:c35b8a23a863, 2015-10-26 (annotated)

Committer:
MikamiUitOpen
Date:
Mon Oct 26 08:06:57 2015 +0000
Revision:
0:c35b8a23a863
Child:
1:2ef356b500f2
1

Who changed what in which revision?

UserRevisionLine numberNew contents of line
MikamiUitOpen 0:c35b8a23a863 1 //-------------------------------------------------------
MikamiUitOpen 0:c35b8a23a863 2 // Class for spectrum analysis using FFT
MikamiUitOpen 0:c35b8a23a863 3 // Copyright (c) 2015 MIKAMI, Naoki, 2015/10/26
MikamiUitOpen 0:c35b8a23a863 4 //-------------------------------------------------------
MikamiUitOpen 0:c35b8a23a863 5
MikamiUitOpen 0:c35b8a23a863 6 #include "FFT_Analysis.hpp"
MikamiUitOpen 0:c35b8a23a863 7
MikamiUitOpen 0:c35b8a23a863 8 namespace Mikami
MikamiUitOpen 0:c35b8a23a863 9 {
MikamiUitOpen 0:c35b8a23a863 10 FftAnalyzer::FftAnalyzer(int nData, int nFft)
MikamiUitOpen 0:c35b8a23a863 11 : N_DATA_(nData), N_FFT_(nFft),
MikamiUitOpen 0:c35b8a23a863 12 hm_(nData-1, nFft), fft_(nFft)
MikamiUitOpen 0:c35b8a23a863 13 {
MikamiUitOpen 0:c35b8a23a863 14 xData = new float[nData]; // Data to be analyzed
MikamiUitOpen 0:c35b8a23a863 15 xFft = new float[nFft]; // Input for FFT
MikamiUitOpen 0:c35b8a23a863 16 yFft = new Complex[nFft/2+1]; // Output of FFT
MikamiUitOpen 0:c35b8a23a863 17 normY = new float[nFft/2+1]; // Powerspectrum
MikamiUitOpen 0:c35b8a23a863 18 }
MikamiUitOpen 0:c35b8a23a863 19
MikamiUitOpen 0:c35b8a23a863 20 FftAnalyzer::~FftAnalyzer()
MikamiUitOpen 0:c35b8a23a863 21 {
MikamiUitOpen 0:c35b8a23a863 22 delete[] xData;
MikamiUitOpen 0:c35b8a23a863 23 delete[] xFft;
MikamiUitOpen 0:c35b8a23a863 24 delete[] yFft;
MikamiUitOpen 0:c35b8a23a863 25 delete[] normY;
MikamiUitOpen 0:c35b8a23a863 26 }
MikamiUitOpen 0:c35b8a23a863 27
MikamiUitOpen 0:c35b8a23a863 28 void FftAnalyzer::Execute(float xn[], float db[])
MikamiUitOpen 0:c35b8a23a863 29 {
MikamiUitOpen 0:c35b8a23a863 30 // Differencing
MikamiUitOpen 0:c35b8a23a863 31 for (int n=0; n<N_DATA_-1; n++)
MikamiUitOpen 0:c35b8a23a863 32 xData[n] = xn[n+1] - xn[n];
MikamiUitOpen 0:c35b8a23a863 33
MikamiUitOpen 0:c35b8a23a863 34 hm_.Execute(xData, xFft); // Windowing and zero-padding
MikamiUitOpen 0:c35b8a23a863 35 fft_.Execute(xFft, yFft); // Execute FFT
MikamiUitOpen 0:c35b8a23a863 36
MikamiUitOpen 0:c35b8a23a863 37 // Squared magnitude
MikamiUitOpen 0:c35b8a23a863 38 for (int n=0; n<=N_FFT_/2; n++)
MikamiUitOpen 0:c35b8a23a863 39 normY[n] = Sqr(yFft[n].real()) + Sqr(yFft[n].imag());
MikamiUitOpen 0:c35b8a23a863 40
MikamiUitOpen 0:c35b8a23a863 41 // Searce maximum
MikamiUitOpen 0:c35b8a23a863 42 float max = 0;
MikamiUitOpen 0:c35b8a23a863 43 for (int n=0; n<=N_FFT_/2; n++)
MikamiUitOpen 0:c35b8a23a863 44 max = (max > normY[n]) ? max : normY[n];
MikamiUitOpen 0:c35b8a23a863 45 float invMax = 1.0f/max;
MikamiUitOpen 0:c35b8a23a863 46
MikamiUitOpen 0:c35b8a23a863 47 // Translate to dB
MikamiUitOpen 0:c35b8a23a863 48 for (int n=0; n<=N_FFT_/2; n++)
MikamiUitOpen 0:c35b8a23a863 49 db[n] = 10.0f*log10f(invMax*normY[n]);
MikamiUitOpen 0:c35b8a23a863 50 }
MikamiUitOpen 0:c35b8a23a863 51 }
MikamiUitOpen 0:c35b8a23a863 52