CQpub0 Mikami / Mbed 2 deprecated FFT_Sampling

The experiment using this program is introduced on "Interface" No.4, CQ publishing Co.,Ltd, 2015. 本プログラムを使った実験は，CQ出版社のインターフェース 2015年4月号で紹介しています．

Dependencies:   DSProcessingIO mbed

FFT_Sampling.cpp@1:655f6a72e47e, 2014-07-29 (annotated)

Committer:
CQpub0Mikami
Date:
Tue Jul 29 06:52:38 2014 +0000
Revision:
1:655f6a72e47e
Parent:
0:c740f515e0b7 
ver.2

Who changed what in which revision?

UserRevisionLine numberNew contents of line
CQpub0Mikami 0:c740f515e0b7 1 //--------------------------------------------------------------
CQpub0Mikami 0:c740f515e0b7 2 // Sampling and Spectrum analysis using FFT
CQpub0Mikami 0:c740f515e0b7 3 // Copyright (c) 2014 MIKAMI, Naoki, 2014/06/29
CQpub0Mikami 0:c740f515e0b7 4 //--------------------------------------------------------------
CQpub0Mikami 0:c740f515e0b7 5
CQpub0Mikami 0:c740f515e0b7 6 #include "mbed.h"
CQpub0Mikami 0:c740f515e0b7 7 #include "AdcInternal.hpp"
CQpub0Mikami 0:c740f515e0b7 8 #include "fftReal.hpp"
CQpub0Mikami 0:c740f515e0b7 9
CQpub0Mikami 0:c740f515e0b7 10 using namespace Mikami;
CQpub0Mikami 0:c740f515e0b7 11
CQpub0Mikami 0:c740f515e0b7 12 // sampling frequency
CQpub0Mikami 0:c740f515e0b7 13 const float FS_ = 10.0e3f;
CQpub0Mikami 0:c740f515e0b7 14 const int N_FFT_ = 256;
CQpub0Mikami 0:c740f515e0b7 15
CQpub0Mikami 0:c740f515e0b7 16 Adc adc_(A0);
CQpub0Mikami 0:c740f515e0b7 17 Ticker timer_; // for timer interrupt
CQpub0Mikami 0:c740f515e0b7 18 DigitalIn userButton_(USER_BUTTON);
CQpub0Mikami 0:c740f515e0b7 19 FftReal fft_(N_FFT_);
CQpub0Mikami 0:c740f515e0b7 20
CQpub0Mikami 0:c740f515e0b7 21 float xn_[N_FFT_+1];
CQpub0Mikami 0:c740f515e0b7 22 volatile int count_;
CQpub0Mikami 0:c740f515e0b7 23
CQpub0Mikami 0:c740f515e0b7 24 // Sampling
CQpub0Mikami 0:c740f515e0b7 25 void TimerIsr()
CQpub0Mikami 0:c740f515e0b7 26 {
CQpub0Mikami 0:c740f515e0b7 27 xn_[count_] = adc_.Read(); // AD
CQpub0Mikami 0:c740f515e0b7 28 count_++;
CQpub0Mikami 0:c740f515e0b7 29 }
CQpub0Mikami 0:c740f515e0b7 30
CQpub0Mikami 0:c740f515e0b7 31 int main()
CQpub0Mikami 0:c740f515e0b7 32 {
CQpub0Mikami 0:c740f515e0b7 33 printf("Ready.\r\n");
CQpub0Mikami 0:c740f515e0b7 34 while(userButton_); // wait for user button pressed
CQpub0Mikami 0:c740f515e0b7 35 printf("User button is pushed!\r\n");
CQpub0Mikami 0:c740f515e0b7 36
CQpub0Mikami 0:c740f515e0b7 37 count_ = 0;
CQpub0Mikami 0:c740f515e0b7 38 timer_.attach_us(&TimerIsr, 1.0e6f/FS_);
CQpub0Mikami 0:c740f515e0b7 39 while (count_ < N_FFT_+1);
CQpub0Mikami 0:c740f515e0b7 40 timer_.detach(); // Detach TimerIsr
CQpub0Mikami 0:c740f515e0b7 41 printf("End of Sampling.\r\n");
CQpub0Mikami 0:c740f515e0b7 42
CQpub0Mikami 0:c740f515e0b7 43 float xnW[N_FFT_]; // for windowed data
CQpub0Mikami 0:c740f515e0b7 44 Complex yk[N_FFT_/2+1];
CQpub0Mikami 0:c740f515e0b7 45 float yDb[N_FFT_/2+1];
CQpub0Mikami 0:c740f515e0b7 46
CQpub0Mikami 0:c740f515e0b7 47 // Windowing
CQpub0Mikami 0:c740f515e0b7 48 float pi2N = 6.283185f/N_FFT_;
CQpub0Mikami 0:c740f515e0b7 49 for (int n=0; n<N_FFT_; n++)
CQpub0Mikami 0:c740f515e0b7 50 xnW[n] = (xn_[n+1] - xn_[n])*(0.54f - 0.46f*cosf(pi2N*n));
CQpub0Mikami 0:c740f515e0b7 51
CQpub0Mikami 0:c740f515e0b7 52 // Execute FFT
CQpub0Mikami 0:c740f515e0b7 53 fft_.Execute(xnW, yk);
CQpub0Mikami 0:c740f515e0b7 54
CQpub0Mikami 0:c740f515e0b7 55 // Square of absolute value of FFT
CQpub0Mikami 0:c740f515e0b7 56 for (int n=0; n<=N_FFT_/2; n++)
CQpub0Mikami 0:c740f515e0b7 57 yDb[n] = norm(yk[n]);
CQpub0Mikami 0:c740f515e0b7 58
CQpub0Mikami 0:c740f515e0b7 59 // Get maximum value of yk[n]
CQpub0Mikami 0:c740f515e0b7 60 float max = 0;
CQpub0Mikami 0:c740f515e0b7 61 for (int n=0; n<=N_FFT_/2; n++)
CQpub0Mikami 0:c740f515e0b7 62 max = (yDb[n] > max) ? yDb[n] : max;
CQpub0Mikami 0:c740f515e0b7 63
CQpub0Mikami 0:c740f515e0b7 64 // Normalized spectra to dB
CQpub0Mikami 0:c740f515e0b7 65 for (int n=0; n<=N_FFT_/2; n++)
CQpub0Mikami 0:c740f515e0b7 66 if (yDb[n] > 0)
CQpub0Mikami 0:c740f515e0b7 67 yDb[n] = 10.0f*log10f(yDb[n]/max);
CQpub0Mikami 0:c740f515e0b7 68 else
CQpub0Mikami 0:c740f515e0b7 69 yDb[n] = -100.0f;
CQpub0Mikami 0:c740f515e0b7 70
CQpub0Mikami 0:c740f515e0b7 71 // Output to terminal
CQpub0Mikami 0:c740f515e0b7 72 float dt = 1.0e3f/FS_;
CQpub0Mikami 0:c740f515e0b7 73 float df = FS_/N_FFT_;
CQpub0Mikami 0:c740f515e0b7 74 for (int n=0; n<N_FFT_; n++)
CQpub0Mikami 0:c740f515e0b7 75 {
CQpub0Mikami 0:c740f515e0b7 76 if (n <= N_FFT_/2)
CQpub0Mikami 0:c740f515e0b7 77 printf("%3d, %4.1f,%8.4f, %10.4f,%6.1f\r\n",
CQpub0Mikami 0:c740f515e0b7 78 n, n*dt, xn_[n], n*df, yDb[n]);
CQpub0Mikami 0:c740f515e0b7 79 else
CQpub0Mikami 0:c740f515e0b7 80 printf("%3d, %4.1f,%8.4f\r\n", n, n*dt, xn_[n]);
CQpub0Mikami 0:c740f515e0b7 81 }
CQpub0Mikami 0:c740f515e0b7 82 }
CQpub0Mikami 0:c740f515e0b7 83