不韋 呂 / Mbed 2 deprecated F746_SD_WavPlayer

Output the audio signal with filtering by IIR filter in the *.wav file on the SD card using onboard CODEC. SD カードの *.wav ファイルのオーディオ信号を遮断周波数可変の IIR フィルタを通して，ボードに搭載されているCODEC で出力する．

Dependencies:   BSP_DISCO_F746NG F746_GUI LCD_DISCO_F746NG SDFileSystem_Warning_Fixed TS_DISCO_F746NG mbed FrequencyResponseDrawer F746_SAI_IO Array_Matrix

MyClasses_Functions/BilinearDesignLH.cpp@11:769d986c10fa, 2016-07-04 (annotated)

Committer:
MikamiUitOpen
Date:
Mon Jul 04 05:59:44 2016 +0000
Revision:
11:769d986c10fa
Parent:
0:04b43b777fae 
12

Who changed what in which revision?

UserRevisionLine numberNew contents of line
MikamiUitOpen 0:04b43b777fae 1 //------------------------------------------------------------------------------
MikamiUitOpen 0:04b43b777fae 2 // Design of Butterworth LPF and HPF using bilinear transform
MikamiUitOpen 0:04b43b777fae 3 //
MikamiUitOpen 0:04b43b777fae 4 // 2016/03/31, Copyright (c) 2016 MIKAMI, Naoki
MikamiUitOpen 0:04b43b777fae 5 //------------------------------------------------------------------------------
MikamiUitOpen 0:04b43b777fae 6
MikamiUitOpen 0:04b43b777fae 7 #include "BilinearDesignLH.hpp"
MikamiUitOpen 0:04b43b777fae 8
MikamiUitOpen 0:04b43b777fae 9 namespace Mikami
MikamiUitOpen 0:04b43b777fae 10 {
MikamiUitOpen 0:04b43b777fae 11 // Execute design
MikamiUitOpen 0:04b43b777fae 12 // input
MikamiUitOpen 0:04b43b777fae 13 // fc: Cutoff frequency
MikamiUitOpen 0:04b43b777fae 14 // pb: Passband (LPF or HPF)
MikamiUitOpen 0:04b43b777fae 15 // output
MikamiUitOpen 0:04b43b777fae 16 // c : Coefficients for cascade structure
MikamiUitOpen 0:04b43b777fae 17 // g : Gain factor for cascade structure
MikamiUitOpen 0:04b43b777fae 18 void BilinearDesign::Execute(float fc, Type pb, Coefs c[], float& g)
MikamiUitOpen 0:04b43b777fae 19 {
MikamiUitOpen 0:04b43b777fae 20 Butterworth();
MikamiUitOpen 0:04b43b777fae 21 Bilinear(fc);
MikamiUitOpen 0:04b43b777fae 22 ToCascade(pb);
MikamiUitOpen 0:04b43b777fae 23 GetGain(pb);
MikamiUitOpen 0:04b43b777fae 24 GetCoefs(c, g);
MikamiUitOpen 0:04b43b777fae 25 }
MikamiUitOpen 0:04b43b777fae 26
MikamiUitOpen 0:04b43b777fae 27 // Get poles for Butterworth characteristics
MikamiUitOpen 0:04b43b777fae 28 void BilinearDesign::Butterworth()
MikamiUitOpen 0:04b43b777fae 29 {
MikamiUitOpen 0:04b43b777fae 30 float pi_2order = PI_/(2.0f*ORDER_);
MikamiUitOpen 0:04b43b777fae 31 for (int j=0; j<ORDER_/2; j++) // Pole with imaginary part >= 0
MikamiUitOpen 0:04b43b777fae 32 {
MikamiUitOpen 0:04b43b777fae 33 float theta = (2.0f*j + 1.0f)*pi_2order;
MikamiUitOpen 0:04b43b777fae 34 sP_[j] = Complex(-cosf(theta), sinf(theta));
MikamiUitOpen 0:04b43b777fae 35 }
MikamiUitOpen 0:04b43b777fae 36 }
MikamiUitOpen 0:04b43b777fae 37
MikamiUitOpen 0:04b43b777fae 38 // Bilinear transform
MikamiUitOpen 0:04b43b777fae 39 // fc: Cutoff frequency
MikamiUitOpen 0:04b43b777fae 40 void BilinearDesign::Bilinear(float fc)
MikamiUitOpen 0:04b43b777fae 41 {
MikamiUitOpen 0:04b43b777fae 42 float wc = tanf(fc*PI_FS_);
MikamiUitOpen 0:04b43b777fae 43 for (int k=0; k<ORDER_/2; k++)
MikamiUitOpen 0:04b43b777fae 44 zP_[k] = (1.0f + wc*sP_[k])/(1.0f - wc*sP_[k]);
MikamiUitOpen 0:04b43b777fae 45 }
MikamiUitOpen 0:04b43b777fae 46
MikamiUitOpen 0:04b43b777fae 47 // Convert to coefficients for cascade structure
MikamiUitOpen 0:04b43b777fae 48 void BilinearDesign::ToCascade(Type pb)
MikamiUitOpen 0:04b43b777fae 49 {
MikamiUitOpen 0:04b43b777fae 50 for (int j=0; j<ORDER_/2; j++)
MikamiUitOpen 0:04b43b777fae 51 {
MikamiUitOpen 0:04b43b777fae 52 ck_[j].a1 = 2.0f*real(zP_[j]); // a1m
MikamiUitOpen 0:04b43b777fae 53 ck_[j].a2 = -norm(zP_[j]); // a2m
MikamiUitOpen 0:04b43b777fae 54 ck_[j].b1 = (pb == LPF) ? 2.0f : -2.0f; // b1m
MikamiUitOpen 0:04b43b777fae 55 ck_[j].b2 = 1.0f; // b2m
MikamiUitOpen 0:04b43b777fae 56 }
MikamiUitOpen 0:04b43b777fae 57 }
MikamiUitOpen 0:04b43b777fae 58
MikamiUitOpen 0:04b43b777fae 59 // Calculate gain factor
MikamiUitOpen 0:04b43b777fae 60 void BilinearDesign::GetGain(Type pb)
MikamiUitOpen 0:04b43b777fae 61 {
MikamiUitOpen 0:04b43b777fae 62 float u = (pb == LPF) ? 1.0f : -1.0f;
MikamiUitOpen 0:04b43b777fae 63 float g0 = 1.0f;
MikamiUitOpen 0:04b43b777fae 64 for (int k=0; k<ORDER_/2; k++)
MikamiUitOpen 0:04b43b777fae 65 g0 = g0*(1.0f - (ck_[k].a1 + ck_[k].a2*u)*u)/
MikamiUitOpen 0:04b43b777fae 66 (1.0f + (ck_[k].b1 + ck_[k].b2*u)*u);
MikamiUitOpen 0:04b43b777fae 67 gain_ = g0;
MikamiUitOpen 0:04b43b777fae 68 }
MikamiUitOpen 0:04b43b777fae 69
MikamiUitOpen 0:04b43b777fae 70 // Get coefficients
MikamiUitOpen 0:04b43b777fae 71 void BilinearDesign::GetCoefs(Coefs c[], float& gain)
MikamiUitOpen 0:04b43b777fae 72 {
MikamiUitOpen 0:04b43b777fae 73 for (int k=0; k<ORDER_/2; k++) c[k] = ck_[k];
MikamiUitOpen 0:04b43b777fae 74 gain = gain_;
MikamiUitOpen 0:04b43b777fae 75 }
MikamiUitOpen 0:04b43b777fae 76 }