不韋 呂
Cutoff frequency variable LPF and HPF by IIR 6th-order Butterworth filter for ST Nucleo F401RE.
Dependencies: UITDSP_ADDA UIT_ACM1602NI UIT_AQM1602 UIT_IIR_Filter mbed
Revision 0:33908268d9ea, committed 2015-09-11
- Comitter:
- MikamiUitOpen
- Date:
- Fri Sep 11 09:54:45 2015 +0000
- Commit message:
- 1
Changed in this revision
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/BilinearDesignLpfHpf/BilinearDesignLH.cpp Fri Sep 11 09:54:45 2015 +0000
@@ -0,0 +1,81 @@
+//------------------------------------------------------------------------------
+// Design of Butterworth LPF and HPF using bilinear transform
+//
+// 2014/06/29, Copyright (c) 2014 MIKAMI, Naoki
+//------------------------------------------------------------------------------
+
+#include "BilinearDesignLH.hpp"
+
+namespace Mikami
+{
+ // Execute design
+ // input
+ // fc: Cutoff frequency
+ // output
+ // c : Coefficients for cascade structure
+ // g : Gain factor for cascade structure
+ void BilinearDesign::Execute(float fc, Coefs c[], float& g)
+ {
+ Butterworth();
+ Bilinear(fc);
+ ToCascade();
+ GetGain();
+ GetCoefs(c, g);
+ }
+
+ // Get poles for Butterworth characteristics
+ void BilinearDesign::Butterworth()
+ {
+ float pi_2order = PI_/(2.0f*ORDER_);
+ for (int j=0; j<ORDER_/2; j++) // Pole with imaginary part >= 0
+ {
+ float theta = (2.0f*j + 1.0f)*pi_2order;
+ sP_[j] = Complex(-cosf(theta), sinf(theta));
+ }
+ }
+
+ // Bilinear transform
+ // fc: Cutoff frequency
+ void BilinearDesign::Bilinear(float fc)
+ {
+ float wc = tanf(fc*PI_FS_);
+ for (int k=0; k<ORDER_/2; k++)
+ zP_[k] = (1.0f + wc*sP_[k])/(1.0f - wc*sP_[k]);
+ }
+
+ // Convert to coefficients for cascade structure
+ void BilinearDesign::ToCascade()
+ {
+ for (int j=0; j<ORDER_/2; j++)
+ {
+ ck_[j].a1 = 2.0f*real(zP_[j]); // a1m
+ ck_[j].a2 = -norm(zP_[j]); // a2m
+ ck_[j].b1 = (PB_ == LPF) ? 2.0f : -2.0f; // b1m
+ }
+ }
+
+ // Calculate gain factor
+ void BilinearDesign::GetGain(){
+ float u = (PB_ == LPF) ? 1.0f : -1.0f;
+ float g0 = 1.0f;
+ for (int k=0; k<ORDER_/2; k++)
+ g0 = g0*(1.0f - (ck_[k].a1 + ck_[k].a2*u)*u)/
+ (1.0f + (ck_[k].b1 + u)*u);
+ gain_ = g0;
+ }
+
+ // Get coefficients
+ void BilinearDesign::GetCoefs(Coefs c[], float& gain)
+ {
+ for (int k=0; k<ORDER_/2; k++)
+ {
+ c[k].a1 = ck_[k].a1;
+ c[k].a2 = ck_[k].a2;
+ c[k].b1 = ck_[k].b1;
+ }
+ gain = gain_;
+ }
+}
+
+
+
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/BilinearDesignLpfHpf/BilinearDesignLH.hpp Fri Sep 11 09:54:45 2015 +0000
@@ -0,0 +1,62 @@
+//------------------------------------------------------------------------------
+// Design of Butterworth LPF and HPF using bilinear transform -- Header
+//
+// 2014/06/29, Copyright (c) 2014 MIKAMI, Naoki
+//------------------------------------------------------------------------------
+
+#ifndef BILINEAR_BUTTERWORTH_HPP
+#define BILINEAR_BUTTERWORTH_HPP
+
+#include "mbed.h"
+#include <complex> // requisite
+
+namespace Mikami
+{
+ typedef complex<float> Complex; // define "Complex"
+
+ class BilinearDesign
+ {
+ public:
+ struct Coefs { float a1, a2, b1; };
+ enum Type { LPF, HPF };
+
+ // Constructor
+ BilinearDesign(int order, float fs, Type pb)
+ : PI_FS_(PI_/fs), ORDER_(order), PB_(pb)
+ {
+ sP_ = new Complex[order/2];
+ zP_ = new Complex[order/2];
+ ck_ = new Coefs[order/2];
+ }
+
+ // Destractor
+ ~BilinearDesign()
+ {
+ delete[] sP_;
+ delete[] zP_;
+ delete[] ck_;
+ }
+
+ // Execution of design
+ void Execute(float fc, Coefs c[], float& g);
+
+ private:
+ static const float PI_ = 3.1415926536f;
+ const float PI_FS_;
+ const int ORDER_;
+ const Type PB_;
+
+ Complex* sP_; // Poles on s-plane
+ Complex* zP_; // Poles on z-plane
+ Coefs* ck_; // Coefficients of transfer function for cascade form
+ float gain_; // Gain factor for cascade form
+
+ void Butterworth();
+ void Bilinear(float fc);
+ void ToCascade();
+ void GetGain();
+ void GetCoefs(Coefs c[], float& gain);
+ };
+}
+#endif // BILINEAR_BUTTERWORTH_HPP
+
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/UITDSP_ADDA.lib Fri Sep 11 09:54:45 2015 +0000 @@ -0,0 +1,1 @@ +http://mbed.org/users/MikamiUitOpen/code/UITDSP_ADDA/#543daa087bd5
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/UIT_ACM1602NI.lib Fri Sep 11 09:54:45 2015 +0000 @@ -0,0 +1,1 @@ +http://mbed.org/users/MikamiUitOpen/code/UIT_ACM1602NI/#b7c761c179c9
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/UIT_AQM1602.lib Fri Sep 11 09:54:45 2015 +0000 @@ -0,0 +1,1 @@ +http://mbed.org/users/MikamiUitOpen/code/UIT_AQM1602/#01336babcccd
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/UIT_IIR_Filter.lib Fri Sep 11 09:54:45 2015 +0000 @@ -0,0 +1,1 @@ +http://mbed.org/users/MikamiUitOpen/code/UIT_IIR_Filter/#2533ed0150e7
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp Fri Sep 11 09:54:45 2015 +0000
@@ -0,0 +1,119 @@
+//--------------------------------------------------------------
+// Cutoff frequency variable LPF and HPF by IIR 8th-order filter
+// A0: Signal to be filtered
+// A2: Value which controls cutoff frequency
+//
+// sw: 0, 2 Through
+// 1: LPF
+// 3: HPF
+// 2015/09/11, Copyright (c) 2015 MIKAMI, Naoki
+//--------------------------------------------------------------
+
+#include "ADC_Interrupt.hpp" // for ADC using interrupt
+#include "DAC_MCP4921.hpp" // for DAC MCP4921, MCP4922
+using namespace Mikami;
+
+#include "BilinearDesignLH.hpp" // for design of IIR filter
+#include "IIR_Cascade.hpp" // for IIR filter of cascade structure
+
+// ACM1602Ni を使う場合は次の define 文をコメントにすること
+#define AQM1602
+
+#ifdef AQM1602
+#include "AQM1602.hpp"
+Aqm1602 Lcd_;
+#else
+#include "ACM1602NI.hpp"
+Acm1602Ni Lcd_;
+#endif
+
+const int FS_ = 24000; // Sampling frequency: 24 kHz
+ADC_Intr myAdc_(A0, FS_, A2);
+DAC_MCP4921 myDac_;
+
+const int ORDER_ = 8;
+IirCascade<ORDER_> iirLH_; // IIR filter object
+
+DigitalIn sw1_(D2, PullDown); // 0: disable filter
+ // 1: enable filter
+DigitalIn sw2_(D3, PullDown);
+
+uint16_t a2_ = 0; // Inputted data from A2 pin
+
+// Interrupt service routine for ADC
+void AdcIsr()
+{
+ float xn = myAdc_.Read(); // Read from A0
+
+ myAdc_.Select2ndChannel(); // Select A2
+ myAdc_.SoftStart(); // ADC start for A2 input
+
+ // Execute IIR filter
+ float yn = iirLH_.Execute(xn);
+
+ if (sw1_ == 0) myDac_.Write(xn); // Using no filter
+ else myDac_.Write(yn); // Using filter
+
+ // Read value which controls cutoff frequency
+ a2_ = myAdc_.ReadWait_u16();
+
+ myAdc_.Select1stChannel(); // Select A0
+ myAdc_.ClearPending_EnableIRQ();// Clear pending interrupt
+ // and enable ADC_IRQn
+}
+
+int main()
+{
+ myDac_.ScfClockTim3(1000000); // cutoff frequency: 10 kHz
+
+ BilinearDesign lpfDsgn(ORDER_, FS_, BilinearDesign::LPF);
+ BilinearDesign hpfDsgn(ORDER_, FS_, BilinearDesign::HPF);
+
+ myAdc_.SetIntrVec(AdcIsr); // Assign ISR for ADC interrupt
+
+ float fc1 = 0;
+ while (true)
+ {
+ // fc: cutoff frequency, 100 -- 2000 Hz
+ float fc = 1900.0f*(a2_/4095.6f) + 100.0f;
+
+ if (sw1_ == 0)
+ {
+ printf("Through\r\n");
+ Lcd_.WriteStringXY("Through ", 0, 0);
+ wait(0.2f);
+ Lcd_.ClearLine(0);
+ fc1 = 0;
+ }
+ else
+ {
+ if (fabs(fc - fc1) > 10.0f)
+ {
+ char str[18];
+ if (sw2_ == 0) sprintf(str, "LPF: fc=%4d Hz", int(fc+0.5f));
+ else sprintf(str, "HPF: fc=%4d Hz", int(fc+0.5f));
+
+ printf("%s\r\n", str);
+ Lcd_.WriteStringXY(str, 0, 0);
+ fc1 = fc;
+
+ // Design new coefficients based on new fc
+ BilinearDesign::Coefs coefs[ORDER_/2];
+ float g0;
+ if (sw2_ == 0) lpfDsgn.Execute(fc, coefs, g0);
+ else hpfDsgn.Execute(fc, coefs, g0);
+ Biquad::Coefs coefsIir[ORDER_/2];
+ // Update new coefficients
+ for (int n=0; n<ORDER_/2; n++)
+ {
+ coefsIir[n].a1 = coefs[n].a1;
+ coefsIir[n].a2 = coefs[n].a2;
+ coefsIir[n].b1 = coefs[n].b1;
+ coefsIir[n].b2 = 1.0f;
+ }
+ iirLH_.SetCoefs(g0, coefsIir);
+ }
+ }
+ wait(0.1f);
+ }
+}
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/mbed.bld Fri Sep 11 09:54:45 2015 +0000 @@ -0,0 +1,1 @@ +http://mbed.org/users/mbed_official/code/mbed/builds/ba1f97679dad \ No newline at end of file