不韋 呂
/
UIT2_IIR_Cascade
IIR filter of cascade form using float type operations and coefficients for ST Nucleo F401RE.
Diff: main.cpp
- Revision:
- 0:8c15b3d0523e
- Child:
- 1:b688b41d0ba1
diff -r 000000000000 -r 8c15b3d0523e main.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/main.cpp Mon Oct 20 23:25:27 2014 +0000 @@ -0,0 +1,69 @@ +//-------------------------------------------------------------- +// IIR フィルタ,縦続形,dfloat で演算 +// Analog Input : A0 +// Analog Output: MCP4922 using SPI +// 2014/10/20, Copyright (c) 2014 MIKAMI, Naoki +//-------------------------------------------------------------- + +#include "mbed.h" + +#include "ADC_Interrupt.hpp" // for ADC using interrupt +#include "DAC_MCP4922.hpp" // for DAC MCP4922 +#include "ScfClockTim3.hpp" // for clock supplied to SCF + +using namespace Mikami; + +const int ORDER_ = 6; // order +struct Un { float u1, u2; }; +struct Coefs { float a1, a2, b1, b2; }; + +// 低域通過フィルタ +// 連立チェビシェフ特性 +// 次数 :6 次 +// 標本化周波数: 12.00 kHz +// 遮断周波数 : 0.40 kHz +// 通過域のリップル: 0.50 dB +// 阻止域の減衰量 :40.00 dB +const Coefs ck_[ORDER_/2] = { + { 1.837790E+00f, -8.507293E-01f, -1.603320E+00f, 1.000000E+00f}, // 1段目 + { 1.904445E+00f, -9.382561E-01f, -1.919647E+00f, 1.000000E+00f}, // 2段目 + { 1.942552E+00f, -9.865720E-01f, -1.942961E+00f, 1.000000E+00f}}; // 3段目 +const float g0_ = 1.000028E-02f; // 利得定数 + +const int FS_ = 12000; // Sampling frequency: 12 kHz +ADC_Base adc_(A0, FS_); // for AD +DAC_MCP4922 myDac_(DAC_MCP4922::DAC_A); // for DA + +int main() +{ + ScfClockTim3(500000); // cutoff frequency: 5 kHz + + Un uk[ORDER_/2]; // 過去の計算結果を格納する配列 + // 過去の入力信号が格納される配列をクリア + for (int k=0; k<ORDER_/2; k++) + { + uk[k].u1 = 0; + uk[k].u2 = 0; + } + + while (true) + { + float xn = adc_.Read(); // Read from A0 + //----------------------------------------------- + + float yk = g0_*xn; + for (int k=0; k<ORDER_/2; k++) + { + float un = ck_[k].a1*uk[k].u1 + ck_[k].a2*uk[k].u2 + yk; + yk = un + ck_[k].b1*uk[k].u1 + + ck_[k].b2*uk[k].u2; + // 計算結果の移動 + uk[k].u2 = uk[k].u1; + uk[k].u1 = un; + } + + //----------------------------------------------- + myDac_.Write(yk); // Write to DAC + } +} + +