main.cpp

00001 //--------------------------------------------------------------
00002 // Cutoff frequency variable LPF by IIR 8th-order filter
00003 //      A0: Signal to be filtered
00004 //      A2: Value which controls cutoff frequency
00005 //
00006 // 2015/09/11, Copyright (c) 2015 MIKAMI, Naoki
00007 //--------------------------------------------------------------
00008 
00009 #include "ADC_Interrupt.hpp"    // for ADC using interrupt
00010 #include "DAC_MCP4921.hpp"      // for DAC MCP4921, MCP4922
00011 using namespace Mikami;
00012 
00013 #include "BilinearDesignLH.hpp" // for design of IIR filter
00014 #include "IIR_Cascade.hpp"      // for IIR filter of cascade structure
00015 
00016 // ACM1602Ni を使う場合は次の define 文をコメントにすること
00017 #define AQM1602
00018 
00019 #ifdef AQM1602
00020 #include "AQM1602.hpp"
00021 Aqm1602 Lcd_;
00022 #else
00023 #include "ACM1602NI.hpp"
00024 Acm1602Ni Lcd_;
00025 #endif
00026 
00027 const int FS_ = 24000;          // Sampling frequency: 24 kHz
00028 ADC_Intr myAdc_(A0, FS_, A2);
00029 DAC_MCP4921 myDac_;
00030 
00031 const int ORDER_ = 8;
00032 IirCascade<ORDER_> iirLpf_;     // IIR filter object
00033 
00034 DigitalIn sw1_(D2, PullDown);   // 0: disable filter
00035                                 // 1: enable filter
00036 
00037 uint16_t a2_ = 0;   // Inputted data from A2 pin
00038 
00039 // Interrupt service routine for ADC
00040 void AdcIsr()
00041 {   
00042     float xn = myAdc_.Read();   // Read from A0
00043 
00044     myAdc_.Select2ndChannel();  // Select A2   
00045     myAdc_.SoftStart();         // ADC start for A2 input
00046 
00047     // Execute IIR filter
00048     float yn = iirLpf_.Execute(xn);
00049 
00050     if (sw1_ == 0) myDac_.Write(xn);    // Using no filter
00051     else           myDac_.Write(yn);    // Using filter
00052 
00053     // Read value which controls cutoff frequency
00054     a2_ = myAdc_.ReadWait_u16();
00055 
00056     myAdc_.Select1stChannel();      // Select A0
00057     myAdc_.ClearPending_EnableIRQ();// Clear pending interrupt
00058                                     // and enable ADC_IRQn
00059 }
00060 
00061 int main()
00062 {
00063     myDac_.ScfClockTim3(1000000);   // cutoff frequency: 10 kHz
00064 
00065     BilinearDesign lpfDsgn(ORDER_, FS_, BilinearDesign::LPF);
00066 
00067     myAdc_.SetIntrVec(AdcIsr);  // Assign ISR for ADC interrupt
00068 
00069     float fc1 = 0;
00070     while (true)
00071     {
00072         // fc: cutoff frequency, 100 -- 2000 Hz
00073         float fc = 1900.0f*(a2_/4095.6f) + 100.0f;
00074 
00075         if (sw1_ == 0)
00076         {
00077             printf("Through\r\n");
00078             Lcd_.WriteStringXY("Through         ", 0, 0);
00079             wait(0.2f);
00080             Lcd_.ClearLine(0);
00081             fc1 = 0;
00082         }
00083         else
00084         {
00085             if (fabs(fc - fc1) > 10.0f)
00086             {
00087                 printf("fc = %4d\r\n", int(fc+0.5f));
00088                 char str[18];
00089                 sprintf(str, "fc = %4d Hz", int(fc+0.5f));
00090                 Lcd_.WriteStringXY(str, 0, 0);
00091                 fc1 = fc;
00092 
00093                 // Design new coefficients based on new fc
00094                 BilinearDesign::Coefs coefsLpf[ORDER_/2];
00095                 float g0;
00096                 lpfDsgn.Execute(fc, coefsLpf, g0);
00097 
00098                 // Update new coefficients
00099                 Biquad::Coefs coefsIir[ORDER_/2];
00100                 for (int n=0; n<ORDER_/2; n++)
00101                 {
00102                     coefsIir[n].a1 = coefsLpf[n].a1;
00103                     coefsIir[n].a2 = coefsLpf[n].a2;
00104                     coefsIir[n].b1 = coefsLpf[n].b1;
00105                     coefsIir[n].b2 = 1.0f;
00106                 }
00107                 iirLpf_.SetCoefs(g0, coefsIir);
00108             }
00109         }
00110         wait(0.1f);
00111     }
00112 }