main.cpp

00001 //------------------------------------------------------------------
00002 // Cutoff frequency variable LPF and HPF by FIR 160th-order filter
00003 //      A0: Signal to be filtered
00004 //      A2: Value which controls cutoff frequency
00005 //
00006 // 2014/12/08, Copyright (c) 2014 MIKAMI, Naoki
00007 //------------------------------------------------------------------
00008 
00009 #include "mbed.h"
00010 
00011 #include "ADC_Interrupt.hpp"    // for ADC using interrupt
00012 #include "DAC_MCP4922.hpp"      // for DAC MCP4922
00013 #include "ACM1602NI.hpp"        // for LCD display
00014 
00015 #include "WindowingDesignLH.hpp" // for design of FIR filter
00016 
00017 using namespace Mikami;
00018 
00019 const int FS_ = 16000;          // Sampling frequency: 16 kHz
00020 ADC_Intr myAdc_(A0, FS_, A1, A2);
00021 DAC_MCP4922 myDac_;
00022 
00023 const int ORDER_ = 160;
00024 float hm_[ORDER_/2+1];
00025 float xn_[ORDER_+1];
00026 
00027 DigitalIn sw1_(D2, PullDown);   // 0: disable filter
00028                                 // 1: enable filter
00029 DigitalIn sw2_(D3, PullDown);   // 0: LPF
00030                                 // 1: HPF
00031 WindowingDesign design_(ORDER_, FS_);
00032 DigitalOut dOut_(D7);
00033 
00034 uint16_t a2_ = 0;   // Inputted data from A2 pin
00035 
00036 // Interrupt service routine for ADC
00037 void AdcIsr()
00038 {   
00039     dOut_.write(1);
00040     xn_[0] = myAdc_.Read();   // Read from A0
00041 
00042     myAdc_.Select3rdChannel();  // Select A2   
00043     myAdc_.SoftStart();         // ADC start for A2 input
00044 
00045     //-----------------------------------------
00046     // Execute FIR filter
00047         float yn = hm_[ORDER_/2]*xn_[ORDER_/2];
00048         for (int k=0; k<ORDER_/2; k++)
00049             yn = yn + hm_[k]*(xn_[k] + xn_[ORDER_-k]);
00050 
00051         for (int k=ORDER_; k>0; k--)
00052             xn_[k] = xn_[k-1];  // move input signals
00053     //-----------------------------------------
00054 
00055     if (sw1_ == 0) myDac_.Write(xn_[0]);    // Using no filter
00056     else           myDac_.Write(yn);        // Using filter
00057 
00058     // Read value which controls cutoff frequency
00059     a2_ = myAdc_.ReadWait_u16();
00060 
00061     myAdc_.Select1stChannel();      // Select A0
00062     myAdc_.ClearPending_EnableIRQ();// Clear pending interrupt
00063                                     // and enable ADC_IRQn
00064     dOut_.write(0);
00065 }
00066 
00067 int main()
00068 {
00069     myDac_.ScfClockTim3(670000);    // cutoff frequency: 6.7 kHz
00070 
00071     Acm1602Ni lcd;  // objetc for display using LCD
00072 
00073     // Clear buffer in FIR filter
00074     for (int n=0; n<=ORDER_; n++)
00075         xn_[n] = 0;
00076     myAdc_.SetIntrVec(AdcIsr);  // Assign ISR for ADC interrupt
00077 
00078     float fc1 = 0;
00079     WindowingDesign::Type pb = WindowingDesign::LPF;
00080     while (true)
00081     {
00082         // fc: cutoff frequency, 100 -- 2000 Hz
00083         float fc = 1900.0f*(a2_/4095.6f) + 100.0f;
00084 
00085         if (sw1_ == 0)
00086         {
00087             printf("Through\r\n");
00088             lcd.ClearLine(1);
00089             lcd.WriteStringXY("Through         ", 0, 0);
00090             wait(0.2f);
00091             lcd.ClearLine(0);           
00092             fc1 = 0;
00093         }
00094         else
00095         {
00096             if (fabs(fc - fc1) > 10.0f)
00097             {
00098                 printf("fc = %4d\r\n", int(fc+0.5f));
00099                 char str[18];
00100                 sprintf(str, "fc = %4d Hz", int(fc+0.5f));
00101                 lcd.WriteStringXY(str, 0, 0);
00102                 if (sw2_ == 0)
00103                 {
00104                     pb = WindowingDesign::LPF;
00105                     printf("LPF\r\n");
00106                     lcd.WriteStringXY("LPF", 0, 1);
00107                 }
00108                 else
00109                 {
00110                     pb = WindowingDesign::HPF;
00111                     printf("HPF\r\n");
00112                     lcd.WriteStringXY("HPF", 0, 1);
00113                 }
00114                 fc1 = fc;
00115 
00116                 // Design new coefficients based on new fc
00117                 design_.Design(ORDER_, pb, fc1, hm_);
00118             }
00119         }
00120         wait(0.1f);
00121     }
00122 }
00123