File content as of revision 0:797a9c10261e:

//--------------------------------------------------------------
// FIR フィルタ，基本的な構造, 固定小数点演算用 DSP 命令を使う
//      Analog Input : A0
//      Analog Output: MCP4922 using SPI
// 2014/10/21, Copyright (c) 2014 MIKAMI, Naoki
//--------------------------------------------------------------

#include "mbed.h"

#include "ADC_Base.hpp"         // for ADC not using interrupt
#include "DAC_MCP4922.hpp"      // for DAC MCP4922
#include "ScfClockTim3.hpp"     // for clock supplied to SCF
#include "Coefficients_200_LPF_Fixed.hpp"

using namespace Mikami;

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

    int16_t xn[ORDER_+1];
    for (int n=0; n<=ORDER_; n++)
        xn[n] = 0;
    
    while (true)
    {
        xn[0] = adc_.Read_u16() - 2047;     // Read from A0
        //-----------------------------------------------

        int32_t yn = hm_[ORDER_]*xn[ORDER_];;
        for (int k=0; k<ORDER_; k+=2)
        {
            uint32_t x = __PKHBT(xn[k], xn[k+1], 16);
            uint32_t h = __PKHBT(hm_[k], hm_[k+1], 16);
            yn = __SMLAD(x, h, yn);     // Dual multiply and accumulate
        }
        for (int k=ORDER_; k>0; k--)
            xn[k] = xn[k-1];        // move input signals

        yn = (yn + 0x8000) >> 16;   // rounding and devide by 32768
        //-----------------------------------------------
        myDac_.Write((uint16_t)(yn + 2047));    // Write to DAC
    }
}