DSP/BIOS and RTDX Using MATLAB, Visual C++, Visual Basic, and LabVIEW - Digital Signal Processing and Applications with the C6713 and C6416 DSK - page 318

// FIR3LP_RTDX.c FIR-3 Lowpass with different BWs using RTDX-MATLAB
#include "lp600.cof" //coeff file LP @ 600 Hz

#include <rtdx.h>
#include <stdio.h>
#include "target.h"
int yn = 0; //initialize filter's output

short dly[N]; //delay samples

short h[N]; //filter characteristics 1xN

short loop = 0;
short sine_table[32]={0,195,383,556,707,831,924,981,1000,981,924,831,
707,556,383,195,0,-195,-383,-556,-707,-831,-924,-981,
-1000,-981,-924,-831,-707,-556,-383,-195};//sine values
short amplitude = 10;
#define BUFFER_SIZE 256
int buffer[BUFFER_SIZE];
int inputsample, outputsample;
short j = 0;
RTDX_CreateInputChannel(ichan); //create input channel

RTDX_CreateOutputChannel(ochan); //create output channel

void main()
{
short i;
TARGET_INITIALIZE();
RTDX_enableInput(&ichan); //enable RTDX channel

RTDX_enableOutput(&ochan); //enable RTDX channel

for (i=0; i<N; i++)
{

dly[i] = 0; //init buffer

h[i] = hlp600[i]; //start addr of LP600 coeff

}
while(1) //infinite loop

{
inputsample=rand()+amplitude*(sine_table[loop]);//generate input
if (loop < 31) ++loop;
else loop = 0;
dly[0]=inputsample; //FIR filter section

yn = 0; //initialize filter output

if (!RTDX_channelBusy(&ichan)) {
RTDX_readNB(&ichan,&h[0],N*sizeof(short));} //input coeff
for (i = 0; i< N; i++)

yn +=(h[i]*dly[i]); //y(n) += h(LP#,i)*x(n-i)

for (i = N-1; i > 0; i--) //starting @ bottom of buffer

dly[i] = dly[i-1]; //update delays

outputsample = (yn >> 15); //filter output

buffer[j] = outputsample; //store output -> buffer

j++;
if (j==BUFFER_SIZE) {

j = 0;
while (RTDX_writing != NULL) {} //wait rtdx write to complete

RTDX_write( &ochan, &buffer[0], BUFFER_SIZE*sizeof(int) );

}
}
}

FIGURE 9.11. C program that implements FIR filters and runs on the DSK. It illustrates
RTDX with MATLAB.