Input and Output with the DSK - Digital Signal Processing and Applications with the C6713 and C6416 DSK - page 52

// Loop_print.c Data acquisition.Loop with data printed to a file

#include "DSK6713_AIC23.h" //codec-DSK support file
Uint32 fs=DSK6713_AIC23_FREQ_8KHZ; //set sampling rate
#include <stdio.h>
#define BUFFER_SIZE 64 //buffer size
int i=0, j=0;
short buffer[BUFFER_SIZE]; //buffer for data
FILE *fptr; //file pointer

interrupt void c_int11() //ISR

{
buffer[i]=((short)input_sample()); //store data in buffer
i++; //increment buffer count

if (i==BUFFER_SIZE - 1) //if buffer full

{
fptr = fopen("sine.dat","w"); //create output data file
for (j=0; j<BUFFER_SIZE; j++)
fprintf(fptr,"%d\n",buffer[j]);//write buffer data to file
fclose(fptr); //close file
i = 0; //initialize buffer count

puts("done"); //finished storing to file

}
output_sample((short)input_sample()); //output data

return; //return from ISR

}

void main()
{
comm_intr(); //init DSK, codec, McBSP
puts("start\n"); //print "start" indicator
while(1);

//infinite loop

}

FIGURE 2.12. Loop program to store I/O data in memory and in a file ( loop_print.c ).

Example 2.6: Loop with Data in a Buffer Printed to a File ( loop_print )

This example extends the preceding loop program so that the acquired input data
are stored in a memory buffer and then printed to a file. Figure 2.12 shows the C
source program loop_print.c (included in the folder loop_print ) that imple-
ments this example. It takes a long time (more than 3000 cycles) to execute the
printf statement in the program (see Example 1.3). This can be reduced to about
30 cycles using DSP/BIOS, introduced in Chapter 9.
After initialization of the DSK, the puts statement prints the word start as an
indicator within the CCS command window; then execution proceeds to the infinite
while loop. Upon each interrupt, execution proceeds to ISR, and a newly acquired
data value is stored in a buffer of size 64.