CCS_Programme 04: Average Power of Sine wave usign Fixed Point Technique in Code Composer Studio

## Average Power of sinusoidal signal using Fixe Point Programming Technique in Code Composer Studio V5



/* programme for calculating average power of a sin waves whose amplitude
 * is A = 0.9 (scaling factor)
 * x[n] = A* sin(2*PI*f0*t)  
 * x[n] = A* sin ((2*PI*f0*nTs))
 * x[n] = A *sin ((2*PI*n)/(fs/f0))
 * f0 is 1000; and sampling frequency fs is 32000
 * fs/f0 = 32
 *
 * for four cycle no of samples are 32*4 = 128;
 *
 * avg power = 1/N [Summation(n=0 to n=N-1){x^2(n)}]; N is no of samples
 */

#include <stdio.h>
#include <math.h>

#define Q15 (unsigned int)32768
#define FS_BY_F0 32
#define PI (float)3.1416
#define SIZE 128
float amp=0.9;
int x[SIZE];
long prod,sum=0;
float avg;

void main()
{
int i;
for (i=0;i<SIZE;i++)
x[i] = (int)(Q15 * amp * sin ((2*PI*i)/FS_BY_F0));

for (i=0;i<SIZE;i++)
{
prod = (long)x[i] * (long)x[i];  //SSI0F30;
prod = prod <<1; //SI0F31
prod = prod >>7; //SI7F24
sum = sum + prod; //SI7F24
}

printf ("before dividing sum is %ld\n",sum);

sum = sum >>7; // dividing by 128 for calculating avg power

// now sum is nearly equal to 1. and just above result is in SI7F24 formate
// converting result in SI0F31 formate

sum = sum <<7;

avg = (float)sum/((unsigned long)Q15<<16);
printf ("average power is %f\n",avg);
}

/*End of Programme*/

**************************************************************
Click on
Project -> build all
then click on  debug
for graph display click on Tool ->Graph->single time

select Acquisition buffer 128
DSP Data type 16 bit signed integer
Start Address:      x
Then finally Click on OK

A Sinusoidal graph with four cycle will display.