December 26, 2012

Sine wave generating from PIC

Hello friends,

To do sinusoidal modulation you need sine wave which can be compared with high frequency carrier(triangular waves). And i was also about to generate Sine modulation so i needed to do this.


      You can generate by calculating sine values at run time also but that is time consuming and keeps your microcontroller busy with calculations only, so I suggest you to make a look up table  and recall the value at run time from there.

      So here is what I have done its a simple task just have a look at the code,....

///////////////////////////////////////////////////////////
#include "pic .h
#include "htc .h"
#define _XTAL_FREQ 4000000

const unsigned char wave[181] ={128,132,137,141,146,150,155,159,163,168,172,176,180,184,188,192,196,200,203,207,210
,214,217,220,223,226,229,232,234,237,239,241,243,245,247,248,250,251,252,253,254,254,
255,255,255,255,255,255,255,255,254,253,252,251,250,248,247,245,243,241,239,237,234,
232,229,226,223,220,217,214,210,207,203,200,196,192,188,184,180,176,172,168,163,
159,155,150,146,141,137,132,128,124,119,115,110,106,101,97,93,88,84,80,76,72,68,64,
60,56,53,49,46,42,39,36,33,30,27,24,22,19,17,15,13,11,9,8,6,5,4,3,2,1,1,0,0,0,0,0,1
,1,2,3,4,5,6,8,9,11,13,15,17,19,22,24,27,30,33,36,39,42,46,49,53,56,60,64,68,72,76,
80,84,88,93,97,101,106,110,115,119,124,128};

int main(void)
{
TRISD = 0x00;
unsigned char i;

for(i=0;i<181 ;i++) {
PORTD = wave[i];
__delay_us(79);
}

return 0;
}

///////////////////////////////////////////////////////////

 But,here instead of using normal DAC to generate sine wave I have here used R-2R ladder(no specific reason).
Here is the schematic.

R-2R ladder in proteus generating sine wave for sine modulation

Here VSM Timer counter is used to measure the frequency generated by R-2R DAC. 


The output of the circuit is as shown below..

Sine wave and vsm counter in proteus

if you want to make frequency variable just keep a variable in delay and update it by any key..... 


For more Proteus projects  click here.

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