hi,
  do u have the ADC calibration done on the processor ?
there is a method of calibration and the link to the folder is below
 
http://focus.ti.com/dsp/docs/dspsupporttechdocsc.tsp?sectionId=3&tabId=409&familyId=510
&abstractName=spra989a
   
  the ADC on 2812 needs calibration for it to be more accurate
   
  also if u need more precise operation then u might want to consider external ADC and that
will communicate to the processor through SCI or SPI
   
  increased accuracy might help ur application i guess
   
  bye

tamilselvi palaniappan <t...@gmail.com> wrote:
    Hi,
   
     Thankyou for your prompt reply.
   
      I have done the reference sine wave generation and ADC output using Code composer 'C'
coding. If I compare the ref sine wave and ADC,  I didnt get the proper sine wave output.
Reference sine wave value is starting with 75(instead of zero) and it goes upto 150.(The one
cycle order is 75,150,75,0,75..........). The processor accepts only unipolar operation. So I
have changed bipolar to unipolar operation using the following C coding. 
   
  for(t=0.0,i=0;i<=60;t=t+.00033,i++)
{
sinn[i]=1*sin(2*pi*fr*t); 
 co  1=sinn[i];
 co2  = co1+1.0;      /*to convert from bipolar to unipolar*/
  co2 = co2/2;
  output=co2;
  }
  The above reference sine wave is incrementing wtih regular order (75,77,79,81.......149).
  The error sine wave output is equal to Error = Ref wave - ADC O/P.(ref sine wave is always
greater than the ADC output).
  I have given 2.5V to ADC via transformer. The ADC value is varying between zero and 120. If I
run the ADC means, the value doesnt increment with regular
order.(50,62,45,76,34,438,45,92,61..........). But  I have gotten the sine wave with 50 Hz
using DAC. So I have constructed a Hardware for Zero Crossing Detector(u told me in the
previous mail). But I didnt get output. If I compare the reference sine wave and ADC means, the
correct output will occur only the REF sine wave is greater than the ADC. If the ADC is greater
the REF means, the error sine wave output  is negative. In that negative error  didnt get the
sine wave. I need only sine wave,  because in the internal PWM, this sine wave is compared with
the triangular wave. So please help how to get the sine wave using C coding?. 
   
                                                                                               
           Thanks & Regards
                                                                                               
             Tamilselvi.P

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