Hello group,

I have a problem.I work on the MSP430P149.
I convert a sine wave every 120s in a ADC way and I made the opposit 
after with the timerB pwm. The problem is that when the signal reach 
500hz the signal doesn't still clean even if i change the filter.
Can you help me please? 

Which part of the signal isn't clean and in what way? The data read or

the data write? If the data write, you must check to see if your PWM 
period is sufficient to allow this frequency to be reproduced, as well 
as the output filter. If the input side, your only filter should be a 
low pass anti-aliasing filter at 4kHz, but you need this to have a sharp 
cut-off, have you tested the design of your filters?

Al

alim0403 wrote:
> Hello group,
> 
> I have a problem.I work on the MSP430P149.
> I convert a sine wave every 120s in a ADC way and I made the opposit 
> after with the timerB pwm. The problem is that when the signal reach 
> 500hz the signal doesn't still clean even if i change the filter.
> Can you help me please? 
> 
> 
> 
> 
> .
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 

It is the data write which isn't clean. The sampling time is 8Khz and
I think that my pwm period is sufficient ( 40 khz). The filter too. so what can
I do?

Thanks.

  ----- Original Message ----- 
  From: onestone 
  To: msp430@msp4... 
  Sent: Thursday, February 05, 2004 9:23 AM
  Subject: Re: [msp430] sine wave


  Which part of the signal isn't clean and in what way? The data read or 
  the data write? If the data write, you must check to see if your PWM 
  period is sufficient to allow this frequency to be reproduced, as well 
  as the output filter. If the input side, your only filter should be a 
  low pass anti-aliasing filter at 4kHz, but you need this to have a sharp 
  cut-off, have you tested the design of your filters?

  Al

  alim0403 wrote:
  > Hello group,
  > 
  > I have a problem.I work on the MSP430P149.
  > I convert a sine wave every 120s in a ADC way and I made the opposit 
  > after with the timerB pwm. The problem is that when the signal reach 
  > 500hz the signal doesn't still clean even if i change the filter.
  > Can you help me please? 
  > 
  > 
  > 
  > 
  > .
  > 
  >  
  > .