Re: [c54x] Sampling Rate for c5402 DSK

Started by Jeff Brower February 28, 2003
Jun Hong-

> Thanks for ur reply and advise.
> I am using the CCS library to set the sampling rate, it works well when
> using polling methods, but it seems to be unconsistent in trying to change
> the rate using Interrupt. Ocassionally I manage to set to the rate I want,
> but after re-powered the board again, it set back to default 8000Khz
> sampling rate again. I found it very frustrated.

Right, that sounds very familiar. The asm code we used got us to the point
where it
was 100% the first time, then not quite as good after that, but still much
than CCS. Note that the asm code uses polling to set the AD50 registers, then
switches to interrupt for real-time operation. Before setting a new rate, be
to turn interrupts off, clear the IFR register, write zero to DXR register, etc.
call the asm code again.

Jeff Brower
DSP sw/hw engineer
Signalogic > -----Original Message-----
> From: Jeff Brower [mailto:]
> Sent: Wednesday, February 26, 2003 10:15 PM
> To: Jun Hong
> Cc:
> Subject: Re: [c54x] Sampling Rate for c5402 DSK
> Jun Hong-
> How do you set the sampling rate? Using your own code, or CCS library? We
> found in
> 2001 that using CCS to initialize the AD50 and setting some of its register
> values,
> including sampling rate, was not always consistent, so we used some asm.
> code to do
> it. It's in the C54x archive:
> http://groups.yahoo.com/group/c54x/message/436
> You might try that and see if you can get it to work.
> Jeff Brower
> DSP sw/hw engineer
> Signalogic
> Junhong wrote:
> >
> > Hi,
> >
> > I encounter a problem with the changing the sampling rate of the onboard
> > codec in C5402 DSK board.
> >
> > I try to set the sampling frequency at 16Khz... but when I test it and
> found
> > out that it cut off at 4Khz instead of 8Khz.... I try to change to other
> > sampling rate, but it still seems to be cutoff at 4kHz.
> >
> > Can anyone advise?
> >
> > Regards,
> > Jun Hong