> -----Original Message-----
> From: Roman Black [SMTP:fastvid@EZY.NET.AU]
> Sent: Wednesday, December 20, 2000 3:57 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [PIC]: fast easy DAC with PIC
>
> Hi, I need to implement 2 DAC with one PIC,
> preferably a 16F84, and I need reasonably
> fine resolution, at least 64 levels, pref
> 128.
>
> I have tried the PWM options, but I need more
> speed, like the ability to adjust from full
> to zero output 32,000 times/sec. Using 20MHz
> PIC and home made PWM I can't even come close.
>
> So, any suggestions on getting 2x analogue
> output from a small PIC at high speed??
> :o)
> -Roman
>
Hmm..quite a high bit rate.  If you use (say) an 8 bit SPI DAC, readily
available in dual packages this will work out to 8 x 2 x 32000 = 512kbits/s.
Most SPI DACs will be easily able to handle this.  I wrote a bit bashed SPI
routine in HiTech C and using 20Mhz clock gave around 700Kbits/s.  Even
assuming this could be optimised in ASM, you aren't going to have an awfull
lot of CPU time left for anything else.  If you choose a PIC with an SSP
module you can offload a LOT of cpu time.

A lower resolution DAC woul eas the problem slightly, but I'm not aware of
anything below 8 bits with an SPI interface, maybe someone else does?

A better solution would be you use a straight parallel DAC if you can afford
the pins.

Mike

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.