[sdiy] FPGA Synth Music

[Jason Tribbeck]

Hi,

> > I did look at the 3A while designing it, but there was something in the
> > datasheets about its power requirements using two supplies that I was
> > unsure about - however, I can't remember what it was, but I think it was
> > something to do with configuration.
> 
> I'm using an XC3S200AVQ100 on my current project:
> 
> http://members.cox.net/ebrombaugh1/synth/dsPIC_fpga/index.html

I did see that, and was the reason for looking at the 3A. I did spot you'd only used one regulator and wondered how :)

> It's working nicely. One of the advantages is that it's slightly cheaper
> than the 250E I used on the previous project. The configuration issue you
> may be thinking of is that there's a little parameter you need to insert
> into the .UCF file to let the part know that it's being given 3.3V for
> VCCaux. That's just so that the internal references know where to set the
> thresholds on some of the I/O standards. Otherwise it works transparently
> with only two supplies (3.3V & 1.2V).

That was the issue - I wasn't sure what kind of damage would occur if you'd accidentally forgotten that setting ;)

Which knowing my luck I would've done for the first board, and then wondered if it was the schematic, layout or soldering that I'd got wrong somehow because it had caused irreparable damage to the chip, which would've put me off making any more boards. But that's worst case scenario :)

I think I also had my 250Es by then as well - I've still got 3 left, so I'll wait for those to be used and then redesign the board to take a 200A.
-- 
Jason Tribbeck