FPGA Central

I've been tossing the idea around of trying to design a device to
generate music and sound effects electronically. In particular, I want
to be able to unplug the sound chip from an old home computer, and
plug in a small board that would upgrade it from the beeps and buzzes
that was all it was capable of, into something a bit snazzier.

Now, I've got a good handle on most of it, I've got an fpga picked out
to clone the old chip with for backwards compatibility, and a friend
has even cooked up a scheme where we can pass enough data back and
forth to the new board that we'd be able to do something with.

We're figuring that we'll put a significant amount of ram on the
thing, up to a few megs perhaps, but at least half a meg. Probably at
least 8-16 megs worth of flash just for some samples... both musical
instruments and sound effects, whatever we can find or make. We just
need a DSP beefy enough, to be able to mix a few (4, 8, several dozen?
Haven't decided.) voices and output to several channels (probably
stereo, but the idea of 5.1 is intriguing).

I've been doing some research already, and I have a basic
understanding of the algorithms to do things like change the pitch and
volume of a sample, or to mix two together, or to a lesser extent even
to add echoes. Learning a new assembly language won't be a stretch for
me.

But I'm nowhere near being able to pick out a DSP for this project.
Can someone give me some advice and suggestions? We need something
fairly cheap, say under $35 in small quantity, ideally under $20.
Jameco sells three TI DSPs (all fixed point) for under $20, but it's
unclear what they're targeted at or whether they are suitable for my
task.

Other than that, I don't have many constraints... if it can handle 6
simultaneous voices or 72, either is cool. We probably want to be able
to do 16bit samples, but it doesn't seem that any choice will limit
that. So, what should I be looking at?

Thanks in advance,
John O.

John Oyler wrote:
> I've been tossing the idea around of trying to design a device to
> generate music and sound effects electronically. In particular, I want
> to be able to unplug the sound chip from an old home computer, and
> plug in a small board that would upgrade it from the beeps and buzzes
> that was all it was capable of, into something a bit snazzier.

If you're using this in a PC, why are you building hardware? Why not
just do the DSP in software on the main CPU through an ordinary sound
card, or the built-in sound interface? Modern PCs are very capable DSP
engines, and nearly all of them (starting with the Pentium MMX) have
vector instruction sets designed to speed up DSP operations.

On Jul 15, 4:20 am, Phil Karn <pk...@speakeasy.net> wrote:
> John Oyler wrote:
> > I've been tossing the idea around of trying to design a device to
> > generate music and sound effects electronically. In particular, I want
> > to be able to unplug the sound chip from an old home computer, and
> > plug in a small board that would upgrade it from the beeps and buzzes
> > that was all it was capable of, into something a bit snazzier.
>
> If you're using this in a PC, why are you building hardware? Why not
> just do the DSP in software on the main CPU through an ordinary sound
> card, or the built-in sound interface? Modern PCs are very capable DSP
> engines, and nearly all of them (starting with the Pentium MMX) have
> vector instruction sets designed to speed up DSP operations.

Because it has an 8bit cpu? Running at 1.79mhz? I did say "old home
computer", as in something straight out of the early 1980s.

It has a socketed chip that does all the sound, and plugging a board
into that socket should work as an upgrade, once I do some voltage
translation.

I've got alot figured out, except which dsp to use.

Thanks,
John O.