[sdiy] FPGA versus audio DSP

[Paul Maddox]

Nicholas,

> Although I think the DIY spirit is great with the release of the new 
> Spartan 3e development board, I am somewhat confused on the hype this has 
> created.  This isn't the first FPGA development kit and even though its 
> said to be very well priced its not dramatically cheaper than a last 
> generation board, for example.
>

BUT, it is the FIRST board with ADC/DAC and USB JTAG programmer on board.
previously you had to buy your own programmer or build your own (serial), 
and I don't recall seeing a previous board with ADC and DACs on.

> What are the advantages of using an FPGA for audio rather than a DSP?

Someone's already answered this, but basically, parallelism.

> The next advantage that crosses my mind is cost of the Spartan 3e versus 
> DSP, but as far as I know there are low cost DPSs out there too. 
> Shouldn't DSP cost be falling as quickly (or almost as quickly) as FPGA?
>

It's hard to do maths in VHDL, not impossibly, but hard.
Also big multiply add (like the 56 bit multiply/add units in the motorola 
DSPs) are very very expensive in FPGA 'real estate'.

> Perhaps I just wish I could get in on the fun.  I took a semester of VHDL 
> and work with microcontrollers frequently, but the concept of writing VHDL 
> for audio synthesis sounds overwhelming to me at the moment.  I suppose I 
> feel the same about analog design, but I don't have much engineering 
> experience yet.
>

If you're ok with digital, and VHDL, you should be fine... just remember to 
break things down into their component parts.
Soon you'll see that an oscillator is just an NCO core with a lookup table.. 
a filter is just a delay line and so on..

> I guess the jump from implementing finite state machines, counters, and 
> multipliers to oscillators, filters, and other musically useful things is 
> intimidating for me.
>

you'd be suprised just *HOW* close they really are.
Remember the origin of analogue modulars lies in analogue computers of day 
gone by.

Paul