FPGA Central

Greetings,

I have one of the Digilent spartan-3 starter boards, and have been
browsing this newsgroup for a while. I think I may be ready to design
a small board of my own. I can't seem to find a minimum circuit to get
the chip running. I'm thinking really simple here...no external RAM,
etc. Just a JTAG interface, clock, and reasonable power/ground methods
(decoupling, etc).

Has anyone seen something like this before?

thanks,
the newcomer

jgknowla1 wrote:
> Greetings,
>
> I have one of the Digilent spartan-3 starter boards, and have been
> browsing this newsgroup for a while. I think I may be ready to
design
> a small board of my own. I can't seem to find a minimum circuit to
get
> the chip running. I'm thinking really simple here...no external RAM,
> etc. Just a JTAG interface, clock, and reasonable power/ground
methods
> (decoupling, etc).
>
> Has anyone seen something like this before?
>
> thanks,
> the newcomer

You would think that the simplest approach is to take the schematic
that
comes with the starter / eval boards and start removing the parts you
don't need. That being said, I have never seen an eval board that was
designed with minimizing component count or board space as a goal.
Most
often the design expands to fill the available PC board real-estate.

So in reality a better place to start is with a design for a commercial
product rather than an evaluation board. The problem is getting access
to the schematic for such boards.

The problem with designing a "minimum" board with a programmable
component is that the design will depend on what you expect to put
into the program of the component. In the case of the FPGA this means
power supply current, I/O voltages, and decoupling in addition to other
components. You could make some estimates for maximum requirements
based on the I/O pin count, the I/O standards, and frequencies you
intend to use. For Xilinx parts look at the "user guide" rather than
the data sheet for useful information on board design and layout. Also
look at the power estimator to get a handle on power supply
requirements.

Good luck,
Gabor

Gabor,

Thanks for the ideas... I was originally not thinking deep enough and
planning on just getting the chip running, then breaking out the IOs to
headers. Of course that doesn't take into account what IO type I would
then want to use and any possible level converters. I guess that's why
there's a market for demo boards, afterall.

thanks,
Josh

You can define a simple design, like <<press a button, turn on
LED>>

Verilog exampl

module top(led, button)

output led
input button

assign led = button

endmodul

Then, you need to specify a constraint file, telling the P&R wher
what FPGA pins to use for 'button' and for 'led'

This is a very basic

Hi,
The B5-X300 Spartan2E board takes the approach of bringing the the FPGA I/Os
out to headers.
http://www.burched.biz/b5x300.html
Not much else on the board, except power supply, a header programmable
oscillator (1 to 100MHz), one test LED, and one test pushbutton switch. It
is a board that you can build into equipment, rather than just use for demo.
Best regards,

Tony Burch
BurchED, Making FPGA Prototyping Easy, http://www.BurchED.biz
BurchED FPGA boards...
* Largest number of accessible I/O pins.
* Widest selection of expansion modules.
* Fast and economical prototyping of professional designs.
* Ideal for advanced-student projects.

"jgknowla1" <[email protected]> wrote in message
news:[email protected] oups.com...
> Gabor,
>
> Thanks for the ideas... I was originally not thinking deep enough and
> planning on just getting the chip running, then breaking out the IOs to
> headers. Of course that doesn't take into account what IO type I would
> then want to use and any possible level converters. I guess that's why
> there's a market for demo boards, afterall.
>
> thanks,
> Josh
>

jgknowla1 wrote:
> Greetings,
>
> I have one of the Digilent spartan-3 starter boards, and have been
> browsing this newsgroup for a while. I think I may be ready to design
> a small board of my own. I can't seem to find a minimum circuit to get
> the chip running. I'm thinking really simple here...no external RAM,
> etc. Just a JTAG interface, clock, and reasonable power/ground methods
> (decoupling, etc).
>
> Has anyone seen something like this before?
>
> thanks,
> the newcomer
>

http://www.trenz-electronic.de has about as minimal of a board you can
get.. Might be worth looking at for your ideas of where to start