--- Bryan Pope <bpope_at_wordstock.com> wrote:
> > I can invent my own - a simple ladder D-to-A to produce a variable
> > voltage out of the parallel port....
>
> What about this: http://www.xess.com/ho03000.html
>
> I can't look at it to verify right now (using Lynx _at_ work and no PDF
> viewer) The one I think you would want is the VGA driver. I believe it
> uses the TTL output of a FPGA to four resistors to output an analog
> signal.
There are a couple of schematics in the pdf - one is a simple 2-bit
scheme with 470 ohm and 1K resistors - 6 bits of color resolution total.
The other schematics just show a digital bus for the colors going off-
page, presumably to a RAMDAC or some such.
Thanks, but not quite. So far, the best candidate is the replica BeBox
load meter circuit - 4-bits each on two bargraphs, but the bargraphs
feed off of a pair of LM3914 comparators. The 4-bit ladder network
there is 1K, 2.2K, 4.7K and 10K - roughly double at each stage.
I do have a Disney Sound Source around here somewhere - it was a similar
device, except it has an RCA jack off the end, for attachment to an
amplifier. Certain games ("Leather Goddesses of Phobos 2" comes to
mind) came with one in the box in case you didn't have a sound card (back
in the i386 days).
-ethan
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Received on Thu Dec 27 2001 - 11:31:07 GMT