On Wed, Aug 30, 2006 at 11:07:29AM -0400, Timothy Miller wrote:
> On 8/30/06, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
>
> > A DDC tool has the interesting property that no modification to either
> > the ASIC or the OGC1 board is necessary to support it. However, there
> > is the question of signal degradation due to transmission line
> > reflections going through two sets of connector-to-board interfaces.
> >
>
> Mostly analog CRTs are the things we're concerned about. For those,
> we have to have a DVI-I to analog adapter. We can have made a custom
> adapter that affects the signal quality the same and splits out the
> DDC signals.
A DVI-to-analog adapter is normally a cable. Good quality ones are
available off the shelf. I haven't seen any that included a board or a box.
However, if you're satisfied that an adapter can be made that splits
off the DDC signals without affecting the video signals, then we can say
that a solution exists in principle. So an outside-the-computer arbitrary
mode setup tool can be made, and _no_ provision for it would have to be
incorporated into either the ASIC or the OGC1. Cool.
Obviously, this would be purely a mode setup tool, and wouldn't have
other uses. I imagine the hardware handshake is complex enough to be most
easily implemented with a microcontroller and on-board firmware. More than
one user interface is possible. Probably the most universal solution would
be to put in both the RS-232 port and the DIP switches; that way only one
board would have to be laid out to satisfy different sorts of users.
It occurs to me that if the tool is built with through-hole DIP ICs and
switches, it can be assembled with ordinary home-shop tools, and sold as a
kit.
One question: can it get its power from the OGC1, if the display
doesn't send any power up the cable?
(All of this assumes that OGC1 and its BIOS actually implement EDID.
Last remarks I saw implied you were leaning that way, but it wasn't final.)
Regarding the SPI tools, I wonder where your thinking has evolved to
since we last threw ideas around?
Does it simplify the ASIC and the board if all devices on the SPI
port are required to emulate the serial EEPROM?
If the EEPROM is big enough, can it supply everything the ASIC needs
to configure itself at power-up?
Can an external EEPROM supply a pre-configured video mode program
along with everything else it stores? (If so, then an intelligent SPI tool
could compute a mode program and impersonate an EEPROM. That shouldn't
require any features to be added to the ASIC, beyond providing a chip select
for an external EEPROM tool.)
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