Making an Analog monitor remember screen geometry. Possible project?

[ssndk]

I have a Hantarex 25" arcade monitor.. it's very nice.. of course, it's not digital, and even though I don't have many personal problems with my geometry being slightly off at some resolutions, it would be nice if it would remember the resolution and set the correct (saved) geometry.

Now, since changing the geometry on my Hantarex involves just turning some potentiometers (changing the resistance on some input points). I have been wondering... Wouldn't it be possible to make a simple digital circuit that would detect the sync frequencies, and digitally adjust the resistance using for example a AD5271 or similar? Then program a microcontroller to handle the processing.

So, detect H-sync, V-sync frequency..and then change resistance according to saved values in an EPROM..

I can't really see any problems with it... and it's seems like a fairly simple circuit. Does anyone here that understands monitors see any problems with this?

[MonMotha]

It sounds overly complicated and failure prone.  Most of those "digital potentiometers" aren't exactly designed to handle the currents or especially voltages seen by monitor remote boards.  Many are actually buffered DACs with reference trickery, though some are in fact resistor strings with FET switches to select wiper position.  Neither design can replace a pot in many of the applications seen on a monitor remote board.

It also won't 100% solve your problems if you just measure sync frequencies.  Many games run at roughly similar timings (similar enough that distinguishing them individually by measurement is difficult) but have differing porches and as such need different geometry settings.  If you're using emulation, it may be more effective to just output settings via e.g. a serial port to tweak things up.

[ssndk]

It also won't 100% solve your problems if you just measure sync frequencies.  Many games run at roughly similar timings (similar enough that distinguishing them individually by measurement is difficult) but have differing porches and as such need different geometry settings.  If you're using emulation, it may be more effective to just output settings via e.g. a serial port to tweak things up.

But that would require editing the source code of MAME to send out the info every time a new game is started.. and It would still require a microcontroller and some form of digital adjustable resistance.. I know that digital potentiometers for higher voltages exists..

Hmm if the timings are really hard to obtain, it would be a problem.. or maybe it just needs higher precision measurements?

Then again.. if it was that simple, they would probably have included it in their monitors to begin with..

[Kevin Mullins]

But that would require editing the source code of MAME to send out the info every time a new game is started..

Can't you already do that with MAME ?
It has it's default settings per game, but you can change it on a per game basis and have it remember those particular settings.

Or am I just misuderstanding something here?
(I don't MAME much)

[Ummon]

Advancemame does this to some extent, and Sailor Sat was (is still?) working on an app that worked with in conjunction with Powerstrip that allowed real-time adjustment of positions and breadth (this latter not working currently).