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Digitizing VGA? (take 2)
urgent asks: "In March of 2002, Ask Slashdot ran this article, wherein advice on 'hardware to digitize the VGA output of a PC' was sought. Most of the responses seemed to assume that remote administration of PC's/servers was the end goal. If you've got control of the software and/or hardware, it's pretty clear there are easier solutions for that. On the other had, there are many legacy and embedded systems where it would be nice to monitor and record display output. For instance, integrating old computerized factory equipment into a SCADA system, or recording old embedded maritime and medical displays (hint: jobs). My dream hardware would be a dongle that connected to a VGA out and could be polled over ethernet or CAN."
There's a plenty of VGA to IP boxes out there:
Heres one: It's bacially a 8-port KVM stwith with a built in computer thar does VNC. infor
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By "legacy and embedded systems" you mean, broadcast-flag enabled HDTV devices?
So really you MUST have compression unless you want to kill the network (and that's assuming you have gigabit) so a simple dongle is out of the question. You are left with KVMs that do this for you (mentioned in another post) and running video over cat5e (not ethernet, it uses the cable) which is also in another post. A simple dongle isn't feasable to run VGA over an Ethernet network.
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So if such hardware exists (and it could certainly be made), this is yet another obstacle to a "secure" PC. Do other standards for connecting displays have Macrovision-style restrictions? Would Palladium hardware obselete all those monitors?
Just attach an LCD display and put it on a flatbed scanner...
But seriously, don't LCD's have a built-in ADC? Some time ago I read somewhere that LCD's with analog connectors ought to be more expensive than LCD's with digital connectors (instead of vice-versa) because they need an ADC. OTOH I think the site where I read that was slashdot; I'm not responsbile for any inaccuracies in this post.
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They have some ISA and PCI -> Serial cards aviable that lets you serial port what would normally be on the screen (text only).
Depending on the legacy system this might be workable.
These are good for extending the output of the devices, but in the end, all you end up is the same monitor connected to a really long cable.
Remember... CAT5 DOES NOT IMPLY TCP/IP. I cannot emphasize this enough. If you plug one of these extenders into a switch, you will probably destroy both the switch and extender. They use cat5 simply because it is cheap and universally availible.
-- If you try to fail and succeed, which have you done? - Uli's moose
I'd think polling the screen for changes and providing a way to push keys would be about all the code you'd need on that level. If you want remote access over a network, you'd need to use the EEPROM for what it was meant for as well - to boot off a network - and add a bit of custom code to turn over control to a network host. That'd be a task, but not too bad.
Otherwise, it'd be a simple project to create a basic TTY interface to an RS232 port or somesuch within that space that would allow you to do BIOS manipulations - the bootstrap code off your cards gets run before you can enter the BIOS setup.
A long, long time ago I wrote a bootstrap program to do port-level I/O with IDE drives and burned it onto an EEPROM, stuck it in my 3C905 (or was it 3C509?). I used it to autodetect IDE drives on machines with BIOS's that didn't support autodetection. Worked like a charm.
This was back in the day of 386's, but I've noticed most network cards I buy still have that empty socket.... I suspect if you put something at a 0x2000 boundary with a valid bootstrap sig and checksum, it'd get run in pretty much the same manner.
I write code.
This link is their technical issues section (no longer on the site) .. it doesn't particularly apply to what this guy is asking though since they are primarily concerned with a conversion of VGA to NTSC -- a much different problem.
LCD monitors do this. There are KVMs that do this. Don't forget that two of those signals are simply trigers and not data that must be captured. The other two break very nicley into 3 8 bit streams. They run at about 300Kbytes per frame or 18000Kbytes per second at VGA uncompressed 60hz. Using a microcontroler this data can be piped directly into an mpeg encoder chip like the one Tivo uses form IBM which could compress that down to a manageable size with little effort. The stream should be able to be distributed with relative ease using a microcontroler with a built in ethernet controler like the tini from dallas. The end result would be a very small device that was relativly inexpensive that did the job he was looking for while being very dongle like. It would also have the ability to distribute it via a controler area network if need be.