LCD controller emulation?

**Casper** · 08-14-2002, 07:07 AM

Hi, I dont know if this has been suggested before, but I was sat thinking about how i was going to make my LCD screen interface with my computer. Composite? VGA controller cards.... various options came up and were all above my head in terms of technical aspects, I understand the basic components of an LCD system. But then I came round to thinking that I have seen (somewhere...) a VGA to composite adapter that plugs directly into the USB port. Would'nt this suggest that it is possible to take the video information created by the graphics card and route it through another port? If this is the case is it not possible to generate a sort of graphics "codec" to process this information before it is output through say a spare parallel port on the PC as an LCD signal.

Another possibility is that one could dircetly "loop" the VGA port to a PARALLEL port and then have a program process these signals, and output an equivalent LCD signal through the SERIAL port.

I am aware that this would create some latency between the signals, however so does the idea of takeing $200 out of my pocket for an LCD controller!! And im certain that if the latency was reduced to a bare minimum, it would produce a very useful firect output solution for touchscreen LCD's.

Dave.

**phil.45** · 08-14-2002, 07:21 AM

No, AFAIK they are just another "fake" USB product trying to cash in on the USB craze at the moment, like those USB desktop personal fans. They do not take the signal from USB, only power. The actual VGA signal comes from your standard VGA port via a cable between the video card and the converter unit.

See this one, about halfway down the page it says "powered from EITHER USB or adaptor", and "15pin PCMCIA connector for connecting to VGA".

**Casper** · 08-14-2002, 07:28 AM

ah i see... not to worry then, but im still confident it is possible to input the graphics information in a way (possibly even take a signal from the back of the VGA socket and input the signal via PCI) and allow the computer to interpret this signal, then output a suitable signal to directly connect the LCD to a port. However I have very limited knowledge of I/O programming and thats why I posted here, because I wanted to share my suggestion. Its basically what a computer is for, processing input data, and outputting the results FAST. Why buy an expensive emulator when you can use the hardware you already have?

**phil.45** · 08-14-2002, 07:35 AM

Originally posted by Casper
processing input data, and outputting the results FAST.

I fear this will be the downfall. If theres one thing the parallel port isnt, its fast. I dont think there any way you could output enough data for an LCD display through the parallel port. At 640x480 60hz 16 colours youd have to send roughly 73728000 bits every second.

**Casper** · 08-14-2002, 07:43 AM

ok... USB or Fireware then? PCI? it must be possible (or I wont be getting a tft

)... I was just wondering if the potential was there for the computer to process the VGA information.

**phil.45** · 08-14-2002, 07:47 AM

If you cant afford the controller then get a composite/svideo TFT instead. If any of this was even possible at resonable cost(ie cheaper than controller boards) everyone here would be doing it.