Using on board LVDS LCD interface to transmit data.

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- d.kuppens
  
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posted
18 years ago

Fri, Mar 3, 2006 10:17 AM

Hi,

I was thinking, some embedded motherboards have an on board LVDS LCD interface. Could I use this to transmit other data than video data? I did a little investigation into this. Seems to me I need to write a custom video driver, and connect the other end of the LVDS to a fpga for which I need to write custom firmware for. The thing that worries me is that I think that the LVDS driver keeps generatating data even when the video memory is not changed. So the problem would be how to synchronize the data? Am I right that I can change the datarate by changing the vertical and horizontal frequency? Has anyone done this before?

Greetz Dennis.

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- Mike Harrison
  
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posted
18 years ago

Fri, Mar 3, 2006 7:58 PM

This ought to work - fill frame buffer with data, wait for frame-sync, fill next buffer etc. I think most modern graphics chips have enough memory to double-buffer the data. Maybe you could use some 'magic colour' values as data start/end/change markers.

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- cs_posting
  
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posted
18 years ago

Fri, Mar 3, 2006 10:01 PM

next buffer etc.

data.

markers.

How about taking a hint from network protocols like TCP and packetizing the data to fit in a frame, with a little header that gives the sequence number of the first byte of data in the packet and the total packet size. The receiver then knows how many bytes to keep, or if the entire packet is a repeate that should be ignored. Since the header is always in a fixed location at the start of the frame buffer ie, sometime after some sync signal), you don't have to rule out any particular data bytes as reserved.

No acknowledgement of course, but you should be able to verify that your data got transmitted at least once just by the timing.