LVDS Switchable Mapping Device

David Brosnan

There are two ways in which 24 bits are packed in LVDS:

a. The more common way is that the most significant color bits are packed into a 4^th LVDS data pair. This is not compatible with 18 bit color packing.

b. The less common way is that the least significant color bits are packed into the 4^th LVDS data bits. This makes more sense, as then the 18 bit panels are compatible with 24 bits, but I guess this idea came late and it is not common.

Are there any LVDS transmitters that have a select pin that would allow us to switch back and forth between these mappings?

over 14 years ago

0 Elias Villegas M. over 14 years ago

TI__Guru* 76130 points

Hello,

There are currently no device with that functionality.

Regards.

0 David Brosnan over 14 years ago in reply to Elias Villegas M.

TI__Prodigy 725 points

Is there a way to achieve this using discrete components?

0 Elias Villegas M. over 14 years ago in reply to David Brosnan

TI__Guru* 76130 points

Hello David,

The bit assignment from the graphics controller to a LVDS transmitter is fixed and critical.

Trying to switch between configurations wold be more related to the graphics controller and I haven't seen such a design.

However, I will forward this to a LVDS expert to see what he thinks.

You can review the information in the following link.

Regards.

http://www.ti.com/lit/an/slla300/slla300.pdf

0 David Brosnan over 14 years ago in reply to Elias Villegas M.

TI__Prodigy 725 points

please let me know as soon as possible. Thanks!

0 RE over 14 years ago in reply to David Brosnan

TI__Mastermind 20985 points

Hi David,

I also haven't seen an LVDS device that provides a quick switch between the 2 formats. I think your options are:

1. Like Elias's idea, the GPU might have a configurable output, so it'd be a software toggle.
2. Make 2 different PCB designs. I don't know your usage, but if you're just testing in a lab and want to connect up many different LCDs on the fly, then having 1 board for each format would be a simple solution.
3. Find a discrete 24-bit to 48-bit switch (or use multiple switches to add up to that many bits).

Thanks,
RE

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LVDS Switchable Mapping Device