DVI - LVDS controller

Feb 20, 2006 3 Replies
H

Hello all,



I am thinking of building a device which will convert DVI output from my graphics card to LVDS to drive my LCD panel. I was originally thinking of using ICs but I wondered if it was possible to do using an fpga?



I have a few general questions regarding using LVDS to drive an lcd panel...



From studying TMDS (DVI signal) and LVDS I have found they are quite

similar. Is it possible to simple translate the 10bits TMDS stream to its 8bit RGB value and then send that out at a slower clock speed over the LVDS interface? If I have this correct, my understanding is DVI works at a much higher frequency than my LCD needs (40MHz). Can i simply 'sample' the DVI signal every 4 clock cycles (if I use the clock/4 from the DVI input), for example? Also the datasheet for my LCD panel indicates it does not specfically have pins for timing information. I have seen chips from National Semiconductors which output LVDS but require vsync and hsync parameters


- I am unsure how this fits into my project - can I not simply send the data to the LCD panel every clock cycle?


Lastly. I am thinking of using a Spartan3 based board (possibly the Raggedstone -

formatting link
to do the conversion. Is this board suitable?


Any advice will be greatly appreciated.


Regards, Kevin

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A

No, you cant use FPGA alone, if you want DVI-LVDS take a TI DVI receiver, chances are that you can connect the display to it almost directly there was an project with free PCB design for this kind of converter but unfortunatly I cant find the link any more.

optionally you may use FPGA *after* the DVI receiver if needed for some reason.

Antti

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H

Thanks for the reply, Antti.

I have seen the TI DVI reciever chip and it seems quite complex. Do you know why this is required? Would it be easier to convert from a VGA signal? I would need ADCs then - I just assumed it would be simpler to convert a signal that's already digital.

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A

no

an Analog VGA to digital is almost even more complex, there is almost only chip available for purchasing (ADI sells only for 20K+ year customer) the available chip is Averlogic AL875, but unfortunatly it is missing internal PLL so you need additionally ICS1523 or similar - I have the Averlogic ADC but not the PLL so cant test it - (I have a pending design inquiry for VGA to usb conversion)

the TI chip is actually pretty simple, the board that I was referring too had pretty much only the TI chip and connectors on the board

Antti

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