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DVI - LVDS controller

Started by helix February 20, 2006
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 - http://www.enterpoint.co.uk/moelbryn/raggedstone1.html) to do the conversion. Is this board suitable? Any advice will be greatly appreciated. Regards, Kevin
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

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.

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