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How to get HDMI / DVI / LVDS interface on my FPGA board

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siddharthakala

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Hi,

Can anyone tell me how to add an HDMI / DVI interface to my fpga board? I have Nexys3 and Lattice ECP3 boards. I have tried searching for VHDCI or FMC with HDMI /DVI but couldnt find one. I dont know anything about HDMI /DVI but am really interested in starting on it.

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tmk85

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I am also interested in adding a DVI (and possibly VGA, HDMI) port on my Nexys 3. I am planning to get a VHDCI cable and connect it to a prototyping board so I can connect various input ports created from slashed male cables.

1. Can I connect DVI directly to IO pins? What do I need to read to know how to get this going?

2. Will the signals have sufficient quality for testing up to mid range resolutions? VHDCI cable will be 1m long and then breadboard/goldpin connections will be made.

3. Is it always better to use a transmitter chip? I am not going to be doing much more on the fpga except receive and transmit DVI so I am assuming that it will be cheaper to utilize the fpga. I consider learning the DVI spec an advantage, but maybe I am underestimating how much time it will take me to implement it without a transmitter chip?

4. Are there any breakout boards for DVI or HDMI ports?
 

imbichie

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tmk85

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Thanks for the tip imbichie. The AD9882 as well as TFP 401/410 receivers/transmitters are good candidates. However my questions remain unanswered and my goal is to cut down product costs by omitting additional ICs if possible.
 

imbichie

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Actually the VGA connector from our PC is in Analog form, so we cant directly feed those analog signals in to our FPGA, so we need to convert those analog things in to digital one, which contains the pixel clock, hsync, vsync, blank pulses and RGB data.

I dont know anything about your board, if your board haven't any support for this, otherwise we need to add some IC's like this.
 

joelby

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You don't strictly need an additional transmitter chip - an FPGA with appropriate output voltage levels can drive a monitor directly, though it's possible that you won't meet the interface specifications strictly or be able to drive very long monitor cables.

I don't know much about the ECP3, but the Nexys3's VHDCI port would be a good candidate for building a simple HDMI adaptor. You might want to look at the schematics for the Digilent Atlys, the Nexys3's big brother, or perhaps the Pipisrello for examples of how it can be done.

If you're serious about working with video, I would probably just upgrade to the Atlys. It has two HDMI inputs and two outputs (though they've botched up the serial control interface for them terribly) and it'll probably be cheaper to use one than to spend a lot of time building your own expansion board.
 
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tmk85

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@joelby Thanks for the input, that's exactly what I thought. I totally understand that it would take me months to fully meet the specs and I only want to make (or fail at making) a proof of concept.

I just bought a second hand VHDCI (used in SCSI) cable and plan to make a DVI / HDMI breakout board. Will probably take me a considerable amount of time since I'm new to making my own PCBs.

I'm not as much interested in video manipulation as in creating hardware with a bare minumum of chips. So switching to Altys won't give me much, but it is a good idea to look at the ICs and circuits there. This is also a good board to learn from: **broken link removed**

@imbichie Right, VGA is analog so an Analog to Digital Converter will be required. Since an additional chip is needed anyway, it might as well be a VGA receiver.

I will definitely post a followup about my project, but I anticipate it will take me a few months to get into it.
 

joelby

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If you want a VGA output, this is pretty simple to do with some resistors and a 15 pin connector. VGA input will need an ADC (unless you do some fancy tricks and use LVDS inputs as comparators).

The Bitec card will certainly do what you want, but you don't really need the extra chip unless your FPGA doesn't support the data rates you require for the resolutions you want. VGA and 1280x1024 shouldn't be a problem with a Spartan-6. Check how much external memory the Nexys3 has if you require a frame buffer.
 
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tmk85

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[...] on my Nexys 3 [...]

1. Can I connect DVI directly to IO pins? What do I need to read to know how to get this going?
[...]
4. Are there any breakout boards for DVI or HDMI ports?

Re 1: Yes, see http://hamsterworks.co.nz/mediawiki/index.php/Dvid_test

Re 4: VModMIB has 4 HDMI ports.

DVI and HDMI both use TMDS, so if you don't need analog RGB compatibility you can use either.

I'm currently creating a clone of the Bitec DVI in/out board with TFP401 and TFP410 from ground up and will try to document it more on my blog in the upcoming months. This has been quite an ambitious project for me.
 

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This got so old that I can go ahead and switch to HDMI, because DVI will be obsolete by the time I'm finished with this :>

Chips to use: ADV7511 & ADV7611

Here is a great blog post with information on how those could be implemented: https://hacks.esar.org.uk/hdmi-light/

Anyone interested in collaborating with me to further develop the ambilight project?
 

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