Converting a 150MHz 48bit bus to 300MHz 24bit bus - Page 1
Forum section: electronics / projects

author: Pentium100
author_rank: Frequent Contributor
timestamp: November 20, 2016, 08:03:04 pm
content: Hello,What would be the easiest way to take 3.3V 48bit 150MHz output and convert it to 24bit 300MHz? Essentially, I want to connect ADV7125 (a 3x8bit DAC that works at up to 300MHz) to the output of ADV7619 (HDMI receiver - at high frequencies it outputs two pixels at once, but the DAC expects one pixel at a time).Standard CMOS chips (74hc...) are too slow (and as far as I know, ECL works at different voltage levels), so, what would be the easiest way to accomplish this?

author: bktemp
author_rank: Super Contributor
timestamp: November 20, 2016, 08:46:34 pm
content: Quote from: blueskull on November 20, 2016, 08:10:44 pmThose dedicated chips are fine if you can get all the necessary datasheets and programming guides. Using official distributors this is impossible, because they aren't interested unless you buy the parts in large volumes. The only way to get the necessary information are leaked documents.Converting from 48bit to 24bit at those datarates isn't easy. Maybe a small FPGA (like Lattice MachXO2) could do the job.

author: Pentium100
author_rank: Frequent Contributor
timestamp: November 20, 2016, 08:58:13 pm
content: Quote from: blueskull on November 20, 2016, 08:10:44 pmI have not found a converter (yet) that can do 1920x1200@85Hz, that results in pixel clock about 270MHz. If I could just buy one (or a single chip that can do this) then it would be great, but I guess the lack of market for high frequency converters made it unprofitable to make one that can work at higher resolutions/refresh rates than 1080p60.Also, HDMI is not a set requirement, the input could be DVI or DisplayPort.So far, I could only find those chips that seem to be suitable for my goal, just that they do not talk to each other.

author: Pentium100
author_rank: Frequent Contributor
timestamp: November 21, 2016, 04:50:43 am
content: Quote from: blueskull on November 20, 2016, 09:55:50 pmI need 1200p85 though (at least p80). As for the input (DVI/HDMI/DP), I can use whichever is the easiest to use. Though if GPUs cannot produce 1200p85 on a digital output, that would be a problem. Is there an easier way to test this than buying ADV7619 and connecting it to the HDMI output (just to see if the video card can work at these settings).

author: Pentium100
author_rank: Frequent Contributor
timestamp: November 21, 2016, 05:08:24 am
content: I currently use gtx780, but I am thinking about building this adapter so that I could use a video card that does not have analog output (say, GTX1080).As I understand, only DP, newer versions of HDMI and dual link DVI can support 1200p85, that of course does not mean that the video card must support this video mode.

author: Pentium100
author_rank: Frequent Contributor
timestamp: November 21, 2016, 05:39:26 am
content: So, I guess using the ADV7619 is OK for this (I couldn't find a better chip for this yet, using multiple chips for dual link DVI seems more difficult than this and still results in two pixels at a time). That leaves the original question - how do I convert its output to a format ADV7125 can understand? For low frequencies I guess I could use a bunch of 74 series logic chips (and a PLL for doubling the clock frequency). But I somehow doubt that there are ones that work at 300MHz...

author: hamster_nz
author_rank: Super Contributor
timestamp: November 21, 2016, 08:20:08 am
content: Quote from: Pentium100 on November 20, 2016, 08:03:04 pmFPGA - and that would be a 'hard' sort of easy.

author: Fungus
author_rank: Super Contributor
timestamp: November 21, 2016, 09:29:33 am
content: Quote from: Pentium100 on November 20, 2016, 08:03:04 pmYep, and people don't normally use boards full of 74HC chips any more, because...Quote from: hamster_nz on November 21, 2016, 08:20:08 am...they have FPGAs for that.

author: Pentium100
author_rank: Frequent Contributor
timestamp: November 21, 2016, 03:33:17 pm
content: Quote from: Fungus on November 21, 2016, 09:29:33 amBoard full of 74 series chips would probably be easier. Anyway, now I'll have to learn to program an FPGA, but learning a new skill is always good.

author: Scrts
author_rank: Frequent Contributor
timestamp: November 21, 2016, 04:14:23 pm
content: Quote from: Pentium100 on November 21, 2016, 03:33:17 pmIt seems like you will have to spare about one year to learn how to do it. Is it worth doing rather than updating the equipment? The price of development, PCB, BoM, etc...

author: Pentium100
author_rank: Frequent Contributor
timestamp: November 23, 2016, 05:30:58 am
content: So, I guess I'll go learn how to program an FPGA (well, even if I fail with this converter, at least I'll have learned something).Can anyone suggest me which FPGA I should use (at least the manufacturer)?Also, which software should I use for making the PCB? In the past, I used SprintLayout to make single sided PCB drawings that I would then etch myself, however, this will need a PCB made by a factory (as I understand, there are some PCB manufacturers that make inexpensive PCBs in low quantities), so I assume the saved files will need to be in a certain format that the manufacturer can use.

author: Pentium100
author_rank: Frequent Contributor
timestamp: November 23, 2016, 06:13:01 am
content: Thank you.By the way, is there any way to make some kind of socket for a QFP chip? That is, I really doubt that my first attempt is going to successful and I would like to reuse the chips in another board. Is there a way to make some kind of "module" from the chip that I could solder and desolder without destroying the chip? I mean something that can work with 300MHz signals. This would allow me to make a test device without the FPGA, just take half of the bus, so I only get every other pixel on the output, but it would allow me to see if this thing even works, for example, if the video card is capable of such output and so on. Then if it works, I insert the FPGA in the middle and make that work.

author: hamster_nz
author_rank: Super Contributor
timestamp: November 23, 2016, 06:32:50 am
content: I have played a bit with EDID. Dont forget that you will need to fiddle with that too...

author: Pentium100
author_rank: Frequent Contributor
timestamp: November 23, 2016, 07:00:10 am
content: Quote from: hamster_nz on November 23, 2016, 06:32:50 amHopefully I'll be able to pull it out of my monitor or create something that says "everything supported" and just set the video mode manually. At least manual setting works for VGA (as the KVM switch I use does not pass EDID info).

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 23, 2016, 08:42:35 am
content: Quote from: Pentium100 on November 23, 2016, 06:13:01 amIt's not hard to desolder QFPs using hot air (less so if you don't care about damaging the PCB) - if you're doing high frequency stuff, the last thing you want is a socket

author: Pentium100
author_rank: Frequent Contributor
timestamp: November 23, 2016, 08:49:54 am
content: Quote from: mikeselectricstuff on November 23, 2016, 08:42:35 amMy success rate with hot air desoldering is not that great. I was thinking whether it would be possible to make a module like the one in my attachment and make it work with 300MHz. If not, then I'll just try to get it right in as few attempts as possible.

author: Scrts
author_rank: Frequent Contributor
timestamp: November 23, 2016, 02:16:39 pm
content: Quote from: blueskull on November 23, 2016, 06:21:01 amTQFP packages usually have slower IO characteristics compared to BGA. However I've done 270MHz on Cyclone II without any issues. Need to put proper constraints though.In terms of development, I'd suggest using development kits then. You can get Cyclone V development kit with HDMI output:http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=167&No=830Then you need to buy an evaluation kit with VGA input. I did not find any VGA input capable daughter cards with HSMC connector, so it has to come from somewhere else.

author: Pentium100
author_rank: Frequent Contributor
timestamp: November 23, 2016, 04:53:55 pm
content: Quote from: Scrts on November 23, 2016, 02:16:39 pmI want HDMI in, VGA out.Anyway, how about a PCI-e connector? That should work at these frequencies, right?Hmm, I think that to me this may be a good project - even if it fails, I'll learn a lot of new stuff that may be useful later.

author: Scrts
author_rank: Frequent Contributor
timestamp: November 23, 2016, 05:54:52 pm
content: Then here you go:Development kit with full range VGA output:http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=167&No=836plushttp://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=68&No=582orhttp://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=68&No=359You can also search for similar boards from other suppliers. Also check this forum sales thread and obviously ebay - some stuff goes cheap there.

author: Pentium100
author_rank: Frequent Contributor
timestamp: November 23, 2016, 09:14:10 pm
content: Thank you, I'll look into those as well.

author: Scrts
author_rank: Frequent Contributor
timestamp: November 27, 2016, 03:38:13 am
content: https://www.amazon.com/techhtv0305m-Gold-plated-Connector-Converter-Hdmi1-3v-1080p/dp/B00KYH6Y9A/ref=gbps_tit_m-5_b061_8699d6f0?smid=ADVT7DDFIN3LQ&pf_rd_p=d570f235-a833-442f-91c1-bc2096fcb061&pf_rd_s=merchandised-search-5&pf_rd_t=101&pf_rd_i=5550342011&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=MEHX8DKHNPHXBSM5ZZ6E

author: Pentium100
author_rank: Frequent Contributor
timestamp: November 27, 2016, 07:16:19 pm
content: Quote from: blueskull on November 27, 2016, 03:44:44 am200MHz pixel clock would not produce 1920x1200@85Hz because of the "invisible" lines/pixels for horizontal and vertical retrace. With those PowerStrip software says that the pixel clock becomes ~273MHz.

author: daveshah
author_rank: Unknown
timestamp: November 27, 2016, 08:33:20 pm
content: Quote from: Pentium100 on November 27, 2016, 07:16:19 pmYou might be able to get away with a lot less blanking, based on the blanking I've used for 1080p FPGA projects you could do 1920x1200x85Hz with a pixel clock of about 233MHz (2200x1245 total)

author: Scrts
author_rank: Frequent Contributor
timestamp: November 28, 2016, 04:26:02 pm
content: I'd say go for 1080p then. The adapter is significantly cheaper than own project. Probably the FPGA itself will cost the same as full adapter.