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@jaseg @manawyrm The Appnote from AMD mentions the KC705 which is available at work...
I have not found a HDMI-FMC card without drivers, so I guess that I need to make one. FPGA + FMC would be kinda cool since it allows different connectors like USB, SFP, ... with a rather simple and cheap adaptor.
I guess the main issue is finding the time and motivation to build any kind of device.
@azonenberg @jaseg I have never used a BERT. For my common use-case of measuring (or estimating) the signal-integrity/margin of cables, what would be the better approach?
BERT or EOM?
What I want is a measurement that tells me that the how good a given signal chain (cable, perhaps switches, retimers) is. So I can exchange components, measure again and remove/replace bad components.
@manawyrm Yeah, that has been on my todo-list for a few years already. Just not with any priority - also because it seems to be non-trivial. I don't have the equipment to do validation measurements either.
TI has a few chips that can do those EyeOpenMonitor plots. At least for HDMI there are cheaper options with easier packages.
This could also be a 'real' product, I can easily imagine a company spending 1k€ on a device that lets the user judge the quality of HDMI wiring.
@manawyrm Thanks, that is exactly the insight I am looking for.
Crosstalk would kinda be possible to measure with this as well, terminating one pair, and measuring another diffpair.
Thinking more about that, it would probably take hours to make a decent measurement of one cable using the tools I currently have available.
So perhaps I need to make a board with the https://www.ti.com/lit/ds/symlink/ds280df810.pdf or a similar device that has a build in eye-monitor.
@manawyrm Only if I am interested in cross-talk between diff-pairs.
With a 'normal' dual port VNA I could connect each vna-port to one SMA on each end of the HDMI cable.
The circuit is completed with the shield/return.
The other SMA connectors most likely need termination to not influence the measurement.
@manawyrm The grounds on those SMAs are not connected to each other. So one diffpair end up as signal + shield/return on one SMA connector.
The idea is that the VNA effectively measures the whole diff-pair this way. Not sure if that is clever or stupid.
I just figured that I also will need some kind of 50R HDMI-Plug for calibration... hmmm...
The alternative plan is to build a more complicated device with a chip that outputs a Eye-Open-Diagram. But I want something simple now.
HDMI is always a pain to debug, so I am looking into measuring cable performance somehow.
Has anyone build a HDMI to Coax adapter board that I can use together with a VNA? I am thinking of having two of them, one on each side of the HDMI-Cable.
Is this a stupid idea anyway? What are your thoughts?
