Electronics > Projects, Designs, and Technical Stuff

PXIe instrument in a regular PC

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I started a thread in the RF section because the device I'm interested in is an RF test instrument.

The actual realization more belongs here I believe so I'm posting this for folks who care.

Here's where I'm at right now.
-Electronics is pretty much done.
-I'm trying to figure out if I can get a sheet metal cage going (probably sendcutsend.com)

Depending on my mood I'm certain it's going to work easy-peasy, but on lonely cold nights, while contemplating about the meaning of life and the universe and stuff I'm not sure if
-the PCIe extension cable won't be too long
-there is some sort of software check for the driver to check the chassis parameters (I know there is some on newer models)
-cooling will be adequate or efficient enough (even with modifications to the PC drive cage)

The PXIe standard is free, but it heavily references the CompactPCI Express standard which is not and I didn't feel like paying $750 for it, so I'm trying to piece this together from random internet resources.

The cage sketch around the device on the first picture has the dimensions of a double height 5.25" drive bay. I was thinking getting a refurbished Dell Optiplex for ~$150 to put it in.

something like this ? 


385 pound  i think ?  and yes  darn expensive  for that board ???

Is it only  pcb or cable lanes ???  possible / direct interfacing without dedicated ic's ??    really intrigued  by your project


Yes, totally like that. I haven't seen this one, so I'm glad as it serves a proof for the validity of the electrical concept.
I just want to make mine somewhat better integrated mechanically.

I was struggling with fitting the whole thing into double 5.25" bay and can't find a good solution.

I was looking at PC cases or old refurb PCs that have 3x 5.25" bays, but they are much rarer, and accessibility is a major point here.

Another idea that I might implement is to ditch the direct PCIe cable and use a Mini SAS HD adapter and cable. I'd have to redo layout completely on the board, but it'd fit a lot better and the cables are cheap. Even with the adapter it's below $50, while the 3M PCIe cable I was looking at before cost almost $100.


My only concern is signal integrity. I don't have a good feel for how much margin I have here. The PXIe-5644, that is the target device for me is Gen 1 PCIe and I found some contradicting info on how does it behave when cabled.

You can push PCIe pretty far in terms of signal integrity.

I ran PCIe trough some ribbon cable and a bunch of bodge wiring at one point (Agilent PC based scope with a proprietary pinout), worked perfectly fine.

I also seen some youtuber chain together a bunch of PCIe extenders to see how far it would work. The huge chain ended up something like 2 meters long before it stopped working.

I'm no pci / pcie specialist, but i think you have differential pairs on some signals   ??? it normally would not be a problem ???


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