Electronics > RF, Microwave, Ham Radio

NI Vector Signal Transceiver

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--- Quote from: Marsupilami on January 13, 2024, 09:53:43 pm ---
--- Quote from: zrq on January 13, 2024, 09:02:52 pm ---I got a very simple GNURadio source working to some extent, there is no fancy zero-copy design but simply niRFSA_FetchIQSingleRecordComplexI16 and memcpy to GNURadio buffers.

--- End quote ---

This is pretty much where I got stuck too. I started looking at the custom buffer implementations, do do a proper no-double-copy version, but I didn't feel the documentation was solid enough for me to safely understand and be able to implement so I gave up.
I would be nice to have an efficient record and playback app though.

--- End quote ---

I think I found the performance bottleneck, apparently the VST is only using 1x 2.5 GT/s PCIe lane, which in principle should run up to 4x. It probably the signal integrity problem with the homemade adapter board, maybe the soldered pressfit connector? and the longer than necessary (0.8m) SFF-8643 cable make it worse?

The link training happens at power-up time, IIRC.  Maybe it's not getting initialized properly.  Try powering up the VST before the PC is turned on, if you're not already doing that. 

The signal integrity of the connector should be fine.  You have to really screw something up badly to make a differential pair perform poorly at these rates.

Mine is good.
PCI current link width = 4 in device manager

It is possible however if any of the TX or RX of the 3 other lanes fails the enumeration the link reverts to 1x.

Thanks for the help, I wonder if is there is anything can help troubleshooting this, a bit more information on where the link training failed would be nice. Well, a PCIe analyzer is certainly beyond my budget. Tried with another VST device and solder the R4 on the 10Gtek board (didn't do that as it appeared to work without it), but still only learned x1.

-> So I figured it out myself, it's simply because the SFF-8643 connector didn't mate properly with the board, so simply all differential pairs except one are not fully connected.  :palm:


--- Quote from: zrq on January 14, 2024, 12:42:53 pm --- the SFF-8643 connector didn't mate properly

--- End quote ---
It's always something like that :D


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