Is it possible to spy the GPIB bus ? (Prologix Ethernet adapter) - Page 1
Forum section: electronics / testgear

author: pmx
author_rank: Contributor
timestamp: September 12, 2025, 08:12:09 pm
content: Hi all,Is it possible to spy the GPIB bus using a Prologix Ethernet adapter ?I'm running Linux, but Window is an option if necessary.I control the Prologix Ethernet interface from Python using low level nertwork access - like a telnet console. For some unknown reasons, (?) I can't make PyVisa to work on my machine.I would like to log everything on the bus (data and control lines) possibly with with some timestamps.I know there is a software doing just that, for NI hardware, but I don't have access to any NI hardware.Any ideas ?

author: voltsandjolts
author_rank: Unknown
timestamp: September 12, 2025, 08:26:05 pm
content: Probably best to use sigrok pulseview and an adapter board which connects the well-known fx2lp logic analyser to the gpib bus.Something like@artag's adapter:https://www.eevblog.com/forum/projects/ar488-arduino-based-gpib-adapter/msg4430986/#msg4430986https://oshpark.com/shared_projects/1FVMoqoQhttps://github.com/artgodwin/Sigrok-sniffer

author: KungFuJosh
author_rank: Super Contributor
timestamp: September 12, 2025, 08:33:48 pm
content: Wireshark might be useful for that.ETA: Since you're connecting via ethernet, I assume Wireshark should be simple enough to use. Never tried it for GPIB, but data is data.

author: Cyclotron
author_rank: Unknown
timestamp: September 13, 2025, 02:16:53 am
content: I'm not sure about your requirements. Do you want to attach to the GPIB between a source and instrument, between instruments, or you want to log the commands sent from your computer through the Prologix?If you simply want to log all data from your computer to the Ethernet Prologx telnet session, then using tcpdump would do it since it's clear text over a telnet port.With a bit of regex and finesse, you could log that into syslog. The other option for PC to Prologix logging would be to have Python use a terminal program that supports logging as an intermediate step.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 13, 2025, 02:35:22 am
content: some projects like that ?https://github.com/Tek-User/GPIB-BUS-MONITORhttps://www.qsl.net/yo4hfu/Sigrok_Analyzer.htmlhttps://github.com/Tek-User/GPIB-BUS-MONITORnot sure if keysight i/o librairies with added programs can, but i think there was one app in them who could read in real time ... to be verified

author: abeyer
author_rank: Frequent Contributor
timestamp: September 13, 2025, 11:21:32 pm
content: There were also some special purpose devices for this, if you want to scour fleabay or similar for a deal. eg theIOtech Analyzer488

author: Cyclotron
author_rank: Unknown
timestamp: September 13, 2025, 11:50:17 pm
content: Quote from: abeyer on September 13, 2025, 11:21:32 pmThank you! I was trying to remember this I think. It was in the back of my mind that I had seen something like this somewhere. I swear I also saw an open-source type system to do this but it may not be specific to GPIB.

author: Tony_G
author_rank: Super Contributor
timestamp: September 14, 2025, 12:25:23 am
content: I think you can probably do what you want to with a "plus" version of an NI adapter (eg GPIB-USB-HS+ or PCI-GPIB+ etc) - Might be cheaper than grabbing that Analyzer488 - Though I have to say that it looks cool - Never used it though:You could also use something like the "HP 59401A HP-IB Bus Analyzer" - I have one around here somewhere but I've never actually needed to try and use it...TonyG

author: coromonadalix
author_rank: Super Contributor
timestamp: September 14, 2025, 08:21:02 pm
content: ask "SteveHx" member about his KISS-488 and a rev 2 he madeif it support logging sniifing etc ...https://www.hxengineering.com/

author: SanderMTI
author_rank: Contributor
timestamp: September 14, 2025, 09:29:33 pm
content: Is it possible to use a Prologix to see what goes on with the GPIB bus signals?NO.The Prologix takes very simple bus read and write commands, what it does with the actual GPIB bus is hidden.The Prologix manual lists the command set.If you really do want to look at what goes on with the GPIB bus signals, you need another GPIB interface which has full bus signal monitoring, configure it as a device (not the controller) and have the Prologix as controller talk to it.However, I suspect that pyvisa not working has a reason other than the GPIB bus signals.Sander

author: pmx
author_rank: Contributor
timestamp: September 15, 2025, 06:43:09 pm
content: Hi all, thanks for the many replies !!Yes, I want to "sniff" the GPIB bus, logging every event as transparently as possible.If I understand correctly, the Prologix can't do a "full sniffing" i.e. the "listen only" mode will only pass the data on the GPIB buss verbatim over the Ethernet, not the state of the control lines.It seems that a logic analyzer or the Arduino Nano sniffer are the way to go ?

author: voltsandjolts
author_rank: Unknown
timestamp: September 15, 2025, 07:07:23 pm
content: Quote from: pmx on September 15, 2025, 06:43:09 pmYup.

author: SanderMTI
author_rank: Contributor
timestamp: September 19, 2025, 12:44:39 am
content: In my opinion, the GPIB bus lines will not be the problem.I would concentrate on who or what is talking to the Prologix,what is sent to it and what it replies.Since it's an ethernet connection, this boils down to monitoring the ethernet channel, and someone already suggested how that can be done.Unless there is something wrong with your particular Prologix, it will do the GPIB data transfers by the book.I have never had any bus transfer issues with mine.As for higher level functions, how the Prologix is configured is important.I have found that out the hard way when I was writing the support code for a USB Prologix.The problem seems to be that "pyvisa doesn't work".Without more information, this is about as helpful as I can be.However, I do think it's a big leap to blame the GPIB bus signals for something which sounds like a higher level problem to me.Sander.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 19, 2025, 01:51:35 am
content: python by itself is a pain in the @.... versions do matters in some cases, had lots of problems controlling scopes sig gens etc ... just by pure telnet scpi commandshad to install very specific modules in python, one version is bad the other is okay, python versions too, 32 or 64 bits toohad to take notes and do backupshad the same problems with the usb arduino gpib adapter thread here, the adapter is not the problem, worked very well with R&S visa, Ni Visa, Keysight packages, mostly for DMM'sIt is how you communicate, handle timeouts, machine detection if needed, if you are a master or a slave, a talker or a listener ... the gpib standard is not absolute, it should be loll, you do or may have some quircks between brands / machines, there was some talk here at some point, now easier with lan ports. usb ports .... unless you really really need gpib or have no choiceyou have old hp gear who will listen to gpib, logic analyzer can do, but you will ned to decipher, or have programs to read what's happeningyou have Pyvisa, LXI tools or other(s), and you may need to adress specific issues, nothing is perfect, your prologix may not be suitable, you may need some Keysight or NI Adapters, wich i may doubtWingpib testcontroller or other sw tools with some duino adapters works wonder, and some "duino gpib" interfaces codes and functionalities have evolved way further than the prologix, many issues are or have been adressed by the makers who listen for bugs and provide solutions here on eevblog ?@PMX np pun, but you are still vague on the equipment you want to use etc .... one prologix for one instrument .. a daisy chain of more ?

author: pmx
author_rank: Contributor
timestamp: September 19, 2025, 09:47:50 pm
content: Hello, thanks for the new replies.In fact, the Prologix interface / the Ethernet connection / PyVISA are not part of my current problem.As I said, my goal is to transparently spy (debug...) the exchanges between a R&S VNA and a Powermeter during a self-calibration procedure.The VNA is supposed to become the GPIB Controller during the calibration process and to read the Powermetrer measurements during a frequency sweep.I expected to use the Prologix interface to spy the GPIB bus (data + control lines), but I understand that it is not possible to spy the control this way (only the data stream).

author: Stray Electron
author_rank: Super Contributor
timestamp: September 20, 2025, 02:48:48 am
content: Quote from: abeyer on September 13, 2025, 11:21:32 pmHP made an analyzer that could capture everything going over the bus and I THINK that you could then retransmit the data to other device(s) on a separate HP-IB bus. IIRC you could also set a bit pattern of the front panel switches and it would stop the bus when it found the matching bit pattern. I had one years ago but I never got a chance to play with it much and I don't recall the model number.I also have (somewhere!) another HP-IP analyzer by a different company but it wasn't nearly as powerful. IIRC it wasn't much more than a break out box that gave you access (test points) to all of the different signals being passed around on the bus.I seem to recall that HP also made box that you could attach to the HP-IB bus and then plug the pods from one of their early logic analyzers (HP-1630?) directly into the box and the LA could catch everything on the bus.

author: Kean
author_rank: Unknown
timestamp: September 20, 2025, 11:51:58 am
content: I know of two commonly available GP-IB analyzers- IOtech Analyzer488 (as mentioned above)- Racal Dana 488 GP-IB AnalyzerThese are both usually available on eBay - right now I see a few of the first, and one of the second. User manuals can be found on the usual places like KO4BB.I have one of the Racal Dana units although I have not used it for ages, and it is quite basic in comparison to the IOtech unit. I've bid on some IOtech ones but not yet got one for a price I'm willing to pay.The user manuals give an idea of the difference in capabilities with the IOtech one being nearly 300 pages, vs about 40 pages for the Racal Dana.