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From: Martin Brown <'''newspam'''@nonad.co.uk>
Newsgroups: sci.electronics.design
Subject: Re: GPIB bus topology
Date: Thu, 2 May 2024 12:09:03 +0100
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On 01/05/2024 22:54, bitrex wrote:
> I have several pieces of HP gear (DMM, counter, Agilent-branded 
> triple-output supply) I'd like to connect to a National Instruments USB 
> to GPIB adapter for some measurements.
> 
> IEEE 488 is somewhat before my time and I see that the connectors are 
> stackable, is there a preferred bus topology for a few pieces of gear? 
> Star, linear/daisy chain with the stack on the interface, linear/daisy 
> chain with the stack on the first piece of gear? Does it matter much in 
> this use case?

IEEE488 is surprisingly tolerant of abuse and unless you have very fast 
(for the day) transient recorders you won't be pushing the speed limits. 
The whole thing is good for about 1MHz flat out if your drivers are up 
to it. Most DVM and test kit is pretty slow but fast enough to be handy.

At 1MHz topology hardly matters but mechanical considerations do! We 
used to use custom IEEE488 cables much longer than the approved length 
on big kit with only a minor slowing down (that was on the HP chipset). 
ie. One longish 5m cable and a few 1m/2m ones at the far end.

Just beware of stacking them more than 3 deep or the stress on the 
connector can pull the board out of the PC. Also beware of metal 
turnings or be sure to have plastic caps on all the stackable backs.

-- 
Martin Brown