Products > Test Equipment

open source GPIB adapter

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pdenisowski:

--- Quote from: dazz1 on April 08, 2024, 08:43:57 am ---Also I suspect the average 1980's/90's engineer would not have paid for the standard and would likely simply connected all of the earths together. 

--- End quote ---

The average engineer working in test and measurement in the 1980s/1990s would either (a) have bought commercial off-the-shelf GPIB adapters and cables and not needed the spec, or (b) would have the spec if they were actually developing GPIB devices.  Ask me how I know :)

That said, I think this is a fantastic project and am very excited to see how it turns out.  Thank you for doing this!

dazz1:
Hi
Given where you work, I would have thought the developers already have breakout boards. :)
Anyway, attached are my drafts. 

Unlike other breakout bds I have seen, my one has a connector that conforms to the HP pseudo standard 40pin Logic Analyser cable. This board will plug directly to my HP scope  that I have, or any HP LA I don't own.  No messing around with probes.

The board will be self documenting.  I am going to add text to the lower silkscreen to show the 40 pin connector signals.  Already done that for the header. 

The header has the same pin-out but exposes the signals and allows for jumpers to be fitted.  Specifically, one use case would be to connect a control signal to the LA CLK.  It also means that someone who does not have a suitable LA type instrument can probe the signals with this board.

I am interested in any feedback to improve the design.

pdenisowski:

--- Quote from: dazz1 on April 08, 2024, 08:49:59 pm ---I am interested in any feedback to improve the design.

--- End quote ---

Frankly, I like it just the way it is - a big improvement over what I've seen so far for GPIB breakout boxes.

dazz1:
Hi
I have polished the design. 
Getting pcb's made and buying parts with MOQ's means I will end up with 5 of these, when I only need one.

Kean:
I believe the intent was that pin 12 should be connected to the cable shield (chassis ground) and not to logic ground.
Pin 24 is the primary logic ground, and pins 18-23 are nominally logic ground but are actually specified as paired with the signal on the pin above (6-11).

Practically all devices I've seen connect pins 18-24 together, and only some also include pin 12 connecting the this common ground.
As an example, schematics of Keithley 199 have pin 12 connecting to chassis, and there is a 1M resistor and 10n capacitor between chassis and logic ground (with optional jumper).

I doubt any of this will make much difference except with very long cables and multiple instruments.

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