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Thread: GPIB Controllers and the LabMaster Ultima

  1. #1
    Join Date
    May 2009
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    Default GPIB Controllers and the LabMaster Ultima

    Ok guys, this is a long shot but...

    Background:
    I have a coherent LabMaster Ultima power meter, but it doesn't have the GPIB option.
    (I will save you the rant on why you only get GPIB when you buy the dual channel model, but the even more expensive modemaster model is stuck with serial...). I greatly prefer GPIB over rs232 for my own reasons, so I want to add the GPIB option to my meter.

    Initial Observations:
    This all started when I noticed that all of the pages to enter an address and otherwise configure the GPIB options are present on my model, and there is a knockout labeled GPIB on the back of the thing--so the only logical step would be to take it apart and see how much hardware is missing.

    The dissection proved to be quite promising, the motherboard seems to have all of the necessary traces for the GPIB option, and has space for 3 chips and a few decoupling caps. (see area in blue, the missing parts to the right are to allow it to be connected directly to a printer--perhaps for another day!)
    Click image for larger version. 

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    Current Progress:
    At this point I am a little stuck, because I don't know what chips are supposed to go there (and there are about a kajillion different 40 pin chips out there). Then I had a bit of a eureka moment, when I remembered that my JD501 (a molectron product, 5-10 years younger than the labmaster, later to be bought by coherent) had a very similar looking trio of chips next to the GPIB connector. Upon closer inspection, they all have the right number of pins (and unsurprisingly, each had a decoupling cap next to it), the 2 smaller chips are SN75160, and the big chip is a IOT7210P. The 75160's are made by TI specifically to interface to the GPIB bus, and the 7210 is an all-in-one GPIB controller chip. Very promising indeed!

    Questions:
    After some googling, it appears that the 7210 is kind of the 8250 (that is, the standard UART for rs232 ports) of GPIB, and there are many different manufactures making variants of the original 7210. It looks like most of them are register/pinout compatible with each other, so I would give myself a 50-50 shot at being able to just move the parts over and praying for the best.

    Do any of you guys have any experience with this type of swap? Or pictures of the motherboard out of a dual channel labmaster by chance?

    Thanks!

  2. #2
    Join Date
    Sep 2006
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    Default

    Even IF you would be able to place the missing parts, don't you think the firmware on this board should be updated after all ?

    ie How much chance do you give yourself that this board actually has an universal firmware ?

  3. #3
    Join Date
    May 2009
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    Default

    I am about 90% sure my firmware supports it, it came with an external rom card that has the modemaster code on it, which has all of the screens for GPIB active.

    I think that so few of these things were sold they didn't bother writing firmware for every possible combination, they just told the board house to not populate the hardware for the options it didn't come with. It seems quite effective for the second input channel, since half the analog board is missing and the other half is packed full of exotic analog chips, but for the gpib/printer I think I just may have the upper hand

  4. #4
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    I know of one example of this practice that proved almost fatal.

    Medtronic, a well known manufacturer of medical equipment makes a defibrillator that can be bought with or without a pacing option. (which enables it to be used as a pacemaker too).
    In physical appearance or in software layout it's totally unrecognizable if the pacing-option is present or not. Causing doctors wasting valuable time wondering why the %$#@!? pacer won't do its job.

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