LJ Device number error


cannonpm

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I am using one LabJack U6, but have plans to add another possibly within a few months. Therefore, I assigned the LJ a unique local ID (I arbitrarily went with 7) in the LJ_ControlPanel.

When I am setting up my channels in the DAQFactory, it asks for the DeviceNumber which is this local ID. If I leave it at the default (0 -- which means the first found LabJack) then all works fine. If I change it to the value of 7, it will intermittently work and not work. About 3/4 of the time I get an error from DAQFactory saying it cannot find Device #7. The other 1/4 of the time it will find it and all is well.

I have tried using D# 6, thinking it is zero-based, but that did not work. If I change it back to 0, then all is fine.

Any idea what may be happening? Thanks.

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I think you need to choose one or the other. Once you use 0, if you want to change it to 7 (or 6 or anything else), you need to make the changes, save the document, then restart. But, as I've said before, DAQFactory basically calls the LabJack UD directly with these parameters so the issue is in the UD, not DAQFactory, so perhaps the LabJack folks will have a comment. The only thing DAQFactory does is make 0 mean first found.

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The number certainly isn't an issue. I believe, however, that once you open a device using first found, you can't then open it again using the direct ID. This creates two connections which conflict with each other. Only by restarting DAQFactory or loading a different document do you close the connection, so if you change from specifying 0 to specifying 7 you have to restart.

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Thank you for the input. Using it, I found out what was causing the problem. When closing DF, I have to wait perhaps 5 seconds or so until the program completely closes out. If I tried to re-open it sooner than that, the old process still had exclusive control over the device at that local ID so the new process could not find it!

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