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VISA control putting devices into remote mode

So, I drop a VISA control on my fp. What I think is happening is when it populates, it is sending an *IDN? command to all the devices in the measurement and automation explorer. The problem with this is, some of the devices are in local mode, but if they detect something coming in over GPIB, they automatically switch to remote. I haven't tested it, but I have replaced the VISA control with a string control whos proper GPIB value is set from an INI file. I'm assuming this will solve the problem.

 

However, is it possible to have the VISA control on the fp and populate without it sending these devices into remote mode?

Message Edited by for(imstuck) on 05-18-2010 11:48 AM
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bumpade bump
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I don't understand what you mean by "So, I drop a VISA control on my fp. What I think is happening is when it populates, it is sending an *IDN? command to all the devices in the measurement and automation explorer".

 

I don't know of any reason why that should happen.  Try running NI-SPY or Portmon before doing this and see if you can capture a *IDN? command going out when it shouldn't be.

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for(imstuck) wrote:

So, I drop a VISA control on my fp. What I think is happening is when it populates, it is sending an *IDN? command to all the devices in the measurement and automation explorer.


The VISA resource control definitely does not send out *IDN? commands when you click on the dropdown button, so that would not be the cause. When you drop down on that control what happens is a bunch of VISA Find Resource calls, which do not initiate a "go to remote" command. What you are describing sounds like some old instruments that misinterpreted controller-level action with being asked to talk.

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Ravens Fan wrote:

I don't understand what you mean by "So, I drop a VISA control on my fp. What I think is happening is when it populates, it is sending an *IDN? command to all the devices in the measurement and automation explorer".

 

I don't know of any reason why that should happen.  Try running NI-SPY or Portmon before doing this and see if you can capture a *IDN? command going out when it shouldn't be.


 

K, I'll do that. I guess what I assumed is when it (VISA ctl) populated its self, it went out and tried to find what instruments were actually there in order to know what to put in the VISA control drop down (i.e. GPIB0::1::INST,GPIB0::2::INST, etc). I assumed it may be doing this with an *IDN? command. I'll run the capture and see what's happening. For some reason when I start my program up, it's clearly sending other devices into remote mode by sending them something over GPIB that I'm not controlling. I know this because if I highlight execution, my code is in the idle state when these devices somehow get switched.

 

Hopefully NI-Spy will show me something.

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smercurio_fc wrote:

The VISA resource control definitely does not send out *IDN? commands when you click on the dropdown button, so that would not be the cause. When you drop down on that control what happens is a bunch of VISA Find Resource calls, which do not initiate a "go to remote" command. What you are describing sounds like some old instruments that misinterpreted controller-level action with being asked to talk.


K, ill look into it more and see. If just using a string control fixes the problem, I'll just use that for now as the connection is going to be read from an ini file  at startup and never need to change anyways.

Message Edited by for(imstuck) on 05-19-2010 08:34 PM
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The VISA control itself does not send out anything.  However, most instrument Initialize drivers have the option to send *IDN and *RST, and the default is True.  So when you run your vi, commands are sent to the instruments.  All GPIB instruments that I have ever worked with will go to remote mode automatically upon receiving GPIB communications.

 

If you are seeing the change to remote mode before running your code and when dropping down the VISA selection box, then it does as smercurio says, it sends out Find Resource calls.  All the instruments see some type of GPIB communications, and they all go to remote mode.  I wish I had a setup to test this theory, but right now I don't.

 

- tbob

Inventor of the WORM Global
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