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Using a USB interface to talk to the UUT

We are using version 7.3.26  of MET/CAL software and we need to talk to the UUT that is on a USB bus, is there a way to communicant with USB? I have seen a few brief discussions, but I would like more information.

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Patrick Butler

Hi Mark this has been in MET/CAL for a while now. Review the help file on the VISA FSC. This will allow you to communicate with USB devices.

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James Smith

Communicating to the UUT via a USB is actually very simple. Using the VISA FSC is primarily what I use now because it works well. You use it in the same way that you would use IEEE or IEEE2 or SCPI. At the beginning of the test it will ask you your communication method. This ONLY works for the UUT. It does not work for the standards. In order to make the standards communicate via USB is another animal. Here is an example of how one would use the VISA FSC. 

 

VISA               SYS:CONF?[I$]

VISA                VSET 50

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Mark Swenson

Thanks for the input I think I am getting closer but not there yet. I have replaced all the "IEEE" with "VISA" in the procedure file. I have added the NI_VISA in the  metcal.ini file, but I get the error at the VISA FSC lines "E1701: FSC VISA: Incorrect special construction or message to long".

 

James had made the comment "At the beginning of the test it will ask you your communication method", can you explain this a little more?

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Krista E.

If VISA recognizes the device it will give you a dropdown of connected devices and you should be able to choose.

Your message may be becasue you replaced the IEEE FSC with the VISA fsc.  IEEE doesn't require a terminating character - Visa does.

Example using the 8845: 

1.001  VISA         [oterm CRLF]

1.002  VISA         [term LF]

1.003  VISA         *RST

1.004  VISA         syst:rem

1.005  VISA         MEAS:VOLT:DC?[I$]

1.006  DISP         [mem2]

Krista

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Mark Swenson

It is recognizing the interface now. I have a VXI frame that I am communicating to with USB, is there an interface or a suggestion of how to create the interface.

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James Smith

I have always been able to just straight up replace IEEE with VISA. The only time I recall having to use term and oterm is when communicating via RS232. Can you copy and paste the exact statement you are trying to send? I do not know the max number of charaters allowed, but I have gotten the incorrect special construction quiet often. It is usually because I tried to use a function that works in IEEE that does not work in VISA such as 

IEEE                                [S 9]MEAS:VOLT:DC?[I]

IEEE                                [SRQ 9,9]MEAS:VOLT:DC?[I]

IEEE                                [SPL 9]MEAS:VOLT:DC?[I]

IEEE                                [EOI ON]MEAS:VOLT:DC?[I]

of when I try to write a formula or functions and I have something in the incorrect place. However, if it just a straight copy and paste from the IEEE that worked then it is most likely a function that is only avavilable via IEEE. 

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James Smith

Glad that got it working. I'll remember that when I use USB in the future.

I am assuming you mean some for of like a GUI? Other than creating a form a diver file that you can querry the operator for values, I do not have anythign on the ability to create an interface. That is currently beyond my knowledge at this point. If you figure it out, let me know. I would be interested in knowing how.

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Krista E.

Yes, true the example I had was communicating with a unit that has a physical usb connection, but the instrument is using RS232 protocal.

Krista

Glad you are running.

 

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Dale Chaudiere

Is this device really USB?  When you plug it into the PC, does it show up as a Windows Serial (i.e. COM) port?

If so, you need to use the PORT FSC, not the VISA FSC.   The VISA FSC does not support setting baud rate, parity, stop bits, flow control, etc.

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