The problem executing reset of serial device by NI-VISA

[CatherineKostrova]

Hello,

we have a problem executing reset of serial device by NI-VISA - after the command execution, the serial device (COM port) is unavailable during 5 seconds. If we read it in this period, we get VI_ERROR_IO error. We tried to reset the device by viClear command.
If we send *RST\n command directly, we got VI_ERROR_IO error directly during this command sending.

Any help will be very appreciated.

[AaronK]

Hi,

Just to make it clear, when you send the reset command, the instrument does in fact reset correct? After the 5 seconds, does the communication continue to work as expected? I am somewhat surprised that you would be getting this error, but when the instrument is resetting, you most likely would not be able to communicate with the device.

You may want to examine a SPY log of the communication to ensure that you are sending exactly what you think you are. One thing that comes to mind is a "double '\n'" at the end of your string. If the term chars are automatically appended, and you send two of them during the reset, the instrument may stop responding before the second char was sent and cause the error. NI-Spy should be able to help you examine cases li
ke that more closely. This can be executed from the tools menu of MAX.

Hope this helps out!

Best Regards,
Aaron K.
Application Engineer
National Instruments

[CatherineKostrova]

Hi Aaron,

thanks for your reply.

Yes, after 5 seconds the communication with the instrument is correct but any READ/WRITE command before this term returns the error.

Related to SPY: it seems we can't use it because SPY works with NI-488.2 but we use NI-VISA.
Related to "double '\n'": we just use "viClear" command from NI-Visa library and have no idea what exactly it sends. According to the documentation, it should send "*CLS\n" and discard read/write buffers.

Regards,
Catherine

[AaronK]

Hi,

Actually, if you have a recent version of NI-VISA, you can turn on VISA logging in the NI-SPY -> View Selections menu.

Sorry I didn't understand the original setup. One more question: Does the same problem happen if you do this interactively? (by right clicking on the com port in MAX and clicking open visa session)

Best Regards,
Aaron K.
Application Engineer
National Instruments