11-21-2018 09:49 PM
I had encountered the same issue when using NI-VISA (v15.0.1) with ATEN USB to Serial Adapter. The VISA Read randomly hangs the system causing the port to be blocked and only recoverable by rebooting the system.
After experimenting with my code, I found that by adding a fixed delay after the VISA Read (in my case 1ms delay) resolved the issue. Previously I had let the loop run without any delay after the VISA Read.
Hope this helps. (at least in some situations)
10-19-2021 10:18 AM
Ran into it as well. This time with a Siglent SPD3303X.
Was able to get it hanging in two ways:
Seems to be caused by implementation of VISA inside device (of course NI should be able to come back after tine out). Speculating is that device keeps bus in 'I am giving you data... state or such'
In this case I was able to restore labview operation by switching supply on/off.
The driver supplied by Siglent has some (not 100% implemented) work-arounds for this, however some functions such as IDN? are not implemented in the driver without modifying it slightly.
10-19-2021 01:34 PM
Some follow up. After fixing this issue, still the communication failed.. After updating firmware in instrument the above work around was no longer needed and the other communication issues were also solved.