Hi
I have a test system with a bunch of USB "serial ports" (they are actually Atmel micros, a duplicate of the Arduino ItsyBitsy, so there's no physical serial port as such).
Leaving aside my misgivings about having 24 of them - the point being to test a load of them in parallel - I have an occasional problem that totally hangs VISA. I suspect electrical noise or similar disrupts things, which I can live with; it's the fact that I can't ever recover the situation in software.
Once I end up in that situation, even after quitting and restarting LabVIEW, a simple VI with only 'Visa Find' or 'Visa Open' in it hangs and can't be aborted. I can close its window but LabVIEW can't quit ("Resetting VI ...") and has to be killed from the task manager.
When I try to open one of the serial ports, NI I/O Trace shows:
1. viOpenDefaultRM (0x121F9560)
Process ID: 0x00000704 Thread ID: 0x000004E4
Start Time: 09:55:16.7393 Call Duration 00:00:00.0089
Status: 0 (VI_SUCCESS)
2. viParseRsrc (0x121F9560, "COM6", 0x105FFBC8, 0x105FFBC4)
Process ID: 0x00000704 Thread ID: 0x000004E4
Start Time: 09:55:16.7483
(note: no status so presumably it's hung)
If I expand "Devices and Interfaces" in MAX, I get an immediate error saying that it timed out waiting for a driver, and then hangs for a minute or so (Windows greys the window out and declares it 'Not responding') before returning but with no devices at all. I/O trace shows nothing in this case.
After messing around with DEVCON.EXE (red herring I think), I found that I can still access the 'serial ports' in question via PuTTY, so it's presumably NI-VISA that's gone AWOL.
A reboot will cause everything to spring into life, but that's not really helpful; presumably what I actually need is a means to prod NI-VISA.
System is: Windows 10 with all updates; LabVIEW 2020; NI-VISA 20.0.0.
Any ideas?
thanks
John