USB to Serial interface problem –VISA device busy occurs after several hours of continous use.

[mattster]

I am using LabVIEW8.5 to communicate with a USB device using a FTDI FT232BL 648-1 controller (chip).  The USB serial converter driver is the latest version available (2.04.06 March 2008).  The USB serial device is sending packets of data at approximately 1s intervals.  OS is win XP with all the latest service packs installed.

My problem is that that VISA/LabVIEW loses contact with this device after several hours (or up to three days was the longest continuous run).  The error I get (from the Measurement & Automation Explorers “Open VISA test panel”) is:

Unable to open session to “ASRL11:INSTR”

Return status code 0Xbfff0072

Status name: VI_ERROR_RSRC_BUSY

The resource is valid, but VISA cannot currently access it”.

During this time I have nothing else trying to communicate with this device and the computer is not being used.  Below is some code to demonstrate how I communicate with this device.

I have two "solutions" to gain access to "COM10" again:

1. Restart windows

2. Remove USB cable, delete the USB Serial Port from the Windows Device Manager, then re-insert USB cable (i.e. reinstall USB Com port)

note: R

estarting LabView or removing the USB and re-inserting it does not help.

Any help or advice would be appreciated!

[MikeS81]

Hi mattster,

i think after you lose the connection, LabVIEW doesn´t close the VISA connection and this can be the problem. Did you try to run only the close function with your com port connected?

Hope it helps.
Mike

[mattster]

Hello Mike,

Thanks for you fast reply and solution to my problem

I did exactly as you suggested and then I could access the port again.

I will modify the code so that when the error occurs again (port not found) I will force the port to close and then re-open it...

Many thanks,

Matthew

[mattster]

My joy was short lived - why it worked once is not clear however now when I close the port the message I receive in NIMax is that the device is OK and then NIMax hangs (I still see NIMax in the Windows task manager but I cannot kill the process?)

VISA Interactive control also hangs and so does LabVIEW when I try to run my application.  The only way I can get things going again is to restart my computer.

Does anyone recognise this problem?!