safely remove usb

[DavidMaidman]

Hi, I am using a USB6211 with windows XP, LabVIEW 2009. The card in integrated in to a measurement device that the user will plug in when they want to take measurements, and then remove once the measurements have been made. The user will do this a number of times accross the duration of the test.

I have written some code that determines when the device is plugged in or disconnected and this seems to work well, however I have randomly had a full windows crash and I am wondering if this is due to the plugging/unplugging of the device from the USB.

I have had a search and the post below implies thats this is safe to do, however I want to make sure that this isnt going to cause me a problem down the line.

Any ideas?

http://forums.ni.com/ni/board/message?board.id=250&message.id=24254&query.id=1441111#M24254

[Mathan]

Do you want to unplug/replug the USB or just a card connect/disconnect is enough. If the latter is enough just switch the card power ON/OFF using any card application if you have or with the help of a small hardware. Please post back if you want more details.

Mathan

[Andrey_Dmitriev]

Hi,

Try to use devcon utility.

With this utility I was able to "reconnect" my USB device programmatically without physical disconnection.

Andrey.

[DavidMaidman · Accepted solution]

Hi, thanks for the replies - the devcon utility might be useful for me in the future however I managed to solve my problem as follows.

In my original code (figure 1) i was trying to access the serial number of the device, which if connected return error = FALSE. If an error was detected i would retry after 5 seconds, however if the device was connected/disconnected whilst comunication was in progress windows would crash.

I have now modified the code to check the active device names (figure 2). If my device is not connected then the search function will return index = -1. Because I am no longer checking the device directly it no longer matters if the device becomes connected/disconnected during the check.

Thanks for the help

[Grudev]

how do you use the devcon utility?

I file that i downloaded from the microsoft website opens up cmd prompt for a second and goes away.

I'm programmatically trying to reset the usb port. (unplug and plug in)

Best Regards,

Ro