Labview stops responding with MCC and Lynx on USB connections

[IAmWhil]

Hello everyone, 

  I have a problem I'm trying to troubleshoot which is causing some very odd behavior.

  First the setup, I'm running labview 7.0 and controlling mass flow controllers, a few relays, and a pump, as well as monitoring / recording system response (flow, temperature, gas composition).

  Some of the mass flow controllers, thermocouples, gas analyzers and flow meters are on a SCB-68 board.  I have one flow controller as well as some pressure sensors attached to the computer via a MCC-1208LS DAQ system.  This is over a wireless usb connection through a Cables Unlimited Wireless USB Adapter (it works very well if you're ever needing wireless usb control!).

  And then lastly I'm running a milliGAT pump via a LYNX controller through USB.  It is a USB to serial connection through VISA in labview.

  Now for the problem's symptoms.

  When I have my system up and running at some random interval of time it will simply stop responding.  I have system run time clocks that continue to tick away, so it looks like the VI up and running.  Buttons are clickable and input fields can be changed.  However clicking the buttons and changing the input fields does nothing.  Additionally I have graphs measuring gas input and gas composition / pressure output.  These stop working as well.  They just freeze up.  Additionally I can not just stop the VI.  Exiting the program yields a "resetting TheNameOfMyProgram VI." message where it hangs for a LONG while.

  I was able to replicate the problem when I had the Lynx and MCC controller on a USB hub over the wireless connection.  When I would try to control the pump and then the flow controller, or set the flow controller and then turn on the pump (lynx controller) in either order, upon making the second control command the system would update once (system updates data every 3 seconds on graphs) and then freeze.

  So I removed the USB hub from the wireless connection and plugged the MCC in directly.  I then plugged the LYNX controller directly into the laptop.  Now I can control all of my flow controllers, relays and pump.  However at some point in time it freezes as described above.

  Has anyone seen something like this before?  Is the excessive data coming in on USB causing a freeze? Does anyone have any suggestions on things to try?  I'm kind of at a loss...

Thanks for the help!

[margasan]

Hell IAmWhil,

Similar behavior has been observed due to excesive usb usage, what happens is that the USB controller stops responding, the result of this is that LabVIEW / OS "feels" that the USB device has been disconnected suddenly, so all drivers/libraries used to control the devices stop responding causing the code to crash, have you tried using an external USB hub externally powered?

Regards

Mart G

[bstreiff]

I can't speak for the MCC/Lynx devices, but for NI USB DAQ devices we have the following KnowledgeBase article about using them with wireless USB hubs: NI KnowledgeBase: Can I Use a Wireless USB Hub with My USB DAQ Device? Perhaps the MCC/Lynx devices encounter similar problems when used in that manner.