USB Plug-n-Play Devices (Windows)

[LV_Pro]

This is grasping at straws, but I figure I'll ask. We have a number of systems, built at different times, but that are currently running Windows 7 Pro, LabVIEW 2012sp1, various DAQmx and driver levels (most are those that would have installed off the 2012sp1 DVD pack), that have been having random reboots. When I run debug view (we salt a lot of debug reporting in the code) that they programs are not at the same point each time, and very rarely is there a actual Windows dump file created, it just reboots, comes up to the back reboot screen that says that Windows was shut down unexpectedly and gives the option to restart Windows normally. This is happening on several machines, all industrial computers of the same model, with differing vintages (they weren't all bought at the same time). I don't know what brand, etc., at the moment, will get with our "hardware guy" that assembles them for that info, just priming the pump now.

As always, Thanks!

[JÞB]

Just to start us thinking .....

I recall a very nasty hardware problem that exhibited like this.  Our asseblers had been taught, incorrectly, to overrtighten all zip-ties in the system.  This caused some crushing internal to some cheap-o(tm) USB cables.  The systems would then "Randomly" short 5V to Gnd and the PC would react just like someone had held down the reset button.

It may have nothing to do with what you are seeing but I thought I'd toss it out there for you as food for thought.

[LV_Pro]

I shudder to think what it took to find that!  I'm looking at all kinds of stuff, but hard to diagnose when Windows doesn't tell you what annoyed it!

[LV_Pro]

Well, I don't have an absolute answer, hard to prove something by a non-event, but one of our engineers has changed the power settings in Windows for the USB and we haven't seen the reboots. Then again, it isn't a very controlled experiment. I will see if I he remembers exactly what he did, my explanation above is rather vague.

[JÞB]

Putnam- 

First answer- About two hours of hair-pulling while Windows booted and booted and booted-  and of course ripping the pc OOS to make sure it was a good PC then one-by one replacing known good test perifrials with system resources.  Good troubleshooting technique is a must!  Lukilly, I used to teach just exactly that!  I don't offten get beat (But it has happened) but have often been surprised by what the problem really was (as I was with that case).

Answer 2 I belive your engineer followed the steps detailed in the USB Devices FAQ

USB Plug-n-Play Devices (Windows)

‎01-22-2012 02:20 PM

In this topic we will discuss some of the common problems that have been observed using USB devices with LabVIEW on Windows operating systems.  Many of these points are also applicable to other environments but the examples will be use the Windows 7 OS.

FAQ 1 : My USB device stops working unexpectedly.

The first thing to look at is the OS power saving options.  There is a global trend towards developing "Green" electronics and energy star ratings are getting fairly common.  "If its not being used shut it off" is nothing new.  Cavemen learned how to bank a fire to preserve energy that would otherwise be wasted.  Likewise, the Windows OS has a power saving feature to shut down power to the USB hubs when no user activity is present.  In Automated systems this feature can cause problems since removing USB hub power will shut down the USB device.   Solution: Use the device manager to change the USB hub Power Options.

FAQ2: I set the power options and my device connection is still unreliable: Remember, those computer USB ports are often the cheapest that can be mounted on the chassis and share the PC system power supply to supply USB Power. Most uses of USB are temporary connections like a thumb drive or a camera.  These connections do not require high reliability since the user is right there interacting with it.  Power surges and fault tolerance at worst cause the operator to retry the data transfer.  Automated systems require a bit more robustness.  Solutions:

1) ALWAYS use an external self powered hub.  Perform your engineering due diligence and inspect the devices specifications too- If you can't find them for that device that should clue you to seek an product from a vendor that WILL publish their specs.

2) High noise environments require the use of ferrites on the USB cable- and don't buy the cheapest cable either! The cheap ones are poorly shielded.  

3) PROTECT the HUB connections-  If you have a USB2.0 device and Joe User plugs in a 1.0 device in a open slot managed by the same hub- Bingo every port on the hub may back convert to USB1.0.  WORSE there are a lot of damaged or marginally engineered USB devices out there.  Joe User's device may cause power fluctuations when it is inserted or removed from the hub just don't let it happen!