11-16-2006 08:17 AM
11-16-2006 12:44 PM
If you plug a USB device into a different USB port, the system recognizes it as a new device. This applies to USB hubs as well, and can be confusing if the device is plugged into the same port in the hub, but the hub itself is connected to a different port in the PC.
I have not seen any changes either in NI USB DAQ products or in USB to serial adapters if they're always plugged into the same port. If they are plugged into the same port, then I would expect that the ports are reenumerated in a different order for some reason, but that sounds weird.
11-16-2006 12:49 PM
Thanks tst.
"... but that sounds weird."
I agree. The customer with two NI USB DAQ devices insisted that the devices were not moved around. He claimed to only do a re-boot. He stoped having problems after I coded up my work-around.
Anyone else seen anything similar?
Ben
11-16-2006 01:46 PM
11-16-2006 02:30 PM
Thank you once again tst!
I found the thread "
DAQmx 8.3 & USB6008?" |
And that sounds like a similar issue.
So I am not the only one seeing this issue.
Anyone else?
Any other idea (aside from forming a club )?
Ben
11-18-2006 11:23 AM
I still concider this Q on resolved!
Could an AE please investigate?
Thank you,
Ben
11-20-2006 01:33 PM
Greetings Ben,
The way the devices will behave when plugged in or when the computer restarts will depend on which driver is being used.
DAQmx Base: DAQmx Base has no memory of previous devices. Devices will be named dev1, dev2, dev3 as they are enumerated. The first detected device will become dev1. For this reason it is possible for the devices to "trade" their names.
Scenario:
1) Begin with two USB devices. Use LSDAQ to note the serial numbers of the devices corresponding to dev1 and dev2.
2) Remove dev1. Note that dev2 now becomes dev1.
3) Re-connect the original dev1. It will now be named dev2 and you have essentially "traded" your device names.
DAQmx: DAQmx will associate a serial number with a device. For this reason, the devices should never trade names unless MAX loses association. This can occur for example if the device is deleted from MAX.
Scenario:
1) Connect one USB device and note the associated name in MAX.
2) Remove the device and note the red "X" in MAX showing the device is not present.
3) Connect a new USB device (different serial number). The new device will show up under a new device name (dev#, where # is the first unused positive integer) and the orignal device will remain with the X. If reconnected, the orignal device will assume the old name and the X will disappear.
Have you been experiencing something which differs from the above scenarios?
Regards,
Jennifer O.
Applications Engineer
National Instruments
11-20-2006 01:40 PM
Thank you Jennifer!
Yes one of the widgets I was using required DAQmx base.
So with the info you have provided, I at least have a story to go with the problem.
This is a "gotcha" that I never heard before now.
Thank you!
Ben