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Avoiding the USB-1208LS concurrent operation error in ULx

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Avoiding the USB-1208LS concurrent operation error in ULx

The USB-1208LS hardware is limited to performing one function at a time.  When the Analog input channels (AI) are read in a clocked scan, no other hardware features (DI, DO, AO, CI) can be used (if attempted, an error will result).   If using the next model up (USB-1208FS, which allows more concurrent operations) is not an option, then you should use a polled reading of the AI channels instead, much like the DI, DO, AO and CI are polled.  

Also note, when using ULx, you should create only one task per function, and keep that task open for the entire program operation.  i.e. do not create and kill tasks repeatedly.  For DI and DO, killing and creating tasks will reset/impact the data of both DIO ports.

The attached NI LabVIEW 2010 example program, written using ULx 2.0, demonstrates reading 4 AI channels, reading a full byte of DI, and writing to a full byte of DO ... all within a while loop.   A screen shot of the wiring diagram is below:

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Article ID: 50377

Last Modified:6/13/2012 1:34:31 PM

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