Change a DAQmx channel property for a single channel from a channel group

[Djaunl]

Hi,

I'm doing some digital output, and I'd like to tristate certain lines in each port. However, I'm having difficulty figuring out how to specify which individual lines to tristate. I input a port and a line range, e.g. PXI-6533/port0/line0:7, specify to use one channel for each line in the DAQmx Create Virtual Channel VI, retrieve the channels from the DAQmx Task Property, and try to operate on the individual channels that way.  However, this results in the following error:

Error -200428 occurred at Property Node DAQmx Channel (arg 1) in tristate_test.vi

Possible reason(s):

Measurements: Value passed to the Task/Channels In control is invalid.

The value must refer to a valid task or valid virtual channels.

Task Name: PXI-6533/port0/line0

The NI knowledge base article that deals with this error code talks about creating a task with the DAQ assistant, or ensuring that a task has been created. However, I'm not using the DAQ assistant, as my I/O is pretty complicated; I'm just using a bunch of virtual channels. 

Is there a way to specify individual channels to changethe properties of without having to create additional virtual channels? I have 48 digital channels I plan to use, so the less virtual channels I have to create the better. 

Please reference the attached VI, which demonstrates the problem I am facing. 

Thanks for any assistance. 

[AdnanZ]

You can only software-time tristate for the 6533/6534. Have a look at the attached example.

[AdnanZ]

And, you need to commit the task before you attempt to tristate.

[Djaunl]

Sorry, I'm not sure I understand what you're telling me. In the example, aren't you tristating all lines? I'm only trying to tristate specific lines on each port. Or does the tristate option only put a high-impedance state on channels that don't have any waveform information associated with them? Also, I'm not entirely sure what is meant by "software-time".

Thanks for the help.