Write One Channel in Multi Channel Task

[fungiscience]

Hello,

I'm trying to write one sample to one virtual channel programmatically with LabVIEW 8.2 in a task configured in MAX (DAQmx simulated device PXI-6225). This task contains 30 different outputs. I don't want necessarily to write all 30 outputs all the time. Is there a way to do that?

I tried with the Task Property Node, with Channels property wired to the Task/virtual channel input of Start/Write/Stop DAQmx VIs, but I get invalid task/virtual channel error (see image 1).

With DAQmx Read Property node, there is a property called Channels to read, which permits to read only certain channel in a task (see image 2). This property doesn't exist in the DAQmx Write Property node...is there is reason for this? Is there another to write only one specific channel in a task?

Thank you!

[eaolson]

QUOTE(fungiscience @ Mar 20 2007, 05:08 PM)

I'm trying to write one sample to one virtual channel programmatically with LabVIEW 8.2 in a task configured in MAX (DAQmx simulated device PXI-6225). This task contains 30 different outputs. I don't want necessarily to write all 30 outputs all the time. Is there a way to do that?

I'm working from memory here, but I don't think so. If your task is configured for 30 channels, you need to update all 30 channels at once. What you can do is keep track of the current output values in an array, update only the array element you want to change, and use DAQmx Write 1D DBL NChan 1Samp to write the entire array to the hardware. You could also set up each channel in a different task, but that becomes complicated if you want to update them simultaneously.