Write to single line with DAQmx

[Greg_NTI]

Hello,

life was so easy with traditional DAQ...

I'm trying to control single lines of DIO cards with DAQmx und CVI 8.0.1 , - the equivalent in traditional DAQ would be "DIG_Out_Line"

What I do:

- I create a task

- I add one channel for each digital line

DAQmxCreateTask (tsk_MAIN_OUTPUT_A, &tMainOutputA);
DAQmxCreateDOChan (tMainOutputA, "Dev1/port0/line0", "Line0",DAQmx_Val_ChanPerLine);

...

...

DAQmxCreateDOChan (tMainOutputA, "Dev1/port0/line7", "Line7",DAQmx_Val_ChanPerLine);
 

When I look into the "WriteFunction" collection, I find all kind of functions that write to tasks, but none which writes to channels...

The examples which comes with CVI only writes to a port, - 8 bit at a time, - which is what I want to avoid...

What am I missing?

Thanks a lot!
Greg

[McKala[DE]]

Hello Greg,

You can control each of the individual lines of a DIO card by using a separate task for each line.  A DAQmx task is a collection of virtual channels, timing and triggering information, and other properties regarding the acquisition or generation. If you want to have the ability to write to a single line you'll want to have each of the lines in separate tasks.  Otherwise, you can include all of the lines in a single task and write to them all at once.

You may find these links helpful since you are just getting started with NI-DAQmx:
Transition from Traditional NI-DAQ to NI-DAQmx
Learn 10 Functions in NI-DAQmx and Solve 80% of Data Acquisition Applications

Post again if you have any further questions,

[Greg_NTI]

Hello Micaela,

I've found out about the difference of tasks and channels in the meantime. However, thanks a lot for answering. The application is running fine now.

Best Regards,

Greg

[MrFingers]

I have a 6516 card and I'm try to control the eight lines on port 3 individually.  I've gone through all the sample code and such.  Is this card capable of this?  Here's the code that I have write now.

Dim digitalWriteTask As Task = New Task()
digitalWriteTask.DOChannels.CreateChannel("Dev1/port3/line0", "port1", ChannelLineGrouping.OneChannelForAllLines)
Dim writer As DigitalSingleChannelWriter = New DigitalSingleChannelWriter(digitalWriteTask.Stream)
writer.WriteSingleSamplePort(True, 1)

I've tried ChannelLineGrouping.OneChannelForEachLine and DigitalMultiChannelWriter with no luck.  I also tried making a task in MAX to control Dev1/port3/line0 and this doesn't work either.  I'm starting to think this isn't supported on this card.

Could any shed some light on this for me.

Thanks in advance,

Gary

[MrFingers]

Doh!  Sorry about that.  I had forgotten to wire the last port.  It works fine now.  It's definitely Monday.