Adding multiple global virtual channels

[dotNet_to_LabW]

Hi,

I had a very simple function written in CVI that adds multiple global virtual channel

DAQmxErrChk (DAQmxAddGlobalChansToTask(g_TaskHandle, linesName)); //linesName consists 2 global virtual channels seperated by ",". E.g. "Power, Com" where Power = port1/line0 & Com = port1/line2

 There is AddGlobalFunction in MEasurement Studio too but it allows adding single channel only:

Task localTask = new Task();
localTask.AddGlobalChannel(linesName); //Get Expetion here = -200486, Specified Channel not in the task. When I give a single channel name..it works
DigitalSingleChannelWriter doWriter = new DigitalSingleChannelWriter(localTask.Stream);
doWriter.WriteSingleSampleMultiLine(true, states); //atates is the array of type bool which consists of value for each channel

 Is it not possible any more to add multiple Global Channels to a task??

We have recently acquired Measurement Studio license and are trying to port/compile/write our old libraries (written in CVI) in it.

- Is there any online help that compares CVI C functions with respective .NET functions of DAQmx?

Thanks in advance!

Ciao

Ricky

[dotNet_to_LabW]

Have been trying this for last 2 days, have also searched number of NI forum messages but have not got solution.

Anyone with slightest of hint?

[dotNet_to_LabW]

Have been trying this for last 2 days, have also searched number of NI forum messages but have not got solution.

Anyone with slightest of hint?

Meanwhile I have gathered some more Information:

- Adding multiple Global channels in LabWindows/CVI is possible using DAQmxAddGlobalChansToTask function where channels are , (comma) seperated

- Also adding multiple Global channels in LabView  where channels are , (comma) seperated.

May be I am wrong but has NI forgotten to implement the same in MeasurementStudio ? Or am I missing something?

[Naity · Accepted solution]

Hi,

it seems like you are correct. The definition of the method specifies that it only adds one channel:

public NationalInstruments.DAQmx.Channel AddGlobalChannel(string channelName)
    Member of NationalInstruments.DAQmx.Task

Summary:
Adds a preconfigured, global channel to the task.

Parameters:
channelName: The name of the global channel to add to the task.

Returns:
The global Channel.

Exceptions:
NationalInstruments.DAQmx.DaqException: The NI-DAQmx driver returned an error.

This could be explained by the fact the function returnes the appropriate instance of the channel object related to the global virtual channel you created. 

I tried to check the code reading 2 Global Virtual Channel using the DAQ Assistant in Measurment Studio but I was not able to get much of it (the generated code makes two consecutive calls of the "CreateVoltageChannel" method.

What happen if you call AddGlobalChannel twice?

Task localTask = new Task();
localTask.AddGlobalChannel("Power");
localTask.AddGlobalChannel("Com");

I did not have time to try this so far, but from my understanding of the help file, I assume it could work.

Best regards

[dotNet_to_LabW]

It worked!

Sorry, I did not even think about calling the function with different channels multiple times.

Thanks for your help!!