How to get channel names from a remote connected PXI with trad. NIDAQ

[christian511]

On my PXI System I do have a working datalogging-application which takes the names of all channels from "Get DAQ ChannelNames.vi". But the application does not work on a machine which is remotely connected to the PXI-System. The "Get DAQ ChannelNames.vi" does not deliver any of the configured channels nor gives an error. Hope somebody can help me with this. I'm using Labview 7.1 with the traditional NIDAQ 7.3.
Thanks for your help.
christian511

[Watermann]

hi christian511,

it looks like this VI really doesn't work with remote/RT system.

http://forums.ni.com/ni/board/message?board.id=280&message.id=409&requireLogin=False

For that the only thing I could find is the following except from the internal database:

"LV calls NI-DAQ's CfqGetAllVirtualChannels to get the list of channel names. This function does not return RDA channel names. So Joe S. added a function to NI-DAQ 6.9 called CfqGetAllVirtualChannelsEx that does return RDA channel names as well as local channel names."

Hope this will help...

[christian511]

Hello Watermann,
Thanks for your comments. Most of my applications use the VI "Get_DAQ_channel_names.vi" to read all configured channel information (names, units, ...) from the MAX. This VI calls a function named "Get_DAQ_Channel_NamesInterface" out of the "C:\Program Files\National Instruments\LabVIEW 7.1\vi.lib\Daq\lvdaq.*" dl-libary.

I tried to call different functions, but it seems that either "CfqGetAllVirtualChannels" nor "CfqGetAllVirtualChannelsEx" are valid names (I tried both names with different combinations e.g. GetAllVirtualChannels, Get_All_Virtual_Channels,..) in this dll. I assume that the fuctionality from NIDAQ 6.9 is available with NIDAQ 7.2/7.3 too. Do I need a different dll to access the "CfqGetAllVirtualChannelsEx" function? Or how do I call these functions integrated in the NIDAQ?

Thank you very much for your help with this.

Christian511

[Watermann]

hi christian,

for the first, I'm sorry: it looks like the "cfgchannel..." I told/quoted you are out of a C library and no VI's.

like you already said:

"Most of my applications use the VI "Get_DAQ_channel_names.vi" to read all configured channel information (names, units, ...) from the MAX. This VI calls a function named "Get_DAQ_Channel_NamesInterface" out of the "C:\Program Files\National Instruments\LabVIEW 7.1\vi.lib\Daq\lvdaq.*" dl-libary."

the channels and tasks are configured in the MAX. and exactly this is the point why you don't get the channel names on your PXI system. because there is no MAX installed. the "Get_channel_names.vi" refers on the informations out of the MAX.

Message Edited by Watermann on 06-16-2005 03:01 AM

Message Edited by Watermann on 06-16-2005 03:02 AM

[christian511]

HI Watermann,

Thank you for the reply. I afraid I could not fully work with(understand) your last replay.

I do have PXI-System with all the DAQ HW and with LabView 7.1, MAX3.1 and NIDAQ 7.2 installed. To aviod working directly on the PXI System I try to develop my applications with a remote connected desktop-machine which has the same SW (LabView 7.1, MAX3.1! and NIDAQ7.2 driver) installed. I'm able to connect the MAX (on my desktop-machine) to the running RDA-server on the PXI and I get all the HW and the configured channels from the PXI. So far so good. Every configuration I do on my desktop-MAX changes remotely the configuration on the PXI System.

So far I discoverd the VI "Get_DAQ_channel_names.vi" reads out the actual MAX-configuration-file which is stored on my machine and does not contain any valid channel configuration information. Like the gys on
http://forums.ni.com/ni/board/message?board.id=280&message.id=409&requireLogin=False
I'm able to work with the channelnames by using the "DAQ Channel Select control" in LV. But my application is made to work on different systems with fixed channel configurations and therefore it reads out all the configured channel information to set up tigger- and measuring-conditions without reconfiguring the MAX and saves the channelinformation with all the measurement data into datafiles. This does not work on a remote connected desktop-machine because the MAX-configuration-file is emty or does not contain a valid configuration information. So all I get out of the VI is an emty channel-names-array.

Hope you (or somebody) can help me with this.

christian511

[Watermann]

hi christian,

sorry, but more then this link I didn't found to this... in the last post there is a "workaround" discribed... you will have to pass the channel informations via datasocket programmatically.

greets!

[ODRulz]

Where are these vi's located (DAQ Channel Select Control, Get DAQ Channel, Get Channel Information, etc)?  I've got LV7.1, MAX 3.1, & LV RT and could not find them on my machine and have thus far been unsuccessful finding them on here.  Also, what exactly is RDA?

[christian511]

Hi ODRulz,

first of all the RDA stands for RemoteDeviceAccess Server. With this you can control DAQ-HW (in my case a PXI-system) using a different PC which has only LV+DAQ+MAX installed and no DAQ-HW. You simply connect with the MAX and the IP address of the remote machine and get the complete MAX-configuration of the remote machine.

Secondly the "DAQ Channel Select Control" is a normal control available on the front panel (no VI!) and you can find all the DAQ VIs under "yourmachine\yourpath\National Instruments\LabVIEW 7.1\vi.lib\Daq\".

Hope this helps.

Christian511

[ODRulz]

I have the same setup you described, a PXI chassis that I want to control remotely with a laptop.  I have been able to control the DAQ channels with DAQmx utilizing TCP meta, but only when I have the physical channel hardwired in the target vi (remote PXI system).  I want to be able to select which device and channel from the host dynamically.  I have not seen how I can identify the channels on the remote system programmatically from the host, or even from the target and then send that info to the host to use.  I have looked through the vi.lib->daqmx folder and libraries and haven't found anything like I mentioned above - or "Get DAQ Channels.vi" or anything similar.  I've found Channel constants and Create Virtual Channel.vi, that's it.  I'm beginning to wonder if I have all the DAQ files installed - I have DAQ 7.4 loaded, I would think that would have everything being mentioned.  What I want to do seems like it would be rather basic for a remote system so I thought these vi's would be already put together, but I seem to be missing something.

I think I might be beginning to see the light.  I'm going to try to grab the channels on the target, possibly put them all in an array, then flatten them and send them to the host where I can unflatten and put them into a channels control there.  Then I should be able to use that control about the same as a standard control, hopefully.  I'll start playing with this and check back to see if this sounds, to you, like I'm on the right track.

Thanks for your help,

Scott

[ODRulz]

Hi Christian511,

I have since found the Get DAQ Channel Names.vi & the DAQ Channel Select control.  The Get Channel Names was in a library called dqchnutl in the DAQ folder as you said, but it wasn't anywhere in the Functions Palette for some reason.  Nonetheless, when I run the Get Name vi it doesn't come back with anything.  I've created a number of Global Channels in MAX and I can see all of my physical channels when I use the DAQmx Physical Channel select control.  In the help file I saw that the Get Names vi returns with all the names and units in the "default configuration file".  How do I add my channels to this file and why aren't they already there?

All I want to do is be able to select which channel to use on the target from the host.  That's not too much to ask is it?  Help?  Anyone?  Bueller?