divided sample clock timebase

[crimolvic]

Hello again,

The task is the synchronization between a PXI 4461 and PXI 4472b. The idea is to export the SampleClockTimebase, SyncPulse and StartTrigger from the master device (4461) to the slave device (4472b).

For exporting the signals I am using the "export signal" property node, please see figure 1. When I run the vi like this I get an error number 89137 (in german):

Fehler -89137 ist bei DAQmx Start Task.vi:12 aufgetreten
Mögliche Ursachen:

Die gewünschte Route kann nicht verwendet werden, da sie Ressourcen erfordert, die zur Zeit von einer anderen Route verwendet wird.

Eigenschaft: SampTaktZeitbasis.AusgAnschl
Zielgerät: PXI1Slot2
Zielanschluss: PXI_Star0

Erforderliche Ressourcen verwendet durch
Task-Name: 4472Messkarte
Quellgerät: PXI1Slot2
Quellenanschluss: DividedSampleClockTimebase
Zielgerät: PXI1Slot3
Zielanschluss: SampleClockTimebase

Task-Name: 4461Messkarte

Without knowing what it is, I have exported the "DividedSampleClockTimebase" and then the vi runs (see figure 2)


My questions:

What are the differences between the "SampleClockTimebase" and "DividedSampleClockTimebase"?
Which one should I export to the PXI_Star0 line?

[Johann.Wagner]

Dear Crimolvic,

not all routes and properties are supported by all cards. Sometimes a route can map with a RTSI cable or lines in PXI System.

Look at your specifications/user manual for properties of your card and look in MAX (Measurement&AutomationExplorer) under your device

and register card for seeing the direkt connection without a cable and indirect with cable or extern connection

In your case the first properties for DaqMxTask isn´t supported but the second...

Best Regards

AE Munich (Germany)

[crimolvic]

Hallo Johann,

At the moment I am working with simulated devices in MAX, so I think that maybe there is something missing in my simulated measurement system in MAX. I am saying this because I am sure that the "SampleClockTimebase" is available as an source from PXI_Star0 line in the 4472b device.

I have 2 vi´s for the synchronization of the devices (see attachment):

- Fig_01: in the first one I only "say" to the 4472b that it must take the "SampleClockTimebase" from the 4461. I do the same with the "SyncPulse" and "StartTrigger" signals.
- Fig_02: in the second one I export the "SampleClockTimebase" from the 4461 to the PXI_Star0 line manually by making use of the Export Signal property node. I do the same with the "SyncPulse" and "StartTrigger" to the PXI_Trigger5 and PXI_Trigger0 lines respectively.

What is the difference?
I think that in the first case the DAQmx driver make the routing connection (id est: it choose the proper lines for exporting/exporting) between the two devices, whereas in the second vi I  choose the lines for the exporting/importing of the signals and certainly I am doing something wrong but I don´t know what it is.
Is there a way to know which are the lines used for exporting/importing the signals in the first vi?


In Fig_03 I have tried another possibility, which also make use of the DAQmx capabilities. I think that this case is a little bit like the one of Fig_01 in that the driver make all the import/export and routing of the signals.

Best regards,
CJMV

Message Edited by crimolvic on 05-03-2007 06:25 AM

[reddog]

The DividedSampleClockTimebase is as its name implies a divided down version of the SampleClockTimebase.  The SampleClockTimebase is the signal used internally by the 446x and is the signal you need to export when synchronizing with other 446x devices.  The DividedSampleClockTimebase is typically half the rate of the SampleClockTimebase and is the signal you need to export when synchronizing with other 447x devices.  In the case of "pulling" the signal versus "pushing" it with the Export Signal VI, the driver has enough logic to determine which version of the timebase is the correct one for the target device and route it appropriately.

[crimolvic]

Hi reddog,

that makes sence. However, I have tried to manually export and import the "SampleClockTimebase" from the 4461 to the 4472b now through the PXI_Star1 line and the vi runs (see attached Fig_04.png). So I still don´t understand:

- On one hand, as you said, Ii could be that I need to use the "DividedSampleClockTimebase" as a source for synchronyzing 446X and 447X devices, and not the "SampleClockTimebase"
- On the other hand, I can make use of the "SampleClockTimebase" (not its devided version) if I export it through other PXI_Star line other than PXI_Star0

So which would be the solution, to share the "DividedSampleClockTimebase" through PXI_Star0, or the "SampleClockTimebase" through a PXI_StarX with X other than 0?

[crimolvic]

Do you know, reddog? or other?

Can anyone please clarify this to me?

than you.
CJMV

[reddog]

I thought I saw somewhere that you were using simulated devices, and I suspect this is the cause of the errors you are seeing.  I tried exporting both the SampleClockTimebase and DividedSampleClockTimebase to PXI_Star0 and PXI_Star1 on real hardware and everthing worked as expected.  When I tried the same thing with simulated hardware, I always received the error you mentioned previously.  This is a limitation of simulation since we only simulate the device and not the PXI chassis or associated resources.  This testing was conducted with DAQmx 8.5. 

My advice to you would be to stick with the "pull" method for routing and not actually use the export signal property node.  This property node isn't really necessary unless you want to export signals to devices that live outside of the DAQmx driver.  In the end, simply specifying the source of the signal without specifying the intermediate PXI trigger or star trigger line will often be more robust since the driver can automatically select amongst the available resources at run time.  For instance, if you specify a specific star trigger line, you will have to modify your code if you ever change the slot position of the cards.  However, if you simply specify the SampleClockTimebase signal as the source, the driver will automatically know from which star trigger line to pull the signal.  I hope this helps to clarify things.

[crimolvic]

Hi reddog,

thank you very much for your helpful answer. I also thought that could be something wrong due to the fact that I am working with simulated devices.

I hope to have my real Hardware soon and try to run my vi´s.

Thank you also for clarify the differences on the routing signal procedure with and without the property node.

You earn the 5 NI stars

Regards,
Crimolvic