Synchronizing pci-6111 and Mi-5411 using a RTSI cable

[facundo]

I was wondering if anyone had any helpful hints for synchronizing a PCI-6111 data acquisition board with a NI-FGEN NI-5411 using labview 7.1 software. I have a VI for the signal generator created that will tigger and generate and appropriate signal and I have a seperate VI that acquires and processes the signal. I purchased an RTSI cable and have already connected the two boards. This is were I get stuck. I have found numerous examples for synchronizing two signal generators (or two DAQ boards) but I havent found an example (or the appropriate VI) to sync the acquisition board and the signal generator.

Any help would be greately appreciated.

[Alan_L]

Facundo,


Before I am able to fully answer your question, I need to know what type of synchronization you are interested in implementing. If your intent is to start both devices simultaneously, then you can achieve that by using one device to send a trigger signal over RTSI and configure the other to wait for that pulse.

Please let me know what you are considering and I will certainly do my best to help you.


Thanks,
Alan L
Applications Engineer
National Instruments

[facundo]

Alan,

We have already synchronized both boards with an external trigger, but we would also like to keep them in sync during the acquisition period by synching the clocks of both devices. We noticed that for very long acquisitions, we start to notice a slight offset between both boards. We think that using the RTSI bus to sync both clocks would be the best choice to solve this but we are open to thers suggestions.

Thanks for your help and quick reply.

Facundo

[Alan_L]

Facundo,

Thank you for the additional information!

The solution here is to configure your 6111 to export its internal 20MHz timebase onto RTSI line 7 (RTSI Clock). Since the 5411 has the ability to phase-lock with external references, you can then call the FGEN function "Configure Ref Clock Source" in order to specify the RTSI Clock as the PLL Reference.

I've attached a screenshot of a LabVIEW block diagram illustrating function calls to the DAQmx function "Connect Terminals" which will enable the 6111 to export its internal clock, and also a call to the corresponding FGEN function for the 5411. (The 6111 is supported under DAQmx in NI-DAQ 7.4 and later).

Please let me know if you have any further questions.

Thanks again,
Alan L

[Kevin H]

Hi Alan,

This is very close to the problem that I am trying to solve.  We have a PCI-6351 that we are trying to synchronize to the 10MHz clock output of a NI PXie-5451.  But the PCI-6351 seems to require a 3 V signal to lock onto while the PXIe-5451 only puts out a 1 V signal.  I think I am missing something because it seems like this should be relatively easy to accomplish.

Thanks for the help.