Set up daqmx timing/trigger on 2 chassis over mxi-express

[brimcd]

I have 2 PXIe chassis (one with an RT controller) connected with PXIe-8384/PXIe-8381 MXI-express boards.

I can see all the devices in both chassis and can set up DAQmx tasks in each chassis individually, but I cannot create any single task that includes a device from both chassis. When there is a device from both chassis in the task, I get:

Error -89125 occurred at DAQmx Start Task.vi:7220002

No registered trigger lines could be found between the devices in the route... make sure there is an available trigger line on the trigger bus shared between the devices.

Can this be done in software? Or do I need to add hardware?  I can't find any docs or examples on this, other than a promising article on Veristand (ni.com/white-paper/14637/en/, Scenario #2) but I can't implement it in MAX or LV. Timing is not critical (50-100 ms is fine), I just need many devices in 2 locations, so the MXI solution seems to fit right in. I thought the solution was to use the local clock on each chassis and configure a shared/exported trigger, but can't find anything that works.

Thanks!

[SSPTest]

Hi brimcd,

To do tight multichassis sync, you'll need a timing card that will go in one of your chassis.  From that timing card, you can generate and export a clock and wire that clock into the second chassis.  The onboard clocks of each PXI system can't communicate effectively unless you have some other protocol to communicate between them (e.g. IEEE 1588, which also requires a timing card).  Since the two chassis are presumably physically close together, physically wiring a clock out of one chassis to the other is your best bet.  To get really tight sync, you can even wire the timing signal from the first chassis back into itself to achieve a matched trace-length and eliminate the skew that comes from the propagation of the signal through lines of different lengths.  You can send triggers roughly the same way.  

[brimcd]

Thanks SSPTest,

So it appears that a board (6672, 6683)  is required for any inter-chassis triggering? Even if the timing requirements are rather loose (50ms).

After trying several things, it appears my options are:

- buy and install timing boards in both chassis

- create separate DAQmx tasks in each chassis, and get whatever timing comes from the start command.

Any other options?

[SSPTest]

brimcd,

To totally circumvent having to buy additional hardware, you can use the clock in/out BNC connectors on the back of the chassis.  Check out this article, which explains it in a little more detail: http://digital.ni.com/public.nsf/allkb/64154143B6B898AA86256C2B006D11CC

Just export the clock from one chassis to the next and you should probably be within your skew spec of 50 ms. 

[brimcd]

Yup - I have a coax between chassis, so the second chassis shows "PXI Clock 10 Source" as "External Built-in Connector" in MAX when I connect them.

The error I can't seem to fix refers to triggers:

"No registered trigger lines could be found between the devices in the route."

[luda.mattski · Accepted solution]

Hey brimcd,

You're correct; there isn't a way to send a trigger between chassis without a timing card.  This link goes into a little more detail:  http://digital.ni.com/public.nsf/allkb/D91582EBF0810F4486256E70004E4145

[brimcd]

Thanks! Not what I wanted to hear, but sometimes the truth hurts.