multiple PXI boards with simultaneous sampling and an analog trigger

[Jloewen]

How do I trigger two PXI-6133 boards with an analog trigger, and with a shared time base?

I am trying to use two PXI-6133 boards, mounted in a PXI-1031 chassis to simultaneously monitor 15 channels and trigger off of an analog input. At time of trigger, the devices need to collect a specified number of points and pass through to the computer.

I have tried the three examples that came with Labview, but haven't had any luck so far. Any advice?

[reddog]

The following modified shipping example worked for me. I created it using simulated devices though, so I didn't test any real world data.

[jtsa]

I've got the same setup and doing roughly the same thing as you with a MXI-4 PXI-PC controller.

Go to this link:

http://zone.ni.com/devzone/conceptd.nsf/webmain/398AC5E81E683F7D86256FB9000D8717

and check out Professional Tools #2 - Data Compaction for High-Speed Streaming to Disk.
you'll want to sue the Cont Acq Voltage from two tasks to file example.

as with reddog's example you need to add a DAQmx Trigger.vi to the master task and select Start Analog Edge. add the required inputs and it should be working.

if you're looking at saving your 15 channels to disk at the full 2.5MS/s rate you will have to consider modifying the example to

1. queue the data before saving to disk and then save the data to disk after the capture has taken place (speeds the read loop to avoid your board buffer being overwritten - look at some examples on queues) when you do this you might want to make sure you have enough ram too.

2. change DAQmx Channel Property AI.DataXferMech to DMA.

3. Change Daqmx Read - WaitMode property to Poll

4. Minimise anything else running at the same time as data capture.

this is what I've done, and have found that each has helped in improving the amount of data I can capture.

-jeff