I have an issue that has been hounding me all week and I am hoping that the community can shed some light on the situation.
I have a PXIe 1065 chassis fully populated with various acquisition cards. THere are a total of 9 "high speed"cards that I am trying to ensure tight synchronization between them. The cards that I am trying to sych:
4462 x2 (DSA)
Currently I have 6 of the cards successfully synch'd by sharing a sample clock and has been proven via sig gen (4300, 6123, 6143, 7853R, 7854R) all running 250 kHz. THe problem lies with the DSA devices having a bit of skew and I am trying to confirm my method of synchronizing. I follow a reference clock synchronization and sample clock sharing scheme (all cards reference PXI backplane which is pll'd to a 6672).
I use the PXIe 4331 as a master device that exports both a sync pulse and an AI start trigger. All cards start off the trigger but only the 4462's utilize the sync pulse. I assumed that if I export the sync pulse from the 4331 (it has tighter synch capabilities with PXIe express, this is my excuse not sure if it is a good one) and let the 4462's sync to the master I would be in good shape. I use the maximum sync pulse delay to set the 4331 and export the sync pulse to a trig line that the 4462's import. All cards start off the pulse and I assumed this would be following reference clock synchronization.
I should mention that I am running the 4462's at 200 kHz and the 4331 at 100 kHz. This is just my current set up. I am looking now to see if I am missing something but ultimately my goal is to have tight synchronization to non-DSA devices in my chassis. I can get great synchronization between two 4462's and am working on proving synchronization between the 4331 and 4462's by themselves.
I have looked for KB articles and the forums but only find pieces to the puzzle (pieces that have painted a great picture) and I am missing the best method to ensure synchronization between these device types.
I can post snips of code to show how I configure synchronization if needed, just for now I thought I would see what ideas people have on methods for doing this. I can program things as I go, I am just a bit stumped on ideas.
Thanks in advance.
I apologize for any confusion, I wrote this as I was running out the door and it may be unclear what I am trying to do (at least it is to me as I re-read it this morning!).
Ultimately I am looking for a solid method to synchronize DSA devices to non-DSA devices (SAR ADC type devices I believe would be the term).
I have two DSA device families:
I am first working on confirming that I am correctly syncronized between these device families running at different rates (100k and 200k respectively). First looking for ideas and possibly any articles that expand on this idea. I will go through my understanding of how DSA devices work in hopes that will shed light on a proper synch method, but would like to see what the community has done in the past as well for reference.
Any thoughts are appreciated.
It looks like the PXIe-4331 can only be synchronized with the Reference Clock and the PXI-4462 can use both as long as it is the master.
The document below is a good starting point:
Thank you for KB Sunaina. I was pulled away Th and Fri to accomplish a few other things and was never able to confirm the 4462 and 4331 synch by themselves.
I believe I follow this scheme for the DSA devices currently and will report back how well I am accomplishing this (share ref clock, share sync pulse, share AI start trig with 4331 as master as advised in KB).
If I can confirm this that will be great.
Do you have any advice concerning getting the DSA devices synched with non-DSA devices (such as a PXIe 4300 or PXI-6123)? Once I get the DSA devices checked out I will continue to check my tirggering schemes to see if I am doing something wrong to cause the skew.
Thanks for the help.
The first document shows how to set up tasks for each type of device in your chassis. The last document reflects why you might see delay when both DSA and non DSA devices are synchronized.