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DAQmx usage for multiple channel read across multiple cards

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Hello everyone,

 

I am trying to use the DAQmx to read all the channels of my PXIe chassis. I have 2 1085 racks with same PXIe4300 AI cards in all slots. I tried to list all the channels in the physical channel input and when I tried to read, it showed me an error about syncing timing across multiple devices.

 

It doesn't show me this error when I read channels from the same card so I am guessing it is something to do with time syncing across different cards? Is there a way to set up the timing to read all the channels on different slots and different racks using the same DAQmx task? 

 

P.S. I am fairly new to LabVIEW 😄

 

 

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From Easily Synchronize and Trigger NI-DAQmx with Channel Expansion

A task can include channels from multiple DSA, SC Express, and X Series devices given the following conditions:

  • The devices must be in a single chassis, and the chassis must be identified in NI MAX.

So you would need separate tasks for each chassis. Search for "4300" in Synchronization Explained. Since NI-4300 does not have any PFI ports to route the trigger signal, you would need another module. PXIe-6674T has the best performance.

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Control Lead | Intelline Inc
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The correct way to synchronize across multiple chassis without timing and synchronization options is to use a 6674T card on each chassis to externally route the triggers.

 

 

Santhosh
Soliton Technologies

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Thank you for your reply!

 

Just a follow up, I don't have the 6674-T and I don't think we accounted for it in purchasing. I am okay with segregating my applications and using different tasks for each chassis because the purpose of each chassis is different so that's fine.

 

In such a case, the master slave synchronization would be enough right?

 

(I could test this to verify but I don't have access to the rig over the weekend hence just throwing it out there =))

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If two chassis are not connected by any means (Timing & Synchronization upgrade, any DAQ device with PFI, or PXIe-6674T), you cannot route any signals between the chassis and do any forms of master-slave synchronization. There are only two separate masters.

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Control Lead | Intelline Inc
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Just to clarify, I am using 2 PXIe 1085 chassis with a single 8840 quad core CPU in chassis 1. The two chassis are linked using a PXIe 8384 MXI express X8 module on each chassis.

 

So does all this hold true for this case as well?

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Solution
Accepted by topic author Silverfang-

@Silverfang- wrote:

Just to clarify, I am using 2 PXIe 1085 chassis with a single 8840 quad core CPU in chassis 1. The two chassis are linked using a PXIe 8384 MXI express X8 module on each chassis.

 

So does all this hold true for this case as well?


MXI device is not capable of routing trigger signals.

PXIe-1085 has two SMB connectors labeled with IN and OUT at the front that allow you to route the 10MHz between chassis. However, synchronization requires either:

  • sharing of sample clock
  • sharing of reference clock (10MHz clock) and a start trigger.

Although PXIe-4300 has two PFI lines but they are only for digital input and cannot export signals.

PXIe-8840 QC has a SMB Front Panel Trigger that might be able to export the signal. You can try to call DAQmx Export Signal (VI) to export the Start Trigger to /<hostname>/TRIG_SMB of controller in the master chassis (Reference: Use SMB Connector on PXI(e) Controller to Route Trigger Signals), then import the trigger using PFI of any PXIe-4300 in the slave chassis. 

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Control Lead | Intelline Inc
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@Silverfang- wrote:

Just to clarify, I am using 2 PXIe 1085 chassis with a single 8840 quad core CPU in chassis 1. The two chassis are linked using a PXIe 8384 MXI express X8 module on each chassis.

 

So does all this hold true for this case as well?


yes, it is still valid for your setup. The MXIe card is used for communication and not synchronization.

Santhosh
Soliton Technologies

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