NI-9425 Digital Input Channel Expansion with DAQmx Real-Time (cRIO-9045)

[Fareed17]

Greetings and I hope that everyone's doing great so far.

Currently, we are exploring the possibilities on using the NI DAQmx Real-Time using cRIO-9045 and NI-9425.

We wonder whether it is possible for us to use this programming mode with channel expansion for distributed digital inputs across the modules and chassis. Our reasonings come from the following articles:

1. How to Achieve High-Accuracy Measurements With NI-DAQmx-Based TSN Devices
2. Easily Synchronize and Trigger NI-DAQmx with Channel Expansion

As we dive into this, we are aware that you would need to modify the task for multiple port from different modules, and we believe it is already resolved by this thread: LabVIEW, Synchronous measurement in cDAQ chassis

However, we simply couldn't apply the same workaround to our setup thus our questions would be:

DI Expansion using For LoopDI Expansion for each line configDI Expansion for all line config

•  Is it even possible for us to do channel expansions with DAQmx Real Time?
•  If not, is there a way for us to do so? 

The reason we would like to experiment this, is because based on the paper presented, we could have the synchronization of the input up to 1 uS (more than enough for our application, which is 10 uS). Do correct us if we are wrong. 

Thank you for your time!

[pipipi0405]

How did you configure your DAQmx Read VI?

[Fareed17]

Hi pipipi0405, 

Thanks for taking a look at this and my apologies for just replying as I was away from site. We have configured our DAQmx Read to N channels and it resolved our issue. We reckoned it might be due to the bug since we didn't change a thing?

Since we could confirm that we could use our DAQmx task within the cRIO, we are wondering on how we could sync between cRIOs? Sync using the TSN Switch is pretty much explained a lot in the forum but it wasn't for the DAQmx real time CMIIW. 

Apparently, we could achieve tight sync with DAQmx by stating them into a single task, but it seems that DAQmx for cRIO won't allow them to be declared in one task as stated at this KB 

We do found the example of cRIO Sync Logging in NI's forum as well but realized that if the DAQmx route is viable, it would be easier for us to implement. 

We realized that what we know is pretty basic so excuse our seemingly basic questions. 

Thanks!