Real-Time Measurement and Control

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Measure 16 strain gages simultaneously with SBRIO 9626 + 2 NI 9235 modules

Hello everyone,


I am currently working on a deformation measuring application. I need to measure 16 strain gages simultaneously, using a SBRIO 9626 + NI 9693 (two C Slots) + 2 NI 9235. I started checking out the example included for measuring strain with shunt calibration on 4 gages with one 9235 module through the FPGA, modded it to read 8 gages without any issue.


The problem comes up when i try to use two modules for reading 16 gages. I modified the getting started example in serveral ways without any success, only can read continuously the 9235 on slot 1, and apparently, i only get an initial reading on the other 9235, and then nothing more. Below is attached the code (note that i am no expert on FPGAs, and i've been trying different configurations, and at some point, not precisely knowing what i was doing Smiley Sad), any advice on how to put both 9235 to work simultaneously will be appreciated.


thank you.

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Message 1 of 4

Hi  luismi911


I took a quick view to your attached VI and it looks like the architecture that you are currently using might not be the most adequate to make the module synchronization, have you already looked at the Basic Synchronizing NI 923x Modules example?


The following screenshot of that example shows how you should make the calls to the modules, start them both together and then make the acquisition in the same sequence, so that they would be on the same FIFO and hence you would be able to read them in the RT host from the same read call.





Hope that you could find this information helpful!


Message 2 of 4
Hi s.jimenez
First of all, thank you for your prompt answer. Regarding your suggestion, i hadn't checked the Basic Synchronizing NI 923x example, my bad Smiley Embarassed. After reading and understanding it a little, i tried to adapt it to my situation, sadly with no success. Some of the mistakes that i corrected were:
  1. one FIFO for acquiring data from both modules
  2. used single I/O nodes for start/stop and acquiring data from both modules
  3. changed the clock settings of the modules to: slot1 module providing clock signal for the slot2 module

the only big difference that i notice between the example is that i added the shunt calibration procedure to the sequence, do you think this is the problem?

summing up, i havent been able to obtain continuous readings from the second module, any additional help could be greatly appreciated.


best regards.


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For anyone following this thread:


the actual issue with my application was not the program itself, apparently one of the 9235 modules was damaged and not operating correctly. I am currently waiting for a replacement.


Thanks again for all the help.

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