Digital IO for a Load Cell using cRIO

[DeltaJ]

Hi All,

I am trying to read outputs from a load cell. The hardware is described at the link below (where it was suggested to the OP that they should use a RIO).

https://forums.ni.com/t5/LabVIEW-Interface-for-Arduino/Weight-measurement-using-load-cell-and-hx711/...

Essentially I need to monitor an input and, when it goes high, generate 25 pulses to a signal line and read corresponding outputs through another line. I've borrowed a cRIO-9074 with a NI9401 module built in due to the timing requirements.

I've some LabVIEW experience but have limited DAQ experience and in particular haven't worked with cRIO at all before. I'd like to get some high level pointers on the best approach / subVIs to use.

• Should I use a timed sequence structure to generate the 25 pulses? Or is there a better VI do do this?
• Should I monitor the signal line using a while loop also? Or how could I best convert this signal to Boolean outputs? What is the best way to synchronize my inputs with the outputs
• My application is that, when the load cell registers a particular force I have to signal retraction of a piston - part of the code is running on a Windows PC (and will require online user input etc). So I guess I'm using the cRIO as a very fast DAQ card. What is the best way to integrate the cRIO DAQ vi into the rest of my code? Should I launch this vi asynchronously and then communicate via queues and/or shared variables? Is there a better option?

Thanks in advance for your help,

Dave

[dracokev]

Hi DeltaJ,

I recommend taking a look at some of the examples for RIO devices if you have limited experience in the subject.

The Hardware Trigger Detection.vi example in particular seems to suit your triggering requirements.

The VI on the FPGA of your RIO device can communicate with Windows (your host) using FIFOs, not shared variables or queues.

Alternatively if you have a Standard Service Program contract with NI, you can self pace the online training on Embedded Control Monitoring which is a course that covers the fundamentals of programming on an FPGA.

[DeltaJ]

Thank you for the feedback - I'll certainly look at these options!

Kind regards,

Dave