count digital events on a Counter with pci-6602 with callback on CVI

[julesjay]

Hi,

I'm using a PCI-6602 card with CVI 8.5 and I need to trig on event.

On every pulse I received, I need to do some actions like increasing a counter, send a message on Rs232 etc.. I don't want to do any loop checking that the counter value has changed. I would like to use a callback to execute this code only on the edge or counter value event.

My problem is that I don't know which function can do this. Is there any way to get an event on a pci-6602? 

 Thanks 

James 

[mehdi.afif]

Hello.

It's completely possible to create a callback that will allow you to do what you want when a edge will occur on an external signal you define.

To do this, you can for exemple create a counting edges task that will use one of the 6602 counters,and the set your external signal to be the source of your sample clock.You'll then be able to register a callback with the function DAQmxRegisterSignalEvent, and your callback will be called each time an edge will occur on your specified sample clock source.

Here's 2 links that explain the events in DAQmx and how to handle them in CVI. The example ReadDigChan-ChangeDetectionEvent.pr that ships with DAQmx examples (Hardware Input and Output<<DAQmx<<Digital measurements) can be very useful to understand how to do. This example creates a signal event callback to detect change detection for digital inputs.

Regards.

[julesjay]

Hi,

Thanks for your answer.

I'm not sure I understand well what you said. Is this code corresponding to it?

        DAQmxCreateTask("",&Task1);
        DAQmxCreateCICountEdgesChan        (Task1,"Dev2/ctr0", "", DAQmx_Val_Rising, 0, DAQmx_Val_CountUp);
        DAQmxSetTimingAttribute                     (Task1, DAQmx_SampClk_Src, "/Dev2/PFI39");
        DAQmxCfgChangeDetectionTiming      (Task1, "/Dev2/PFI39", "Dev2/port0/line31", DAQmx_Val_ContSamps, 1);
        DAQmxRegisterSignalEvent                  (Task1, DAQmx_Val_ChangeDetectionEvent,0,ChangeDetectionCallback,NULL);
 

James

[mehdi.afif]

Hello.

The function DAQmxRegisterSignalEvent allows you to choose on which event you want to run your callback. For you, the event will be Sample Clock and not Change detection Event.

Regards.

[julesjay · Accepted solution]

That's right. If made it earlier without change detection and it works.

thanks for your help.