Generating Event using PCI 6110

[Arvind]

I want to generate an Event using the Config_ATrig_Even_Message function. I am using the external analog trigger to generate my trigger. What is the value I need to send in the 'chanStr' parameter for an external analog trigger in a PCI 6110 card?

Arvind

[JeremyB]

Dear Arvind,

Details of the function prototype are given in the NI-DAQ Function Reference Manual. The chanStr parameter points to the analog input channel that you want to monitor for the trigger event.

The example provided with the NI-DAQ Manual is "AI5" but obviously you will need to choose an appropriate channel for your application and board (NI 6110 having 4 analog input channels so you could use AI0 - AI3).

You can download the NI-DAQ Function Reference Manual for version 6.6 from the NI web site - alternatively it should have been installed with your NI-DAQ installation on Start>>Programs>>National Instruments>>NI-DAQ.....

From memory, because this is a high-level NI-DAQ function, you must not use AI_Configure after having called Config
_ATrig_Even_Message. You can potentially change the input range and polarity of the input using AI_Configure and this could mess up the event triggering. The NI-DAQ Function Reference Manual has more details.

Jeremy

[Arvind]

I know I can use AI0-AI3 if I want to use one of my four Analog input channels to generate the Event. But I don't want to use up the Analog input channels, instead I want to use the External Analog Trigger to generate the Event using the function Config_ATrig_Even_Message. By the way I am using Visual C++ 6.0. My DAQ board is the PCI-6110 and it is connected to the BNC-2110 connector block. The External Analog trigger is connected to the PFI0 pin.

The following web page: http://zone.ni.com/devzone/conceptd.nsf/webmain/BC6E35C087CFE31986256802007B8C6A?OpenDocument

talks about using the trigger channel to generate the Event, instead of using one of the Analog input channels, because that would be an inefficient way to use a analog input channel. But
they don't tell how to do it.

Any help would be appreciated.

Arvind

[JeremyB]

You do not need to use a separate dedicated trigger input should you wish to use an analog signal to trigger your acquisition - it is possible to get the NI 6110 to analyze any of the four input signals that you are acquiring, looking for the trigger conditions to be met. I get the impression from your response that my suggestion would tie up an analog input (AI0-3) unnecessarily? This is not the case with the NI 6110 and it will mean that you can go ahead and use the Config_ATrig_Event function

The only instance where you might need to consider using the PFI0 pin is if you
a) need to trigger the acquisition from a digital trigger
b) need to use all four analog input channels plus an additional analog input for the trigger that is unr
elated to the four acquisition channels.

The following page provides some good advice about triggering and specifically discusses the function calls required should you wish to use and PFI0 pin as an analog trigger input:

http://zone.ni.com/devzone/conceptd.nsf/webmain/2A03115556FB233386256870005BB522?opendocument&node=DZ52308_US

The following page gives some more detailed information about handling events generated by your data acquisition board:

http://zone.ni.com/devzone/conceptd.nsf/webmain/7B95597F3C6138F8862567EB006C9638?opendocument

I would suggest that the method using Config_ATrig_Event is perhaps the simplest but I hope the above information gives you enough scope to consider all the alternatives

Jeremy

[Arvind]

Jeremy,
Thanks for the information. I am going to try what you have said. If it is okay with you could you send me an e-mail at arvind@beer.com, if I need some clarifications on the information you have posted?

Thanks,
Arvind