Config_DAQ_Event_Message DAQ event 3 or 4

[Niranjan]

Hi,
I am trying to use Config_DAQ_Event_Message with event 3 or 4. I am acquiring a waveform (similar to sine wave). Now i want interrupt or callback to be fired every time input signal (AI) crosses a fixed threshold value. For example, every time signal passes -60 mV, i want to trap the event and record down the time or index at which signal crossed threshold value (-60 mV in my example). I guess i need to set trigger value 0 to my threshold. I tried doing it but i didn't get desired results. Trigger value 0 for event DAQ 3 must be in binary. does that mean i have to convert threshold (-60) to binary number? Has anyone used Config_DAQ_Event_Message? Does anyone has example code for DAQ event 3 or 4?
cheers
Niranjan

[Sastry V.]

Hello,

The DAQTrigVal0 and 1 are binary implies you have to select values between -32767 and 32768 for a 16 bit board. These values would linearly map to -10V to +10 V depending on the card.

Once these values are known to you, then using the Config_DAQ Event_Message will be just sames as you use for any other DAQ Events.

You may find examples by typing config_daq_event_message in the search box at http://www.ni.com/support.

I am attaching a simple program that I tried to write that will demonstrate. I havent worked much on it though.

Sincerely,
Sastry V
Applications Engineer
National Instruments