how to acquire and read data before trigger?

[Cris Brown]

Hi, all:  

         I want to acquire a impluse signal, and the data when the signal begins is very important to me. So, I want to using a digStart trigger to acquire it, but then i'll lose what i want, maybe i can acquire it continuously, and use the trigger to start read the buffer after a delay(in order to wait the signal end), i don't know if there is any ANSI C functions I can use to do it in this way. I am using PCI6220, DAQmx9.02 and ANSI C.   If anyone have some info on this please let me know. thinks.

[DAQ_LabVIEW]

Hi Cris Brown:

               From your application,I suggest that you can use DAQmxCfgDigEdgeRefTrig function; define  pretrigger samples fitting for your application.

Try it. Best Regard!