How to lock phase of analog input with USB6009

[alcesleone]

I'm trying to figure out if its possible to lock the phase of analog input with a USB6009. I'm using the C++ API and the example files. I'm running a basic 50Hz sine wave into USB6009 and reading in values with the "Cont Acq-Int Clk" example. When I printf the first value - data[0] - the value will slowly drift. I'm not exactly certain how to lock onto this signal. Is this a triggering issue? I know the USB6009 doesn't have an analog trigger mode. Does anyone have any ideas?

Thanks and best regards,
Matt

[CWolf]

Matt,

You are correct that the USB 6009 does not support analog triggering.  If you could output a square wave that was phase locked to the sine wave, you could use that as a digital trigger on PFI 1. 

-Christina