We want a USB camera to start acquisition when a TTL edge is detected by our NI PCI 6013 card (WinXP), with minimal time delay (<0.1 ms).
It works fine, but too slow and unpredictable. CCD acquisition occurs at a 1.5 KHz rate, by calling a DLL inside labview, which is working fine. We do not miss a single pulse once we start calling the DLL in the for-loop, USB + camera + labview are fast enough. The problem seems to be the unpredictable time delay between detecting the edge and calling the DLL. The current program is attached.
Right now, a dummy voltage measurement is performed, triggered on the falling TTL edge. Of course, the voltage measurement itself costs time unfortunately. I am looking for a smarter way of progamming, such that execution proceeds directly after TTL edge recognition. Any ideas?
Background:
1.5 kHz laser system, which gives electric triggers to the CCD controller and chopper. Part of the laserlight is modulated by an optical chopper, which gives a TTL signal to communicate the current state: blocking or open. We want to start acquisition with a known chopper state.
