Hello twilight,
if you need to generate a digital pulsetrain the 6015 might not be the best hardware for that task. This is because the digital IO lines cannot be hardware timed. You need to drive them programmatically with software timing, which of course can have som jitter and variations in the timebase.
Depending on what you need to do, the static DIO lines of the Daqpad can be accurate enough, though.
There are VIs in the LabVIEW example library that show you how to program the digital lines. Look for VIs that are called "Write digital channel ..." or similar.
regards
Ingo Schumacher
Systems Engineering Manager CEERNational Instruments Germany