I have a GPS unit that sends a PPS (Pulse Per Second) to NI 6229. The PPS signal is a TTL signal of 3.3V. The PPS signal is sent to NI 6229 at 1Hz. The issue is that the NI cannot seem to read the PPS signal. I have looked at the oscilloscope, and I can see the signal. I don't know what's going on. Please help!! Just an assumption, could the reason why NI card cannot read the signal is due to the speed of the TTL signal.
How are you trying to read it? What is the pulsewidth of the signal?
Open up MAX, open a test panel for your device, choose counter i/o edge counting mode. If the pulsewidth is very small, this will be much more effective than polling the signal via standard digital input.
Thank you. I just realized that it was a timing issue. The GPS unit was sending PPS signal in microsecond while i was reading in millisecond. I had to convert the PPS Signal to millisecond.