I am using a USB-6009 multifunction DAQ with Windows 10, nidaqmx-python 0.5.5 and Python 3.6 as a digital counter on the PFI0 port. The counter tests good in NI MAX 17. Also, if I read multiple samples, the counter does increment as expected when presented with a 1 kHz square wave.
However, I find that the counter state is reset before every read operation. In other words, if I read 1 sample at a time, I will get the value "0" or "1" as an output. If I read, for example, 1000 samples at once, each sample (more or less, depending on sampling rate) is incrementing as expected.
I am using the example code in ci_count_edges.py, which uses i_channels.add_ci_count_edges_chan().
The underlying NI DAQ MX function is DAQmxReadCounterU32Ex(), which isn't supposed to do this. Therefore, the cause is a bit of a mystery to me.
Any ideas on why the counter is not maintaining state between calls to DAQmxReadCounterU32Ex()?
