I want to write a U8 array containing 1M samples to the port of an NI 9401 connected to a cDAQ-9185. The problem encountered is the following: When I write an array of U8 containing 1M samples, only 1000 samples are generated on the port of the NI 9401. On the other hand, the vi write sees again that 1M samples have been written. To verify the problem, I use an oscilloscope to see lines 0 to 4, as well as a counter on line 0 of the port. the counter counts 500 pulses, which corresponds to 1000 samples at line output 0. The problem does not come from the frequency because we have the same symptom at 100 HZ 100 kHz and 1 MHz which is the frequency at which I wish to write. Do you have any idea where the problem comes from?
Yes, this is because you missed wiring these parameters of DAQmx timing and those default values were to generate 1000 samples per channel and stop the task.
If you know the number of samples to generate, wire that number to the samples per channel parameter of DAQmx timing.