I'm new to NI-DAQ, so hopefully I didn't bring up a common topic.
Using a NI-DAQ 6143 S card I'm sampling 8 voltages simultaneously from a C++ application working with the ANSI C DAQmx drivers. The sampling clock is an external digtial speed encoder pulse train. Thus, it's frequency varies and I'm primarily interested in the voltage at known encoder positions. After 4096 clock edges the task is done. So far no problem.
While the relationship between encoder position and voltages is the top most important thing I have to measure, I also need to know the speed of the motor accurately since it may not be stable during one revolution. What I was able to do is to use ctr0 to measure the half period time of the encoder signal giving me an accurate speed information. So far so good.
Now... I cannot figure out how to synchronize the to measurements. What I would like to do is this:
The Start Trigger starts the acquisition of 4100x8 analog voltages AND also stores the current value of ctr0 (running off the internal 20 MHz clock) in the acquisition buffer on every falling sample clock edge.
Is there a way to add such a "counter read" to my analog input task rather than creating a second tasks I cannot synchronize? It would be fine just to get a "raw"counter value with eachconversion of the analog voltages even without scaling.
The point is that the application software is too slow to read the external Start Trigger signal and then kick off the analog and the counter task. The external trigger must start both measurements else I can't relate the measured values to the exact position of the motor.
Any suggestions are welcome.
