Can I measure the fan speed by NI 9401 & cRIO 9075 under Scan Interface?

Hi,

I'm currently using NI 9401 & cRIO 9075 to develop a project, that is to control the CPU fans.

Since I have to communicate with other instruments by serial port so that I have a module of NI 9870 to implement the instrument control.

I've finished the instrument control part under scan mode, and would like to add the function of reading fan speed.

Now I wonder if there is some problem when I choose the Scan Interface to deverlop the program.

I found the following tutorial that it uses the FPGA interface to impement the PWM control and frequency acquisition.

http://www.ni.com/white-paper/3230/en/

So if the function of fan control is only developed under FPGA interface, I have to rewrite the instrument control part, seems to be a little complicated...