Hi Hamed,
First of all, Connect microcontroller to usb, and write C program on this controller for whatever job you want to be done, PDA will send data to microcontroller to perform proper action. Or,
sensor send signal to this microcontroller, and it send digital version
to PDA via usb. I am not too good with it and attaching two articles for the same:
http://www.arduino.cc/
http://www.ti.com/tool/ez430-f2013
Do update us again.
Thank you
Anil