Thanks man...currently I'm using pwm_input.cpp ( driver code ) and I can find the rpm using the pulse time period. I can connect my sensor to AUX Pin 5 and using the variation in pulse duration I can calculate the propeller rpm.
For this currently I'm using pwm_input test command from the terminal. But this code doesn't publish the value to the pwm_input topic ( there is no ORB_publish() ) . Secondly I want to run this code using ISR and start the driver as well as publishing time_period of pulses to the topic once the controller is powered on.
Can you just tell me the direction to proceed.