AWOL:
No-one said you added them on a whim, but you can get rid of the error message with a simple cast.
The only reason to have volatile qualifier is for polling loops on registers, and the only register you poll is the one associated with the echo pin.
Gotcha. I assumed there was some very good reason why it was asking for a volatile qualifier. The only value now with a volatile qualifier is *_echoInput
With that said, it didn't change my code size at all, so I suspect the compiler optimized the code identically both with and without the volatile qualifier. Or, maybe I just got lucky and the compiled code is just coincidentally the same length.
Tim