Automative:
First of, wich version of the IDE are you using?I quote form an old forum post:
which version of the IDE are you using?There was a bug that caused the pulsIn() code to premature timeout, see - http://arduino.cc/forum/index.php/topic,74813.0.html -
it should be fixed in the 1.0.1. version.Also I read that pulseIn is not good for use with an ultrasonic sensor but it should give you some result.
In my opinion, you can use pulseIn with every PIN, correct me if I'm wrong someone...
My NewPing library doesn't use pulseIn (it uses all low-level port register calls). This not only works a lot better, it's MUCH faster, more accurate and generates smaller compiled program size. NewPing works with older versions of the IDE as well as v1.0/1.01.
Pin 13 should be avoided due to the LED attached to the pin. I have no problems using pin 13. But, certain models of Arduino and certain revisions have noted problems when using pin 13. So, whenever there's a problem I always suggest not using pin 13, just in case. Also, it's a good idea to try connecting to different pins just in case one of the pins on the ATmega is fried.
Tim