Ultrasonic help (interrupts and analog triggers)

[jrz126]

I'm trying to use the Parallax PING module.
http://www.parallax.com/dl/docs/prod...-PING-v1.3.pdf

I came up with my own way of doing it, (see the second picture). The diodes keep the Digital output and PING module from fighting each other when the sonar is outputting the pulse width. I added a second diode so I could maybe keep the digital output from causing an interrupt.

It kinda works, but it only triggers the interrupt maybe 50% of the time. I get timeouts the other times.

Anyone familar with the analog triggers/interrupts? or thoughts on a better way to do it?