I have AMP 2.6 with Arducopter 2.3.
I have Sonar MB1040 LV-MaxSonar-EZ4.
it;'s connected in A0 with Signal in AN port of the sonar.
but I can figure out how to get the "Sonar enable" checkbox "checkable", is always disabled. Sonar clicks if you put the ear near, so look to be working.