I plan to add a depth finder to my Blue ROV (v1 ROV with Pixhawk + Raspberry Pi) to determine the distance from the bottom. Initially I would like to display the distance in QGC. Eventually I would like to implement a distance-from-bottom hold capability. Since this is similar to the altitude hold feature in Ardupilot, I hope there is a straight-forward way to plug in my bottom finder and implement this capability.
My initial assumption is that that I will need to write a program on the Raspberry Pi to receive the distance to bottom info convert it into MAV messages. However, I suspect there may be an easier way. Suggestions?