The first flight was quite eventful with the quad taking off on its own due to an integer rollover causing the throttle to go from 0 to 255 when I lowered the sticks to much. After a couple of hours bug fixing the code on the controller the quad was finally again maneuverable without any hick ups.
I added a menu where I could precisely control the variables like distance of the obstacle, time it would override the pitch control, the scan interval and the override pitch value of the collision detection code on the receiver as well turn it off and on remotely of course.
Now I could finally test how the collision detection was working. And it worked partially. It would set the pitch of the quad to a set value moving it back a little bit from the obstacle. But the ultrasonic sensor was having a hard time correctly detecting it.
It seems that the position of the ultrasonic sensor isn't ideal because possibly some of the waves bounce off the underside of the quad itself.
More flights tomorrow...