Also, just for the record, APM hardware is VERY VERY OLD and NOT SUPPORTED. Please, everyone, stop buying them when about the same price you can get a pixhawk or a pixracer. I hate to say it but there are plenty of clones of these boards available too.
Get a pixhawk (of some sort) , and you won’t regret it… many cool new features,
http://ardupilot.org/copter/docs/common-choosing-a-flight-controller.html
pixracer: smaller hardware for smaller airframes with less features and lower cost
pixhawk: well proven mainstream hardware , also called "pixhawk1"
pixhawk2: latest and greatest pixhawk version, used in the solo, and now being sold on their own.
( other hardware’s are also available, but these three are the most popular options)
Buzz.