Recently I was rebuilding my multi-rotor (x-type quad) and switching from the CC3D flight controller (which I love) to the APM 2.6 (ReadyToFlyer from Ready to Flyer Quads) flight controller. I wanted to add GPS and compass to enable fully autonomous flight, so I added the uBlox 6M GPS W/ Mounting backplane and compass module. Once I installed the GPS module and tried to configure it, I realized there was a lot I didn’t know, and very little clear information on how to set this unit up. Let me help the next guy with what I learned.
Installing the Board
The first problem I had was the actual installation of the board. There are no markings on the board that indicate which way is supposed to be mounted facing up and which side should be facing forward, so I guessed.
I mounted the board with the connectors facing upward (seemed logical – this way I had easy access to them), and the circular component toward the front-left. THIS IS WRONG!
This is not the correct mounting configuration. Of course it took me a lot of trial and error and digging through forums until I discovered the correct mounting configuration. I had m mounted the board upside down.
The correct mounting is with the text that reads “Ublox GPS Module V2.0” facing up and to the front of the multi-rotor. The small black component is the compass and should be oriented to the front-right (this puts the green LED to the front-left).
This is the CORRECT orientation. Make sure you connect the wiring harness before you mount the board. Once it is mounted it will be hard to access the connector.
Configuration of the GPS/Compass is Mission Planner
In the Mission Planner configuration (Initial Setup) there is a step for configuring the compass. Excluding “Manual” there are two options that target the APM flight controller. Although “APM with External Compass” sounds like the correct choice, the correct choice is “APM with OnBoard Compass”. This option sets the Compass Orientation to ROTATION_NONE. This means that the compass is upright and facing forward (the “APM with External Compass” option is for the 3DR GPS/Compass which is mounted upside done, so it sets the orientation to ROTATION_ROLL_180).
A Note On Radio Configuration
While trying to figure out the Compass Orientation I was thrown off by a Radio Configuration that I was unaware of. Every time I did a test flight, the quad copter would pitch backward whenever I pushed the pitch forward. I mistakenly thought this was somehow due to the compass orientation when in fact it was due to the pitch being inverted in Mission Planner.
In the Radio Configuration section, when I pushed the pitch up, the Pitch green bar would go up,. and when I pushed pitch down the Pitch green bar would go down. THIS IS WRONG. In Mission Planner the pitch needs to be inverted (so when you push pitch up the Pitch green bar goes down). To solve this I when into the configuration settings in my Turnigy 9X transmitter and reversed the elevator settings (FUNC SETTINGS | REVERSE | ELE).