Connecting an Flytrex Core To HK APM 2.7

I have been a Flytrex user for coming up on about a year now. Ever since I brought my first quad(Phantom 2V+) I recently decided I wanted to build one from scratch. For the controller I went with the APM. Because I will still be flying my Phantom I want all my missions to be in one place so I brought another flytrex core to go with my APM quad.

However when I tried to hook it all up nothing would fit. The APM cable sold by Flytrex would just not work. I soon found out that the APM cable sold works with the 3DR GPS and not the HK APM GPS package.

Undeterred I figured out that it is not too difficult to modify the cable to work with one caveat.

First Step

Cut the 3 wires going to the Flytrex Core plug. Give yourself enough cable length.


Now remember that caveat I mentioned above. Well here it is. The power wires are reversed from how everyone else does it. The black wire is + and the red wire is -. Fortunately the HK APM has good Reverse Polarity Protection so my quad was saved.

The remaining blue wire is the Flytrex RX wire and this needs to be attached to the corresponding TX wire on the GPS module.

On the HK APM the TX wire is the Green one or Pin 3

It's up to you on how you connect all the wires.

The way I did it was to cut the TX cable on my GPS cable and splice in the cable. You could also remove the wire from the plug and undo the crimp and re-crimp it with the Flytrex RX wire.

Rather than splice the GND and VCC wires I soldered a header plug(like a Servo or ESC plug) on to the 2 flytrex power wires(remember these are reversed) and plugged it directly into the power terminals in the A0 - A11 or inputs(See Below) terminals on the APM.

Hopefully this helps someone out. The reverse polarity was a particularly annoying thing to find out.

Tags: Flytrex, APM, APM 2.7, Quadcopter


Welcome. is run by Geoff Evans.

Geoff also runs Geo Com Ltd who build and run web sites web apps etc.

In my off time I build/tinker with Arduino, Raspberry Pi, Beaglebone etc. I have made and minted may custom PCB's.

Over the years I have been involved with many stage productions both on stage, back stage, and sometimes on the very rear occasion front of house. In 2008 I won the AMI Showdown Award for sound design in ACG Senior College's Production of "The Player Project"

Depending on when I find time I will post here most likely about the above subjects. You can get me most of the times by the links below. I monitor Twitter but frequent posting will be rare.

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