RMRC Recruit / AR900 “Phönix” Build

After having experienced the fun of sending a Parott Disco on a long waypoint mission and then losing it in high winds, I wanted to build something even better – but use readily available components this time. If you want to make the same one, I suggest learning from various YouTube videos, such as Painless360 – and then see my notes here for specific areas that I had trouble with.

I used DJI FPV, and a Matek 765. While you can use an F405, the pinouts are different, so you won’t be able to use my notes.

Battery is 3S2P with Sanyo 18650 that are 3400mAh each and held by this frame: https://www.thingiverse.com/thing:4340601

Use Velcro to mount everything except for the camera mount, which I glued in place to eliminate wobble.

Make sure 765 is oriented with the plane icon on it pointing forward. If you pick another orientation, there is a way to configure it to work, but it is more steps.

ArduPilot Setup

You have to do the normal setup as in the docs – I am only mentioning unusual things that I had to change and that were not in the docs. Here are some of those trouble spots:

Airspeed: You can install like my photo, or in the wing. You do not need to connect both tubes. Just connect to the straight connector and cut off the angled one. Also, it doesn’t matter which inlet you connect the tube to on the sensor as either will work because it just changes to the one that it sees more pressure on.

In Mission Planner, go to Setup->Optional Hardware->Airspeed

Select “Use Airspeed”
Ignore Pin for now.

Set Type to Analog

Now in Mission Planner, go to Config-> Full Parameter Tree

Change ARSPD_PIN to 10

Click on Write Params on the right side of the app.

In DJI googles, under Servo Setup, set AIL to reverse. All others stay not-reversed.

In Mission Planner, Setup->Mandatory Hardware->Servo Output
Set function in this order: Throttle, Disabled, Elevon Left, Elevon Right. The rest are disabled. Elevon Right is reversed.

Go into Config->Full Parameter Tree->RCMAP
Pitch (2), Roll (1), Throttle (3), Yaw (4)

Matek 765 connections:

Airspeed sensor uses Sig (yellow), 5v (red), and GND (black). These connect on the F765 to the area to the right of the SD slot where it says 5v, AIS, and GND.

GPS 880 Connections:

Yellow SDA on GPS goes to DA1 on the F765
Black GND on the GPS goes to one of the G
White TX on the GPS goes to RX2on the F765
Green RX on the GPS goes to TX2 on the F765
Red VCC on the GPS goes to 4v5 on the F765

Gray SCL on the GPS goes to CL1 on the F765

DJI FPV air unit:

You will have to extend the wires – I used 26 gauge servo wire and solder and heat-shrink tubing.

Red Power goes to the 9V pin on the F765
Black Power GND goes to one of the G pins on the far right edge of the board.
White UART RX goes to TX1 on the F765

Gray UART TX goes to RX1 on the F765

Brown Signal GND goes to one of the G next to the 9v pin
Yellow DJI HDL Signal goes to the RX6 pin on the F765

3DRV2 telemetry radio wiring:

Pin 2 on the 3DR goes to TX7 on the F765
Pin 3 on the 3DR goes to RX7 on the F765
Pin 1 on the 3DR goes to 5V on the F765
Pin 6 on the 3DR goes to G on the F765

RTS and CTS are not used.

Servo connections:

The throttle “servo” wire goes to S1, Vx, and G (the first servo connection)
The left elevon servo goes to the S3 servo position.
The right elevon servo goes to the S4 servo position.