Connectors and pinout

Last updated 3 days ago

This section gives an overview of the pinout for various ports on the RDDRONE-FMUK66.

Connector and cable standard

Most interfaces on the RDDRONE-FMUK66 use the JST-GH connectors as specified in the Dronecode Autopilot Connector Standard. The PWM interface uses "standard" RC hobby servo connections. These PWM connectors are 3 pins spaced 0.100" apart.

Two different cables with JST-GH connector.

The male JST-GH connector has a clip on top. As described in the Dronecode standard, the first (leftmost) wire is usually the positive voltage. In some cables this wire is red. The last (rightmost) wire is ground. The wires in between carry different kinds of signals, depending on the function.

Overview of connector locations

The following pictures give an overview of all connectors (and LED indicators) on the RDDRONE-FMUK66. Most of the labels in the pictures are the same as the labels on the PCB itself. Below you can find further details about the functions of the different ports.

Port locations on the RDDRONE-FMUK66.
Servorail on the bottom of the FMU. It has a BEC input and PWM outputs.

The information below is being moved to different pages. This is work in progress.

Serial port

The serial port can be used to communicate with the FMU either remotely or with a companion computer. Often telemetry radios are connected to this port to provide a wireless connection with a ground control station. By default, PX4 listens and communicates using the MAVLink protocol on this port.

The levelshifter used in the current revision of the board does not work well with long cables. You should keep the cable between the board and the radio very short (preferably shorter than 10 cm or 4 inch).

Flow control is not enabled currently. You should not connect the RTS and CTS pins.

The labelling of RX and TX is inconsistent on some radios. RX on the FMU should connect to TX on the radio, but we often see that TX on the FMU connects to the pin labelled TX on the radio.

Telemetry radios usually have different variants. The 433 MHz version is used in Europe, while 915 MHz is used in the USA. Make sure you have the right version for your location.

USB interface

Reset button

LED indicators

Micro SD card slot

Arming switch

The arming switch is a safety feature which prevents take-off when the switch is not active. Further information about the arming switch itself is available at a seperate page.


NFC/I2C bus

SPI bus

Debug interface

Analog-digital converters

CAN busses

The RDDRONE-FMUK66 features two CAN (Controller Area Network) busses. PX4 implements the UAVCAN protocol, and supports some motor controllers, sensors and GPS solutions with a CAN interface. The current HoverGames kit does not include any hardware with a CAN interface, except the FMU itself.

Automotive ethernet

The FMU has a TJA110x two wire automotive ethernet (100BASE-T1) transceiver . However, this is not yet supported by PX4. Adding driver support to PX4 and implementing the protocol might become a HoverGames task/challenge in the future.

Ultrasound sensor

Infrared receiver/transmitter