Interfaces¶

Here, an overview of the communication interfaces used within the Highdra system is given. It lists the protocols and buses employed for data exchange between the MB, BMS, MMB, and the Skynode/FlightController. The main interfaces discussed include CAN/Cyphal, Serial/UART/Mavlink, and PWM.

CAN / Cyphal¶

The Firmware of the Highdra communicates internally on the CAN bus. CAN offers an electrical robust channel with differential signals and allows a decentralized structure. The communication of BMS, MMB and MB uses the Cyphal protocol.

This internal bus is labeled CAN-3 (on the MB).

Additionally there is a second CAN bus (and a third, redundant bus) to enable communication of the ESC with the Skynode/FlightController. External payloads are attached to this CAN-1 bus as well and the MB may participate as observer.

The third bus, CAN-2, is a redundant and safety oriented bus, used only for communication from the Skynode/FlightController to the ESC. It has no payload and no other participants like the MB.

CAN usage

The CAN based (primary & redundant) communication of the FlightController is currently disabled.
For ESC control PWM modulation is used (see below).

Serial / Uart / Mavlink¶

The Skynode/FlightController include a serial UART based bus as well. It is connected internally to sensors (GPS, Gyro, IMU, etc.) and to the MB. This communication is used for internal states, commands and to transmit sensor data. The used protocol is Mavlink.

Mavlink usage

The Skynode/FlightController connects the system #1 to the Telem3 interface and routes common messages towards the MB.

PWM¶

A deprecated but still in use method for data transfer is PWM. It has electrical drawbacks but offers a simple pulse width modulation.

PWM usage

PWM is still used for - ESC control from FlightController - LandingGear command emit from Skynode (received by MB and translated to Cyphal/CAN)