Kakute F4 AIO V2 to Raspberry Pi 4 - MAVLink connection issues

ArduRover
1

I am building a terrestrial rover using a Kakute F4 AIO V2 running ArduRover 4.x and a Raspberry Pi 4B (OS with Desktop). I am trying to establish a MAVLink connection between the two via UART to control the rover over a 4G/LTE tethering connection and manage video streaming.

Wiring:

  • RPi Pin 14 (TX) → Kakute R6 (UART6)

  • RPi Pin 15 (RX) → Kakute T6 (UART6)

  • RPi Pin 6 (GND) → Kakute GND (Common ground confirmed).

  • Voltage on Kakute TX pad measured at 3.24V.

Current Parameters (Full.param):

  • SERIAL1_PROTOCOL = 2 (MAVLink 2)

  • SERIAL1_BAUD = 57 (57600)

  • SERIAL1_OPTIONS = 0

  • BRD_ALT_CONFIG = 0

  • (Note: On this board, UART6 physical is mapped to SERIAL1 in software).

Troubleshooting performed:

  1. Loopback Test on RPi: Connected RPi TX to RX, verified serial communication works (cat returns echoed characters).

  2. Service Conflicts: Disabled Serial Console and Login Shell on RPi via raspi-config. Disabled Bluetooth (disable-bt) in config.txt to ensure /dev/serial0 maps to ttyAMA0.

  3. Alternative Ports: Tried connecting to UART4 (SERIAL3) and UART3 (SERIAL5) with corresponding parameter changes, but no heartbeat received.

  4. Signal Monitoring: Used stty and cat /dev/serial0 on RPi; no incoming data/garbage characters visible even after swapping TX/RX lines.

  5. Isolation Test: Disabled ELRS (SERIAL3_PROTOCOL = -1), GPS, and OSD to reduce CPU load on the F4 processor, but the serial port remains silent.

  6. Inversion Test: Tried SERIAL1_OPTIONS = 8 (Invert RX/TX) in case of hardware inverters on UART6, with no luck.

The issue: Despite the Raspberry’s UART being functional and the Kakute showing correct voltage on the pads, no MAVLink packets are being received by the RPi (tested via MAVProxy and raw cat).

Is there any specific hardware limitation on the Kakute F4 AIO V2 regarding UART6/UART4 when used with ArduPilot? Are there DMA conflicts or specific BRD_ALT_CONFIG settings required to “wake up” these ports for MAVLink telemetry?

Any help would be greatly appreciated!

2

Hello! No one knows how to give me a hand? :grin: