Hello,
I am trying to connect a RadioMaster AX12 ExpressLRS transmitter and a serial ELRS receiver to a BlueBoat/Navigator using CRSF over UART. My immediate goal is reliable RC input; arm/disarm will be configured only after the channels work.
System
- BlueBoat with Navigator flight controller
- ArduRover 4.7.1 Stable
- BlueOS 1.4.5
- QGroundControl: 4.2.7
- RadioMaster AX12, internal ELRS transmitter
- Generic 2.4 GHz serial ELRS receiver, with RX, TX, 5V, and GND pads
AX12 / receiver status
- AX12 internal ELRS: Transmitter mode, RFBaud 921600, Packet Rate 500 Hz 2.4 GHz, Telemetry Std 1:128, Wide switch mode, Model Match Off.
- Receiver binds successfully: steady green LED when the AX12 is on, yellow blinking when it is off.
- Receiver WebUI:
- Serial Protocol = CRSF
- Model Match disabled
- Force telemetry off disabled
- Lock on first connection enabled
- AirPort serial device disabled
Wiring tested
I initially used the Navigator SERIAL 1 six-pin connector:
- Pin 1 / 5V → receiver 5V
- Pin 2 / Navigator TX → receiver RX
- Pin 3 / Navigator RX → receiver TX
- Pin 6 / GND → receiver GND
I checked continuity with a meter:
- Receiver TX reaches Navigator pin 3 / RX.
- Receiver RX reaches Navigator pin 2 / TX.
ArduRover configuration
- SERIAL1_PROTOCOL = RCIN
- SERIAL1_BAUD = 57600
- SERIAL1_OPTIONS = None
- RC_PROTOCOLS = All
- RSSI_TYPE = ReceiverProtocol
- RC_OPTIONS:
- “Use 420kbaud for ELRS protocol” enabled
- “Log RC input bytes” enabled
- “Ignore RC Receiver” disabled
- No BlueOS Serial Bridge is configured.
I also prepared SERIAL 3 as an alternative:
- SERIAL3_PROTOCOL = RCIN
- SERIAL3_BAUD = 57600
- SERIAL3_OPTIONS = None
I understand the Navigator port mapping is:
- SERIAL 1 → /dev/ttyS0
- SERIAL 3 → /dev/ttyAMA1
- SERIAL 4 → /dev/ttyAMA2
- SERIAL 5 → /dev/ttyAMA3
Observed result
QGroundControl reports 0 detected radio channels.
In BlueOS MAVLink Inspector, I subscribed to RC_CHANNELS. ArduRover sends the RC_CHANNELS message, but its contents are:
- chancount = 0
- chan1_raw through chan18_raw = 0
- rssi = 0
This appears to mean that the Navigator is not receiving or decoding valid CRSF data.
Important finding
In the receiver WebUI, UART baud was set to 420000.
Questions
- Is receiver UART baud = 420000 the correct value for an ELRS CRSF receiver connected to a Navigator UART with RC_OPTIONS 420kbaud enabled?
- Can CRSF RC input be used on Navigator SERIAL 1, SERIAL 3, or SERIAL 4, or are any of these restricted on BlueBoat?
- How does the physical Navigator UART data path connect to the Raspberry Pi Linux paths, for example SERIAL 1 → /dev/ttyS0? How does ArduPilot SERIAL1_PROTOCOL = RCIN receive that data?
- Could a BlueOS service, UART mapping, or port ownership issue block CRSF input even when no Serial Bridge is configured?
- Is an RC_CHANNELS message with chancount = 0 definitive evidence that no valid receiver UART data reaches ArduPilot?
- what Navigator-specific diagnostic do you recommend next?
Thank you.
