Sirius ELRS MAVLink Telemetry - ArduPilot Firmware

I. MAVLink Mode Working Principle

1.1 Data Link Architecture

After enabling MAVLink functionality, the system establishes a complete bidirectional communication link:

Downlink (Telemetry): The aircraft sends data such as GPS position, barometric altitude, battery voltage, and attitude angles back to the RC transmitter through the receiver.

Uplink (Control): The channel commands from the RC transmitter are sent to the aircraft through the receiver.

1.2 MAVLink vs CRSF Mode Comparison

Feature	CRSF Mode	MAVLink Mode
Communication Direction	Unidirectional (Transmitter → Aircraft)	Bidirectional (Transmitter ↔ Aircraft)
Transmission Content	Control signals + limited telemetry	Control signals + telemetry data
Bandwidth Requirements	Low	Medium to High
Typical Applications	Basic flight control	Long-range flight, mission planning, real-time monitoring

1.3 Practical Application Scenarios

• Real-time Monitoring: RC transmitter screen displays aircraft position, altitude, battery level, speed, and other critical data
• Remote Diagnostics: Analyze aircraft status through telemetry data to quickly locate faults
• Ground Station Connection: Use with ground control stations like MissionPlanner for mission planning and flight monitoring

II. Equipment List

2.1 Flight Controller

• CoreWing F405 WING V2

2.2 Wireless Communication Modules

• Transmitter: Sirius 2.4G ELRS
• Receiver: SkyGuy Nano 2G4 RX

2.3 RC Transmitter

• Recommended: RadioMaster TX16S
• Compatible: Other RC transmitters supporting CRSF protocol

III. RC Transmitter Basic Settings

3.1 Enable External Transmitter

1. Enter the model settings menu and find the "SETUP" page
2. Turn off "Internal RF Mode"
3. Turn on "External RF Mode"
4. Set "Mode" to CRSF and "Baudrate" to 5.25M

Important

Why set "Baudrate" to 5.25M?

If set to 400k, it may not be possible to enter the ExpressLRS Lua script;

If set to 1.87M, it may not be possible to set Packet Rate to F1000.

3.2 Settings Reference

Black and White Screen Transmitter:

Color Screen Transmitter:

3.3 Transmitter and Receiver Binding

Important

For transmitter and receiver binding tutorial, refer to: How to bind ELRS Transmitter/Transmitter with Receiver

IV. Firmware Upgrade

Important Note

Before using MAVLink mode, the following firmware must be upgraded to the specified versions:

• Transmitter Firmware: ≥ 3.5.6 (factory firmware)

• Receiver Firmware: ≥ 3.5.6 (factory firmware)

• Backpack Firmware: ≥ CW 1.5.4 (CoreWing customized version)

  The above firmware can be upgraded through the CoreWing APP.

For information on how to update the ELRS firmware of the Sirius transmitter and SkyGuy receiver using the CoreWing APP, please refer to the following article:

V. MAVLink Mode Parameter Configuration

Note

When configuring transmitter parameters, ensure the receiver is powered off to avoid configuration issues.

5.1 Transmitter Parameter Settings

In the RC transmitter ExpressLRS script page, configure according to the following table:

Configuration Item	Setting Value	Description
Data Rate	F1000	Frequency 1000Hz, sensitivity -104dBm
Telemetry Ratio	1:2	Ratio mode, rate 19921bps
Mode Switch	Hybrid	Hybrid mode
Link Mode	MAVLink	Telemetry protocol

5.2 Receiver Parameter Settings

1. RC transmitter enters ExpressLRS script → Select Other Devices

2. Select SG Nano 2G4 RX receiver

3. Set the receiver protocol to MAVLINK, keep other parameters at default

6. Flight Controller Configuration

6.1 Hardware Connection

UART Selection Guide

CoreWing Flight Controller Receiver Connection Method:

• Must be connected to UART6

• Reason: UART6 has built-in DMA support and can stably run at high baud rates of 460800bps

  ⚠️ Note: Other UARTs (like UART4) are hardware compatible but lack DMA support, preventing proper MAVLink communication.

6.2 Flight Controller Parameter Settings

Method 1: One-click Configuration (Recommended)

1. Open CoreWing APP → Connect to flight controller → Enter the RC Transmitter Calibration page
2. Click Receiver

3. Select ELRS MAVLink → Click Next

4. Select UART6 → Click Next

5. Click Finish, the flight controller will automatically restart

6. Verify connection: Return to the RC transmitter calibration page and check if channel values change with stick movements

Method 2: Manual Parameter Configuration

1. Open CoreWing APP → Go to the All Parameters page

2. Search SERIAL6

3. Set the following parameters:

   • SERIAL6_PROTOCOL = 2 (MAVLink)
   • SERIAL6_BAUD = 460 (460800)

4. Click save and restart the flight controller
5. Verify connection: Check if channel values on the RC transmitter calibration page are normal

7. Ground Control Station Connection

7.1 CoreWing APP - Bluetooth Connection

Step 1: Configure Backpack

1. Go to ExpressLRS script on RC transmitter → Click Backpack settings

2. Set Backpack to On

3. Set Telemetry to BLE (Bluetooth)

4. Restart the RC transmitter to apply settings

Step 2: APP Connection

5. Open CoreWing APP → Click "+" → Select Bluetooth connection

6. Find the CoreWing Sirius-xxxx device and click to connect

Step 3: View Telemetry

After successful connection, go to the telemetry viewing page, and the information bar will display aircraft data transmitted back from the VTX:

7.2 CoreWing APP - WiFi Connection

Step 1: Configure Backpack

1. Enter Backpack settings

2. Set Telemetry to WiFi

3. Restart the RC transmitter to apply settings

Step 2: Phone WiFi Connection

Find the ExpressLRS TX Backpack 000000 WiFi and connect (password: expresslrs)

Step 3: APP Connection

1. Open CoreWing APP → Click "+" → Select ELRS Backpack connection

WiFi Connection Tip

If the phone WiFi is not connected to a network starting with ExpressLRS, the following prompt will be displayed:

Step 4: View Telemetry

After successful connection, the telemetry page displays aircraft data:

7.3 MissionPlanner Ground Control Station Connection

Step 1: Configure Backpack WiFi

1. Enter Backpack settings

2. Set Telemetry to WiFi

3. Restart the RC transmitter to apply settings

Step 2: Computer WiFi Connection

Find the ExpressLRS TX Backpack 000000 WiFi and connect (password: expresslrs)

Step 3: MissionPlanner Connection Configuration

1. Open MissionPlanner

2. Select UDP connection mode

3. Set baud rate to 115200

4. Set port to 14550

5. Click connect

   

   

   Step 4: Verify Connection

   After successful connection, click Connection Statistics to view MAVLink telemetry link status:

   

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