Upgrading ELRS Firmware for Downconverters and SkyGuy Receivers

Warning

Firmware upgrade order: Receiver → Backpack → TX

I. Principle

The CoreWing APP is equipped with firmware upgrade functionality for the Sirius transmitter and receiver. ELRS firmware updates can be completed directly within the CoreWing APP, which is more efficient and convenient compared to traditional ELRS upgrade methods.

Before upgrading the firmware, it is recommended to confirm whether you will be using ELRS CRSF mode or ELRS MAVLink mode for subsequent use. The two modes have different focuses and are suitable for different scenarios:

Comparison Item	ELRS CRSF Mode	ELRS MAVLink Mode
Primary Use	Primarily for standard remote control	Primarily for remote control + telemetry + ground control station data link
Transmission Content	Channel control signals + basic telemetry	Channel control signals + complete MAVLink telemetry data
Transmitter Experience	Simpler setup, suitable for direct flying	Can be combined with Lua, APP, or ground control station to view more flight status
Bandwidth Usage	Lower	Medium to high
Recommended Use Cases	Daily flying, sport flying, training, standard fixed-wing flying	Long-distance flights, mission aircraft, aerial surveying, line patrol, scenarios requiring real-time data viewing with CoreWing APP or Mission Planner

Tips

If you only want your aircraft to stably receive remote control commands, using CRSF mode is simpler;
if you also need ground control station telemetry, mission planning, and real-time aircraft status monitoring, then MAVLink mode is more suitable.

II. Device Preparation

Flight Controller (choose any one)

• CoreWing F405 WING V2

Wireless Communication Modules

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

RC Transmitter

• Recommended: RadioMaster TX16S
• Compatible: Other RC transmitters that support the CRSF protocol

III. Basic Setup and Binding

3.1 Enable Transmitter

1. Enter the model settings menu and find the "SETUP" page
2. Turn off "Internal RF Mode" (built-in RF)
3. Turn on "External RF Mode" (external RF)
4. Set "Mode" to CRSF and "Baudrate" to 1.87M

3.2 Enable Transmitter Detailed Settings

Color Screen Transmitter

Black and White Screen Transmitter

3.3 Receiver Connection Instructions

Important

Connection method between CoreWing F405 WING V2 flight controller and receiver

1. Interface requirement: Must connect to Serial Port 6

2. Reason:

   • Serial Port 6 has built-in DMA support
   • Supports high baud rate communication at 460800bps

⚠️ Note: Although other serial ports (like Serial Port 4) are hardware compatible, this port does not support DMA, and will not be able to communicate properly if the receiver uses Mavlink mode.

3.4 Transmitter and Receiver Binding

Important

For a tutorial on binding the transmitter and receiver, refer to: How to bind ELRS transmitter/receiver with receiver

IV. Firmware Upgrade

4.1 Receiver Firmware Upgrade

Step 1: Enter Receiver WiFi Mode

• Method 1: Automatically enters after power-on and waiting for 60 seconds
• Method 2: Force entry by holding the BAT button for 5 seconds
• Method 3: Enter the ExpressLRS Lua script, find WiFi Connectivity, and click Enable Rx WiFi

RGB LED Indications for Receiver WiFi Mode:

RGB LED (Skyguy Receiver)

Single Color LED

Step 2: Upgrade Using CoreWing APP

1. Open CoreWing APP → Enter the toolbar

2. Click Sirius Upgrade

3. Select ELRS, click Receiver

ELRS-CRSF Mode

If using ELRS CRSF mode, select the receiver firmware with CRSF suffix

ELRS-Mavlink Mode

If using ELRS Mavlink mode, select the receiver firmware with Mavlink suffix

The following content uses Mavlink as an example

5. Click Direct Update

6. Click Start Upload

WiFi Connection Instructions

If prompted that you are not connected to a WiFi starting with ExpressLRS, please open your phone's WiFi settings to connect. The default password is: expresslrs (lowercase)

Connect to ExpressLRS RX WiFi (password: expresslrs)

8. If this page appears, click close and select Do not use internet connection (or keep current connection)

9. Click Start Upload again

10. Wait for the firmware upload to complete, which will display Flashing Success

4.2 Backpack Firmware Upgrade

Step 1: Start Backpack WiFi

1. RC transmitter enters ExpressLRS script → Select WiFi Connectivity

2. Select antenna Backpack WiFi and enable it

3. Enter the WiFi running page (automatically exits after about 5 seconds, WiFi remains active)

Step 2: Upgrade Using CoreWing APP

4. Open CoreWing APP → Enter the toolbar

5. Click Sirius Upgrade

6. Select ELRS, click Backpack

ELRS-CRSF Mode

If using ELRS CRSF mode, select the backpack firmware with CRSF suffix

ELRS-Mavlink Mode

If using ELRS Mavlink mode, select the backpack firmware with Mavlink suffix

The following content uses Mavlink as an example

7. Click Direct Update

8. Click Start Upload

9. Click to open WiFi settings

10. Connect to ExpressLRS Backpack WiFi (password: expresslrs)

11. If this page appears, click close and select Do not use internet connection (or keep current connection)

12. Click Start Upload again

13. Wait for the firmware upload to complete, which will display Flashing Success

4.3 Antenna Firmware Upgrade

Step 1: Start Antenna WiFi

1. RC transmitter enters system menu, open ExpressLRS script
2. Select WiFi Connectivity → WiFi Connectivity in sequence

3. Enable antenna WiFi

4. Stay on the WiFi running page

Step 2: Upgrade Using CoreWing APP

Open CoreWing APP → Enter the toolbar → Click ExpressLRS

5. Click Sirius Upgrade

6. Select ELRS, click Antenna

ELRS-CRSF Mode

If using ELRS CRSF mode, select the antenna firmware with CRSF suffix

ELRS-Mavlink Mode

If using ELRS Mavlink mode, select the antenna firmware with Mavlink suffix

The following content uses Mavlink as an example

7. Click Direct Update

8. Click Start Upload

9. Click to open WiFi settings

10. Connect to ExpressLRS TX WiFi (password: expresslrs)

11. If this page appears, click close and select Do not use internet connection (or keep current connection)

12. Click Start Upload again

13. Wait for the firmware upload to complete, which will display Flashing Success

Technical Support QR Code

If you have any questions, please scan the code to contact technical support: