Order #ORDER 8968 - Sub250 Dolly25 - flash Flight conntroller

Help Unmanned Tech
1

Order Number: ORDER 8968
Product Name: Sub250 Dolly25
Brand: Sub250
flashing flight connrtroller
having problems flashing FC

2

Hi Mark,

Thanks for reaching out about your Sub250 DollyFly25 V2 HD O4 Pro GPS (Order #8968). Happy to help you get that flight controller sorted!

Here are the key details for flashing your FC:

Flight Controller: Sub250 Red Fox A3 45A AIO
Betaflight Target: SUB250REDFOXF722AIO
Factory Firmware: Betaflight 4.4.3

Important — USB Connection:
Your drone’s FC does not have a USB port directly on the board. It uses an external USB-C adapter board (SH1.0 5-pin to Type-C) that should have been included in the box. Make sure you’re using this adapter to connect the FC to your PC.

Flashing Steps:

  1. Download and run the ImpulseRC Driver Fixer tool (free) to ensure correct USB drivers are installed.
  2. Use Betaflight Configurator (latest version from betaflight.com).
  3. Connect the USB-C adapter to the FC’s SH1.0 port, then plug USB-C into your PC.
  4. If the FC connects normally, go to the Firmware Flasher tab, select target SUB250REDFOXF722AIO, choose your firmware version, and click Flash Firmware.
  5. If you can’t connect, you’ll need to enter DFU mode: hold the boot button on the USB-C adapter board while plugging in USB, keep holding for 2–3 seconds, then release. The dropdown should show “DFU”.

Quick Checks:

  • Make sure you’re using a USB data cable (not a charge-only cable).
  • Disconnect all peripherals (GPS, DJI O4 Air Unit, receiver, etc.) from the FC’s UARTs before flashing — only the USB should be connected.
  • Plug directly into your PC (no USB hubs), preferably a USB 2.0 port.
  • Close all other software that might be using the COM port.

To help you further, could you let me know:

  • What exactly is happening when you try to flash? (e.g., won’t connect at all, can’t enter DFU mode, flash fails with an error, etc.)
  • Are you using the SH1.0 to USB-C adapter cable that came with the drone?
  • What operating system are you on (Windows 10/11, Mac, Linux)?

Once we know what symptoms you’re seeing, we can narrow it down quickly. If it turns out to be a hardware issue with the FC, we’ll get that sorted out for you too.

Best regards,
The Unmanned Tech Team