How to unbrick the RX receiver and TX high-frequency head

I. Principle

Unbricking refers to fixing a device that cannot start or function properly due to failed firmware updates or incorrect configurations. For ExpressLRS or other flight controller devices, "unbricking" typically means restoring to normal working condition.
All receivers based on ESP are equipped with a bootloader mode, which cannot be damaged or tampered with. Even if you completely mess up the firmware upgrade, you can still restore the receiver to normal state through this default bootloader.
So technically, your receiver won't be bricked unless you have damaged the hardware itself.
But for the sake of explanation, we can use "bricked" or "soft-bricked" to refer to receivers that don't work properly and don't perform as expected.

II. Unbricking RX Module

Follow these steps carefully to restore your "bricked" receiver.

1. Ensure your receiver is powered on only when connected to a LiPo battery.

• If your receiver only powers on when connected to USB, move the receiver's 5v wire to a 5v pad that only powers on when connected to LiPo.
  • Set a multimeter to DC voltage mode. Plug USB into your flight controller. Disconnect the LiPo.
  • Probe/check each 5v pad on the flight controller.
  • The 5v pad that reads 0v on the multimeter is the pad that only powers on when connected to LiPo.
  • Solder your receiver's 5v wire to this pad.
• If in the above steps, you cannot find a 5v pad suitable for this procedure, follow these steps:
  • Disconnect the receiver's 5v wire from the 5v pad on the flight controller.
  • Solder wires of different lengths to any 5v pad on the flight controller.
  • Expose an appropriate length of conductor on this wire, which you can later connect to the receiver's 5v wire.

2. If you connected the LiPo in the previous step, disconnect it. Also, unplug the flight controller from the computer.
3. Prepare the receiver for bootloader mode.

• If your receiver has pads, bridge them together with solder.
• If your receiver has a button, use alligator clips to keep the button pressed.
• If your receiver has only a boot pad, connect it to the ground plane.
  Example receiver with Boot Pad:
  
  Example receiver with BOOT button:
  

Important

Do not skip this step even if your receiver's LED indicator is only constantly lit, to ensure the receiver is indeed in Bootloader state.

4. Connect to Betaflight or INAV Configurator, ensuring the flight controller is properly configured for ExpressLRS. Set Telemetry to Disabled.
5. Save and restart. Close Betaflight Configurator. Also, close any other applications that might be using the COM port.
6. Unplug and replug the USB cable. This ensures the connection between the flight controller and computer is fresh, and the COM port is not occupied or in use.
7. In ExpressLRS Configurator, select the firmware version you want to restore. Also, select your Device Category and Device Target, and set the firmware options you normally use.
8. Set the Flashing Method to Betaflight Passthrough.
   
9. Click the Flash button. Wait for PASSTHROUGH DONE to appear in the Build Log, then power on the receiver.
   

Important

If you don't see PASSTHROUGH DONE, it may be because you skipped some of the above steps or incorrectly configured the flight controller. Please repeat the above steps again

After powering on the receiver, the receiver's LED will be constantly lit.

10. Wait for the process to complete, hoping to see a success message. Otherwise, repeat the above process or try other methods (such as reflashing through an FTDI/UART adapter).
11. You can now turn off the flight controller's power and disconnect the LiPo battery or USB cable.
12. Remove the bridged or grounded pads, or if your receiver has a button, remove the alligator clips used to press the button.
13. Power on the receiver again to verify that it has returned to normal working condition.

Video Guide:

(This video is from YouTube channel DeltaGeek)

III. Unbricking TX Module

Most ExpressLRS TX modules based on ESP support firmware recovery through UART flashing or ETX Passthrough flashing method. Use either of these methods to restore your ESP-based TX module.
For ExpressLRS TX modules based on STM, recovery can be done through the STLink flashing method.
ExpressLRS TX modules are less prone to errors during the update process, especially when you follow the official flashing guide.
———— This article is referenced from ExpressLRS Getting Started: https://www.expresslrs.org/quick-start/unbricking/#help-i-bricked-my-rx**