SpeedyBee ELRS Nano RX - bricked and looks unrecoverable using button / BF passthrough..?

[sudden delta]

Hello flasher community :-),

looks like I'm stuck with the first hard2recover bricked receiver. It has solid red LED on, but is not bound to my transmitter / no reactions.

I have wired it to my F4 V5 Ominbus FC, and serial protocol was ok at the very beginning and it did start flashing. After 3% points it stopped, potentially due to power supply becoming a little instable (had the RX powered from 5V pin off the FC, FC connected to PC over an old USB hub. When doing this, startup beeper on the FC sounds a little detuned, unlike when powering the FC over battery).

I have tried following the recovery guides (e.g. pressed the RX button during power up, disabled telemetry in Betaflight, then tried BF passthrough flashing), however I always end up with the following error message in Configurator (see image).

What am I doing wrong. Do I need an FTDI adapter next, or will it not change anything for the better?

Thank you for hints.

BR, Reinhard

[hot tangle]

Show a clear photo of the receiver wiring

And then follow the !recovery flash procedure

[desert summit]

Follow these steps to recover a bricked RX:

- Move the 5V wire going to the receiver to a 5V pad that only powers on when a LiPo is connected 
- Disable Telemetry in Betaflight
- Save and Reboot
- Close Betaflight Configurator and unplug USB and LiPo
- Bridge the boot pads or hold down the boot button on the receiver
- Plug in USB
- Click "Flash" in the ExpressLRS Configurator, after selecting via Betaflight Passthrough method
- Wait for the line PASSTHROUGH DONE to appear
- Plug in LiPo (with boot button held down/bridged)
- Wait for the process to finish (with success hopefully)
- Unplug everything, unbridge the boot pads, then power on to confirm the LED blinks, and then goes into WiFi mode

Comprehensive guide here: https://www.expresslrs.org/quick-start/unbricking/

[sudden delta]

I did follow the guide. Red LED is always on, even when de-soldering RX/TX and just applying power to RX. 3 times quick power cycle also does not change anything.

..regardless whether I'm holding down the button during power-up or not..

Will power RX from independent DC power supply now and go exactly by the timing 'when line in configurator appears', to not leave anything untried..

Same result.. 🥴

Setup was like this:

(when I connected FC to USB, the RX remained un-powered <btw, why are we supposed to hold down the bootloader button on the RX when no power is applied??>. Next step powering up the 5V power supply to supply the RX - while keeping button pressed down)

[hot tangle]

This won't work as you have no ground on the FC

Follow the recovery flash procedure exactly

Or get a FTDI and flash using that

[sudden delta]

ok, you mean common GND btw external power source for RX and FC is needed.

let me try this (w/o making a GND loop hopefully. Maybe I finally change over to using a LiPo instead of the power supply..)

.. I will measure all 5V pins on the FC first - maybe there are some which are only powered when connecting to LiPo..

Aargh, this darn Omnibus has ALL 5V pins connected to USB, ie ALL of them show 3.xV when only connecting FC to USB, without LiPo connected 🙁

tried pins on left/right side whatsoever..

..even the RAM pin on top is 'USB hot'

Will try another FC, in case I find one 🙂

[hot tangle]

Use the DC power supply. Disconnect the 5v wire from the FC, connect it to the power supply, and connect the ground to the FC. Hold down the boot button, plug in USB, click flash, when PASSTHROUGH DONE appears, turn on the power supply

[sudden delta]

ok, will do. Was scared about a GND loop (power supply having another potential on GND than FC, causing 5V voltage differential being an arbitrary, much higher value). Hope I will not fry the FC.. 😃 BTW, just found an old Fortini and tried to bring it back to life. Not so easy, for some reason connecting 12V from power supply to BAT+/- pins does not work. Will revert to Omnibus and go by your guidance then. Fingers crossed..

crocodile clamp = 5V from power supply. rdy-set-go!..

1st time no luck

5x = no 🙁

tried different timings, to be closer to 'PASSTHROUGH DONE' message, and sometimes a little more delay > no winner

RX shows solid red light all the time