Feature Request: flashing firmware over uart using ELRS backpack as bridge possible?

[pfreundl]

Hi :)

idk weather this is possible, but i saw that the happymodel backpack module has full spi functionality (clk, mi, mo, cs) and i was wondering if it would be possible to flash devices connected to that spi via backpack? I thought you could load precompiled firmware for any uart device onto your radios sd card, pass it to the backpack tx and send it to a backpack rx connected to the respective device. this would allow you to flash pretty much anything with a uart over the backpack system.

how i imaginge the implementation:

• since backpack is based on transmitting small messages via esp now which is limited to 250-byte payloads and precompiled firmware would be a lot larger, you would need to implement another two way protocol layer within this payload to handle correct transmission (and retransmission if nessessary) of the firmware.

• you would also need some software on the rx side to stitch the packages back together and translate them to spi (i guess the latter part exists already?)

• you could choose if you wanted the spi communication functionality integrated into the transmitted package (then you have to translate the precompiled software to spi commands before loading it on the radio -- maybe integrate non elrs firmware compilation into elrs configurator to get it to the correct format) or if the backpack rx knows how to do that (maybe it does it already, i have no knowledge of spi communication or flashing firmware over it -- hardware compatibility issues?).

it would be really cool if that would work, but there are probably hardware or software limits i don't know of. if so, please tell me, i would appreciate a bit of insight into the workings of elrs backpack :)

thank you for reading and thinking this through :)

greetings

[dzervas]

Flashing over BT is something that is already done by speedybee. You essentially have a BT-UART (not SPI) bridge (with HC-07 or ESP32) and you use the bluetooth link as the port. That's a solved problem (and ELRS 3.0 will support it natively with a WiFi bridge, not BT).

Problems start though when you try to flash using the Tx. It's tremendous amount of work to implement an ESP flasher from the ground up for another ESP MCU (so that the Tx can flash the Rx) and really, I can't see much of a use for it. You'll have to compile everything beforehand anyway...