Is it possible to enter serial bootloader from application?

[robdobson]

I have been using some ESP32 development boards which don't have sufficient capacitance on EN to allow reliable operation of esptool.

Several of these are now in use and some of them refuse to enter serial bootloader mode so I can't re-flash them.

I have Micropython installed on them and I am wondering if there might be a way to write a Micropython script to put the chip into serial bootloader mode so that esptool (perhaps modified to remove the RTS DTR line waggling code) can be used to flash them?

Any ideas?

[pratik2440]

I cannot answer this without having information on your hardware (i.e. what is accessible physically and what is not).
If your board is in a product that the end user is using and can only access a USB connector to re-flash the board, that can be tough.
Do you have access to the EN line via a reset button of something? Just pressing it repeatedly when the ESP tries to flash the board will sometimes cause the right sequence and enter boot mode.

It really depends on what you/end user can do with the hardware.