fn enter_bootloader() -> !Expand description
Resets into the ROM USB-CDC download mode (bootloader).
(0,1) is a plain reset: the boot target is decided by the
FORCE_DOWNLOAD_BOOT flag, which the (1,0) state arms. esptool’s
--before usb-reset walk therefore lands in the bootloader. The flag is
only cleared again by inv flash after flashing (esptool write-reg)
— the ROM bootloader does not clear it itself.