firmware binaries for HC32F460 Series MCUs include a special ICG (Initialisation Configuration) section, which is used to configure the chip on reset. this section is only used when booting without a bootloader, and is not needed when booting with a bootloader.
the boot_mode option allows you to choose between two modes:
primary: the ICG section is included, and the firmware supports booting with OR without a bootloader. This is the default.secondary: the ICG section is not included, and the firmware can only be booted with a bootloader. This saves about 1.5k of flash space.
Note
if you are unsure which mode to use, use primary.
the primary boot mode still supports booting with a bootloader, only the other way around is not supported.
Caution
do not attempt to boot a firmware with boot_mode=secondary without a bootloader.
since there will be code in the ICG section, the chip may be configured incorrectly.
this could cause anything from weird behaviour to the chip being permanently damaged.
the boot_mode option can be set in the board definition file, or in the platformio.ini file.
platformio.ini:
[env:my_env]
# ...
board_build.boot_mode = secondary