Chapter 2. API Reference
CONFIG_BOOTLOADER_SKIP_VALIDATE_ON_POWER_ON
Skip image validation from power on reset (READ HELP FIRST)
Found in: Bootloader config
Some applications need to boot very quickly from power on. By default, the entire app binary is read
from flash and verified which takes up a significant portion of the boot time.
Enabling this option will skip validation of the app when the SoC boots from power on. Note that in this
case it’s not possible for the bootloader to detect if an app image is corrupted in the flash, therefore it’
s not possible to safely fall back to a different app partition. Flash corruption of this kind is unlikely but
can happen if there is a serious firmware bug or physical damage.
Following other reset types, the bootloader will still validate the app image. This increases the chances
that flash corruption resulting in a crash can be detected following soft reset, and the bootloader will fall
back to a valid app image. To increase the chances of successfully recovering from a flash corruption
event, keep the option BOOTLOADER_WDT_ENABLE enabled and consider also enabling BOOT-
LOADER_WDT_DISABLE_IN_USER_CODE - then manually disable the RTC Watchdog once the
app is running. In addition, enable both the Task and Interrupt watchdog timers with reset options set.
Default value:
• No (disabled)
CONFIG_BOOTLOADER_SKIP_VALIDATE_ALWAYS
Skip image validation always (READ HELP FIRST)
Found in: Bootloader config
Selecting this option prevents the bootloader from ever validating the app image before booting it. Any
flash corruption of the selected app partition will make the entire SoC unbootable.
Although flash corruption is a very rare case, it is not recommended to select this option. Consider
selecting “Skip image validation from power on reset”instead. However, if boot time is the only
important factor then it can be enabled.
Default value:
• No (disabled)
CONFIG_BOOTLOADER_CUSTOM_RESERVE_RTC
Reserve RTC FAST memory for custom purposes
Found in: Bootloader config
This option allows the customer to place data in the RTC FAST memory, this area remains valid when
rebooted, except for power loss. This memory is located at a fixed address and is available for both
the bootloader and the application. (The application and bootoloader must be compiled with the same
option). The RTC FAST memory has access only through PRO_CPU.
Default value:
• No (disabled)
CONFIG_BOOTLOADER_CUSTOM_RESERVE_RTC_SIZE
Size in bytes for custom purposes
Found in: Bootloader config > CONFIG_BOOTLOADER_CUSTOM_RESERVE_RTC
This option reserves in RTC FAST memory the area for custom purposes. If you want to create your
own bootloader and save more information in this area of memory, you can increase it. It must be a
multiple of 4 bytes. This area (rtc_retain_mem_t) is reserved and has access from the bootloader and
an application.
Espressif Systems 1068
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