SPI Flash and External SPI RAM Configuration

If a board with Octal Flash resets before the second-stage bootloader:

this may mean that the necessary efuses are not correctly burnt. Please check the eFuse bits of the chip using command espefuse.py summary.

The ROM bootloader relies on an eFuse bit FLASH_TYPE to reset the Flash into the default mode (SPI mode). If this bit is not burnt and the flash is working in OPI mode, ROM bootloader may not be able to read from the flash and load the following images.

If you enabled CONFIG_ESPTOOLPY_OCT_FLASH, and there's an error log saying:

this means:

either you're using a board with a Quad Flash

or you're using a board with an Octal Flash, but the eFuse bit FLASH_TYPE isn't burnt. Espressif guarantees this bit during module manufacturing, but if the module is manufactured by others, this may happen.

Here is a method to burn the eFuse bit:

Note

This step is irreversible. Please do check if your hardware is actually using an Octal Flash.