Boot Process

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tommie edited this page Nov 15, 2014 · 13 revisions

Overview

Reset vector is 40000000h (unconfirmed).
Boots into Xtensa SROM (unconfirmed).
Transfers control to Espressif code in IROM0 (unconfirmed).
Starts executing ESP SDK-code shadowed SPI ROM (unconfirmed).

ESP Boot Modes

The Espressif code can boot in different modes, selected on power-up based on GPIO pin levels.

GPIO0	GPIO2	MTDO	Description
L	H	L	UART, download code from UART.
H	H	L	SPI, boot from SPI Flash.
x	x	H	SDIO, boot from SD-card.

References