ESP8266 datasheet(21/117 Pages) ESPRESSIF

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3. SPI Compatibility Mode User Guide

SPI Compatibility Mode User

Guide

3.1. Functional Overview

This protocol uses the SDIO mode of the ESP8266 to communicate with other processor's

SPI hosts. The electrical interface is connected through signal line No.4, including the

SCLK, MOSI, MISO and interrupt signal No.1 in the SPI protocol (note: no CS signal).

Downloading the ESP8266 SDIO can be different from downloading other programs. When

the ESP8266 starts, the system reads the pin shared by the SPI interface and the SDIO

interface by default. Therefore, the SDIO module communication protocol should be used.

The ESP8266 should start in the SDIO mode, and then, the host will start the chip in the

ESP8266 RAM through the SDIO downloaded programs. The majority of the programs that

directly use CPU CACHE to call FLASH can be burnt to the FLASH chip connected to the

HSPI interface beforehand.

Data received or sent by the ESP8266 SDIO is processed directly by the DMA module that

supports linked list index.

The ESP8266 can receive and send the SDIO packets efﬁciently without using the CPU. It

does so through the address of the memory map linked list.

3.2. DEMO Solution

3.2.1. Introduction

The host is the Red Dragon demo board with STM32F103ZET6 as its core.The software is

the FreeRTOS system developed by the IAR platform. The slave is the ESP_IOT reference

board, which is based on the v0.9.3 SDK development.

3.2.2. ESP8266 Software Compiling and Downloading

•

In the SDIO communication demo

\esp_iot_sdk_v0.9.3_sdio_demo\ap, use the

compiler to compile and generate the bin documents for downloading in order to

complete the ESP8266 DEMO work.

•

ibmain.a in SDIO communication demo

\esp_iot_sdk_v0.9.3_sdio_demo\lib is

different from the version released in v0.9.3. When you use the released version of

the SDK, use

libmain.a in the DEMO to replace the original one. The new libmain.a

will start the chip, and exchange the SPI module that reads FLASH and the HSPI

mapping pin. Then, you can use DEMO to compile and generate.

•

Copy

eagle.app.v6.irom0text.bin in SDIO communication demo

\esp_iot_sdk_v0.9.3_sdio_demo\bin to SDIO communication demoboard

Espressif

! /!

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2017.05

ESP8266 Datasheet(PDF) 21 Page - ESPRESSIF SYSTEMS (SHANGHAI) CO., LTD.

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