ESP8266 datasheet(72/117 Pages) ESPRESSIF

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8. HSPI Host Multi-device API

HSPI Host Multi-device API

8.1. Functional Overview

ESP8266 encapsulates two SPI (Serial Peripheral Interfaces) bus segments, shortly named

SPI and HSPI. SPI bus is especially used to read CPU programming code from the external

Flash, while HSPI bus is used for SPI device communication.

When ESP8266 is working as a host, HSPI bus can operate with three user devices,

besides, it also supports one external Flash writing operation. User devices are supported

through selection with CS lines. To be more speciﬁc,

In the above-mentioned ways of connection, SPI bus shares the same external Flash with

HSPI bus. Apart from the memory occupied by programs and related conﬁgurations, the

rest Flash memory can all be used for reading and writing of user programs.

8.2. Hardware Connection

Generally speaking, SPI slave devices specify four logic signals: SCLK, MOSI, MISO, and

CS.

HSPI bus can operate with three different user devices, the ways of connection are

explained below:

Mode

Device Name

HSPI Default IO

User device 1

SPI OVERLAP and CS1

User device 2

SPI OVERLAP and CS2

User device 3

SPI OVERLAP and CS0

Flash

⚠ Notice:

• Operation with devices via HSPI host implemented by software programming is not supported in the

API functions.

•

When downloading user programs, the clock frequency of SPI bus used for reading Flash data should

be set at 80 MHz. SPI clock frequency should be speciﬁed as 80 MHz at SPI OVERLAP and CS1

mode or SPI OVERLAP and CS2 mode.

Mode

Pin Name of Host ESP8266

SPI bus Signal Line

HSPI Default IO

MTDO

MTCK

MOSI

MTDI

MISO

Espressif

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2017.05

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