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4. SPI Communication User Guide

4.2.2. Master SPI Communication Format Supported by Current API

The API function of ESP8266 SPI has two master initialization modes: one supports most

of the general signals and the other is designed for driving a colored LCD screen. The

device needs non-standard 9 bits SPI communication format. Please refer to

Section 4.4.1

for detailed information.

4.3. ESP8266 SPI Slave Protocol Format

4.3.1. SPI Slave Clock Polarity Conﬁguration Requirement

The master device clock polarity conﬁguration of ESP8266 SPI slave communication

should be set with idle low power , rising edge sampling and falling edge data

transformation. Please make sure to keep low power for CS in a 16’s reading/writing

process. If the CS power is raised to high level while sending, the internal state of slave will

be reset.

4.3.2. Communication Format Supported by Slave SPI

Slave ESP8266SPI communication format is almost the same as that of the master mode,

i.e. command+address+read/write data, but the slave read/write operation has its

hardware command and undeletable address, which is,

•

Command: a must; length: 3 ~ 16 bits; master output and slave input (MOSI).

•

Address: a must; length: 1 ~ 32 bits master output and slave input (MOSI).

•

Read/write data: optional; length: 0 ~ 512 bits (64 Bytes); master output and slave

input (MOSI) or master input and slave output (MISO).

4.3.3. Command Deﬁnition Supported by Slave SPI

The length of slave receiving command should at least be 3 bits. For low 3 bits, there are

hardware reading and writing operation, which is,

•

010 (slave receiving) : Write the data sent by master into the register of slave data

caching via MOSI, i.e. SPI_FLASH_C0 to SPI_FLASH_C15.

•

011 (slave sending): Send the data in the register of slave data caching (from

SPI_FLASH_C0 to SPI_FLASH_C15) to master via MOSI.

•

110 (slave receiving and sending): Send slave data caching to MISO and write the

master data in MOSI into data caching SPI_FLASH_C0 to SPI_FLASH_C15.

⚠ Notice:

Other vales are used to read and write the status register of slave SPI, SPI_FLASH_STATUS. Please do not

use it because the difference between communication format and data caching reading/writing might lead to

slave read/write error.

Espressif

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2017.05

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