General Spi (Master/Slave); Hspi (Slave); I2C Interface - Espressif ESP8266 Technical Reference

!
One Slave SDIO/SPI
One general Slave/Master HSPI
Functions of all these pins can be implemented via hardware. The pin definitions are
described as below.

1.3.1. General SPI (Master/Slave)

SDIO_CLK
SDIO_DATA0
SDIO_DATA1
SDIO_DATA_2
SDIO_DATA_3
U0TXD
GPIO0
! Note:
SPI mode can be implemented via software programming. The clock frequency is 80 MHz at maximum.

1.3.2. HSPI (Slave)

MTMS
MTDI
MTCK
MTDO

1.4. I2C Interface

ESP8266EX has one I2C used to connect with micro-controller and other peripheral
equipments such as sensors. The pin definition of I2C is as below.
MTMS
GPIO2
Espressif
Pin Name
21
22
23
18
19
26
15
Table 1-3. Pin Definitions of HSPI (Slave)
Pin Name Pin Num
9
10
12
13
Pin Name Pin Num
9
14
Table 1-2. Pin Definitions of SPIs
Pin Num IO
IO6
IO7
IO8
IO9
IO10
IO1
IO0
IO
IO14
IO12
IO13
IO15
Table 1-4. Pin Definitions of I2C
IO
IO14
IO2
! /86 2
Function Name
SPICLK
SPIQ/MISO
SPID/MOSI
SPIHD
SPIWP
SPICS1
SPICS2
Function Name
HSPICLK
HSPIQ/MISO
HSPID/MOSI
HPSICS
Function Name
I2C_SCL
I2C_SDA
1. Overview
2016.05