Data Sheet
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Espressif Systems
ESP8266 Datasheet
3.3.2. SDIO / SPI (Slave)
Table 9 Pin Definitions of SDIO / SPI (Slave)
3.3.3. HSPI (Master/Slave)
Table 10 Pin Definitions of HSPI (Master/Slave)
Note:
• SPI mode can be implemented via software programming. The clock frequency can reach up to
a maximum value of 80MHz.
• Function of Slave SDIO/SPI interface can be implemented via hardware, and linked list DMA
(Direct Memory Access) is supported, software overheads are smaller. However, there is no
linked list DMA on general SPI and HSPI, and the software overheads are larger, therefore, the
data transmitting speed will be restrained by software processing speed.
3.4. Inter-integrated Circuit Interface (I2C)
One I2C, which is mainly used to connect with micro controller and other peripheral equipment such
as sensors, is defined by ESP8266EX. The present pin definition of I2C is as defined below:
Pin Name
Pin Num
IO
Function Name
SDIO_CLK
21
IO6
SPI_SLAVE_CLK
SDIO_DATA0
22
IO7
SPI_SLAVE_MISO
SDIO_DATA1
23
IO8
SPI_SLAVE_INT
SDIO_DATA_2
18
IO9
NC
SDIO_DATA_3
19
IO10
SPI_SLAVE_CS
SDIO_CMD
20
IO11
SPI_SLAVE_MOSI
Pin Name
Pin Num
IO
Function Name
MTMS
9
IO14
HSPICLK
MTDI
10
IO12
HSPIQ/MISO
MTCK
12
IO13
HSPID/MOSI
MTDO
13
IO15
HPSICS
Espressif Systems / August 1, 2015
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