Espressif Systems ESP8266 Series Hardware Design Manuallines page 8

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Pin
1 VDDA
2 LNA
3 VDD3P3
4 VDD3P3
5 VDD_RTC
TOUT
6
7 CHIP_EN
8 XPD_DCDC
MTMS
9
10 MTDI
11 VDDPST
MTCK
12
13 MTDO
14 GPIO2
15 GPIO0
16 GPIO4
17 VDDPST
18 SDIO_DATA_2
19 SDIO_DATA_3
20 SDIO_CMD
21 SDIO_CLK
22 SDIO_DATA_0
23 SDIO_DATA_1
Espressif
Table 1-2. ESP8266EX Pin Definitions
Name Type
P
I/O
P
P
P
I
I
I/O
I/O
I/O
P
I/O
I/O
I/O
I/O
I/O
P
I/O
I/O
I/O
I/O
I/O
I/O
Function
Analog Power 2.5V ~ 3.6V
RF antenna interface
Chip output impedance=39+j6 Ω. It is suggested that users retain
the π-type matching network which matches the antenna.
Amplifier Power 2.5V ~ 3.6V
Amplifier Power 2.5V ~ 3.6V
NC (1.1V)
ADC pin. It can be used to test the power-supply voltage of
VDD3P3 (Pin3 and Pin4) and the input power voltage of TOUT (Pin
6). However, these two functions cannot be used simultaneously.
Chip Enable
High: On, chip works properly
Low: Off, small current consumed
Deep-sleep wakeup (need to be connected to EXT_RSTB);
GPIO16
GPIO 14; HSPI_CLK
GPIO 12; HSPI_MISO
Digital/IO Power Supply (1.8V ~ 3.3V)
GPIO 13; HSPI_MOSI; UART0_CTS
GPIO 15; HSPI_CS; UART0_RTS
UART Tx during flash programming; GPIO2
GPIO0; SPI_CS2
GPIO 4
Digital/IO Power Supply (1.8V ~ 3.3V)
Connects to SD_D2 (Series R: 200Ω); SPIHD; HSPIHD; GPIO 9
Connects to SD_D3 (Series R: 200Ω); SPIWP; HSPIWP; GPIO 10
Connects to SD_CMD (Series R: 200Ω); SPI_CS0; GPIO 11
Connects to SD_CLK (Series R: 200Ω); SPI_CLK; GPIO 6
Connects to SD_D0 (Series R: 200Ω); SPI_MSIO; GPIO 7
Connects to SD_D1 (Series R: 200Ω); SPI_MOSI; GPIO 8
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1. ESP8266EX
2018.12