Pin definition

ESP8266EX chip pinout is something like this:

Pin	Name	Type	Function
1	VDDA	P	Analog Power 3.0 ~3.6V
2	LNA	I/O	RF Antenna Interface,Chip Output Impedance=50 Ω No matching required but we recommend that the π- type matching network is retained.
3	VDD3P3	P	Amplifier Power 3.0~3.6V
4	VDD3P3	P	Amplifier Power 3.0~3.6V
5	VDD_RTC	P	NC(1.1V)
6	TOUT	I	ADC Pin
7	CHIP_EN	I	Chip Enable. High: On, chip works properly; Low: Off, small current
8	XPD_DCDC	I/O	Deep-Sleep Wakeup;GPIO16
9	MTMS	I/O	GPIO14; HSPICLK
10	MTDI	I/O	GPIO12;HSPIQ
11	VDDPST	P	Digital/IO Power Supply (1.8V~3.3V)
12	MTCK	I/O	GPIO13;HSPID
13	MTDO	I/O	GPIO15;HSPICS
14	GPIO2	I/O	UART Tx during flash progamming; GPIO2
15	GPIO0	I/O	GPIO0;SPICS2
16	GPIO4	I/O	GPIO4
17	VDDPST	P	Digital/IO Power Supply (1.8V~3.3V)
18	SDIO_DATA_2	I/O	Connect to SD_D2 (Series R 200Ω);SPIHD; HSPIHD
19	SDIO_DATA_3	I/O	Connect to SD_D3 (Series R 200Ω); SPIWP; HSPIWP
20	SDIO_CMD	I/O	Connect to SD_CMD(Series R 200Ω); SPICS0
21	SDIO_CLK	I/O	Connect to SD_CLK (Series R 200Ω); SPICLK
22	SDIO_DATA_0	I/O	Connect to SD_D0 (Series R 200Ω); SPIQ
23	SDIO_DATA_1	I/O	Connect to SD_D1 (Series R 200Ω); SPID
24	GPIO5	I/O	GPIO5
25	U0RXD	I/O	UART Rx during flash progamming; GPIO3
26	U0TXD	I/O	UART Tx during flash progamming; GPIO1; SPICS1
27	XTAL_OUT	I/O	Connect to crystal output, can be used to provide BT clock input
28	XTAL_IN	I/O	Connect to crystal input
29	VDDD	P	Analog Power 3.0~3.6V
30	VDDA	P	Analog Power 3.0~3.6V
31	RES12K	I	Connect to series R 12kΩ to ground
32	EXT_RSTB	I	External reset signal (Low: Active)
Note: GPIO2, GPIO0, MTDO can be configurable as 3-bit SDIO mode