Espressif Systems ESP8266EX, Hardware User'S Manual, Page: 11 / 48

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Espressif Systems
ESP8266EX
Hardware User Guide
Table 2 Attributes and Functions of Pins
Note : GPIO2, GPIO0, MTDO can be configurable as 3-bit SDIO mode.
Pin Name Type Function
24 GPIO5 I/O GPIO5
25 U0RXD I/O UART Rx during flash programming; GPIO3
26 U0TXD I/O UART Tx during flash progamming; GPIO1; SPI_CS1
27 XTAL_OUT I/O
Connect to crystal oscillator output, can be used to provide BT
clock input
28 XTAL_IN I/O Connect to crystal oscillator input
29 VDDD P Analog Power 3.0V~3.6V
30 VDDA P Analog Power 3.0V~3.6V
31 RES12K I
Serial connection with a 12 k Ω resistor and connect to the
ground
32 EXT_RSTB I External reset signal (Low voltage level: Active)
Espressif Systems / Jun 1, 2015 11 48