Espressif ESP8266 Series System Description page 27

There are altogether 18 pinouts. The pin distribution and definitions are listed in Table 3-1
below:
NO.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Espressif
Table 3-1: ESP-WROOM-02 Pinouts
Pin name
3V3
EN
IO14
IO12
IO13
IO15
IO2
IO0
GND
IO4
RXD
TXD
GND
IO5
RST
It can be used to test the power-supply voltage of VDD3P3 (Pin3 and
TOUT Pin4) and the input power voltage of TOUT (Pin 6). These two functions
GPIO16; Wake up the chipset from deep sleep mode when connected to
IO16
GND
24 27 /
Function
3.3 V power supply (VDD)
Chip enable pin. Active high
GPIO14; HSPI_CLK
GPIO12; HSPI_MISO
GPIO13; HSPI_MOSI; UART0_CTS
GPIO15; MTDO; HSPICS; UART0_RTS
GPIO2; UART1_TXD
GPIO0
GND
GPIO4
UART0_RXD; GPIO3
UART0_TXD; GPIO1
GND
GPIO5
Reset
cannot be used simultaneously.
RST pin.
GND
ESP-WROOM
2016.06