Espressif Systems ESP8266EX, Hardware User'S Manual, Page: 33 / 48

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Espressif Systems
ESP8266EX
Hardware User Guide
Table 5 Pin Definitions of ESP-WROOM-02 WiFi Module
Connect the 3.3V power-supply pin to an external 3.3V power source, for 3.3V is the power-supply
for both analog circuit and digital circuit.
When working, normally the voltage level of the EN pin, WiFi enable pin, should be set high.
SMD Module features two working modes: one is UART Download mode, the other is Flash Boot
mode. UART Download mode means that user programs can be written into the Flash or Memory by
flash downloading tools. If the programs are burnt into the Memory, the programs can run only when
the device is powered on, once the device is powered off, the programs in the Memory will be
erased. However, when the programs are burnt into the Flash, they will be stored in it, and can be
invoked and used at any time.
NO. Pin Name Function
1 3V3 3.3V power supply (VDD)
2 EN Chip enable pin. Active high.
3 IO14 GPIO14; HSPI_CLK
4 IO12 GPIO12; HSPI_MISO
5 IO13 GPIO13; HSPI_MOSI; UART0_CTS
6 IO15 GPIO15; MTDO; HSPICS; UART0_RTS
7 IO2 GPIO2; UART1_TXD
8 IO0 GPIO0
9 GND GND
10 IO4 GPIO4
11 RXD UART0_RXD; GPIO3
12 TXD UART0_TXD; GPIO1
13 GND GND
14 IO5 GPIO5
15 RST Reset the module
16 TOUT
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.
17 IO16 GPIO16; can be used to wake up the chipset from deep sleep mode.
18 GND GND
Espressif Systems / Jun 1, 2015 33 48