Data Sheet
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Espressif Systems
ESP8266 Datasheet
3. Pins and Definitions
The chipset encapsulates variable analog and data transmission I/Os, descriptions and definitions of
which are explained below in detail.
3.1. GPIO
3.1.1. General Purpose Input/Output Interface (GPIO)
There are up to 17 GPIO pins. They can be assigned to various functions by the firmware. Each GPIO
can be configured with internal pull-up (except XPD_DCDC, which is configured with internal pull-
down), input available for sampling by a software register, input triggering an edge or level CPU
interrupt, input triggering a level wakeup interrupt, open-drain or push-pull output driver, or output
source from a software register, or a sigma-delta PWM DAC.
These pins are multiplexed with other functions such as I2C, I2S, UART, PWM, IR Remote Control, etc.
Data I/O soldering pad is bidirectional and tri-state that include data input and output controlling
buffer. Besides, I/O can be set as a specific state and remains like this. For example, if you intend to
lower the power consumption of the chip, all data input and output enable signals can be set as
remaining low power state. You can transport some specific state into the I/O. When the I/O is not
powered by external circuits, the I/O will remain to be the state that it was used the last time. Some
positive feedback is generated by the state-remaining function of the pins, therefore, if the external
driving power must be stronger than the positive feedback. Even so, the driving power that is
needed is within 5uA.
Table 6 Pin Definitions of GPIOs
All digital IO pins are protected from over-voltage with a snap-back circuit connected between the
pad and ground. The snap back voltage is typically about 6V, and the holding voltage is 5.8V. This
Variables
Symbol
Min
Max
Unit
Input Low Voltage
V
IL
-0.3
0.25×V
IO
V
Input High Voltage
V
IH
0.75×V
IO
3.3
V
Input Leakage Current
I
IL
50
nA
Output Low Voltage
V
OL
0.1×V
IO
V
Output High Voltage
V
OH
0.8×V
IO
V
Input Pin Resistance Value
C
pad
2
pF
VDDIO
V
IO
1.8
3.3
V
Maximum Driving Power
I
MAX
12
mA
Temerpature
T
amb
-40
125
°C
Espressif Systems / August 1, 2015
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