Generic ESP8266

All ESP8266-based devices are supported by ESPHome. Simply select ESP8266 when the ESPHome wizard asks you for your platform and choose a board type from this link when the wizard asks you for the board type.

# Example configuration entry
esphome:
  name: livingroom
  platform: ESP8266
  board: <BOARD_TYPE>

Many boards have a pin numbering for the exposed pins that is different from the internally used ones. ESPHome tries to map the silk-screen pin numbers into the internal pin numbers with a few boards, but for generic ESP8266 boards it is often required to just use the internal pin numbers. To do this, just prefix all pins with GPIO, for example GPIO0 for the pin with the internal pin number 0.

Some notes on the pins:

  • GPIO6 - GPIO11, GPIO0, GPIO2 and GPIO15 are often already used by the internal flash interface and boot mode detection. So it’s best to avoid using these pins.

  • GPIO17 additionally has an ADC connected to it. See the Analog To Digital Sensor to read voltages (in the range from 0 to 1.0V) on this pin.

# Example configuration entry
esphome:
  name: livingroom
  platform: ESP8266
  board: nodemcuv2

binary_sensor:
  - platform: gpio
    name: "Pin GPIO17"
    pin: GPIO17

Special Pins

GPIO0

Controls Boot Mode

GPIO1

UART TX pin

GPIO2

Controls Boot Mode

GPIO3

UART RX pin

GPIO6

SDIO/Flash CLK pin

GPIO7

SDIO/Flash Data 0 pin

GPIO8

SDIO/Flash Data 1 pin

GPIO9

SDIO/Flash Data 2 pin (qio/qout only)

GPIO10

SDIO/Flash Data 3 pin (qio/qout only)

GPIO11

SDIO/Flash CMD pin

GPIO12

Attached to Hardware SPI controller MISO

GPIO13

Attached to Hardware SPI controller MOSI

GPIO14

Attached to Hardware SPI controller CLK

GPIO15

Controls Boot Mode; Attached to Hardware SPI controller CS

GPIO16

Special pin that can be accessed from RTC, and is Deep-Sleep wakeup pin

TOUT aka GPIO17

ADC pin for measuring voltages, can only be used as analog input pin

This means effectively only the following pins can be used as general purpose GPIO:

Pin

Restrictions

State after Reset

GPIO0

If HIGH on boot

Weak Pull Up

GPIO2

If HIGH on boot

Weak Pull Up

GPIO4

High Impedance

GPIO5

High Impedance

GPIO6

Weak Pull Up

GPIO12

Weak Pull Up

GPIO13

Weak Pull Up

GPIO14

Weak Pull Up

GPIO15

If LOW on boot

Weak Pull Up

GPIO16

Has pull-down (but no pull-up resistor

Weak Pull Down

Boot Modes

On each boot, the ESP8266 will check three pins to determine in which boot mode to enter. There are three boot modes:

Mode

GPIO0

GPIO2

GPIO15

boot mode:

Boot from Flash (normal)

HIGH

HIGH

LOW

3

Download Code from UART

LOW

HIGH

LOW

1

Boot from SD-Card

ANY

ANY

HIGH

4-7

You can identify these on boot-up by looking at the UART output, the first number in the boot mode: line tells you what mode was selected

ets Jan  8 2013,rst cause:4, boot mode:(3,6)

The first lines when viewing the UART logs might have unrecognized characters. This is because the ESP8266 bootloader uses a baudrate of 76800, whereas the program uses 115200.

Reset Causes

Additionally, the first line also contains the reset cause. These reset causes are documented:

0

Undefined

1

Power On Reboot

2

External reset or deep-sleep wakeup

4

Hardware WDT reset

After a software reset, the reset cause will not change.

Electrical Characteristics

Parameter

Min.

Typical

Max.

Unit

Operating Temperature

-40

125

°C

Working Voltage V_IO

2.5

3.3

3.6

V

V_IL - INPUT voltage level to be considered LOW

-0.3

0.25*V_IO

V

V_IH - INPUT voltage level to be considered HIGH

0.75*V_IO

3.6

V

V_OL - OUTPUT voltage level for LOW

0.1*V_IO

V

V_OH - OUTPUT voltage level for HIGH

0.8*V_IO

V

I_MAX - Maximum current for GPIO

12

mA

Power Consumption in Deep Sleep

20

µA

Power Consumption in Active Mode

120

mA

Source: ESP8266EX datasheet

The internal pull up/down resistors have values of 30kΩ to 100kΩ (source).

See Also