esphome-docs/devices/esp8266.rst

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Generic ESP8266
===============
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.. seo::
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:description: Instructions for using generic ESP8266s with ESPHome.
:image: esp8266.png
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:keywords: ESP8266
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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
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from `this link <http://docs.platformio.org/en/latest/platforms/espressif8266.html>`__ when the wizard
asks you for the board type.
.. code-block:: yaml
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# Example configuration entry
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esphome:
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name: livingroom
platform: ESP8266
board: <BOARD_TYPE>
Many boards have a pin numbering for the exposed pins that is different from the internally used
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ones. ESPHome tries to map the silk-screen pin numbers into the internal pin numbers with a few
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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 :doc:`/components/sensor/adc`
to read voltages (in the range from 0 to 1.0V) on this pin.
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.. code-block:: yaml
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# Example configuration entry
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esphome:
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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
=================== =============================================
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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 Weak Pull Down
resistor
========== ============================== ==============================
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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
.. code-block:: text
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**.
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These reset causes `are documented
<https://www.espressif.com/sites/default/files/documentation/esp8266_reset_causes_and_common_fatal_exception_causes_en.pdf>`__:
== ===================================
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.
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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
=========================================================== =========== =========== =========== ===========
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Source: `ESP8266EX datasheet <https://www.espressif.com/sites/default/files/documentation/0a-esp8266ex_datasheet_en.pdf>`__
The internal pull up/down resistors have values of 30kΩ to 100kΩ
(`source <https://bbs.espressif.com/viewtopic.php?t=1079>`__).
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See Also
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--------
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- :doc:`nodemcu_esp8266`
- :ghedit:`Edit`