NodeMCU ESP8266

• Board summary
• ESPHome support
• Pinout
  • Pins
• References

Board summary

NodeMCU ESP8266 board with micro-USB connector (USB-C variants are also available)

ESPHome support

Board config:

esp8266:
  board: nodemcuv2

Config for status_led (on some boards):

light:

  # This is the built-in blue status LED
  - platform: status_led
    name: "Status LED"
    id: esp_status_led
    icon: "mdi:alarm-light"
    entity_category: "config"
    restore_mode: ALWAYS_OFF
    pin:
      number: D4
      inverted: true

  # Only present on some boards, this is the built in AUX led, next to the UART chip
  - platform: status_led
    name: "AUX LED"
    id: esp_aux_led
    icon: "mdi:alarm-light"
    entity_category: "config"
    restore_mode: ALWAYS_OFF
    pin:
      number: D0
      inverted: true

Pinout

Pins

The NodeMCU pin numbering on the silkscreen (e.g. D0, A0) is different from the internal pin numbering. ESPHome knows how to map the silkscreen pins numbers to internal pin numbers⁴.

The ESP8266 can only use the designed pins for each interface (SPI, UART, I²C, etc), other pins can't be used for them.

Some notes about pins on NodeMCU ESP8266³:

• The internal pull-up/-down resistors have values of $30k\Omega$ to $100k\Omega$⁵.
• In some cases pins marked as INTERNAL on the pinout can be used.
• D0 can be used to wake the device up from deep sleep if the pin is connected to the RESET pin.
• D3, D4, D8: Strapping pins that control boot mode. If these are used as general purpose GPIO pins they should be in the default states to boot from flash:
  • D3 (GPIO0): HIGH
  • D4 (GPIO2): HIGH (blue status led)
  • D8 (GPIO15): LOW
• D4 (GPIO2): connected to blue status_led, in inverted mode.
• D0 (GPIO16, only on some boards): AUX LED next to the UART chip, in inverted mode.
• A0 (GPIO17): ADC pin, measures voltages from $10$ to $1V$. Can be used as a normal GPIO pin.
• VIN: Voltage input, board can be powered by external power supply on this pin. Some boards support up to $12V$, other $5V$.
• ENABLE/RESET: Board resets when these pins are triggered. Difference is how they handle voltages above $3.3V$.

When the ESP8266 boots, the three strapping pins are checked to determine which boot mode to enter³:

The reset causes are documented in the datasheet and are as follows:

On boot, the first line in the UART output tells you which boot mode was used and the reset cause:

rst cause:4, boot mode:(3,6)

Here the reset cause was 4 and the boot mode was 3.

References