What are GPIO pins on the ESP8266 and ESP32?

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When reading up on the ESP32 and ESP8266 microcontrollers or boards using them, you will often hear the acronym GPIOs or GPIO pins. These pins also exist on the beloved Raspberry Pi, which might be running Home Assistant, and Arduino. GPIOs are what ESPHome uses to gather data from sensors, detect button pushes, push data to other devices, and more.

  • How many GPIO pins does an ESPHome project need?
  • How GPIO pins work in ESPHome

    General-purpose input/output pins (which is what GPIO stands for) can be designated in software, such as ESPHome, as an input or output pin and used for a wide range of purposes. When a GPIO pin on an ESP8266 is designated as an output, it can be set to high (3.3V) or low (0V). And conversely, a pin can be read as high (3.3V) or low (0V) if it is designated as an input.

    GPIO pins on an ESP8266 NodeMCU that can be used by ESPHome.
    GPIO pins on either side of a NodeMCU ESP8266 development kit
    GPIO pins on a Raspberry Pi
    GPIO behind the Ethernet port on a Raspberry Pi

    You could, if you wanted to, hook up a bunch of individual LEDs (with the appropriate resistors) to the GPIO pins and turn them on or off by either setting the output to high or low.

    As a real-world example, if you’re using an ESP8266 to control addressable LEDs, the pin connected to the LEDs will be configured as an output pin. It is sending commands, such as turn on or turn off, to the LED controller. If you were to hook up a BMP280 temperature and humidity sensor, the GPIO pin to which it is connected would act as an input pin, collecting data from the sensor.

    How many GPIO pins does an ESPHome project need?

    There is no one answer to how many GPIO pins an ESPHome project needs. It all depends on the scope of the project. What can be said is whether you should go with an ESP8266 board, or an ESP32 board. The ESP8266 has 17 GPIO pins, and might not be suited to larger projects. The ESP32 doubles that number to 34 × programmable GPIO pins.

    A portrait photo oif Liam Alexander Colman, the author, creator, and owner of Home Assistant Guide wearing a suit.

    About Liam Alexander Colman

    is an experienced Home Assistant user who has been utilizing the platform for a variety of projects over an extended period. His journey began with a Raspberry Pi, which quickly grew to three Raspberry Pis and eventually a full-fledged server. Liam's current operating system of choice is Unraid, with Home Assistant comfortably running in a Docker container.
    With a deep understanding of the intricacies of Home Assistant, Liam has an impressive setup, consisting of various Zigbee devices, and seamless integrations with existing products such as his Android TV box. For those interested in learning more about Liam's experience with Home Assistant, he shares his insights on how he first started using the platform and his subsequent journey.

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