Recommended input pins¶

Recommended ESP8266 input pins¶

The following ESP8266 GPIO pins are recommended for as input pins.

GPIO4
GPIO5
GPIO12
GPIO13
GPIO14
GPIO16

The following ESP8266 GPIO pins should be used with caution. There is a risk that the state of the pins can affect the boot sequence. When possible, use other GPIO pins.

GPIO0 - used to detect boot-mode. Bootloader runs when pin is low during powerup.
GPIO2 - used to detect boot-mode. Attached to pull-up resistor.
GPIO15 - used to detect boot-mode. Attached to pull-down resistor.

One pin does not support interrupts.

GPIO16 - does not support interrupts.

Recommended ESP32 input pins¶

The following ESP32 GPIO pins should be used with caution. There is a risk that the state of the pins can affect the boot sequence. When possible, use other GPIO pins.

GPIO0 - used to detect boot-mode. Bootloader runs when pin is low during powerup. Internal pull-up resistor.
GPIO2 - used to enter serial bootloader. Internal pull-down resistor.
GPIO4 - technical reference indicates this is a strapping pin, but usage is not described. Internal pull-down resistor.
GPIO5 - used to configure SDIO Slave. Internal pull-up resistor.
GPIO12 - used to select flash voltage. Internal pull-down resistor.
GPIO15 - used to configure silencing of boot messages. Internal pull-up resistor.