ESP8266 – Best Pins to Use

ESP8266 Peripherals

The pins highlighted in green are OK to use. The ones highlighted in yellow are OK to use, but you need to pay attention because they may have unexpected behavior mainly at boot. The pins highlighted in red are not recommended to use as inputs or outputs.

Label GPIOx Input Output At the Boot Notes
D3 GPIO00 pull-up OK Boot fails if pulled-down Connected to FLASH button
D10 GPIO01 TX OK HIGH
Boot fails if pulled-down
UARTS (Serial ports)
debug output
D4 GPIO02 pull-up OK HIGH
Boot fails if pulled-down
D9 GPIO03 OK RX HIGH UARTS (Serial ports)
D2 GPIO04 OK OK (PWM)
 SDA (I2C)
D1 GPIO05 OK OK  SCL (I2C)
   
 SD2 GPIO09 HIGH
 SD3 GPIO10 HIGH
D6 GPIO12 OK OK (PWM)
SPI (MISO)
D7 GPIO13 OK OK SPI (MOSI)
D5 GPIO14 OK OK (PWM)
SPI (SCLK)
D8 GPIO15 pull-down OK (PWM)
Boot fails if pulled-up SPI (CS)
D0 GPIO16 no Int. HIGH wake up from deep sleep
A0 ADC0 Analog X 10-bit ADC input range of 0 – 1.0V

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