ESP8266 GPIO

Internal pull-up/-down resistors

• GPIO 0-15 all have a built-in pull-up resistor, just like in an Arduino. GPIO16 has a built-in pull-down resistor.

GPIO16

• D0(GPIO16) can only be used as gpio read/write. No support for open-drain/interrupt/pwm/i2c/ow.

• https://nodemcu.readthedocs.io/en/master/modules/gpio/
• https://tttapa.github.io/ESP8266/Chap04%20-%20Microcontroller.html

D1 (5)
D2 (4)
D3 (0)
D4 (2)

#define D5 (14)
#define D6 (12)
#define D7 (13)
#define D8 (15)

#define RX (3)
#define TX (1)