The D1 is a WiFi capable ESP8266 based development board in the form of the Arduino UNO board format. This board is compatible with the Arduino IDE and with NodeMCU. The D1 also features an on-board switching power supply which allows you to power the board from a power supply up to 24V, 11 GPIO pins (can be used as input/output/PWM/I²C, except D0), and 1 analog input. The PWM resolution is 10bit (1MHz frequency). The integrated 5V switching power supply (1A) is followed by an 3.3V LDO to supply power for the Wifi module and the 3.3V output (power supply for sensors and shields). Please pay attention when you connect other active periphery to the I/O pins, because this is a 3.3V logic level device and higher levels on any pin will destroy it. The max. input voltage for the analog pin is 3.2V.
|A0||Analog input, max 3.3V input||A0|
|D3||IO, 10k Pull-up||GPIO0|
|D4||IO, 10k Pull-up, BUILTIN_LED||GPIO2|
|D8||IO, 10k Pull-down, SS||GPIO15|
All of the IO pins have interrupt/pwm/I2C/one-wire support except D0
All of the IO pins run at 3.3V.