D1 Mini Wemos

The D1 mini is a mini wifi board based on ESP-8266EX

Features:
11 digital input/output pins, all pins have interrupt/pwm/I2C/one-wire supported (except D0)
1 analog input(3.2V max input)
a Micro USB connection
Compatible with Arduino
Compatible with nodemcu

Tutorial:
Get started in Arduino
Get started in NodeMCU

Technical specs:

Microcontroller ESP-8266EX
Operating Voltage 3.3V
Digital I/O Pins 11
Analog Input Pins 1(Max input: 3.2V)
Clock Speed 80MHz/160MHz
Flash 4M bytes
Length 34.2mm
Width 25.6mm
Weight 10g

Pin:

Pin Function ESP-8266 Pin
TX TXD TXD
RX RXD RXD
A0 Analog input, max 3.3V input A0
D0 IO GPIO16
D1 IO, SCL GPIO5
D2 IO, SDA GPIO4
D3 IO, 10k Pull-up GPIO0
D4 IO, 10k Pull-up, BUILTIN_LED GPIO2
D5 IO, SCK GPIO14
D6 IO, MISO GPIO12
D7 IO, MOSI GPIO13
D8 IO, 10k Pull-down, SS GPIO15
G Ground GND
5V 5V –
3V3 3.3V 3.3V
RST Reset RST
All of the IO pins have interrupt/pwm/I2C/one-wire support except D0
All of the IO pins run at 3.3V.

Driver:
CH340G USB to UART driver