Wemos D1 Mini Lite

Maker Tech:
The Wemos D1 Mini Lite is an IoT board based on the popular ESP8266 chip from Expressiff. The board is Arduino compatible and provides the smallest form factor of any other ESP8266 board available. The Lite version is a cheaper design by Wemos that does not include the metal shielding of most boards including the original Wemos D1 Mini. 
 
11 digital input/output pins, all pins have interrupt/pwm/I2C/one-wire supported(except D0)
1 analog input(3.3V max input)
4MB flash
a Micro USB connection