The NodeMcu is an open-source firmware and development kit that helps you to prototype your IOT product within a few Lua script lines.
low-cost WiFi solution programmable with the Lua scripting language
on-board USB-serial adaptor
PCB antenna (no external antenna required)
10 GPIO pins, each GPIO can be PWM, I2C, 1-wire
powered via microB USB
operating voltage: 5 VDC (USB)