Based on the ESP-8266EX.
Arduino Compatible, you can use it on Arduino IDE.
NodeMcu Compatible
11 Digital I/O pins
1 Analog Input pin
OTA -- Wireless Upload(Program)
On board switching power supply -- Max 24V input, 5V 1A output
What's new about V2.1.0
Use BRT (Bias Resistor Transistor), easier into flash mode.
Optimize the circuit, the system is more stable.