VKmaker ESPDuino Development Board ESP-13 UNO R3 With Wifi From ESP8266

Wonderful little board, at a great price. My only problem with it is that any code that depends on <avr.h> or <avr/io.h> or other AVR headers will not work without modification - several common sensors depend on the delayMicroseconds that AVR provides and would not work as a result.