ESP8266 is a very popular WiFi enabled microcontroller. Thanks to very attractive price and huge possibilities quickly became a very popular choice - especially in domain of home automation. However bare ESP8266 is a bit tricky for beginners. It requires stable power supply, and sophisticated programming method. Wemos D1 mini solves all those inconveniences. Basically it's very similar to NodeMCU module. The main difference is size.
Wemos D1 module it's a small board with ESP8266EX chip. On board there is also USB-UART converter (popular CP2104). Because of that, all you need to start programming is simple USB cable.
Wemos D1 provides 9 GPIO ports with PWM, I2C, SPI and 1-Wire support. Thanks to 3.3V LDO module can be powered directly from USB port via microUSB power supply.
They are 3 basic methods to use Wemos. AT commands, LUA programming language with NodeMCU firmware and simplest and our favorite Arduino IDE.
The D0, D1, D2, … numbers printed on the board are different from what Micropython uses – because originally those boards were made for a different software. Make sure to refer to the image below to determine which pins are which.
|A0||Analog input, max 3.3V input||A0|
|D3||IO, 10k Pull-up||GPIO0|
|D4||IO, 10k Pull-up, BUILTIN_LED||GPIO2|
|D8||IO, 10k Pull-down, SS||GPIO15|