Diagram Pin Pin Function ESP-8266 Pin TX TXD TXD RX RXD RXD A0 Analog input, max 3.3V input A0 D0 IO GPIO16 D1 IO, SCL GPIO5 D2 IO, SDA GPIO4 D3 IO,10k Pull-up GPIO0 D4 IO, 10k pull-up, BUILTIN_LED GPIO2
The D1 mini is a mini wifi board based on ESP-8266EX from WeMos.cc.
If you are using a NodeMCU firmware on you ESP take note on the GPIO table mapping. All access is based on the I/O index number on the NodeMCU dev kits, not the internal GPIO pin.
This is a ESP8266 NodeMCU board from LoLin.