ESP8266 NodeMcuFirst step when building this sensor is to upload correct firmware to our ESP8266 module. We will use node NodeMCU firmware. This firmware is capable of executing LUA script. Latest NodeMCU firmware can be download here NodeMCU. Read ESP8266 firmware update tutorial for instructions how to update ESP8266 firmware. SP8266 NodeMcuFirst step when building this sensor is to upload correct firmware to our ESP8266 module. We will use node NodeMCU