Si7021 IoT node NodeMCU with a Si7021 temperature and humidity sensor as an IoT node. See http://particleflux.codes/post/2019/iot-temperature-and-humidity-sensor/ Wiring NodeMCU D1 to Si7021 SCL NodeMCU D2 to Si7021 SDA NodeMCU 3V to Si7021 VIN NodeMCU GND to Si7021 GND