A basic example showing how to enable I2C communications between an ESP8266 (NodeMCU) and an Arduino UNO. The ESP8266 is the master and the UNO is the slave. As far as I know, the ESP8266 cannot be used as a slave.
This code is mainly based on the code written by Nicholas Zambetti http://www.zambetti.com.
Warning: The UNO is designed to work with 5.5V while the ESP8266 is designed for 3.3V. So far, I have not fried my ESP.
Connecting the two devices is done by connecting
- UNO A4 <-> ESP8266 D3 (SDA)
- UNO A5 <-> ESP8266 D4 (SCL)
