Fixed built-in Master I²C driver for Arduino ESP8266 core. Sorry it doesn't support slave I²C mode.
| Board | SDA | SCL | Level |
|---|---|---|---|
| ESP8266 | GPIO4 | GPIO5 | 3.3v/5v |
| ESP8266 ESP-01 | GPIO0/D5 | GPIO2/D3 | 3.3v/5v |
| NodeMCU 1.0, WeMos D1 Mini | GPIO4/D2 | GPIO5/D1 | 3.3v/5v |
Copy and replace "twi.h", "core_esp8266_si2c.cpp" in folder %USERPROFILE%\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.5.2\cores\esp8266
Copy and replace "Wire.h", "Wire.cpp" in folder %USERPROFILE%\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.5.2\libraries\Wire
If you want to keep the original files - just change the file extension* to "twi.h.OLD" and etc. Then you always can go back.
*if you change the file name you get an error at compile time
Special thanks to Tech-TX(StanJ)