ESP8266 Community Forum

For an IOT device, if it is not setup already, I want it to start it in AP mode, get the credentials for the router from smartphone connecting to this AP and then go ahead and sign into the router. What I find is that the eeprom is not erased when the program is uploaded and so it is signing into the router based on previous run. How do I erase previous ssid, password information? I am using ESP8266-12. What will be the specific location where the information is stored?
Thanks