ESP32 Forum

My understanding is that when working with I2C, the bus is open drain meaning that the neither the master nor the slave will ever pull a line high ... but will instead pull it only low or open circuit. As such, there needs to be a default high which is commonly achieved with a 4.7KOhm resistor on the lines pulling them default high. In our ESP32 story, do we need explicit external pull up resistors or is this taken care of for us by configuring I2C or do we need to explicitly define the mapped pins as pulled-up ... or some other story.

As far as I'm aware, you need external pull-up resistors to get any performance out of the I2C port. You could enable the internal pull-ups, but they are to weak to pull up the lines quickly enough.