In order to use the I/O lines of this peripheral, the I/O pins must be configured using the I/O Pin Controller (PORT).
When the SERCOM is used in I2C mode, the SERCOM controls the direction and value of the I/O pins. The PORT Control bit (PINCFGn.DRVSTR) is still effective for the SERCOM output pins. The PORT Control bit (PINCFGn.PULLEN) is still effective on the SERCOM input pins, but is limited to the enabling/disabling of a pull down only (it is not possible to enable/disable a pull up). If the receiver or transmitter is disabled, these pins can be used for other purposes.