35.2.2.3 Receive Data Polarity
The polarity of the receive data is controlled with the RXPOL bit. The default
      state of this bit is ‘0’, which selects high true receive Idle and data bits.
      Setting the RXPOL bit to ‘1’ will invert the receive data, resulting in low
      true Idle and data bits. The RXPOL bit controls receive data polarity in all modes.
