57.7.5 IrDA Mode

The USART features an IrDA mode supplying half-duplex point-to-point wireless communication. It embeds the modulator and demodulator which allows a glueless connection to the infrared transceivers, as shown in the following figure. The modulator and demodulator are compliant with the IrDA specification version 1.1 and support data transfer speeds ranging from 2.4 kbit/s to 115.2 kbit/s.

The USART IrDA mode is enabled by setting the FLEX_US_MR.USART_MODE field to the value 0x8. The IrDA Filter register (FLEX_US_IF) allows configuring the demodulator filter. The USART transmitter and receiver operate in a normal Asynchronous mode and all parameters are accessible. Note that the modulator and the demodulator are activated.

Figure 57-33. Connection to IrDA Transceivers

The receiver and the transmitter must be enabled or disabled according to the direction of the transmission to be managed.

To receive IrDA signals, the following needs to be done:

  • Disable TX and Enable RX
  • Configure the TXD pin as PIO and set it as an output to 0 (to avoid LED transmission). Disable the internal pullup (better for power consumption).
  • Receive data