761
SAM4CP [DATASHEET]
43051E–ATPL–08/14
36.6.5 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
Figure 36-32
.
The modulator and demodulator are compliant with the IrDA specification version 1.1 and support data transfer speeds
ranging from 2.4 kB/s to 115.2 kB/s.
The IrDA mode is enabled by setting the USART_MODE field in US_MR to the value 0x8. The IrDA Filter Register
(US_IF) is used to configure 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 36-32. Connection to IrDA Transceivers
The receiver and the transmitter must be enabled or disabled depending on 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 emission). Disable the internal pull-up
(better for power consumption).
Receive data.
36.6.5.1 IrDA Modulation
For baud rates up to and including 115.2 kB/s, the RZI modulation scheme is used. “0” is represented by a light pulse of
3/16th of a bit time. Some examples of signal pulse duration are shown in
Table 36-11
.
IrDA
Transceivers
RXD
RX
TXD
TX
USART
Demodulator
Modulator
Receiver
Transmitter
Table 36-11. IrDA Pulse Duration
Baud Rate
Pulse Duration (3/16)
2.4 kB/s
78.13
μ
s
9.6 kB/s
19.53
μ
s
19.2 kB/s
9.77
μ
s
38.4 kB/s
4.88
μ
s
57.6 kB/s
3.26
μ
s
115.2 kB/s
1.63
μ
s