Atmel SAM9X25, Manual

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SAM9X25
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SAM9X25
39.7.5 IrDA Mode
The USART features an IrDA mode supplying half-duplex point-to-point wireless communica-
tion. It embeds the modulator and demodulator which allows a glueless connection to the
infrared transceivers, as shown in
Figure 39-32 . 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 USART IrDA mode is enabled by setting the USART_MODE field in the Mode Register
(US_MR) to the value 0x8. The IrDA Filter Register (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 39-32. 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 emission). Disable
the internal pull-up (better for power consumption).
• Receive data
39.7.5.1 IrDA Modulation
For baud rates up to and including 115.2 Kbits/sec, 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 39-12 .
IrDA
Transceivers
RXD RX
TXD
TX
USART
Demodulator
Modulator
Receiver
Transmitter
Table 39-12. IrDA Pulse Duration
Baud Rate Pulse Duration (3/16)
2.4 Kb/s 78.13 μs
9.6 Kb/s 19.53 μs
19.2 Kb/s 9.77 μs
38.4 Kb/s 4.88 μs
57.6 Kb/s 3.26 μs
115.2 Kb/s 1.63 μs