Datasheet

SAM9G20
DS60001516A-page 468  2017 Microchip Technology Inc.
Figure 31-33: 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 at 0 (to avoid LED emission). Disable the internal pull-up (better for power con-
sumption).
• Receive data
31.6.5.1 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 31-9.
Figure 31-34 shows an example of character transmission.
Figure 31-34: IrDA Modulation
Table 31-9: 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
IrDA
Transceivers
RXD RX
TXD
TX
USART
Demodulator
Modulator
Receiver
Transmitter
Bit Period
Bit Period
3
16
Start
Bit
Data Bits
Stop
Bit
0
0
0
0
0
1
11
1
1
Transmitter
Output
TXD