Atmel Evaluation Kit AT91SAM9G25-EK AT91SAM9G25-EK Data Sheet

800

SAM9G25 [DATASHEET]

11032C–ATARM–25-Jan-13

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:

z

Disable TX and Enable RX

z

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).

z

Receive data

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 

.

 shows an example of character transmission.

IrDA 

Transceivers

RXD

RX

TXD

TX

USART

Demodulator

Modulator

Receiver

Transmitter

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

Bit Period

Bit Period

3

16

Start

Bit

Data Bits

Stop

Bit

0

0

0

0

0

1

1

1

1

1

Transmitter

Output

TXD