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LIN (LOCAL INTERCONNECT NETWORK) SOLUTIONS

4.1 IMPLEMENTATION ON THE ST72254G2 - SOFTWARE EMULATED SCI

4.1.1 Step by Step Configuration

lin_config.h

Setting Group

Comments

Text line in lin_config.h

CPU operating frequency

An external resonator of 16 Mhz

is used. As a result the internal

CPU frequency is 8MHz. So

“FCPU” is set to 8000000.

#define FCPU

8000000

Communication peripheral

The ST72254 has no SCI periph-

eral on chip. As a result the

UART communication has to be

emulated by one of the 16bit tim-

er TimerA or TimerB. TimerA is

chosen in this example. As a re-

sult “UART_TIMERA” is defined

and “UART_TIMERB” and “SCI”

are commented out.

#define UART_TIMERA

//#define UART_TIMERB

//#define SCI

LIN RX and LIN TX pin definition

Depending on the constraints of

the board layout and according to

the ST72254 pinout we select the

Input Capture 1 pin and the Out-

put Compare 1 pin for respective-

ly the LIN RX and LIN TX signals.

The Input Capture 1 pin of Time-

rA is linked to the Port B pin 0

(see pin description in the MCU

datasheet). As a result

LIN_RX_PINNB” is set to 0. Port

B data register has the address

0x04. As a result

“LIN_PORT_ADD” is defined to

0x04

#define UART_IC1

//#define UART_IC2

#define UART_OC1

//#define UART_OC2

#define LIN_PORT_ADD

0x04

#define LIN_RX_PINNB

Timeouts

The UART communication is al-

ready using one input capture

and one output compare of Time-

rA. Setting TimerA for the timeout

handling will complement the use

of the timer. So we define

“TIMEOUT_TIMERA“. Output

Compare 1 is already used by the

UART communication (see

UART_OC1) so we define the

output compare 2 for the time-

outs handling.

#define TIMEOUT_TIMERA

//#define TIMEOUT_TIMERB

//#define TIMEOUT_OC1

#define TIMEOUT_OC2

LIN baudrate

The example LIN baudrate is

9600 Baud.

#define BAUDRATE

9600

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