Implementing a LIN slave node with STM8AL board

AN4101

12/21

Doc ID 23127 Rev 1

6

Implementing a LIN slave node with STM8AL board

6.1

STM8AL microcontroller USART features

USART does not embed any particular LIN features. A LIN slave node can be implemented

by building a break detection based on a 00h data reception with a framing error (FE flag).

An external resonator or crystal is required in order to meet the ±1.5% maximum clock

deviation allowed by the LIN standard.

6.2

Software algorithm

The software algorithm described below is implemented in the demonstration software of

the STM8A-DISCOVERY (STM8AL microcontroller).

6.2.1

LIN state machine

The LIN task is called regularly by the main routine. This task is a basic LIN slave driver that

implements a state machine with the following states:

●

Idle

●

Break

●

SynchField

●

Identifier

●

DataReception

●

DataTransmission

6.2.2

LINUART interrupt

The LINUART interrupt reads and clears the hardware flags in the LINUART registers, and

sets the appropriate software flags to allow transitions in the basic LIN driver state machine:

●

BreakReceived, which is set if both of the following conditions are met:

–

a data byte with the value 00h is in the data register (DR)

–

the framing error flag (FE) is set

●

DataReceived, which is set if the RXNE flag is set

●

ReceptionError, which is set if the framing error flag (FE) or the overrun flag (OR) is

set