AN4101

Implementing a LIN master node with STM8AF board

Doc ID 23127 Rev 1

9/21

4

Implementing a LIN master node with STM8AF board

4.1

STM8AF microcontroller LINUART and USART features for

LIN master

The LINUART and USART inside the STM8AF microcontroller implement both generation

and detection of LIN Breaks.

LIN Break generation allows sending of 13-bit Breaks on the TX pin, thanks to the LIN

protocol requirement.

LIN Break detection allows detection of feedback from the LIN transceiver, before the Synch

Field (55h data byte) transmission is requested on the TX pin. There is a dedicated flag,

LBDF, which may or may not trigger the receive interrupt depending on the LBDIE bit

configuration.

4.2

Software algorithm

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

the STM8A-DISCOVERY (STM8AF microcontroller). Refer to Section 7.2: STM8AF

software description for details.

4.2.1

LIN state machine

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

that implements a state machine with the following states:

●

Idle

●

Break

●

SynchField

●

Identifier

●

DataReception

●

DataTransmission

4.2.2

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 the break detection flag (LBDF) is set in the interrupt

routine

●

DataReceived, which is set if the RXNE flag is set

●

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

is set