LIN protocol basic questions.

[embpic]

I am very new to LIN protocol and read that it is single wire bus and slave not required crystal as it clocked by Master.
so my question is
1) if master provide clock to slave then same wire can't used as data.
2 so how to provide clock to slave.
3) As LIN is implemented using USART. so it is having already frame structure as start byte data and then stop. so then how
provide sync break of 13- bit.

4) Is this protocol software based implementation? If yes how?
5) Like CAN is it there any LIN transceiver?

 

[btbass]

Lin uses he same protocol as RS232 so Standard Uarts can be used to keep the costs low.
A lin message starts with a break field then a sync field. Sync is a byte field with the data value 0x55. The slave uses the sync field to implement auto baud rate setting. Some uarts are Enhanced USART Modules to help support the Lin protocol. You have to write software to support Lin protocol. Sample code on Microchip.
Yes, you do need a transceiver to interface a micro to the Lin bus.

 

[embpic]

then what is difference between the LIN and UART protocol.

 

[btbass]

Not a lot in terms of hardware. You need a Lin transceiver to connect to the Lin bus and a Uart to handle the messages.

Quite a lot in terms of message frame format. Not easily summed up in a few words.

The main properties of the LIN bus are:
. single-master / multiple-slave concept
. low cost silicon implementation based on common UART/SCI interface hardware.
. self synchronization without quartz or ceramics resonator in the slave nodes
. deterministic signal transmission
. low cost single-wire implementation
. speed up to 20kbit/s.

The Lin spec can be downloaded from the Internet. It is a large document that needs to be studied to fully get to grips with Lin.

 

[embpic]

what about clock?
is it asynchronous communication?

 

[btbass]

Yes, it is asynchronous communication the same as RS232. Each byte is sent serial data format (8N1-coding) same as RS232.
The Master sets the baud rate. Each Message starts with a break and then sync byte of 0x55.
The slaves use the sync byte to adjust their baud rate to synchronize on the bus clock. (Auto baud)

 

[embpic]

thank you means i need only UART communication at controller's side
and next to controller i'll need LIN transeiver. and then towards LIN interface node's.

and again LIN transeiver and UART back to controller.

 

[embpic]

LIN mostly used to complement the CAN controller. Is it right?