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Topic: LIN Sync Break MCP2021 (Read 2106 times) previous topic - next topic

Numlock

I want to spy on the traffic on a vehicle's LIN network, but I have a question about sending the transceiver serial data.

The transceiver I am using is Microchips MCP2021 which connects to the USART pins, and when I send out serial data the MCP2021 sends out the same serial message bit for bit.

But the LIN specification wants me to send a "Sync Break" where at least 13 recessive bits (well specifically bit times) are sent at the start of a message.

It seems that I have to write a special function to send a proper Sync Break but a quick read through the data sheet for my older mega board (ATmega1280) makes me think this wouldn't be possible, at least not with the built in hardware USART.

Other than this special sync break character, everything else appears to be straightforward UART stuff.  I have two LIN nodes I built and can use my o-scope to see that they are successfully exchanging LIN messages, other than that the sync break's are not LIN compliant.

The question I have is if anybody else has done this or can tell me if I am mistaken about the USART or the LIN sync break field needing to be so long.



Woobatron

Hi Numlock

Did you ever find a solution for this?  I have some automotive lighting devices that I'd like to control from the Arduino.  For it to act as master it needs to send the sync break.  Sounds similar to your situation.

Thanks

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