The Pico LIN decoder already pulls the ID from the protected identifier in the decode table. Slaves look at the parity bits to ensure the message is valid and either ignore the following data, listen to other slaves or respond to the ID in the response field. The full 8 bits make up the protected identifier. The ID is made up of 6 bits and 2 parity bits. The Identifier section is one of the more important sections in the message as it delivers the instructions to the slaves as to what information the master needs to receive. It is typical to see this byte in HEX as 0x55. This 8bit sync byte is used to ensure the slaves match the baud rate of the master. Because of the length of this section, it cannot be mistaken for any other message.ĭirectly following the break is the sync byte. It is usually quite long, taking up at least 11 bits with most modern vehicles seeing 13 bits and more. The break acts as a notice for all the nodes on the bus to listen up as a message is about to broadcast. The header is made of the break, the sync byte and the ID field. The LIN specification document that I have referred to during writing this article can be found here. Voltages for this signal are generally a switching voltage from battery voltage to ground which is why it can be often mistaken for a PWM signal. LIN works on a master and multiple slave concept, such as a central electronics ECU which communicates with all the door locks. It is a lot lower cost than that of CAN due to its single wire properties and is primarily used in places where high speed communication isn’t required. LIN can support up to 16 ECUs, 1 master and 15 slaves. LIN is a single wire, bi-directional data bus transmitting at relatively low speeds with a max speed of 20kBaud (kbits/s) with typical speeds of 9.6kBaud and 19.2kBaud. To help with this post some basic understanding of LIN is required. Please don’t confuse LIN controlled alternators with PWM or BSD which are typically found on Ford and BMW respectively. For LIN you would need a LDF (Lin Description File) which holds the key to unlocking the data. LIN is fully customizable meaning VM’s can give ID values to any ECU or control unit making it like CAN in this sense if you want to decode it to a higher level you will need a DBC file to interpret the decode data. There are devices better suited for this job out there on the market but when it’s all you have, there is a lot we can still do. As with the other network forum posts we have to remember that PicoScope is not a dedicated data logger. It tends to crop up on non-safety critical communications where speed isn’t a priority. LIN, Local Interconnect Network, it seems to be everywhere! HVAC, door locks, heated seats, mirrors, battery monitoring and charging systems.
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