Memo: EE - Comm | LIN Bus Protocol

(2024/11/16)

Feature image is from: iDoka/awesome-linbus
Included by lin · GitHub Topics · GitHub
Searched by LIN Protocol — One Wire Protocol for Automotive Applications - Electronics Lab in Google image
Init search by lin protocol in DDG

① Overview

References:

LIN Bus Explained - A Simple Intro (2023) - CSS Electronics
- Found by searching lin总线 in biliibli.
LIN protocol 2.2A- Specification Package - lin-cia.org

Notes:

Single signal wire: Master sends request to the bus, and slaves send response to the bus.
- Example of the Left-hand side Front door module controls the rest 3 windows ^r1-bili:
- Only one task exclusively occupies the bus at a time.
- A suppliment bus of CAN
- Control window, wiper, door
One master task and 16 slave tasks (including master node)
1. Master task means publishing header, which can only be done by the master node.
2. Slave task means sending data. Slave node can only publish data, but they can’t publish header.
Low-cost, low-speed with potential delay, requiring response space

② Frame Structure

References:

Notes:

(2024-10-07)

A complete packet can be divided into 5 parts:
1. Break field (A long period of dominant value, at least 13 dominant bits) for letting slaves be aware of there is a frame on the bus.
  - One break field followed by 4 to 11 byte fields ^r3-Docs-p.29, including: Sync, PID, 1-8 Data, checksum
2. Sync: 1 byte 0x55 (0101_0101). Note that the waveform on bus is reversed: 1010,1010 ^r2-Bili
  - Slaves’ clock are syncronized based the falling edges. That’s why the 1010,1010 is used.
3. Protected ID
4. Data field
5. Checksum
Packet diagram:

packet-beta title A LIN Frame carried 2 bytes of data 0-12: "Break Field" 13: "Break delimiter" 14: "Start bit (0)" 15-22: "Sync (0x55)" 23: "Stop bit (1)" 24: "Start bit" 25-32: "PID (8 bit)" 33: "Stop bit" 34: "start bit" 35-42: "1 data (8 bit)" 43: "Stop bit" 44: "Start bit" 45-52: "1 byte data" 53: "Stop bit" 54: "Start bit" 55-62: "Checksum" 63: "Stop bit"

Terminologies:
1. Every byte field is enclosed by a Start bit 0 ahead and a Stop bit 1 at the end. ^r3-Docs-p.29.
2. Byte fields refer to 4 types of field: Sync field, Protected id field, each Data field. Whereas the Break field is at least 14 bits, which is the only field that doesn’t comply the structure of a byte field. ^r3-Docs-p.30.
3. Frame length should be calculated as a sum of two portaions: Header + Response, as the response can be published by a slave ^r3-Docs-p.32.
  - The time of sending a frame counts not only sending bits, but also the “Response space” and “Inter-byte spaces”.
  - There is an “inter-byte space” betwen every 2 “Byte file”. The gap betwen Break field and the Sync field is not an “inter-byte field”, because the Break field is not a “Byte field”.

0 is dominant value, while 1 is recessive value.
If the data field is empty, this packet is called a Hearbeat packet, used to inform salaves that the master is online and keep the salves aweak.
Distinguish master and slave from the waveform: the master is of lower voltage, while the slave’s lower bound is higher.
- The bottom edge of the packet published by the master node is flat. While the packet carrying slave’s data has a lader.
A complete dialog (cycle) between master and a slave consists of 4 packets:
- Sequence diagram for a conversation:
  
  sequenceDiagram Master->>Slave: Heartbeat packet Note over Master,Slave: Wait Master->>Slave: Instruction packet Note over Master,Slave: Wait Master-->>Slave: Request packet header Slave-->>Master: Response Note over Master,Slave: Wait Master-)Slave: Following Instruction

Protected ID

References:

LIN通讯_报文帧结构的PID及数据段 - HappytoShare Followed by v1

Notes:

A 1-byte (8 bits) protected identifier field includes: 2 bits for parity and 6 bits for frame identifier
1. Frame ID ranges from 0 to 63, corresponding to hex code: 0x00 ~ 0x3F, where the 2 frames: 0x3C (60) and 0x3B (61) are used to carry diagnostic and configuration data. And 0x3E and 0x3D are reserved for future protocol enhancement.
  - 6 frame types:
    
    FrameID 0-59 60
    
    Type Unconditional
2. Each frame id corresponds to a unique Protected ID, so a lookup table can be used in programs. ^{LIN总线代码详解-1 - 20:52}
2 Parity calculation based on Exclusive OR ⊕ and NOT ¬:
- P0 = ID0 ⊕ ID1 ⊕ ID2 ⊕ ID4
- P1 = ¬ (ID1 ⊕ ID3 ⊕ ID4 ⊕ ID5)
The frame identifier ranges 0 ~ 63, resulting 64 types of frames.
Transmission starts from ID0 upwards to P1
Examples:
1. Given a frame identifier: 38 (10_0110)
  
  P0 = 0 ⊕ 1 ⊕ 1 ⊕ 0 = 0
  
  P1 = ¬ (1 ⊕ 0 ⊕ 0 ⊕ 1) = 1
  
  Protected Id = 1010,0110
  
  The wave on bus:

FrameID	0-59	60
Type	Unconditional

Data Field

A frame can carry 0 ~ 8 bytes of data. Each data is a byte field.

A byte field is 10-bit length (SCI format):
Bit transmission starts from d0 and ends at d7

For example, a data is 0101,1110

The wave on bus is:

Checksum

(2024-10-09)

Two types of checksums:
1. Classic checksum is a sum of all Data bytes without including the protected id field;
2. Enhanced checksum sums up all Data bytes including the protected id.
The frames in LIN version 1.x use Classic checksum. Whereas the frames LIN version 2.x use Enhanced checksum.

Note the diagnostic frames (0x3C & 0x3D) always use the classic checksum because their IDs are fixed. ^{HKACO - 41:00}
Checksum calculation when assembling the frame before transmission:
1. Sum up all Data fields
  - Since the checksum is only of 1 byte (8 bits), once an intermediate sum got larger than 255 (more than 1 byte), a 255 (0xFF) needs to be subtracted.
2. Flip all bits of the sum.
Validate the checksum once the receiver received the frame.
1. Sum up all Data, but not followed by flipping all bits;
2. Add the Data sum to the frame checksum, expecting their sum is 0xFF.
Example:

Given a frame to be published on the bus:
1. Break field: 13 bits of 0 and 1 bit of 1;
2. Sync field (8 bits): 0101,0101 (0x55);
3. Protected id (8 bits): 1010,0110 (0xA6), if the frame id is 38;
4. Data (length varies from 8 to 64 bits), e.g., 1001,0011 (0x93, Decimal: 147)
Then, the checksum to be appended is:
1. Sum all Data: 1001,0011 (smaller than 0xFF, which is not needed to be subtracted)
2. Flip all bits

Example 1: Two Unconditional frames with LIN 2.2A ^{HappytoShare - 07:47}

FrameID	PID	Data1	Data2	Data3	Data4	Data5	Data6	Data7	Data8	V2	DL
0x30	0xF0	0x00	0xFF							0x0F	2
0x31	0xB1	0x00	0x00	0x59	0x53	0x7f	0x14	0x00	0xff	0x0E	8

Extended checksum:

	+data2	+PID	Inverted
Add	00	00	F0
	+ FF	+ F0
	—–	——	——
Sum	FF	F0	0F
Sub	00

Frame ID: 0x31

	+data2	+data3	+data4	+data5	+data6	+data7	+PID	Inverted
Add	00	00	59	AC	2C	40	40	F1
	+ 00	+ 59	+ 53	+ 7f	+ 14	+ ff	+ B1
	——	——	-	-	-	-	-	-
Sum	00	59	AC	12B	40	-	F1
Sub				2C		40		0E

Subtracting 0xFF (256) can be figuratively performed by: removing the highest 1 (meaning 256) and add 1. ^{HKACO - 42:20}
Flip 0xF1 (1111,0001) -> 0000,1110 (E)

Waveform

Problem:

Use the logic analyzer: “Saleae Pro 8” to prob a LIN header transmitted by the Master RL78/F24

References:

逻辑分析仪 Saleae Logic 16使用 - 程序员老吴的文章 - 知乎
- Searched by 逻辑分析仪用法 in DDG
logic-lin-data/README.md at master · ma-lwa-re/logic-lin-data - GitHub
- Searched by Saleae for LIN protocol in DDG

Notes:

(2024-12-16)

Prob a LIN frame using Saleae logic analyzer ^r1-知乎
- Actions:
Extension for parsing LIN frame ^r2-GitHub

Oscilloscope

References:
1. LIN PID Protected ID LUT Look Up Table - 곰집사노리터
Actions:
1. Send LIN frame

Results:

(2025-07-16T17:06)

A 0x29 frame and a 0x47 frame without response.

1 bit duration is around 50~60 us

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0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 1 1 0 1 1 1 0 0 0 0 0 1 1 1 1 1 0 0 1 1 1 1 0 0 0 1 0
  |   |                 | |                 | |                 | |                 |
  S   S                 S S                 S S                 S S                 S
  t   t                 t t                 t t                 t t                 t
  o   a                 o a                 o a                 o a                 o
  p   r                 p r                 p r                 p r                 p
      t                   t                   t                   t
         Sync                PID=0xDD            Data 0 = F0        Data 1 = 1E

PID = 0xDD, corresponding to the frame ID 29 ^r1-LUT
The PID field in the second frame is 0b01101111 (i.e., reversed 0b1111,0110), 0x6F, corresponding to frame ID 47

(2025-07-17T09:37)

A 0x50 frame

Note:

The waveform displayed on the osilloscope is reversed from the signal.
There might be some recessive bits (1) after the end bit of the last byte field. And the following first 0 is the start of the next byte field.

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0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 0 1 0 0 1 1 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1
    |   |                 | |                 | |                 | |                 |
    s   s                 e s                 s s                 s s                 s
    t   t                 n t                 t t                 t t                 t
    o   a                 d a                 o a                 o a                 o
    p   r                   r                 p r                 p r                 p
        t                   t                   t                   t                  
           Sync = 0x55            PID=0x32          Data 0 = 0          Data 1 = 0

Sync field: 0101,0101 (0x55)
PID: 0011,0010

(2025-08-19T10:30)

Master header + Master data followed by Master header + Slave data
- LIN messages:
- The time interval between the end of a command frame and the start of a response frame
- Time interval between the start of a command frame to the start of response data
- A Master frame occupies the bus for 5ms, A Request frame take up the bus for 8ms:
- Time length of a Master frame
- Time length of a Response frame
- Time from the end of the command frame to the start of the response frame
- Time after the master releases the bus
- Time length of 13 bits
- Time length of 8 bits: 1010_1010

③ Frame Transfer

(2024-10-09)

Sequence:

Request frame (header + data) published by the master node.
Wait some time for slaves recognizing and processing
Master node publish a header asking information
One of the 15 slave nodes publishs its data on the bus.

Sleep and Wakeup

④ Diagnostic

References:

Frame Structure

Overall:

Both MasterReq and SlaveResp can be a single frame SF or multiple frames (first frame FF + consecutive frame CF)

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                          .-- SF
            .-- MasterReq-+
Diagnostic  |             '-- FF + CF
frame      -+
            |             .-- SF
            '-- SlaveResp-+
                          '-- FF + CF

Single Frame

(2025-02-24)

Notes:

Data field contains 8 bytes ^P02-11:52:
- The first 2 data bytes are occupied by NAD (Node address) and PCI (protocol control information), so one frame can only carry 6 bytes data (48 bits) at most.
A MasterReq is a single frame:
- Byte0 is SID (service ID)
A SlaveResp is a single frame:

NAD: Node Address

NAD	Description
0	Sleep Command
1 - 125 (0x01 - 0x7D)	Physical address of slave node
126 (0x7E)	Function Address, 只在诊断报文中使用，不允许用在节点配置中
127 (0x7F)	Broadcast address
128-255 (0x80-0xFF)	Customized

PCI indicates the type of 3 kinds of PDU: SF (single frame), FF (first frame), and CF (consecutive frame) ^r1-虹科

type	b7, b6, b5, b4	b3, b2, b1, b0
SF	0 0 0 0	有效数据字节数
FF	0 0 0 1	有效数据字节数的高 4 位, 会与后面的 `LEN` 组成一个 12 位的data: max:`FFF`
CF	0 0 1 0	包编号

If the data is less than 8 bytes, a SF is enough. Otherwise, there will be FF and CF
第一个 CF 的包编号是 0x1
Examples: 0x06= SF + 6 Bytes, 0x10 = FF + less than 255 (FF) Bytes, 0x21 = CF + pdu index is 1.

SID (Service Identifier) ^P2-25:52
- Used in MasterReq
- Two kinds of services: Diagnostic and Node configuration
  
  |Values | Services |

First, Consecu Frame

A MasterReq is a First Frame + multiple Consecutive frame:
- LEN is an additional segment added in the single frame, while reducing one data byte field.
- Similarly, the First Frame for a SlaveResp is included LEN based on the single frame of a SlaveResp
The consecutive frame CF structure in the MasterReq and SlaveResp is the same: containing 6 data byte field

packet-beta title CF (Data Field) 0-7: "NAD" 8-15: "PCI" 16-23: "D1" 24-31: "D2" 32-39: "D3" 40-47: "D4" 48-55: "D5" 56-63: "D6"

Example log in SimpleConf console:

FrameID	Data
0x3C	0x7f, 0x10, 0x19, 0xaa, 0x01, 0x02, 0x03, 0x04
0x3C	0x7f, 0x21, 0x05, 0x06, 0x07, 0x08, 0x09, 0x10
0x3C	0x7f, 0x22, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16
0x3C	0x7f, 0x23, 0x17, 0x18, 0x19, 0x20, 0x21, 0x22
0x3C	0x7f, 0x24, 0x23, 0x24, 0xff, 0xff, 0xff, 0xff

0x7f : NAD = Broadcast address, informing all nodes
0x10 : PCI = First frame, no more than 0xFF bytes data
0x19 : LEN, Length (Number of byte of data) = 25 bytes
0xaa : SID, Service ID
0x01 - 0x04 : Data = 4 byte in the First Frame
0x21: PCI = CF, PDU index is 0x1
25 bytes data is from 0xaa to 0x24

Node Configuration Services

(2025-02-24)

Objective: Modify the NAD or Protected ID using the 0x3C frame with Service IDs ranging from 0xB0 ~ 0xB7 ^r1-02
- Each service corresponds to a master request, and is transmitted as a single frame SF ^r3-Docs

Example 22 Service

Notes:

(2025/02/24)

SID = 22 ^{r1-02-1:10:19}

UDS Services

Notes:

Unified Diagnostic Service ^r4-Docs
- SID list ^Wikipedia

Send Diagnostic Frames

(2025-02-14)

Notes:

“RAW” vs “DTL” ^r1-02
- RAW: Type 8 bytes for each frame manually.
- DTL: Enter the total number of data bytes, followed by inputing the data values only, without repeatedly typing the NAD and PCI, as they are identical for a diagnostic frame. The entire data will be split into a First Frame and multiple Consecutive Frames.
Protocol > Execute service ^r2-虹科

Clock Freq

(2024-10-10)

Bit Timing
- T0 is the first falling edge, and T1 is the last falling edge in the sync field.
- Therefore, the length of a bit is:
  
  $\frac{(T1-T0)}{8}$
- If the buad rate is 19,200, the bit timing is 52 us

Lin Driver Receiver

Linworks

(2024-10-11)

搭配硬件：上位机（Babylin）

STM32-LIN

(2024-10-08)

References:

LIN总线代码详解-1 - bilibili - bili_17503743935 Followed by v1)

RL78/F23

References:

RL78/F23, F24 Setup Procedure for LIN Communication in Slave Mode (Guidance)
- Searched by No option for R7F123xxx in renesas lin configurator in Google
RL78/F23, F24 Setup Procedure for LIN Communication in Master Mode (Guidance)
- Inspired by r1
How to Create a LIN Project with Smart Configurator on e² studio - YouTube - RenesasPresents
- Shared by Kaushik
RL78/F2x RLIN3 Module- Software Integration System
- Generated by Smart Configurator

Notes:

(2024-11-13)

The Master-mode settings of a RL78 in the r2-Docs p.3 is consistent with the video: r3-YouTube
- fCLK = 40M MHz, Use Pin13 & Pin14

Example: R78/F12 UART

References:

RL78G13 Utilising the Serial Array Unit (SAU) in LIN Communications Sample Code - R01AN0912EG0100 (Nov 23, 2011)
- Also can be searched by the document number in Search | Renesas
RL78/F12 LIN Slave Mode (UARTF) - Renesas - R01AN1839ED0100 (Sep 25, 2013)
- Pages: p.3 p.4
Search | Renesas
- Searched by Code Utilising the Serial Array Unit (SAU) in LIN Communications site:renesas.com in DDG
Universal asynchronous receiver-transmitter - Wikipedia
LIN Protocol Specification - Revision 2.2A (December 31, 2010)

Notes:

(2024-11-19)

Tutorial for a CubeSuite+ project (LIN.mtpj) demonstrates the usage of a SAU module implementing LIN communication ^r1-SAU.
Sample code of the UARTF module on an RL78/F12 (Slave mode) communicating with an RL78/F14 (Master) through the LIN Driver ^r2-RL78/F12.

(2024-11-20)

UART is different from LIN ^r2-p.3 in terms of aspects for a protocol ^r4-Wiki:

Features	UART	LIN
#wires	2 (Tx-Rx)	1 (Mst-Slv)
Direction	Full-duplex	Half-duplex
Syncronize	Baud rate	Baud rate
Signals	TTL
Distance		40 m
Dominant

They both have No Clock wires, so the waveform-parsing syncronization is achieved by the baud rate between the two parties of the communication.
As LIN is used for the situation that one master controlling multiple slaves, so it only has a single wire.
Since there is only one single wire shared by the many “users”,
1. Only the master can send frame Headers. When the master is about to publish a frame header, it pull down the bus for 13 dominant bits followed by at leat 1 recessive bit as a break delimiter.
2. The header issued by the master includes two fields: a Sync field and a PID. ^r5-Lin-p29
  - The baud rate is inicated by the “Sync break field” (0x55) to enable the target slave to match up its baud rate.
  - The PID field is used for generating interruptions, which can be generated after a slave received the PID completely (as PID only can be sent by the Master) ^r-F12-p4.
3. The slave response is of 9 bytes at most:
  
  The reponse consists of two portions:
  1. 8 bytes data at the most
  2. 1 byte of Checksum

Sample Code:

(2024-11-19)

init function
- Reasons:
  1. Analogous to Arduino’s Serial.begin(19200).
  2. No user operations are required. The code on the slave will keep running: waiting for the header from the Master.
  3. The LIN transceiver must be use with a UART?
  4. The UART of an MCU need to be initialized: Clock, baud rate, enable interrupts, header format.

Call APIs

References:

RLIN3 Module Software Integration System
【AutoSAR】只讲干货!一文看懂LIN通信_lin通讯-CSDN博客
- Select the word: l_sys_init in the r1-Manual P.100 > 豆包桌面版: “AI搜索”
LIN Middleware - GitHub Pages - Infineon.github.io
- Searched by #define ld_send_message(ch, length, NAD, data) ApMLinDiag_vogSendMessage_DMY(ch, length, NAD, data) in DDG
LIN 入门 - Renesas Electronics (Oct 25, 2010)
- Searched by l_sys_init() LIN 通信代码 in Google

Notes:

(2024-12-04)

The functions of the library rlin3 are not many ^{r4-Manual Ch8}.

(2024-12-26)

A scheduler is necessary to master ^r1-SIS.
- A scheduler can be implemented with a timer

(2024-12-27)

Add the the lin conf (/src/r_rlin3_lib/r_lin_drv/Channel0/conf) into compiler. Otherwise, the following code will run into an error: Undefined external symbol "_l_sys_init"

Actions:

The following code can be built without errors:

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#include "r_smc_entry.h"
#include "conflin_0.h"

int main (void);

int main(void)
{
    EI();
	// Initialize the LIN core
	if (l_sys_init()) {
		// Initialization successful
	} else {
		// Initialization failed
	}

	// Your application code here

    return 0;
}

Execute processes based on the returned initialization result
- Reasons
  1. l_sys_init() is an alias for the ApMLin_u1gInitSys() (hintted by VSCode copilot).
    - Prompt: “@workspace How to use this function: l_sys_init()?”

Call the LIN2.1 API in an individual source file for a channel.

Reasons:
1. The r1-Manual P.33 mentioned the source code for each channel should be separated.

Actions:

Creat a hardware layer source file

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// hw/lin_channel_0.c

#include "conflin_0.h"

u1 init_lin_ch0(void)
{
	if (l_sys_init())
	{
		//
		return L_FAIL;
	}
	else
	{
		return L_SUCCESS;
	}
}

The difference between l_bytes_wr and ld_send_message()
- Reasons:
  1. The r1-Manual doesn’t contain explanation about ld_send_message()
  2. conflin_0.h:
    1 2 3
    
    #define ld_send_message(ch, length, NAD, data) ApMLinDiag_vogSendMessage_DMY(ch, length, NAD, data) #define l_bytes_wr ApLin_vogWriteBytesSig
- Actions:
  1. l_bytes_wr is used to write a byte to a signal, contributes to a frame ^{r4-入门 P.51}. ld_send_message is used to send a diagnostic frame ^r3-infineon
- Analysis:
  1. I guess the frames are sent automatically according to the schedule: l_sch_tick().

(2024-12-29)

A schedule is created and the variable is generated by LIN Configurator, defined in conflin_0.h
- Reasons:
  1. Call l_sch_set(LIN_CHANNEL0, SCH0, 0U); after initializing LIN ^{r1-Manual p40}.
  2. The LIN transceiver needs +12V battery