The diagnostic accomplishment of Slave node in LIN network

[xpye_jlu]

Hello, all

  How does slave node accomplish the diagnostic information in vehicle LIN network?
  Usally there are two kinds of method:
  One is that slave node memorizes DTC information and then transmits to master, and master sends slave's DTC through CAN bus to tester;
  The other is that slave node only sends dignostic information through normal LIN message through LIN bus rather than memorizes DTC information, master receives these information through LIN bus and memorizes slave's DTC information according to requirment, then master sends slave's DTC through CAN bus to tester.
  Anyone who knows which method is usually used by OEM for their cars?

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[Allen Pothoof]

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It has been my experience, LIN and otherwise, that each module maintained their own history of DTCs.  (Of course, it has also been my experience that most systems don't go through a "master" node unless it is a gateway or bridge.)
 
If  you think about it, that only makes sense: there are a lot of modules, each of which have different requirements for what,  and how many DTCs they keep track of; in aggregate, that takes a lot of memory, which would make for an expensive chip.  In addition, they all have different requirements for how to age these DTCs: ignition cycles or miles, not to mention how many.  Why put all that logic in a single module? 
 
I'm normally a fan of a centralized data repository, with standardized accesses.  But the range of requirements spread across multiple nodes matches a distributed architecture to a "T".
 
Regards,
Allen Pothoof 
 

> Date: Wed, 24 Jun 2009 07:15:40 +0000
> From: xpye_jlu@...
> To: canlist@...
> Subject: [CANLIST] The diagnostic accomplishment of Slave node in LIN network
>
> Hello, all
>
> How does slave node accomplish the diagnostic information in vehicle LIN network?
> Usally there are two kinds of method:
> One is that slave node memorizes DTC information and then transmits to master, and master sends slave's DTC through CAN bus to tester;
> The other is that slave node only sends dignostic information through normal LIN message through LIN bus rather than memorizes DTC information, master receives these information through LIN bus and memorizes slave's DTC information according to requirment, then master sends slave's DTC through CAN bus to tester.
> Anyone who knows which method is usually used by OEM for their cars?
>
> --
> Archives and useful links: http://groups.yahoo.com/group/CANbus
> Subscribe and unsubscribe at www.vector-informatik.com/canlist/
> Report any problems to <canlist-owner@...>

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[SkandanTech CAN]

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Xpye_jlu / Allen Pothoof,

My experience developing LIN for the Master Node is that there is one Application Scheduling Table and one Diagnostics Scheduling Table in the LDF database.

To perform Diagnostics of the LIN Slave, the LIN Master has to switch Scheduling  Tables and read Diagnostic Services over LIN Ids 0x3C and 0x3D.

The Slave ECUs are inclined in supporting the Mandatory SID 0xB2 to read Serial Number of the Slave ECU (for Plant and Engineering Menu).

The Slave ECUs are inclined in supporting CAN-style Start/Stop Diagnostic Session through Special SIDs.

 

But there is resistance to storing DTCs in the Slave ECU.

The argument has always been that LIN as a protocol is designed for low cost ECUs and adding an EEPROM would add to the cost of the Slave ECUs.

In atleast 2 vehicle programs we had to detect KeyMalfunction DTC of a Haptic Controller (LIN Slave) in the LIN Master

and Display Unavailable to User due to Overheat DTC of a Rear Seat Entertainment (LIN Slave) in the LIN Master.

 

Will be definitely interested in knowing industry-wide practices in LIN Diagnostics.

 

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-----Original Message-----
From: canlist-owner@... [mailto:canlist-owner@...]On Behalf Of Allen Pothoof
Sent: Mittwoch, 24. Juni 2009 16:08
To: canlist@...
Subject: RE: [CANLIST] The diagnostic accomplishment of Slave node in LIN network

It has been my experience, LIN and otherwise, that each module maintained their own history of DTCs.  (Of course, it has also been my experience that most systems don't go through a "master" node unless it is a gateway or bridge.)
 
If  you think about it, that only makes sense: there are a lot of modules, each of which have different requirements for what,  and how many DTCs they keep track of; in aggregate, that takes a lot of memory, which would make for an expensive chip.  In addition, they all have different requirements for how to age these DTCs: ignition cycles or miles, not to mention how many.  Why put all that logic in a single module? 
 
I'm normally a fan of a centralized data repository, with standardized accesses.  But the range of requirements spread across multiple nodes matches a distributed architecture to a "T".
 
Regards,
Allen Pothoof 
 

> Date: Wed, 24 Jun 2009 07:15:40 +0000
> From: xpye_jlu@...
> To: canlist@...
> Subject: [CANLIST] The diagnostic accomplishment of Slave node in LIN network
>
> Hello, all
>
> How does slave node accomplish the diagnostic information in vehicle LIN network?
> Usally there are two kinds of method:
> One is that slave node memorizes DTC information and then transmits to master, and master sends slave's DTC through CAN bus to tester;
> The other is that slave node only sends dignostic information through normal LIN message through LIN bus rather than memorizes DTC information, master receives these information through LIN bus and memorizes slave's DTC information according to requirment, then master sends slave's DTC through CAN bus to tester.
> Anyone who knows which method is usually used by OEM for their cars?
>
> --
> Archives and useful links: http://groups.yahoo.com/group/CANbus
> Subscribe and unsubscribe at www.vector-informatik.com/canlist/
> Report any problems to <canlist-owner@...>

---

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