TECH ARTICLE

EB tresos Classic AUTOSAR：
BSW - Diagnostic stack Basic Technology Analysis

Basic concepts and module division of AUTOSAR diagnostic modules, detailing DCM, DEM, FIM functions, and UDS diagnostic service processes to help master in-vehicle diagnostic core technologies.

This article is based on the video content of 'EB tresos Classic AUTOSAR BSW – Diagnostic stack Basic Training' provided by Elektrobit. The video introduces the basic concepts and module division of the AUTOSAR diagnostic modules, detailing the functions and roles of EB tresos diagnostic modules like Dem, Dcm, Fim, Det, and DccM, as well as the diagnostic service requests and corresponding processes under the UDS protocol, including common functional descriptions. This will help automotive electronics developers and in-vehicle diagnostic system development teams master AUTOSAR diagnostic core technologies and improve development efficiency.

1. Core Objectives of the Diagnostic Stack

The main task of the diagnostic stack is to implement standardized vehicle diagnostic protocols (e.g., UDS ISO 14229), allowing external diagnostic testers to communicate with the ECU to read fault codes, clear records, execute tests, or perform software updates (flashing).

2. Three Core Modules (DCM, DEM, FIM)

The video details the three pillar modules of the diagnostic stack, each performing its duties and closely collaborating:

forum DCM (Diagnostic Communication Manager)

Positioning:Diagnostic Communication Manager.

Function:Responsible for processing external diagnostic requests. It parses UDS services (e.g., Read Data 0x22, Write Data 0x2E) and returns the results to the tester. It also manages diagnostic sessions and security access.

inventory_2 DEM (Diagnostic Event Manager)

Positioning:Diagnostic Event Manager.

Function:Responsible for processing 'Diagnostic Events'. When the software detects an anomaly, DEM records the corresponding Diagnostic Trouble Code (DTC) and stores relevant environmental information (Freeze Frames) for subsequent maintenance analysis.

block FIM (Function Inhibition Manager)

Positioning:Function Inhibition Manager.

Function:Determines whether to suspend certain software functions based on the fault status recorded by DEM. For example, if a throttle sensor fault is detected, FIM will notify the control logic to stop the cruise control function to ensure driving safety.

3. Diagnostic Development Workflow

In EB tresos Studio, configuring the diagnostic stack generally follows these steps:

  • description
    Import Diagnostic Description File: Usually a CDD (Diagnostic Description) or ODX file, defining which UDS services are supported.
  • build
    Configure DCM: Set diagnostic services, DID (Data Identifiers), and communication parameters.
  • tune
    Configure DEM: Define diagnostic events, DTC priority, and storage mechanisms (initial occurrence, confirmed occurrence, etc.).
  • integration_instructions
    Generate Code: Generate the corresponding BSW code via the EB tresos tool.

4. Diagnostic Communication Path

The flow path of diagnostic messages is typically:

External Diagnostic Tester arrow_right_alt Communication Hardware (CAN/Eth) arrow_right_alt PduR arrow_right_alt DCM sync_alt DEM / SWC

Tutorial Video

play_circle Watch the full video on Bilibili