Diagnostics Log and Tracing

Introduction and goals

The Diagnostic, Log and Tracing (DLT) provides a log and trace interface in ECUs. The standardized protocol for logging inside ECU is specified in the AUTOSAR 4.0 DLT, and GENIVI has an open source project dlt-daemon that follows those standards.

Besides dlt-daemon, GENIVI offers dlt-viewer which is another software that allows a client to connect to the dlt-daemon and receive logs remotely.

Since PELUX is GENIVI compliant, we have decided to integrate GENIVIs' DLT component which also works with dlt-viewer.

In order to view dlt logs, you can refer to the guide Reading System Logs with DLT.

Requirements overview

Log and Trace

DLT logs are targeted at OEM-s (developers, testers), since they show technical information and give an overview of the processes. During the development, it is entirely up to the developers to decide what to store on the DLT logs.

On a PELUX image, the dlt-daemon package is already integrated and enabled.

In order to get DLT logs remotely, dlt-viewer is required.

Basic usage

The dlt-daemon runs by default when the PELUX image boots up. dlt-daemon usage can be found on https://github.com/GENIVI/dlt-daemon. Cheat-sheets and further documentation can be found on https://github.com/GENIVI/dlt-daemon/tree/master/doc (Although the documentation here is outdated, it can be very helpful giving insight into architecture).

dlt-daemon stores offline-log database on /tmp file system.

In order to view the logs via dlt-viewer, you need to install it on your machine first. Instructions are available on the repository. Once dlt-viewer is built, its binaries are found on build/bin/dlt-viewer and the GUI can be launched via command ./dlt-viewer . You will need to find the IP address of the host, finding the IP address depends on the hardware where PELUX is running.

Optionally, Blue PiraT 2 can be configured to work with dlt-daemon, through which multiple gigabytes of logs can be stored.

Basic requirements

Unicode support PELUX default encoding is UTF-8 for all logging messages. GENIVI dlt-daemon works well with UTF-8 as well.

Dynamic Log adjustments The amount of logs, especially in Trace mode, can be overwhelming. Applications that produce DLT logs should have the functionality of enabling/disabling logs or adjusting the level of log outputs. Ideally each logging call should dynamically check boolean condition and just do nothing if logs are dynamically disabled. It will reduce log traffic inside the system and improve performance in general.

GENIVI DLT provides a back channel from dlt-viewer to applications that generate DLT logs. The user can precisely change log levels for each application individually from the dlt-viewer UI. The user request will reach each application and disable logs in the place they are actually produced.

Quality Goals

Reliability Reliability is a key quality for DLT. Developers and testers rely on the logs provided by dlt-daemon to find errors and understand behavior of applications. If the logs will be faulty, there will be a very big struggle to debug the error, or understand the behavior.


  • Software Developers

  • QA Engineers


GENIVI's dlt-daemon stores an offline log database on in-RAM file system /tmp/dlt_offlinetrace_20120101_005302.dlt. The size limits for the log files should be adjusted at HU startup based on amount of RAM available. E.g. a Premium HU with 16GB of RAM can use 200MB of offline storage. On the other hand, 4GB of ram uses 50MB of offline storage or less.

Solution Strategy

DLT logs are automotive industry standard. Industry expects any automotive software to support it. Since PELUX is a part of the open source community, we use a component developed by GENIVI.

Below are the open source software that we use from the DLT component.

Since GENIVI dlt-daemon supports only C applications, another third party software is required to support C++. Currently, PELUX uses ivi-logging.

Building blocks view

Level 1


Level 2


Design decisions

In order to integrate the dlt component with PELUX, we needed a wrapper which is capable of handling C++ applications. Currently ivi-logging is integrated as part of the dlt component. This software was initially developed by Pelagicore but is not actively maintained at this time.





Diagnostics Log and Tracing


Head Unit


Electronic Control Unit


Transmission Control Protocol


Graphic user interface