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Authored by Alexander Wenzel

0.0.1, 2012/10/11: Initial version

Overview

DLT is quite easy to use. As an application developer you only need to follow some steps as described in this document.

Initialization:

  • Link your application against the DLT library
  • Include the DLT header file
  • Register your application 
  • Define all contexts 
  • Register all contexts 

Now you are ready to write your logs.

Termination:

  • Unregister all contexts 
  • Unregister application 

Link your application to DLT library
If you compile your application with cmake, you have to add the following lines to your CMakeLists.txt;

find_package(PkgConfig) 
pkg_check_modules(DLT REQUIRED automotive-dlt)

and use the variables $\{DLT_INCLUDE_DIRS\} and $\{DLT_LIBRARIES\} for the DLT include and library paths.

Include the DLT Header

To use DLT you have to include the DLT header file in each file you want to use DLT. Here's an example;

#include <dlt.h>

 

 

---- Register your application ------------------------- You have to register your application as early as possible during the initialisation of your application. You have to call the DLT_REGISTER_APP(). It is only allowed to call DLT_REGISTER_APP() *once* in your application. You have to provide a application id, which size is maximum four charcters long. In this example we use "MAPP". And you can provide also a description for your application, here it is "Test Application for Logging". ---- int main(int argc, const char\* argv\[\]) { DLT_REGISTER_APP("MAPP","Test Application for Logging"); } ---- .Important notes: * If your application uses fork(), you may not call DLT_REGISTER_APP before fork(). And fork() should never be called after DLT_REGISTER_APP. This is because of state information and inter process communication channel to daemon would be copied to new process, but threads would be not. If you are not sure where you are calling DLT_REGISTER_APP() the first time, you can initialise the DLT user library by calling the initialisation routine directly. ---- dlt_user_init(); ---- * DLT_REGISTER_APP is asynchronous. It may take some milliseconds to establish the IPC channel. Because of this, you might lose messages if you log immediately after registering. Typically this is not a problem, but may arise especially with simple examples. Define all contexts -------------------- You can create as many contexts as you like. You can declare one or more contexts in a C or CPP file. Each context is only allowed to be declared once. You have to provide a unique variable name for your context. ---- #include <dlt.h> DLT_DECLARE_CONTEXT(myContext1); DLT_DECLARE_CONTEXT(myContext2); DLT_DECLARE_CONTEXT(myContext3); ---- If you want to use a context in another C or CPP file, you can import the context by calling ---- #include <dlt.h> DLT_IMPORT_CONTEXT(myContext1); DLT_IMPORT_CONTEXT(myContext2); DLT_IMPORT_CONTEXT(myContext3); ---- Register all contexts ---------------------- After you have registered your application you must register your contexts, early during initialisation of your application. Do not call DLT_REGISTER_CONTEXT() before DLT_REGISTER_APP(). During registration of each context, you must provide a context id, which size is maximum four charcters long. In this example we use "TESX". And you can provide also a description for your context, here it is "Test Context X for Logging". ---- int main(int argc, const char\* argv\[\]) { DLT_REGISTER_APP("MAPP","Test Application for Logging"); DLT_REGISTER_CONTEXT(myContext1,"TES1","Test Context 1 for Logging"); DLT_REGISTER_CONTEXT(myContext2,"TES2","Test Context 2 for Logging"); DLT_REGISTER_CONTEXT(myContext3,"TES3","Test Context 3 for Logging"); } ---- Create your logs ---------------- Now you can start creating your logs. Each log command consist of the context, the log level and a variable number of logging parameters. Log Level ~~~~~~~~~ The log level must be one of the following values: [options="header"] |================================================================== | Log level | Description | DLT_LOG_FATAL | fatal system error | DLT_LOG_ERROR | error with impact to correct functionality | DLT_LOG_WARN | warning, correct behaviour could not be ensured | DLT_LOG_INFO | informational (default) | DLT_LOG_DEBUG | debug | DLT_LOG_VERBOSE | highest grade of information |================================================================== DLT_LOG_FATAL, DLT_LOG_ERROR and DLT_LOG_WARN should be used in your application, when something is going wrong. DLT_LOG_INFO should be used to send the most important information. DLT_LOG_DEBUG and DLT_LOG_VERBOSE should be only used for testing information. Each context is set by default to DLT_LOG_INFO log level. All log message are send, which use this loglevel or a lower loglevel. If you also want to see DLT_LOG_DEBUG and DLT_LOG_VERBOSE log messages, you have to raise the log level with the DLT viewer. Logging parameters ~~~~~~~~~~~~~~~~~~ The following parameter types can be used. You can add one or more parameters to a single log message. The size of all logging parameters together should not exceed 2kBytes, including the DLT message header. [options="header"] |=============================================================== | Type | Description | DLT_STRING(TEXT) | String | DLT_RAW(BUF,LENGTH) | Raw buffer | DLT_INT(VAR) | Integer variable, dependent on platform | DLT_INT16(VAR) | Integer 16 Bit variable | DLT_INT32(VAR) | Integer 32 Bit variable | DLT_INT64(VAR) | Integer 64 bit variable | DLT_UINT(VAR) | Unsigned integer variable | DLT_UINT16(VAR) | Unsigned 16 Bit integer variable | DLT_UINT32(VAR) | Unsigned 32 Bit integer variable | DLT_UINT64(VAR) | Unsigned 64 bit integer variable | DLT_BOOL(VAR) | Boolean variable | DLT_FLOAT32(VAR) | Float 32 Bit variable | DLT_FLOAT64(VAR) | Float 64 Bitvariable |=============================================================== Logging command ~~~~~~~~~~~~~~~ Here are some examples for complete log messages. The contexts must be registered before. ---- DLT_LOG(myContext1,DLT_LOG_ERROR,DLT_INT(5),DLT_STRING("This is a error")); DLT_LOG(myContext2,DLT_LOG_INFO,DLT_INT(5),DLT_STRING("But this only information")); DLT_LOG(myContext3,DLT_LOG_DEBUG,DLT_INT(5),DLT_STRING("But this only information")); ---- Unregister contexts and applications ------------------------------------ Before terminating your application you must unregister all registered contexts and unregister at last your application. ---- int main(int argc, const char\* argv\[\]) { DLT_REGISTER_APP("MAPP","Test Application for Logging"); DLT_REGISTER_CONTEXT(myContext1,"TES1","Test Context 1 for Logging"); DLT_REGISTER_CONTEXT(myContext2,"TES2","Test Context 2 for Logging"); DLT_REGISTER_CONTEXT(myContext3,"TES3","Test Context 3 for Logging"); DLT_UNREGISTER_CONTEXT(myContext1); DLT_UNREGISTER_CONTEXT(myContext2); DLT_UNREGISTER_CONTEXT(myContext3); DLT_UNREGISTER_APP(); return 0; } ---- Example ------- Finally here is a complete example for using DLT: .dlt_example.c ---- #include <stdio.h> #include <dlt.h> DLT_DECLARE_CONTEXT(myContext1); DLT_DECLARE_CONTEXT(myContext2); DLT_DECLARE_CONTEXT(myContext3); int main() { /* register application */ DLT_REGISTER_APP("MAPP","Test Application for Logging"); /* register all contexts */ DLT_REGISTER_CONTEXT(myContext1,"TES1","Test Context 1 for Logging"); DLT_REGISTER_CONTEXT(myContext2,"TES2","Test Context 2 for Logging"); DLT_REGISTER_CONTEXT(myContext3,"TES3","Test Context 3 for Logging"); /* Write your logs */ DLT_LOG(myContext1,DLT_LOG_ERROR,DLT_INT(5),DLT_STRING("This is a error")); DLT_LOG(myContext2,DLT_LOG_INFO,DLT_INT(5),DLT_STRING("But this only information")); DLT_LOG(myContext3,DLT_LOG_DEBUG,DLT_INT(5),DLT_STRING("But this only information")); /* Sleep some time to avoid a flaw in dlt-daemon that would eat your messages if you deregister while it still processes your registration */ sleep(3); /* unregister your contexts */ DLT_UNREGISTER_CONTEXT(myContext1); DLT_UNREGISTER_CONTEXT(myContext2); DLT_UNREGISTER_CONTEXT(myContext3); /* unregister your application */ DLT_UNREGISTER_APP(); return 0; } ---- .CMakeLists.txt ---- cmake_minimum_required(VERSION 2.6) find_package(PkgConfig) pkg_check_modules(DLT REQUIRED automotive-dlt) include_directories("${DLT_INCLUDE_DIRS}") project(DLTexample) add_executable(dlt_example dlt_example.c) target_link_libraries(dlt_example ${DLT_LIBRARIES}) ---- .Build steps ---- mkdir build cd build cmake .. make ----

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