AtmegaSim

The goal of this project is to join a Java program with an Atmega microcontroller C program, in order to improve debugging capabilities. For example if you have to implement a communicaton protocol stack between a Java program on the one side and a microcontroller on the other side.

This project is created and tested with Netbeans 8.2 under Linux. The usage of other IDEs, versions or operating systems may cause problems which have not been checked up to now.

Build and run

Follow the following procedure to build and run this project...

1. git clone <repository>
2. cd <repository>/AtmegaSimJava
3. ant jar
   Now the Java project is build and the tool javah creates the file AtmegaSimSharedLib/src/jni_App.h which is needed by the shared library project. You can also use Netbeans, open the project and build the project.
4. cd ../AtmegaSimSharedLib
5. make
   Now the native shared library is build and saved in...
   AtmegaSimSharedLib/dist/Debug_linux_Gnu-Linux/libAtmegaSimSharedLib.so
6. cd ..
7. Start the application with...
   java -Djava.library.path=$(pwd)/AtmegaSimJava -jar AtmegaSimJava/dist/AtmegaSimJava.jar

The shell will replace $(pwd) (print working directory) by the current directory path. The Define java.library.path must be set, otherwise the shared library will not be found by the Java VM. An alternative is to locate the library file (or a symbolic link) in the directory /usr/java/packages/lib/amd64/

Java Project

See subproject AtmegaSimJava

The Java Native Interface (JNI) is used to bind the native shared library libAtmegaSimSharedLib.so with the Java VM. The library file itself is build in the subproject AtmegaSimSharedLib and only a symbolic link is used to make the library available for Javas System.load(..). An alternative systemwide location is /usr/java/packages/lib/amd64/.

So you need to build AtmegaSimSharedLib first, before you can start the Java application.

Native Shared Library C Project

See subproject AtmegaSimSharedLib.

In the directory src are the the source files for building the native shared library. The files global.h, app.h and app.c are only symbolic links to the original microcontroller project ArduinoNano.

The project is compiled and linked with the GNU -g option, to support debugging information inside the shared library.

Please check the correct location of:

• /usr/lib/jvm/java-8-oracle/include/linux
• /usr/lib/jvm/java-8-oracle/include/jni.h

If you cannot find these two header files there, you have to set the proper directory. Open Netbeans project properties, category Build/C++ Compile and set include directories to the location of your Java Development Kit. You will also find these settings in configurations.xml.

The header files are needed by jni_App.c.

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Debugging with gdb

See also:

• https://www.gnu.org/software/gdb/gdb.html
• https://www.cs.cmu.edu/~gilpin/tutorial/
• http://www.dirac.org/linux/gdb/

At first start the Java GUI application and afterwards the GNU-Debugger gdb. Using two different shells would make sense.

Start in a first shell (or use Netbeans IDE to start the Java application):

1. cd <project-dir>/AtmegaSimJava
2. java -Djava.library.path=$(pwd) -jar dist/AtmegaSimJava.jar &

... and in a second shell:

1. sudo -i
2. gdb

Now you have to attach the GNU-Debugger to the running Java program. For the command attach you need the process identifier (the PID) of the running Java application. This PID is shown in the title bar of the Java GUI application.

After attachment you can pause the program with pressing CTRL+C. Now you can use the following commands to debug your 'simulated' microcontroller program.

attach <pid>
detach

info source
info functions
info breakpoints
info proc map

list <function>
break <line>

frame
continue
next
info args
info locals
info

With break you can set breakpoints. With next you step over the call of functions. With step you can step into functions. With continue you can continue the program up to next breakpoint. You can also use abbreviations (b, n, s, c).

For example:

attach 7123
list Java_jni_App_main
break 126
c

list
n
n
s
n

detach
quit