JAVA-BASED REAL-TIME PROGRAMMING

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4. Exercises and Labs 4.3 Lab 1 – Alarmclock In this lab you are going to implement your alarm clock system designed in the previous exercise. The target system is an AVR board equipped with LCD display and six buttons. You will develop the software in three steps: • Implementing the alarm clock in Java using semaphores, executing it on a Java emulator • Compile the Java code to C and execute on a PC simulator • Cross-compile to the AVR board and execute on the actual hardware Java is the choice language in the course, but really small embedded systems may not have the resources for executing Java directly. This is the case here. However, almost all small system are capable of executing C code, so therefore we translate the code to C through a tool and compile it, first towards PC and linux for testing, and then towards the real hardware. Note: in the 2012 edition of the course in Lund, the AVR board will not be available (the hardware is broken). Therefore only the two first items should be done. Note: in the Helsingborg RT course, only the first item should be done, since the Java2C-translator will not be available. Preparation It is generally a good idea to start programming before the lab occasion. The handout code is available on the course homepage as a zipped Eclipse workspace. Remember that the emulator should be run as an applet. 108 2012-08-29 16:05
4.3. Lab 1 – Alarmclock You will implement your real-time system in the todo folder by modifying the present AlarmClock class and adding further classes as your design requires. You should try to translate your code to C from time to time. Read below for a bit of advice on making your Java code compatible with the translation tool. C on linux-PC The Java2C translator requires Java 1.4 and runs only on the school linux computers. For those that like to work remote it is possible to transfer the code using sftp to your home folder at login.student.lth.se and login using ssh (-Y to bring X to the client). A good X client is needed (windows users can install cygwin, mac should already have an X client, as well as linux). Translation script Translating from Java to C and compiling can be a cumbersome process. Therefore a build script has been prepared for you to hide most of the grizzly details. To build for the PC you need to stand (using a terminal) where the todo and done source folders are located (typically workspace/project/src) and type: /usr/local/cs/rtp/lab/build_clock.sh Answer Y to build for the host (linux) system. If all goes well, after some time you will get a statement asking you to press return to run the resulting compiled program. If something goes wrong you will be informed that the build failed and you can look at the build.err files located in the build_lnx and build_lnx/build folders to try to determine what went wrong. Some advice The Java to C translator cannot cope with the entire Java language and framework. Also, from an embedded systems point of view it is best to import as little as possible to minimize memory requirements. Avoid * when importing, just import the classes that are needed. For the lab a very small subset is necessary: • Thread • System.currentTimeMillis() • LJRT semaphores – se.lth.cs.realtime.semaphore.Semaphore – se.lth.cs.realtime.semaphore.MutexSem – se.lth.cs.realtime.semaphore.CountingSem 109
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JAVA-BASED REAL-TIME PROGRAMMING Kl
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• Each piece of software must be
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Contents I Concurrent programming i
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Part I Concurrent programming in Ja
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1. Introduction pany depends on the
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1. Introduction control may be dela
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Chapter 2 Fundamentals Goal: Review
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2.2. Our physical world is parallel
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2.4. Concurrency a trend that the p
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2.4. Concurrency Behind the term co
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2.4. Concurrency in functions like
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2.5. Interrupts, pre-emption, and r
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2.5. Interrupts, pre-emption, and r
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2.6. Models of concurrent execution
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Object properties Implicit mutual e
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2.6. Models of concurrent execution
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2.7 Multi-process programming 2.7.
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2.9. Software issues In this chapte
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Chapter 3 Multi-Threaded Programmin
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3.1.1 Thread creation At start of a
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to foresee the value actually retur
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3.1. Threads first obtains the curr
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the run-time system (that is, the s
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3.1.6 Thread interruption and termi
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• If the operation of an industri
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3.2. Resources and mutual exclusion
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JAVA-BASED REAL-TIME PROGRAMMING

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