Lab22: RTOS

預期目標

• 在 QEMU 模擬的 STM32 環境中，嘗試執行 FreeRTOS<http://www.freertos.org/>_ 並且學習相關的操作
  • 熟悉 FreeRTOS 的內部運作機制
• 學習 memory mangement
  • 實作 malloc 和驗證其功能
  • 搭配 Week #5</embedded/2013-w5>_ 進度，學習 heap, stack 的規劃
  • defragmentation

FreeRTOS

• The Architecture of Open Source Applications: FreeRTOS<http://www.aosabook.org/en/freertos.html>_
  • 簡體中文翻譯<http://www.ituring.com.cn/article/4063>_

FreeRTOS: Memory management

• Memory Management<http://www.freertos.org/a00111.html>_
• The RTOS kernel allocates RAM each time a task, queue, mutex, software timer or semaphore is created. The standard C library malloc() and free() functions can sometimes be used for this purpose, but …
  • they are not always available on embedded systems,
  • they take up valuable code space,
  • they are not thread safe, and
  • they are not deterministic (the amount of time taken to execute the function will differ from call to call)

hack-malloc

• git clone git@github.com:embedded2013/hack-malloc.git # 或 `git clone git://github.com:embedded2013/hack-malloc.git
• cd hack-malloc && make
• ./tryit # Ctrl-C 停止輸出
• 參考畫面輸出：

.. code-block:: prettyprint

tryit.c 68: try to allocate 1648 bytes
tryit.c 70: malloc returned 0x61595c
allocate a block, size 1648
tryit.c 68: try to allocate 1582 bytes
tryit.c 70: malloc returned 0x615fe8
allocate a block, size 1582
tryit.c 68: try to allocate 1037 bytes
tryit.c 70: malloc returned (nil)
free a block, size 1648
tryit.c 68: try to allocate 1815 bytes
tryit.c 70: malloc returned (nil)
free a block, size 1582

參考作業提案

作業繳交方式

• 更新作業提案到共筆網站: Lab 22 / 作業共筆<https://embedded2013.hackpad.com/Lab21-RTOS-shzzlckJ50f>，需要標注自己的 ID，可參考 Lab 20 / 作業共筆<https://embedded2013.hackpad.com/Lab20-GNU-Toolchain-zI6gzN3uv1c> 格式
• 在 Oct 25, 2013 前，將符合作業提案的程式碼，提交到自行 fork 的 repository
  • https://github.com/embedded2013/freertos

參考資訊

• FreeRTOS Implementation<http://www.freertos.org/implementation/main.html>_