--- title: Lab22: RTOS toc: no ... 預期目標 ------- * 在 QEMU 模擬的 STM32 環境中,嘗試執行 `FreeRTOS`_ 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`` / ``free`` 和驗證其功能 - 搭配 `Week #5`_ 進度,學習 heap, stack 的規劃 - defragmentation FreeRTOS --------------- * `The Architecture of Open Source Applications: FreeRTOS`_ - `簡體中文翻譯`_ FreeRTOS: Memory management ------------------------------- - `Memory Management`_ - 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) - 檢查 freertos 目錄的 Makefile,目前使用 ``$(FREERTOS_SRC)/portable/MemMang/heap_1.c``,可更換為 ``heap_2.c`` hack-malloc ------------------- * 簡易 malloc/free 測試程式,以亂數指定若干不同大小的 memory region,持續進行 malloc 和 free 操作 * ``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 -------------------- * 將 `hack-malloc`_ 移植回去 FreeRTOS,並且配合 `Lab 21,在 shell 中建立一個命令: ``mmtest`` - 加分: 將 ``tryit`` 移植回去 ``rtenv`` * 修改 ``hack-malloc/tryit.c`` 的 prng (pseudorandom number generator),用 inline assembly 重寫該函式 * 提出檢驗 FreeRTOS/rtenv 中 ``malloc`` / ``free`` 功能的方法 (需要提案描述) - 加分: defragmentation 的途徑 作業繳交方式 ------------------- * 更新作業提案到共筆網站: `Lab 22 / 作業共筆`_,需要標注自己的 ID,可參考 `Lab 20 / 作業共筆`_ 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`_ * `ARM GCC Inline Assembler Cookbook`_