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embedded/Lab2

Changes from bcfb1fb78027430ed75ef327be9a20c211c98897 to 0c314f57d12413eca46ce545714677871409b4c9

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title: Lab2: GNU Toolchain and Git
toc: no
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預期目標
-------
- 學習 GNU Toolchain 的使用
- 藉由 `coroutine<http://en.wikipedia.org/wiki/Coroutine>`_ 的實做,作為日後 RTOS 學習的準備
- 以 Git 管理與追蹤開發過程

預先準備
-------
- 在本 wiki 註冊帳號
- 在 `GitCafe<https://gitcafe.com>`_ 註冊帳號
  - 確認在 Account Settings 加入 SSH Key
  - 可參考「`產生 SSH key 給 Bitbucket/Github 使用<http://nyllep.wordpress.com/2012/01/21/sshkey-for-bitbucket/>`_」一文

- 注意:若使用公用電腦,可切換到 root 後,建立新的使用者帳號
  - sudo su
  - adduser 指定帳號名稱
  - sudoedit /etc/group
  - 在 /etc/group 確保該帳號已加入 **admin** 群組,如:
    - admin:x:115:ncku,帳戶名稱

- 將註冊的帳號名稱,通知課程主持人或助教,於 `Organization **embedded2012**<https://gitcafe.com/embedded2012>`_ 加入用於紀錄開發動態的 Git repository
  - 範例: `P-jserv<https://gitcafe.com/embedded2012/P-jserv>`_,最好與 wiki 帳號名稱一致,以利於識別
  - 點選 **SSH (Read+Write)** 可得到 git repository 的位址,如上例為

    ``git@gitcafe.com:embedded2012/P-jserv.git``

- 注意:到 2012 年年底前,repository 的存取權限應該設定為 private
- 參閱 `Git 簡易操作</git>`_

QEMU_STM32 + QEMU 操作
----------------------
- 開啟一個終端機,作以下輸入

.. code-block:: prettyprint

    cd Lab-2/demo
    make qemudbg

- 開啟另一個終端機,準備透過 gdb 來追蹤程式。下列 (gdb) 開頭的指令表示在 GDB 內部操作

.. code-block:: prettyprint

    cd Lab-2/demo
    arm-none-eabi-gdb
    (gdb) file main.elf 
    Reading symbols from Lab-2/demo/main.elf...done.
    (gdb) b main
    Breakpoint 1 at 0x2206: file main.c, line 8.
    (gdb) target remote :3333
    Remote debugging using :3333
    Reset_Handler ()
        at libraries/CMSIS/CM3/DeviceSupport/ST/STM32F10x/startup/gcc_ride7/startup_stm32f10x_md.s:67
    67	  movs	r1, #0
    (gdb) c
    Continuing.
    
    Breakpoint 1, main () at main.c:8
    8		RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
    (gdb) list
    3	
    4	int main(void)
    5	{
    6		int last_button_state, new_button_state;
    7	
    8		RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
    9		RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC | RCC_APB2Periph_GPIOA, ENABLE);
    10						
    11		/* Configure PC.12 as output push-pull (LED) */
    12		GPIO_WriteBit(GPIOC,GPIO_Pin_12,Bit_SET);
    (gdb) b 23
    Breakpoint 2 at 0x2264: file main.c, line 23.
    (gdb) c
    Continuing.
    
    Breakpoint 2, main () at main.c:23
    23			new_button_state = GPIOA->IDR & 0x00000001;
    (gdb) n
    (gdb) p new_button_state
    $1 = 0
    (gdb) info breakpoints 
    Num     Type           Disp Enb Address    What
    1       breakpoint     keep y   0x00002206 in main at main.c:8
    breakpoint already hit 1 time
    2       breakpoint     keep y   0x00002264 in main at main.c:23
    breakpoint already hit 1 time
    (gdb) del 2
    (gdb) watch GPIOC->ODR
    Hardware watchpoint 3: GPIOC->ODR
    (gdb) c
    Continuing.

- 在 QEMU monitor 內作以下輸入,試圖模擬按鈕的動作

.. code-block:: prettyprint

    sendkey b

- 隨後可發現 GDB 畫面出現變化:
 
.. code-block:: prettyprint

    Hardware watchpoint 3: GPIOC->ODR

    Old value = 4096
    New value = 0
    main () at main.c:29
    29			last_button_state = new_button_state;


Coroutines
----------
- "Coroutines are computer program components that generalize subroutines to allow multiple entry points for suspending and resuming execution at certain locations. Coroutines are well-suited for implementing more familiar program components such as cooperative tasks, iterators, infinite lists and pipes."
  * http://en.wikipedia.org/wiki/Coroutine

- 使用 coroutine 實做 user-level thread
  * http://blog.linux.org.tw/~jserv/archives/001848.html

- Coroutine in FPPA
  * http://godspeedlee.myweb.hinet.net/coroutine.html

- 淺談coroutine與gevent
  * http://blog.ez2learn.com/2010/07/17/talk-about-coroutine-and-gevent/

參考資訊
-------
- debugger 和 software emulator
  * opencsl.openfoundry.org/Lab05_debugger.rst.html
  * http://www.cis.nctu.edu.tw/~is92004/article/gdb.htm
- GDB 筆記
  * http://loda.hala01.com/2012/04/gdb%E7%AD%86%E8%A8%98/
- 以 GDB 重新學習 C 語言程式設計
  * http://www.slideshare.net/jserv/clang-usinggdb

小提示
-----
- Ubuntu Linux 預設的文字編輯器為 nano,對許多習慣於 vi/vim 的使用者來說,較為不便,可透過以下指令選擇:

    ``sudo update-alternatives --config editor``