Add description of LED support
git-svn-id: https://nuttx.svn.sourceforge.net/svnroot/nuttx/trunk@1767 7fd9a85b-ad96-42d3-883c-3090e2eb8679
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<h1><big><font color="#3c34ec">
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<i>NuttX RTOS Porting Guide</i>
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</font></big></h1>
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<p>Last Updated: April 19, 2009</p>
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<p>Last Updated: May 9, 2009</p>
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</td>
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</tr>
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</table>
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@ -92,10 +92,16 @@
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<a href="#exports">4.2 APIs Exported by NuttX to Architecture-Specific Logic</a>
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<ul>
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<a href="#osstart">4.2.1 <code>os_start()</code></a><br>
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<a href="#listmgmt">4.2.2 OS List Management APIs</a><br><br>
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<a href="#listmgmt">4.2.2 OS List Management APIs</a><br>
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<a href="#schedprocesstimer">4.2.3 <code>sched_process_timer()</code></a><br>
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<a href="#irqdispatch">4.2.4 <code>irq_dispatch()</code></a>
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</ul>
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<a href="#ledsupport">4.3 LED Support</a>
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<ul>
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<a href="#ledheaders">4.3.1 Header Files</a><br>
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<a href="#leddefinitions">4.3.2 LED Definitions</a><br>
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<a href="#ledapis">4.3.3 Common LED interfaces</a>
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</ul>
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</ul>
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<a href="#NxFileSystem">5.0 NuttX File System</a><br>
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<a href="#apndxconfigs">Appendix A: NuttX Configuration Settings</a><br>
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@ -1423,6 +1429,142 @@ The system can be re-made subsequently by just typing <code>make</code>.
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the appropriate, registered handling logic.
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</p>
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<h2><a name="ledsupport">4.3 LED Support</a></h2>
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<p>
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A board architecture may or may not have LEDs.
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If the board does have LEDs, then most architectures provide similar LED support that is enabled when <code>CONFIG_ARCH_LEDS</code>
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is selected in the NuttX configuration file.
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This LED support is part of architecture-specific logic and is not managed by the core NuttX logic.
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However, the support provided by each architecture is sufficiently similar that it can be documented here.
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</p>
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<h3><a name="ledheaders">4.3.1 Header Files</a></h3>
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<p>
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LED-related definitions are provided in two header files:
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<ul>
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<li>
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LED definitions are provided for each board in the <code>board.h</code> that resides
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in the <code><i><board-name></i>/include/board.h</code> file (which is also
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linked to <code>include/arch/board/board.h</code> when the RTOS is configured).
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Those definitions are discussed <a href="#leddefinitions">below</a>.
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</li>
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<li>
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The board-specific logic provides unique instances of the LED interfaces.
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This is because the implementation of LED support may be very different
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on different boards.
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Prototypes for these board-specific implementations are, however, provided
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in architecture-common header files.
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That header file is usually at <code><i><arch-name></i>/src/common/up_internal.h</code>,
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but could be at other locations in particular architectures.
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These prototypes are discussed <a href="#ledapis">below</a>.
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</li>
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</ul>
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</p>
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<h3><a name="leddefinitions">4.3.2 LED Definitions</a></h3>
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<p>
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The implementation of LED support is very specific to a board architecture.
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Some boards have several LEDS, others have only one or two.
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Some have none.
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Others LED matrices and show alphnumeric data, etc.
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The NuttX logic does not refer to specific LEDS, rather, it refers to an event to be shown on the LEDS
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in whatever manner is appropriate for the board;
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the way that this event is presented depends upon the hardware available on the board.
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</p>
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<p>
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The model used by NuttX is that the board can show 8 events defined as follows in <code><i><board-name></i>/include/board.h</code>:
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</p>
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<ul><pre>
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#define LED_STARTED ??
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#define LED_HEAPALLOCATE ??
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#define LED_IRQSENABLED ??
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#define LED_STACKCREATED ??
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#define LED_INIRQ ??
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#define LED_SIGNAL ??
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#define LED_ASSERTION ??
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#define LED_PANIC ??
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</pre></ul>
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<p>
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The specific value assigned to each pre-processor variable can be whatever makes the implementation easiest for the board logic.
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The <i>meaning</i> associated with each definition is as follows:
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</p>
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<ul>
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<li>
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<code>LED_STARTED</code> is the value that describes the setting of the LEDs when the LED logic is first initialized.
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This LED value is set but never cleared.
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</li>
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<li>
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<code>LED_HEAPALLOCATE</code> indicates that the NuttX heap has been configured.
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This is an important place in the boot sequence because if the memory is configured wrong, it will probably crash leaving this LED setting.
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This LED value is set but never cleared.
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</li>
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<li>
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<code>LED_IRQSENABLED</code> indicates that interrupts have been enabled.
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Again, during bring-up (or if there are hardware problems), it is very likely that the system may crash just when interrupts are enabled, leaving this setting on the LEDs.
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This LED value is set but never cleared.
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</li>
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<li>
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<code>LED_STACKCREATED</code> is set each time a new stack is created.
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If set, it means that the system attempted to start at least one new thread.
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This LED value is set but never cleared.
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</li>
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<li>
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<code>LED_INIRQ</code> is set and cleared on entry and exit from each interrupt.
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If interrupts are working okay, this LED will have a dull glow.
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</li>
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<li>
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<code>LED_SIGNAL</code> is set and cleared on entry and exit from a signal handler.
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Signal handlers are tricky so this is especially useful during bring-up or a new architecture.
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</li>
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<li>
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<code>LED_ASSERTION</code> is set if an assertion occurs.
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</li>
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<li>
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<code>LED_PANIC</code> will blink at around 1Hz if the system panics and hangs.
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</li>
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</ul>
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<h3><a name="ledapis">4.3.3 Common LED interfaces</a></h3>
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<p>
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The <code><i><arch-name></i>/src/common/up_internal.h</code> probably has definitions
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like:
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</p>
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<ul><pre>
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/* Defined in board/up_leds.c */
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#ifdef CONFIG_ARCH_LEDS
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extern void up_ledinit(void);
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extern void up_ledon(int led);
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extern void up_ledoff(int led);
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#else
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# define up_ledinit()
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# define up_ledon(led)
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# define up_ledoff(led)
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#endif
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</pre></ul>
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<p>
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Where:
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<p>
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<ul>
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<li>
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<code>void up_ledinit(void)</code> is called early in power-up initialization to initialize the LED hardware.
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</li>
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<li>
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<code>up_ledon(int led)</code> is called to instantiate the LED presentation of the event.
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The <code>led</code> argument is one of the definitions provided in <code><i><board-name></i>/include/board.h</code>.
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</li>
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<li>
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<code>up_ledoff(int led</code>is called to terminate the LED presentation of the event.
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The <code>led</code> argument is one of the definitions provided in <code><i><board-name></i>/include/board.h</code>.
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Note that only <code>LED_INIRQ</code>, <code>LED_SIGNAL</code>, <code>LED_ASSERTION</code>, and <code>LED_PANIC</code>
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indications are terminated.
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</li>
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</ul>
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<table width ="100%">
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<tr bgcolor="#e4e4e4">
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<td>
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