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git-svn-id: https://nuttx.svn.sourceforge.net/svnroot/nuttx/trunk@1417 7fd9a85b-ad96-42d3-883c-3090e2eb8679
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<td valign="top" width="22"><img height="20" width="20" src="favicon.ico"></td>
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<td>
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<a href="#overview">Overview</a>.<br>
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What is NuttX?
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What is NuttX? Look at all those files and features... How can it be a tiny OS?
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</td>
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</tr>
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<tr>
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@ -476,7 +476,7 @@
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<td><br></td>
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<td>
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<p>
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<li>Bult-in USB trace functionality for USB debug.</li>
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<li>Built-in USB trace functionality for USB debug.</li>
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</p>
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</tr>
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@ -497,7 +497,7 @@
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<td><br></td>
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<td>
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<p>
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<li>Graphics library and tiny windowing system under developement.</li>
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<li>Graphics library and tiny windowing system under development.</li>
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</p>
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</tr>
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</table></center>
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@ -505,7 +505,7 @@
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<p>
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<b>NuttX Add-Ons</b>.
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The following packages are available to extend the basic NuttX feature set:
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<p>
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</p>
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<center><table width="90%">
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<tr>
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@ -539,9 +539,126 @@
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<a href="http://sourceforge.net/project/showfiles.php?group_id=189573">SourceForge</a>
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website.</li>
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</p>
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</td>
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</tr>
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</table></center>
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<p>
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<b>Look at all those files and features... How can it be a tiny OS?</b>.
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The NuttX feature list (above) is fairly long and if you look at the NuttX
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source tree, you will see that there are hundreds of source files comprising
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NuttX. How can NuttX be a tiny OS will all of that?
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</p>
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<center><table width="90%">
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<tr>
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<td valign="top" width="22"><img height="20" width="20" src="favicon.ico"></td>
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<td bgcolor="#5eaee1">
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<b>Lots of Features -- More can be smaller!</b>
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</td>
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</tr>
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<tr>
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<td><br></td>
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<td>
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<p>
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The philosophy behind that NuttX is that lots of features are great... <i>BUT</i>
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also that if you don't use those features, then you should not have to pay a penalty
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for the unused features.
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And, with NuttX, you don't! If you don't use a feature, it will not
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be included in the final executable binary.
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You only have to pay the penalty of increased footprint for the features
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that you actually use.
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</p>
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<p>
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Using a variety of technologies, NuttX can scale from the very tiny to
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the moderate-size system. I have executed NuttX with some simple applications
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in as little as 32Kb <i>total</i> memory (code and data).
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On the other hand, I often run richly featured NuttX builds that require
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memory up to 100Kb.
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</p>
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</td>
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</tr>
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<tr>
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<td valign="top" width="22"><img height="20" width="20" src="favicon.ico"></td>
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<td bgcolor="#5eaee1">
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<b>Many, many files -- More really is smaller!</b>
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</td>
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</tr>
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<tr>
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<td><br></td>
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<td>
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<p>
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One may be intimidated by the size NuttX source tree. There are hundreds of source files!
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How can that be a tiny OS?
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Actually, the large number of files is one of the tricks to keep NuttX small and
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as scalable as possible.
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Most files contain only a single function.
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Sometimes just one tiny function with only a few lines of code.
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Why?
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</p>
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<ul>
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<li>
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<b>Static Libraries</b>.
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Because in the NuttX build processed, objects are compiled and saved into
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<i>static libraries</i> (<i>archives</i>).
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Then, when the file executable is linked, only the object files that are needed
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are extracted from the archive and added to the final executable.
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By having many, many tiny source files, you can assure that no code that you do
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not execute is ever included in the link.
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And by having many, tiny source files you have better granularity --
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if you don't use that tiny function of even just a few lines of code, it will
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not be included in the binary.
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</li>
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</ul>
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</td>
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</tr>
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<tr>
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<td valign="top" width="22"><img height="20" width="20" src="favicon.ico"></td>
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<td bgcolor="#5eaee1">
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<b>Other Tricks</b>
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</td>
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</tr>
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<tr>
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<td><br></td>
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<td>
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<p>
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As mentioned above, the use of many, tiny source files and linking from static
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libraries keeps the size of NuttX down.
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Other tricks used in NuttX include:
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</p>
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<ul>
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<li>
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<b>Configuration Files</b>.
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Before you build NuttX, you must provide a configuration file that specifies
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what features you plan to use and which features you do not.
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This configuration file contains a long list of settings that control
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what is built into NuttX and what is not.
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There are hundreds of such settings
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(see the <a href="NuttxPortingGuide.html#apndxconfigs">NuttX Porting Guide</a>
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for a partial list that excludes platform specific settings).
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These many, many configuration options allow NuttX to be highly tuned to
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meet size requirements.
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The downside to all of these configuration options is that it greatly
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complicates the maintenance of NuttX -- but that is my problem, not yours.
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</li>
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<li>
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<b>Weak Symbols</b>
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The GNU toolchain supports <i>weak</i> symbols and these also help to keep
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the size of NuttX down.
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Weak symbols prevent object files from being drawn into the link even if they
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are accessed from source code.
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Careful use of weak symbols is another trick for keep unused code out of the
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final binary.
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</li>
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</ul>
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</td>
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</tr>
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</table></center>
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<table width ="100%">
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<tr bgcolor="#e4e4e4">
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<td>
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@ -569,11 +686,11 @@
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This allows <code>poll()</code>/<code>select()</code> to wake-up on new connections to a listener socket.
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</li>
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<li>Added definition of a framebuffer driver and implement framebuffer drivers for the
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simulated platform and the TI DM320 (untested as of the inital check-in).
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simulated platform and the TI DM320 (untested as of the initial check-in).
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</li>
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<li>Partially developed a graphics framework based on the framebuffer drivers, however,
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this will not be ready for use for a few more release.
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Currently this includes only a few color conversion routines and some rasteizing functions.
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Currently this includes only a few color conversion routines and some rasterizing functions.
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A tiny windowing system is under development but not ready for check-in yet.
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<li>Added support for fixed precision math.
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</li>
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<p>
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<b>STATUS:</b>
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This port boots and passes the OS test (examples/ostest).
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The port is complete and verifed. As of NuttX 0.3.17, the port includes:
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The port is complete and verified. As of NuttX 0.3.17, the port includes:
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timer interrupts, serial console, USB driver, and SPI-based MMC/SD card
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support. A verifed NuttShell (NSH) configuration is also available.
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support. A verified NuttShell (NSH) configuration is also available.
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</p>
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</td>
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</tr>
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</p>
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<p>
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<b>STATUS:</b>
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The basic port (timer interrupts, serial ports, network, framebuffe, etc.) is complete.
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The basic port (timer interrupts, serial ports, network, framebuffer, etc.) is complete.
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All implemented features have been verified with the exception of the USB device-side
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driver; that implementation is complete but completely untested.
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</p>
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</p>
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<p>
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<b>STATUS:</b>
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This port is availble as of release 0.3.18 of NuttX. The port is basically complete
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This port is available as of release 0.3.18 of NuttX. The port is basically complete
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and many examples run correctly. However, there are remaining instabilities that
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make the port un-usable. The nature of these is not understood; the behavior is
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that certain SH-1 instructions stop working as advertised. This could be a silicon
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Binary file not shown.
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After Width: | Height: | Size: 5.8 KiB |
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@ -18,6 +18,7 @@ at the present, but here is the longer term roadmap:
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NXTOOLKIT - A set of C graphics tools that provide higher-level window drawing
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operations. The toolkit can be used for window-oriented graphics
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without NXWIDGETS and is built on top of NX.
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NXFONTS - A set of C graphics tools for present (bitmap) font images.
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NX - The tiny NuttX windowing system. This includes both a small-footprint,
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single user implementaton (NXSU as described below) and a somewhat
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larger multi-user implentation (NXMU as described below). Both
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@ -33,6 +34,7 @@ Related Header Files
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include/nuttx/nxglib.h -- Describes the NXGLIB C interfaces
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include/nuttx/nx.h -- Describes the NX C interfaces
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include/nutt/nxtk.h -- Describe the NXTOOLKIT C interfaces
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include/nutt/nxfont.h -- Describe sthe NXFONT C interfaces
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include/nuttx/nxwidgets.h -- Will describe the NXWIDGETS classes (no longer planned)
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Directories:
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queue to serialize window operations from many threads. The multi-user front-end
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is selected when CONFIG_NX_MULTIUSER is defined in the NuttX configuration file.
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graphics/nxtoolkit
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graphics/nxfonts
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This is where the NXFONTS implementation resides. This is a relatively low-
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level set of charset set/glyph management APIs. See include/nuttx/nxfonts.h
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graphics/nxtk
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This is where the NXTOOLKIT implementation resides. This toolkit is built on
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top of NX and works with either the single-user or multi-user NX version. See
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include/nuttx/nxtk.h
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