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<h1><big><font color="#3c34ec"><i>NuttX RTOS</i></font></big></h1>
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<h1>Table of Contents</h1>
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<a href="#overview">Overview</a>.<br>
What is NuttX? Look at all those files and features... How can it be a tiny OS?
<td valign="top" width="22"><img height="20" width="20" src="favicon.ico"></td>
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<a href="#downloads">Downloads</a>.<br>
Where can I get NuttX? What is the current development status?
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<td valign="top" width="22"><img height="20" width="20" src="favicon.ico"></td>
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<a href="#platforms">Supported Platforms</a>.<br>
What target platforms has NuttX been ported to?
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<td valign="top" width="22"><img height="20" width="20" src="favicon.ico"></td>
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<a href="#environments">Development Environments</a>.<br>
What kinds of host cross-development platforms can be used with NuttX?
</td>
<td valign="top" width="22"><img height="20" width="20" src="favicon.ico"></td>
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<a href="#footprint">Memory Footprint</a>.<br>
Just how big is it? Do I have enough memory to use NuttX?
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<td valign="top" width="22"><img height="20" width="20" src="favicon.ico"></td>
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<a href="#licensing">Licensing</a>.<br>
Are there any licensing restrictions for the use of NuttX? (Almost none)
Will there be problems if I link my proprietary code with NuttX? (No)
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<td valign="top" width="22"><img height="20" width="20" src="favicon.ico"></td>
<td>
<a href="#history">Release History</a><br>
What has changed in the last release of NuttX?
What unreleased changes are pending in CVS?
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<td valign="top" width="22"><img height="20" width="20" src="favicon.ico"></td>
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<a href="#TODO">Bugs, Issues, <i>Things-To-Do</i></a>.<br>
Software is never finished nor ever tested well enough.
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<a href="#documentation">Other Documentation</a>.<br>
What other NuttX documentation is available?
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<td valign="top" width="22"><img height="20" width="20" src="favicon.ico"></td>
<td>
<a href="#trademarks">Trademarks</a>.<br>
Some of the words used in this document belong to other people.
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<a name="overview"><h1>Overview</h1></a>
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Nuttx is a real timed embedded operating system (RTOS).
Its goals are:
<p>
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<b>Small Footprint</b>
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Usable in all but the tightest micro-controller environments,
The focus is on the tiny-to-small, deeply embedded environment.
</p>
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<b>Rich Feature OS Set</b>
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The goal is to provide implementations of most standard POSIX OS interfaces
to support a rich, multi-threaded development environment for deeply embedded
NON-GOALS: (1) It is not a goal to provide the rich level of OS
features like those provided with Linux.
Small footprint is more important than features.
Standard compliance is more important than small footprint.
(2) There is no MMU-based support for processes.
At present, NuttX assumes a flat address space.
</p>
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<b>Highly Scalable</b>
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Fully scalable from tiny (8-bit) to moderate embedded (32-bit).
Scalability with rich feature set is accomplished with:
Many tiny source files, link from static libraries, highly configurable, use of
weak symbols when available.
</p>
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<b>Standards Compliance</b>
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<p>
NuttX strives to achieve a high degree of standards compliance.
The primary governing standards are POSIX and ANSI standards.
Additional standard APIs from Unix and other common RTOS's are
adopted for functionality not available under these standards
or for functionality that is not appropriate for the deeply-embedded
RTOS (such as <code>fork()</code>).
</p>
<p>
Because of this standards conformance, software developed under other
standard OSs (such as Linux) should port easily to NuttX.
</p>
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<b>Real-Time</b>
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Fully pre-emptible, fixed priority and round-robin scheduling.
</p>
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<b>Totally Open</b>
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<b>Feature Set</b>.
Key features of NuttX include:
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<b>Standards Compliant Core Task Management</b>
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<li>Highly configurable.</li>
</p>
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<li>Easily extensible to new processor architectures, SoC architecture, or board architectures.
A <a href="NuttxPortingGuide.html">Porting Guide</a> is in development.</li>
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<li>POSIX/ANSI-like task controls, named message queues, counting semaphores, clocks/timers, signals, pthreads, environment variables, filesystem.</li>
</p>
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<li>Well documented in the NuttX <a href="NuttxUserGuide.html">User Guide</a>.</li>
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<b>File system</b>
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<li>Network, USB (device), serial, CAN, driver architecture.</li>
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<li>RAMDISK, pipes, FIFO, <code>/dev/null</code>, <code>/dev/zero</code> drivers.</li>
</p>
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<li>Mount-able volumes. Bind mountpoint, filesystem, and block device driver.</li>
</p>
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<li>Generic driver for SPI-based MMC/SD cards.</li>
</p>
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<li>ROMFS filesystem support.</li>
</p>
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<b>C Library</b>
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<b>Networking</b>
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<b>USB Device Support</b>
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<li><i>Gadget</i>-like architecture for USB device controller drivers and device-dependent USB class drivers.</li>
</p>
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<li>USB device controller drivers available for the NXP LPC214x and TI DM320.</li>
</p>
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<p>
<li>Device-dependent USB class drivers available for USB serial and for USB mass storage.</li>
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<b>Graphics Support</b>
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<p>
<li>Framebuffer drivers.</li>
</p>
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<p>
<li>
NX: A graphics library, tiny windowing system and tiny font support.
Documented in the <a href="NXGraphicsSubsystem.html">NX Graphics Subsystem</a>
manual.
</li>
<p>
<b>NuttX Add-Ons</b>.
The following packages are available to extend the basic NuttX feature set:
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<b>NuttShell (NSH)</b>
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<p>
<li>A small, scalable, bash-like shell for NuttX with rich feature set and small footprint.
See the <a href="NuttShell.html">NuttShell User Guide</a>.</li>
</p>
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<b>Pascal Compiler with NuttX runtime P-Code interpreter add-on</b>
</td>
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<td>
<p>
<li>The Pascal add-on is available for download from the
<a href="http://sourceforge.net/project/showfiles.php?group_id=189573">SourceForge</a>
website.</li>
</p>
</td>
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</table></center>
<p>
<b>Look at all those files and features... How can it be a tiny OS?</b>.
The NuttX feature list (above) is fairly long and if you look at the NuttX
source tree, you will see that there are hundreds of source files comprising
NuttX. How can NuttX be a tiny OS with all of that?
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<b>Lots of Features -- More can be smaller!</b>
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<p>
The philosophy behind that NuttX is that lots of features are great... <i>BUT</i>
also that if you don't use those features, then you should not have to pay a penalty
for the unused features.
And, with NuttX, you don't! If you don't use a feature, it will not
be included in the final executable binary.
You only have to pay the penalty of increased footprint for the features
that you actually use.
</p>
<p>
Using a variety of technologies, NuttX can scale from the very tiny to
the moderate-size system. I have executed NuttX with some simple applications
in as little as 32Kb <i>total</i> memory (code and data).
On the other hand, typical, richly featured NuttX builds require more like 64Kb
(and if all of the features are used, this can push 100Kb).
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<b>Many, many files -- More really is smaller!</b>
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<p>
One may be intimidated by the size NuttX source tree. There are hundreds of source files!
How can that be a tiny OS?
Actually, the large number of files is one of the tricks to keep NuttX small and
as scalable as possible.
Most files contain only a single function.
Sometimes just one tiny function with only a few lines of code.
Why?
</p>
<ul>
<li>
<b>Static Libraries</b>.
Because in the NuttX build processed, objects are compiled and saved into
<i>static libraries</i> (<i>archives</i>).
Then, when the file executable is linked, only the object files that are needed
are extracted from the archive and added to the final executable.
By having many, many tiny source files, you can assure that no code that you do
not execute is ever included in the link.
And by having many, tiny source files you have better granularity --
if you don't use that tiny function of even just a few lines of code, it will
not be included in the binary.
</li>
</ul>
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<b>Other Tricks</b>
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<p>
As mentioned above, the use of many, tiny source files and linking from static
libraries keeps the size of NuttX down.
Other tricks used in NuttX include:
</p>
<ul>
<li>
<b>Configuration Files</b>.
Before you build NuttX, you must provide a configuration file that specifies
what features you plan to use and which features you do not.
This configuration file contains a long list of settings that control
what is built into NuttX and what is not.
There are hundreds of such settings
(see the <a href="NuttxPortingGuide.html#apndxconfigs">NuttX Porting Guide</a>
for a partial list that excludes platform specific settings).
These many, many configuration options allow NuttX to be highly tuned to
meet size requirements.
The downside to all of these configuration options is that it greatly
complicates the maintenance of NuttX -- but that is my problem, not yours.
</li>
<li>
<b>Weak Symbols</b>
The GNU toolchain supports <i>weak</i> symbols and these also help to keep
the size of NuttX down.
Weak symbols prevent object files from being drawn into the link even if they
are accessed from source code.
Careful use of weak symbols is another trick for keep unused code out of the
final binary.
</li>
</ul>
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<a name="downloads"><h1>Downloads</h1></a>
</td>
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</table>
<p><b>nuttx-0.4.2</b>.
The 34<sup>th</sup> release of NuttX (nuttx-0.4.2) is available for download
from the <a href="http://sourceforge.net/project/showfiles.php?group_id=189573">SourceForge</a>
website.
The change log associated with the release is available <a href="#currentrelease">here</a>.
These unreleased changes are listed <a href="#pendingchanges">here</a>.
This release adds no new OS features but does include support for two new architectures:
Basic support has been integrated and verified for the ez80f910200zcog-d board (eZ80F91-based).
That basic support includes timer interrupts and serial console.
Ongoing work includes an EMAC driver that should be integrated for the next release nuttx-0.4.2.
</p>
<p>
eZ80Acclaim! support has been in the code base for some time, but has only just
been integrated due to toolchain issues.
</p>
<li>
<p>Renesas M16C/20</b>.
Support for the Renesas SKP16C20 board has been included in the NuttX source tree.
However, as was with the eZ80Acclaim!, testing and integration of that port is stalled due to toolchain issues.
</p>
</li>
These changes were verified only on the ZiLOG ez80f910200zcog-d platform. Please report any errors to me.
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<a name="platforms"><h1>Supported Platforms</h1></a>
</td>
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<b>Linux User Mode</b>
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<td><br></td>
<td>
A user-mode port of NuttX to the x86 Linux/Cygwin platform is available.
The purpose of this port is primarily to support OS feature development.
<b>STATUS:</b>
Does not support interrupts but is otherwise fully functional.
<td valign="top"><img height="20" width="20" src="favicon.ico"></td>
<b>TI TMS320C5471</b> (also called <b>C5471</b> or <b>TMS320DA180</b> or <b>DA180</b>).
NuttX operates on the ARM7 of this dual core processor.
This port uses the <a href="http://www.spectrumdigital.com/">Spectrum Digital</a>
evaluation board with a GNU arm-elf toolchain* under Linux or Cygwin.
<b>STATUS:</b>
This port is complete, verified, and included in the initial NuttX release.
</p>
</td>
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<td><br></td>
<td><hr></td>
</tr>
patacongo
committed
<tr>
<td><br></td>
<td>
<p>
<b>NXP LPC214x</b>.
Support is provided for the NXP LPC214x family of processors. In particular,
support is provided for the mcu123.com lpc214x evaluation board (LPC2148).
This port also used the GNU arm-elf toolchain* under Linux or Cygwin.
patacongo
committed
</p>
<p>
<b>STATUS:</b>
The port is complete and verified. As of NuttX 0.3.17, the port includes:
timer interrupts, serial console, USB driver, and SPI-based MMC/SD card
patacongo
committed
</p>
</td>
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<td><br></td>
<td><hr></td>
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<td><br></td>
<td>
<p>
<b>STMicro STR71x</b>.
Support is provided for the STMicro STR71x family of processors. In particular,
support is provided for the Olimex STR-P711 evaluation board.
This port also used the GNU arm-elf toolchain* under Linux or Cygwin.
</p>
<p>
<b>STATUS:</b>
Coding is complete on the basic port (boot logic, system time, serial console),
but no testing has been performed due to some problems I am having with my
JTAG wiggler and OpenOCD on Linux.
</p>
</td>
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</td>
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<td><br></td>
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<p>
<b>TI TMS320DM320</b> (also called <b>DM320</b>).
NuttX operates on the ARM9 of this dual core processor.
This port uses the
<a href="http://wiki.neurostechnology.com/index.php/Developer_Welcome">Neuros OSD</a>
The basic port (timer interrupts, serial ports, network, framebuffer, etc.) is complete.
All implemented features have been verified with the exception of the USB device-side
driver; that implementation is complete but completely untested.
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<b>8052 Microcontroller</b>
</td>
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<td><br></td>
<td>
This port uses the <a href="http://www.pjrc.com/">PJRC</a> 87C52 development system
and the <a href="http://sdcc.sourceforge.net/">SDCC</a> toolchain under Linux or Cygwin.
<b>STATUS:</b>
This port is complete but not stable with timer interrupts enabled.
There seems to be some issue when the stack pointer enters into the indirect IRAM
address space during interrupt handling.
This architecture has not been built in some time will likely have some compilation
problems because of SDCC compiler differences.
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<b>Renesas/Hitachi SuperH</b>
</td>
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<tr>
<td><br></td>
<td>
<p>
<b>SH-1 SH7032</b>.
This port uses the Hitachi SH-1 Low-Cost Evaluation Board (SH1_LCEVB1), US7032EVB,
with a GNU arm-elf toolchain* under Linux or Cygwin.
</p>
<p>
<b>STATUS:</b>
This port is available as of release 0.3.18 of NuttX. The port is basically complete
and many examples run correctly. However, there are remaining instabilities that
make the port un-usable. The nature of these is not understood; the behavior is
that certain SH-1 instructions stop working as advertised. This could be a silicon
problem, some pipeline issue that is not handled properly by the gcc 3.4.5 toolchain
(which has very limit SH-1 support to begin with), or perhaps with the CMON debugger.
At any rate, I have exhausted all of the energy that I am willing to put into this cool
old processor for the time being.
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<td bgcolor="#5eaee1">
<b>Renesas M16C/26</b>
</td>
</tr>
<tr>
<td><br></td>
<td>
<p>
<b>Renesas M16C/26 Microncontroller</b>.
This port uses the Renesas SKP16C26 Starter kit and the GNU M32C toolchain.
The development environment is either Linux or Cygwin under WinXP.
</p>
<p>
<b>STATUS:</b>
Initial source files released in nuttx-0.4.2.
At this point, the port has not been integrated; the target cannot be built
because the GNU <code>m16c-elf-ld</code> link fails with the following message:
</p>
<ul>
<code>m32c-elf-ld: BFD (GNU Binutils) 2.19 assertion fail /home/Owner/projects/nuttx/buildroot/toolchain_build_m32c/binutils-2.19/bfd/elf32-m32c.c:482</code>
</ul>
<p>Where the reference line is:</p>
<ul><pre>
/* If the symbol is out of range for a 16-bit address,
we must have allocated a plt entry. */
BFD_ASSERT (*plt_offset != (bfd_vma) -1);
</pre></ul>
<p>
No workaround is known at this time. This is a show stopper for M16C for
the time being.
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<b>Zilog Z16F</b>
</td>
</tr>
<tr>
<td><br></td>
<td>
<p>
<b>Zilog z16f Microncontroller</b>.
This port use the Zilog z16f2800100zcog development kit and the Zilog
ZDS-II Windows command line tools.
The initial release of support for the z16f was made available in NuttX version 0.3.7.
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<b>Zilog eZ80Acclaim! Microncontroller</b>.
<ul>
<li>One uses the ZiLOG ez80f0910200kitg development kit, and
<li>The other uses the ZiLOG ez80f0910200zcog-d development kit.
</ul>
Both boards are based on the eZ80F091 part and both use the Zilog ZDS-II
Windows command line tools.
The development environment is Cygwin under WinXP.
<b>STATUS:</b>
Testing with the ZiLOG ez80f0910200kitg has been performed only on the on the ZDS-II simulator.
However, support for the ZiLOG ez80f0910200zcog-d is complete.
The first integrated version was released in NuttX version 0.4.2.
As of this writing, that port provides basic board support with a serial console.
An eZ80F09 EMAC driver has been developed, but not fully tested as of that release.
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<b>Zilog Z8Encore!</b>
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<p>
<b>Zilog Z8Encore! Microncontroller</b>.
This port uses the either:
</p>
<ul>
<li>Zilog z8encore000zco development kit, Z8F6403 part, or</li>
<li>Zilog z8f64200100kit development kit, Z8F6423 part</li>
</ul>
<p>
and the Zilog ZDS-II Windows command line tools.
The development environment is Cygwin under WinXP.
</p>
<p>
<b>STATUS:</b>
This release has been verified only on the ZiLOG ZDS-II Z8Encore! chip simulation
as of nuttx-0.3.9.
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