NuttX RTOSLast Updated: January 6, 2009 |
Table of Contents |
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Overview |
Goals. Nuttx is a real timed embedded operating system (RTOS). Its goals are:
Small Footprint | |
Usable in all but the tightest micro-controller environments, The focus is on the tiny-to-small, deeply embedded environment. | |
Rich Feature OS Set | |
The goal is to provide implementations of most standard POSIX OS interfaces to support a rich, multi-threaded development environment for deeply embedded processors. 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. | |
Highly Scalable | |
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. | |
Standards Compliance | |
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 Because of this standards conformance, software developed under other standard OSs (such as Linux) should port easily to NuttX. | |
Real-Time | |
Fully pre-emptible, fixed priority and round-robin scheduling. | |
Totally Open | |
Non-restrictive BSD license. |
Feature Set. Key features of NuttX include:
Standards Compliant Core Task Management | |
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File system | |
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/dev/null , /dev/zero drivers. | |
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C Library | |
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Networking | |
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USB Device Support | |
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Graphics Support | |
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NuttX Add-Ons. The following packages are available to extend the basic NuttX feature set:
NuttShell (NSH) | |
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Pascal Compiler with NuttX runtime P-Code interpreter add-on | |
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Look at all those files and features... How can it be a tiny OS?. 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?
Lots of Features -- More can be smaller! | |
The philosophy behind that NuttX is that lots of features are great... BUT 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. 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 total 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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Many, many files -- More really is smaller! | |
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?
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Other Tricks | |
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:
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Downloads |
nuttx-0.4.0. The 32nd release of NuttX (nuttx-0.4.10) is available for download from the SourceForge website. The change log associated with the release is available here. Unreleased changes after this release are available in CVS. These unreleased changes are listed here.
This release adds graphics support and a tiny windowing subsystem. That new graphics subystem is documented in a user manual. No other substantial changes were made.The version number was bumped up to 0.4.0 in part to reflect the new graphics subsystem, but also to recognize the NuttX is approaching complete functionality. In the 0.3.x versions, network support was added, Pascal P-code runtime support was added, FAT and ROMFS filesystems were added, MMC/SD and USB device support were added. There were also numerous extensions to the NuttShell, NuttX APIs, and architecture ports.
These changes were verified only on the NuttX simulation platform with X11 windows simulating a device framebuffer. Please report any errors to me.
Supported Platforms |
Linux User Mode | |
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. STATUS: Does not support interrupts but is otherwise fully functional. |
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ARM7TDMI. | |
TI TMS320C5471 (also called C5471 or TMS320DA180 or DA180). NuttX operates on the ARM7 of this dual core processor. This port uses the Spectrum Digital evaluation board with a GNU arm-elf toolchain* under Linux or Cygwin. STATUS: This port is complete, verified, and included in the initial NuttX release. |
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NXP LPC214x. 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. STATUS: This port boots and passes the OS test (examples/ostest). 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 support. A verified NuttShell (NSH) configuration is also available. |
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STMicro STR71x. 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. STATUS: 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. |
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ARM926EJS. | |
TI TMS320DM320 (also called DM320). NuttX operates on the ARM9 of this dual core processor. This port uses the Neuros OSD with a GNU arm-elf toolchain* under Linux or Cygwin. STATUS: 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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8052 Microcontroller | |
PJRC 87C52 Development Board. This port uses the PJRC 87C52 development system and the SDCC toolchain under Linux or Cygwin. STATUS: 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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Renesas/Hitachi SuperH | |
SH-1 SH7032. This port uses the Hitachi SH-1 Low-Cost Evaluation Board (SH1_LCEVB1), US7032EVB, with a GNU arm-elf toolchain* under Linux or Cygwin. STATUS: 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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Zilog Z16F | |
Zilog z16f Microncontroller. This port use the Zilog z16f2800100zcog development kit and the Zilog ZDS-II Windows command line tools. The development environment is Cygwin under WinXP. STATUS: The initial release of support for the z16f was made available in NuttX version 0.3.7. |
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Zilog eZ80 Acclaim! | |
Zilog eZ80Acclaim! Microncontroller. This port uses the ZiLOG ez80f0910200kitg development kit, eZ80F091 part and the Zilog ZDS-II Windows command line tools. The development environment is Cygwin under WinXP. STATUS: This is a work in progress. Verified ez80 support will be announced in a future NuttX release. |
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Zilog Z8Encore! | |
Zilog Z8Encore! Microncontroller. This port uses the either:
and the Zilog ZDS-II Windows command line tools. The development environment is Cygwin under WinXP. STATUS: This release has been verified only on the ZiLOG ZDS-II Z8Encore! chip simulation as of nuttx-0.3.9. |
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Zilog Z80 | |
Z80 Instruction Set Simulator. This port uses the SDCC toolchain under Linux or Cygwin (verified using version 2.6.0). This port has been verified using only a Z80 instruction simulator. That simulator can be found in the NuttX CVS here. STATUS: This port is complete and stable to the extent that it can be tested using an instruction set simulator. |
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Other ports | |
There are partial ports for the TI TMS320DM270 and for MIPS. |
* A highly modified buildroot is available that may be used to build a NuttX-compatible ELF toolchain under Linux or Cygwin. Configurations are available in that buildroot to support ARM, m68k, m68hc11, m68hc12, and SuperH ports.
Development Environments |
Linux + GNU make + GCC/binutils | |
The is the most natural development environment for NuttX. Any version of the GCC/binutils toolchain may be used. There is a highly modified buildroot available for download from the NuttX SourceForge page. This download may be used to build a NuttX-compatible ELF toolchain under Linux or Cygwin. That toolchain will support ARM, m68k, m68hc11, m68hc12, and SuperH ports. The buildroot CVS may be accessed in the NuttX CVS. |
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Linux + GNU make + SDCC | |
Also very usable is the Linux environment using the SDCC compiler. The SDCC compiler provides support for the 8051/2, z80, hc08, and other microcontrollers. The SDCC-based logic is less well exercised and you will likely find some compilation issues if you use parts of NuttX with SDCC that have not been well-tested. |
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Cygwin + GNU make + GCC/binutils | |
This combination works well too. It works just as well as the native Linux environment except that compilation and build times are a little longer. The custom NuttX buildroot referenced above may be build in the Cygwin environment as well. |
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Cygwin + GNU make + SDCC | |
I have never tried this combination, but it would probably work just fine. |
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Cygwin + GNU make + Windows Native Toolchain | |
This is a tougher environment. In this case, the Windows native toolchain is unaware of the the Cygwin sandbox and, instead, operates in the native Windows environment. The primary difficulties with this are:
Fortunately, this conversion is done simply using the The NuttX make system works around this limitation by copying the platform specific directories in place. These copied directories make work a little more complex, but otherwise work well. At present, on the Zilog Z16F port uses a native Windows toolchain (the Zilog ZDS-II toolchain). | |
Other Environments? | |
The primary environmental dependency of NuttX are (1) GNU make, (2) bash scripting, and (3) Linux utilities (such as sed). If you have other platforms that support GNU make or make utilities that are compatible with GNU make, then it is very likely that NuttX would work in that environment as well (with some porting effort). If GNU make is not supported, then some significant modification of the Make system would be required. |
Memory Footprint |
C5471 (ARM7) The build for this ARM7 target that includes most of the OS features and a broad range of OS tests. The size of this executable as given by the Linux size command is (3/9/07):
text data bss dec hex filename 53272 428 3568 57268 dfb4 nuttx
DM320 (ARM9) This build for the ARM9 target includes a significant subset of OS features, a filesystem, Ethernet driver, full TCP/IP, UDP and (minimal) ICMP stacks (via uIP) and a small network test application: (11/8/07, configuration netconfig, examples/nettest)
text data bss dec hex filename 49472 296 3972 53740 d1ec nuttx
Another build for the ARM9 target includes a minimal OS feature set, Ethernet driver, full TCP/IP and (minimal) ICMP stacks, and a small webserver: (11/20/07, configuration uipconfig, examples/uip)
text data bss dec hex filename 52040 72 4148 56260 dbc4 nuttx
87C52 A reduced functionality OS test for the 8052 target requires only about 18-19Kb:
Stack starts at: 0x21 (sp set to 0x20) with 223 bytes available. Other memory: Name Start End Size Max ---------------- -------- -------- -------- -------- PAGED EXT. RAM 0 256 EXTERNAL RAM 0x0100 0x02fd 510 7936 ROM/EPROM/FLASH 0x2100 0x6e55 19798 24384
Licensing |
NuttX is available under the highly permissive BSD license. Other than some fine print that you agree to respect the copyright you should feel absolutely free to use NuttX in any environment and without any concern for jeopardizing any proprietary software that you may link with it.
Release History |
The current NuttX Change Log is available in CVS here. ChangeLog snapshots associated with the current release are available below.
Change Logs for All NuttX Releases |
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ChangeLog for Current Releases |
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Unreleased Changes |
ChangeLog for Current Release |
Unreleased Changes |
Bugs, Issues, Things-To-Do |
The current list of NuttX Things-To-Do in CVS here. A snapshot of the To-Do list associated with the current release are available here.
Other Documentation |
User Guide | |
Porting Guide | |
NuttShell (NSH) | |
NX Graphics Subsystem | |
Change Log | |
To-Do List |
Trademarks |
NOTE: NuttX is not licensed to use the POSIX trademark. NuttX uses the POSIX standard as a development guideline only.