# NuttX RTOS Last Updated: October 27, 2010

# Table of Contents

| Overview. What is NuttX? Look at all those files and features... How can it be a tiny OS?
| NuttX Discussion Group. Do you want to talk about NuttX features? Do you need some help? Problems? Bugs?
| Downloads. Where can I get NuttX? What is the current development status?
| Supported Platforms. What target platforms has NuttX been ported to?
| Development Environments. What kinds of host cross-development platforms can be used with NuttX?
| Memory Footprint. Just how big is it? Do I have enough memory to use NuttX?
| Licensing. 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)
| Release History What has changed in the last release of NuttX? What unreleased changes are pending in CVS?
| Bugs, Issues, Things-To-Do. Software is never finished nor ever tested well enough. (Do you want to help develop NuttX? If so, send me an email).
| Other Documentation. What other NuttX documentation is available?
| Trademarks. Some of the words used in this document belong to other people.

# 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 `fork()`). 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.
| GNU Toolchains
| Compatible GNU toolchains based on buildroot available for download to provide a complete development environment for many architectures.

Feature Set. Key features of NuttX include:

| Standards Compliant Core Task Management
| Modular, micro-kernel
| Fully pre-emptible.
| Naturally scalable.
| Highly configurable.
| Easily extensible to new processor architectures, SoC architecture, or board architectures. A Porting Guide is in development.
| FIFO and round-robin scheduling.
| Realtime, deterministic, with support for priority inheritance
| POSIX/ANSI-like task controls, named message queues, counting semaphores, clocks/timers, signals, pthreads, environment variables, filesystem.
| VxWorks-like task management and watchdog timers.
| BSD socket interface.
| Extensions to manage pre-emption.
| On-demand paging.
| Well documented in the NuttX User Guide.
| File system
| Tiny in-memory, root pseudo-file-system.
| Supports character and block drivers.
| Network, USB (device), serial, CAN, driver architecture.
| RAMDISK, pipes, FIFO, `/dev/null`, `/dev/zero` drivers.
| Mount-able volumes. Bind mountpoint, filesystem, and block device driver.
| FAT12/16/32 filesystem support.
| Generic driver for SPI-based MMC/SD/SDH cards.
| ROMFS filesystem support.
| NXFLAT. A new binary format call NXFLAT that can be used to execute separately linked programs in place in a file system.
| C Library
| Fully integrated into the OS.
| Networking
| TCP/IP, UDP, ICMP, IGMPv2 (client) stacks.
| Small footprint (based on uIP).
| BSD compatible socket layer.
| Networking utilities (DHCP, SMTP, TELNET, TFTP, HTTP)
| A NuttX port of Jeff Poskanzer's THTTPD HTTP server integrated with NXFLAT to provide true, embedded CGI.
| FLASH Support
| MTD-inspired interface for Memory Technology Devices.
| FTL. Simple Flash Translation Layer support file systems on FLASH.
| Support for SPI-based FLASH devices.
| USB Device Support
| Gadget-like architecture for USB device controller drivers and device-dependent USB class drivers.
| USB device controller drivers available for the NXP LPC214x, LPC313x, STMicro STM32 and TI DM320.
| Device-dependent USB class drivers available for USB serial and for USB mass storage.
| Built-in USB trace functionality for USB debug.
| Graphics Support
| Framebuffer drivers.
| LCD drivers for both parallel and SPI LCDs and OLEDs.
| NX: A graphics library, tiny windowing system and tiny font support that works with either framebuffer or LCD drivers. Documented in the NX Graphics Subsystem manual.

NuttX Add-Ons. The following packages are available to extend the basic NuttX feature set:

| NuttShell (NSH)
| A small, scalable, bash-like shell for NuttX with rich feature set and small footprint. See the NuttShell User Guide.
| Pascal Compiler with NuttX runtime P-Code interpreter add-on
| The Pascal add-on is available for download from the SourceForge website.

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).
| 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? Static Libraries. Because in the NuttX build processed, objects are compiled and saved into static libraries (archives). 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.
| 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: Configuration Files. 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 NuttX Porting Guide 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. Weak Symbols The GNU toolchain supports weak 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.

# NuttX Discussion Group

Most Nuttx-related discussion occurs on the Yahoo! NuttX group. You are cordially invited to join. I make a special effort to answer any questions and provide any help that I can.

# Downloads

nuttx-5.12 Release Notes:

This 59th release of NuttX, Version 5.12, was made on October 26, 2010 and 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 is primarily a bugfix release and includes some important corrections to the code:

- Fixed an important error in the signal trampoline logic. Essentially, interrupts are re-enabled while the signal handler executes, but the logic to re-disable the interrupts before returning from the signal handler trampoline was missing. Under certain circumstances, this can cause stack corruption. This was discovered by David Hewson on an ARM9 platform, but since the code has been leveraged, the bug has been propogated from ARM to Cortex-M3, AVR32, M16C, SH1, ZNEO, eZ80, Z8, and Z80 -- almost every architecture. The correction has been incorporated for all architectures but only verified on a few.

Other notable changes in NuttX-5.12 include:

- A complete port for the AVR32 (AT32UC3B0256) is incorporated in the source tree. Testing of this port is underway now. This release was made before verifying this port in order to get the important bugfix in place.
- Other miscellaneous bugfix and enhancements as noted in the ChangeLog.

# 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.
| 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.
| 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. Development Environments: 1) Linux with native Linux GNU toolchain, 2) Cygwin with Cygwin GNU toolchain, or 3) Cygwin with Windows native toolchain (CodeSourcery or devkitARM). A DIY toolchain for Linux or Cygwin is provided by the NuttX buildroot package.
| NXP LPC2378. Support is provided for the NXP LPC2378 MCU. In particular, support is provided for the Olimex-LPC2378 development board. This port was contributed by Rommel Marcelo is was first released in NuttX-5.3. This port also used the GNU arm-elf toolchain* under Linux or Cygwin. STATUS: This port boots and passes the OS test (examples/ostest) and includes a working implementation of the NuttShell (NSH). The port is complete and verified. As of NuttX 5.3, the port includes only basic timer interrupts and serial console support. Development Environments: (Same as for the NXP LPC214x).
| 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: Integration is complete on the basic port (boot logic, system time, serial console). Two configurations have been verified: (1) The board boots and passes the OS test with console output visible on UART0, and the NuttShell (NSH) is fully functional with interrupt driven serial console. An SPI driver is available but only partially tested. Additional features are needed: USB driver, MMC integration, to name two (the slot on the board appears to accept on MMC card dimensions; I have only SD cards). An SPI-based ENC29J60 Ethernet driver for add-on hardware is under development and should be available in the NuttX 5.5 release. Development Environments: 1) Linux with native Linux GNU toolchain, 2) Cygwin with Cygwin GNU toolchain, or 3) Cygwin with Windows native toolchain (CodeSourcery or devkitARM). A DIY toolchain for Linux or Cygwin is provided by the NuttX buildroot package.
| ARM920T.
| Freescale MC9328MX1 or i.MX1. This port uses the Freescale MX1ADS development board with a GNU arm-elf toolchain* under either Linux or Cygwin. STATUS: This port has stalled due to development tool issues. Coding is complete on the basic port (timer, serial console, SPI).
| 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. The port was performed using the OSD v1.0, development board. 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 untested.
| NXP LPC3131. The port for the NXP LPC3131 on the Embedded Artists EA3131 development board was first released in NuttX-5.1 with a GNU arm-elf or arm-eabi toolchain* under Linux or Cygwin (but was not functional until NuttX-5.2). STATUS: The basic EA3131 port is complete and verified in NuttX-5.2 This basic port includes basic boot-up, serial console, and timer interrupts. This port was extended in NuttX 5.3 with a USB high speed driver contributed by David Hewson. David also contributed I2C and SPI drivers plus several important LPC313x USB bug fixes that appear in the NuttX 5.6 release. This port has been verified using the NuttX OS test, USB serial and mass storage tests and includes a working implementation of the NuttShell (NSH). Support for on-demand paging has been developed for the EA3131. That support would all execute of a program in SPI FLASH by paging code sections out of SPI flash as needed. However, as of this writing, I have not had the opportunity to verify this new feature.
| ARM Cortex-M3.
| Luminary/TI LM3S6918. This port uses the Micromint Eagle-100 development board with a GNU arm-elf toolchain* under either Linux or Cygwin. STATUS: The initial, release of this port was included in NuttX version 0.4.6. The current port includes timer, serial console, Ethernet, SSI, and microSD support. There are working configurations the NuttX OS test, to run the NuttShell (NSH), the NuttX networking test, and the uIP web server. Development Environments: 1) Linux with native Linux GNU toolchain, 2) Cygwin with Cygwin GNU toolchain, or 3) Cygwin with Windows native toolchain (CodeSourcery or devkitARM). A DIY toolchain for Linux or Cygwin is provided by the NuttX buildroot package.
| Luminary/TI LM3S6965. This port uses the Stellaris LM3S6965 Ethernet Evalution Kit with a GNU arm-elf toolchain* under either Linux or Cygwin. STATUS: This port was released in NuttX 5.5. Features are the same as with the Eagle-100 LM3S6918 described above. The examples/ostest configuration has been successfully verified and an NSH configuration with telnet support is available. MMC/SD and Networking support was not been thoroughly verified: Current development efforts are focused on porting the NuttX window system (NX) to work with the Evaluation Kits OLED display. NOTE: As it is configured now, you MUST have a network connected. Otherwise, the NSH prompt will not come up because the Ethernet driver is waiting for the network to come up. Development Environments: See the Eagle-100 LM3S6918 above.
| Luminary/TI LM3S8962. This port uses the Stellaris EKC-LM3S8962 Ethernet+CAN Evalution Kit with a GNU arm-elf toolchain* under either Linux or Cygwin. Contributed by Larry Arnold. STATUS: This port was released in NuttX 5.10. Features are the same as with the Eagle-100 LM3S6918 described above.
| Luminary/TI LM3S9B96. Header file support was contributed by Tiago Maluta for this part. However, no complete board support configuration is available as of this writing.
| STMicro STM32F103x. This port uses the STMicro STM3210E-EVAL development board that features the STM32F103ZET6 MCU. This port uses a GNU arm-elf toolchain* under either Linux or Cygwin (with native Windows GNU tools or Cygwin-based GNU tools). STATUS: The basic STM32 port was released in NuttX version 0.4.12. The basic port includes boot-up logic, interrupt driven serial console, and system timer interrupts. The 0.4.13 release added support for SPI, serial FLASH, and USB device.; The 4.14 release added support for buttons and SDIO-based MMC/SD and verifed DMA support. Verified configurations are available for NuttX OS test, the NuttShell (NSH) example, the USB serial device class, and the USB mass storage device class example. Development Environments: 1) Linux with native Linux GNU toolchain, 2) Cygwin with Cygwin GNU toolchain, or 3) Cygwin with Windows native toolchain (RIDE7, CodeSourcery or devkitARM). A DIY toolchain for Linux or Cygwin is provided by the NuttX buildroot package.
| Atmel AT91SAM3U. This port uses the Atmel SAM3U-EK development board that features the AT91SAM3U4E MCU. This port uses a GNU arm-elf or arm-eabi toolchain* under either Linux or Cygwin (with native Windows GNU tools or Cygwin-based GNU tools). STATUS: The basic SAM3U-EK port was released in NuttX version 5.1. The basic port includes boot-up logic, interrupt driven serial console, and system timer interrupts. That release passes the NuttX OS test and is proven to have a valid OS implementation. A configuration to support the NuttShell is also included. NuttX version 5.4 adds support for the HX8347 LCD on the SAM3U-EK board. This LCD support includes an example using the NX graphics system. Subsequent NuttX releases will extend this port and add support for SDIO-based SD cards and USB device (and possible LCD support). These extensions may or may not happen by the Nuttx 5.5 release as my plate is kind of full now. Development Environments: 1) Linux with native Linux GNU toolchain, 2) Cygwin with Cygwin GNU toolchain, or 3) Cygwin with Windows native toolchain (CodeSourcery or devkitARM). A DIY toolchain for Linux or Cygwin is provided by the NuttX buildroot package.
| NXP LPC1768. Configurations are available for two boards: The Nucleus 2G board from 2G Engineering, and The mbed board from mbed.org (Contributed by Dave Marples). Both boards feature the NXP LPC1768 MCU and a GNU arm-elf or arm-eabi toolchain* under either Linux or Cygwin (with native Windows GNU tools or Cygwin-based GNU tools). STATUS: Some initial files for the LPC17xx family were released in NuttX 5.6, but the first functional release for the NXP LPC1768/Nucleus2G occured with NuttX 5.7 with some additional enhancements through NuttX-5.9. That initial, 5.6, basic release included timer interrupts and a serial console and was verified using the NuttX OS test (`examples/ostest`). Configurations available include include a verified NuttShell (NSH) configuration (see the NSH User Guide). The NSH configuration support the Nucleus2G's microSD slot and additional configurations are available to exercise the the USB serial and USB mass storage devices. However, due to some technical reasons, neither the SPI nor the USB device drivers are fully verified. (Although it has been reported to me that the SPI microSD is functional on other platforms). Support for the mbed board was contributed by Dave Marples and released in NuttX-5.11. Development Environments: 1) Linux with native Linux GNU toolchain, 2) Cygwin with Cygwin GNU toolchain, or 3) Cygwin with Windows native toolchain (CodeSourcery or devkitARM). A DIY toolchain for Linux or Cygwin is provided by the NuttX buildroot package.
| 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.
| Frescale M68HSC12
| MC9S12NE64. This port uses the Freescale DEMO9S12NE64 Evaluation Board with a GNU arm-elf toolchain* under Linux or Cygwin. STATUS: This port only fragmentary as of NuttX-5.0. Some initial pieces appear in that release, but much more is needed. Time permitting, the HCS12 port may be available int NuttX5.1.
| Atmel AVR32
| AV32DEV1. This port uses the www.mcuzon.com AVRDEV1 board based on the Atmel AT32UC3B0256 MCU. This port requires a special GNU avr32 toolchain available from atmel.com website. This is a windows native toolchain and so can be used only under Cygwin on Windows. STATUS: This port is currently under development. All code is complete for the basic NuttX port including header files for all AT32UC3* peripherals. Testing of this port is underway now. The untest AVR32 is present in the 5.12 release of NuttX. It is hoped that the first, verified AVR32 port will be released in version 5.13 of NuttX.
| 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.
| Renesas M16C/26
| Renesas M16C/26 Microncontroller. This port uses the Renesas SKP16C26 Starter kit and the GNU M32C toolchain. The development environment is either Linux or Cygwin under WinXP. STATUS: 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 `m16c-elf-ld` link fails with the following message: `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` Where the reference line is:
    /* 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);
No workaround is known at this time. This is a show stopper for M16C for the time being.
| 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.
| Zilog eZ80 Acclaim!
| Zilog eZ80Acclaim! Microncontroller. There are two eZ80Acclaim! ports: One uses the ZiLOG ez80f0910200kitg development kit, and The other uses the ZiLOG ez80f0910200zcog-d development kit. 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. STATUS: Integration and testing of NuttX on the ZiLOG ez80f0910200zcog-d is complete. The first integrated version was released in NuttX version 0.4.2 (with important early bugfixes in 0.4.3 and 0.4.4). As of this writing, that port provides basic board support with a serial console, SPI, and eZ80F91 EMAC driver.
| Zilog Z8Encore!
| Zilog Z8Encore! Microncontroller. This port uses the either: Zilog z8encore000zco development kit, Z8F6403 part, or Zilog z8f64200100kit development kit, Z8F6423 part 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.
| 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.
| XTRS: TRS-80 Model I/III/4/4P Emulator for Unix. A very similar Z80 port is available for XTRS, the TRS-80 Model I/III/4/4P Emulator for Unix. That port also uses the SDCC toolchain under Linux or Cygwin (verified using version 2.6.0). STATUS: Basically the same as for the Z80 instruction set simulator. This port was contributed by Jacques Pelletier.
| 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.
| 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.
| 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.
| Cygwin + GNU `make` + SDCC
| I have never tried this combination, but it would probably work just fine.
| Cygwin + GNU `make` + Windows Native Toolchain
| This is a tougher environment. In this case, the Windows native toolchain is unaware of the Cygwin sandbox and, instead, operates in the native Windows environment. The primary difficulties with this are: Paths. Full paths for the native toolchain must follow Windows standards. For example, the path `/home/my\ name/nuttx/include` my have to be converted to something like `'C:\cygwin\home\my name\nuttx\include'` to be usable by the toolchain. Fortunately, this conversion is done simply using the `cygpath` utility. Symbolic Links NuttX depends on symbolic links to install platform-specific directories in the build system. On Linux, true symbolic links are used. On Cygwin, emulated symbolic links are used. Unfortunately, for native Windows applications that operate outside of the Cygwin sandbox, these symbolic links cannot be used. 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. NOTE: In this environment, it should be possible to use the NTFS `mklink` command to create links. This should only require a minor modification to the build scripts (see `tools/winlink.sh` script). Dependencies NuttX uses the GCC compiler's `-M` option to generate make dependencies. These dependencies are retained in files called `Make.deps` throughout the system. For compilers other than GCC, there is no support for making dependencies in this way. For Windows native GCC compilers, the generated dependencies are windows paths and not directly usable in the Cygwin make. By default, dependencies are surpressed for these compilers as well. NOTE: dependencies are suppress by setting the make variable `MKDEPS` to point to the do-nothing dependency script, `tools/mknulldeps.sh`. Dependencies can be enabled for the Windows native GCC compilers by setting `MKDEPS` to point to `$(TOPDIR)/tools/mkdeps.sh --winpaths $(TOPDIR)`. Supported Windows Native Toolchains. At present, only the Zilog Z16F, z8Encore, and eZ80Acclaim ports use a non-GCC native Windows toolchain(the Zilog ZDS-II toolchain). Support for Windows native GCC toolchains (CodeSourcery and devkitARM) is currently implemented for the NXP LPC214x, STMicro STR71x, and Luminary LMS6918 ARM ports. (but could easily be extended to any other GCC-based platform with a small effort).
| Other Environments? Windows Native `make` + Windows Native Toolchain?
| Environment Dependencies. The primary environmental dependency of NuttX are (1) GNU make, (2) bash scripting, and (3) Linux utilities (such as cat, sed, etc.). 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. GNUWin32. For example, with suitable make system changes, it should be possible to use native GNU tools (such as those from GNUWin32) to build NuttX. However, that environment has not been used as of this writing. NOTE: One of the members on the NuttX forum reported that they successful built NuttX using such a GNUWin32-based, Windows native environment. They reported that the only necessary change was to the use the NTFS mklink command to create links (see `tools/winlink.sh` script).

# 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
| ChangeLog for the Current Releases
| Unreleased Changes

ChangeLog for the Current Release

    nuttx-5.12 2010-10-26 Gregory Nutt <spudmonkey@racsa.co.cr>

    	* arch/avr - Add a place to support AVR family processors.
    	* arch/avr/include/avr32 and arch/avr/src/avr32 - Add support for AVR32
    	  (all of the AVR32 is a work in progress).
    	* arch/avr/include/at32uc3 and arch/avr/src/at32uc3 - Add support
    	  for the AVR32 UC3A/B family of AVR32 MCUs.
    	* confgs/avr32dev1 - Add support for the Atmel AVR32DEV1 board featuring
    	  the AT32UC3B0256 MCU.  This board is produced by www.mcuzone.com.
    	* include/stdlib.h, lib/Makefile, lib/lib_abs.c, lib/lib_labs.c,
    	  lib_labs.c, lib_llabs.c, lib_imaxabs.c - Add abs(), labs(), llabs(), and
    	  imaxabs().
    	* Add include/inttypes.h
    	* arch/hc/src/mc9s12ne64 - This hcs12 port grew a few more files.  But it
    	  is still a long way from complete.
    	* arch/*/src/*/*_sigdeliver.c - Fixed a serious error in the signal
    	  trampoline logic.  Essentially, interrupts are re-enabled while the
    	  signal handler executes, but the logic to re-disable the interrupts
    	  before returning from the signal handler trampoline was missing.  Under
    	  certain circumstances, this can cause stack corruption.  This was
    	  discovered by David Hewson on an ARM9 platform, but since the code
    	  has been leveraged, the bug has been propogated from ARM to Cortex-M3,
    	  AVR32, M16C, SH1, ZNEO, eZ80, Z8, and Z80 -- almost every architecture.
    	  The correction has been incorporated for all architectures but only
    	  verified on a few.

    pascal-2.0 2009-12-21 Gregory Nutt <spudmonkey@racsa.co.cr>

    	* Updated to use standard C99 types in stdint.h and
    	  stdbool.h.  This change was necessary for compatibility
    	  with NuttX-5.0 (any beyond).

    buildroot-1.8 2009-12-21 <spudmonkey@racsa.co.cr>

    	* configs/cortexm3-defconfig-4.3.3: Added support for NuttX NXFLAT
    	  tools.
    	* configs/arm7tdmi-defconfig-4.3.3: Update to arm7tdmi-defconfig-4.2.4.
    	  Also builds NuttX NXFLAT tools.
    	* configs/m68hc12-defconfig-4.3.3: Update to m68ch11-defconfig.
    	* configs/m68hc12-defconfig-3.4.6: There are problems building GCC
    	  4.3.3 for the hc12.
    	* configs/m32c-defconfig-4.2.4: Added genromfs
    	* configs/m32c-defconfig-4.3.3: Update to m32c-defconfig-4.2.4

Unreleased Changes

    nuttx-5.13 2010-xx-xx Gregory Nutt <spudmonkey@racsa.co.cr>

    	* lib/lib_strnlen.c -- Added POSIX 2008 strnlen() function.  Contributed
    	  by Michael Hrabanek.
    	* Fix wild, consistent naming error.  For some reason, I called the at32uc3*
    	  parts at91uc* everywhere.  Fixed by changing lots of files.

    pascal-2.1 2010-xx-xx Gregory Nutt <spudmonkey@racsa.co.cr>

    buildroot-1.9 2010-xx-xx

    	* configs/arm926t-defconfig-4.3.3: update arm926t-defconfig-4.2.4
    	* configs/arm926t-defconfig-nxflat: NXFLAT-only configuration for
    	  arm926
    	* toolchain/gdb/gdb.mk - Remove ncurses dependency from gdb_target target.
    	* toolchain/gdb/gdb.mk - Added --disable-werror to GDB configuration line.
    	  GDB 6.8 won't build because the tarball was released with -Werror enabled and
    	  the build stops on the first warning.

# 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)
| NXFLAT Binary Format
| NX Graphics Subsystem
| Demand Paging
| NuttX README Files
| Change Log
| To-Do List

# Trademarks

- ARM, ARM7 ARM7TDMI, ARM9, ARM920T, ARM926EJS Cortex-M3 are trademarks of Advanced RISC Machines, Limited.
- Cygwin is a trademark of Red Hat, Incorporated.
- Linux is a registered trademark of Linus Torvalds.
- Eagle-100 is a trademark of Micromint USA, LLC.
- LPC2148 is a trademark of NXP Semiconductors.
- TI is a tradename of Texas Instruments Incorporated.
- UNIX is a registered trademark of The Open Group.
- VxWorks is a registered trademark of Wind River Systems, Incorporated.
- ZDS, ZNEO, Z16F, Z80, and Zilog are a registered trademark of Zilog, Inc.

NOTE: NuttX is not licensed to use the POSIX trademark. NuttX uses the POSIX standard as a development guideline only.