NuttX RTOS

Last Updated: April 28, 2011

	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 SVN?
	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.
	May be built either as an open, flat embedded RTOS or as a separtely built, secure micro-kernel with a system call interface.
	Well documented in the NuttX User Guide.
	File system
	Tiny in-memory, root pseudo-file-system.
	Supports character and block drivers.
	Network, USB (host), USB (device), serial, CAN, driver architectures.
	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.
	SLIP
	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 and FRAM devices.
	USB Host Support
	USB host architecture for USB host controller drivers and device-dependent USB class drivers.
	USB host controller drivers available for the NXP LPC17xx.
	Device-dependent USB class drivers available for USB mass storage and HID keyboard.
	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 LPC17xx, 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-6.1 Release Notes:

The 68^th release of NuttX, Version 6.1, was made on April 10, 2011 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 SVN. These unreleased changes are listed here.

The 6.0 release introduced a detach-able application environment to build applications outside of the NuttX source tree. The primary purpose of this release is to correct numerous build problems introduced by that architectural change:

In many newer environments, NuttX produced strange Makefile errors but built correctly in older environments. A fix provided by Rafael Noronha was incorporated and is reported to fix those build problems.
The apps/ directory build system would not handle Windows-native toolchains due to obscure path formatting issues.
And other problems as detailed in the change log.

Many additional changes were made in the 6.1 release for another major architectural change: NuttX will now build as a seperately linked micro-kernel. In this build option the RTOS builds as a kernel, applications build separtate and interface with kernel via system calls. Applications run in user mode and kernel logic users in kernel-mode. This provides a secure environment for NuttX. This feature is fully coded in NuttX-6.1, but has not been tested due to higher priority tasks that have arisen.

Related to this change, support for the Cortex-M3 memory protection unit (MPU) has been integrated with the NuttX kernel build to provide an even higher level of security.

NOTE: This kernel build is an option; the default build configuration is still the standard, flat, unsecured RTOS as in previous releases.

Additional new features in this release:

Support for LPC17xx GPIO interrupts (with much support from Decio Renno).
Basic timer support for STM32 (Contributed by Uros Platise)
A binfs file system. This is a tiny psuedo file system that lets named appliations to be viewed and accessed in NSH under the /bin directory.
An I2C-based driver for the LIS331DL MEMS motion sensor (Contributed by Uros Platise).
A board configuration for the Embedded Artists LPCXpresso LPC1768 board.
The user_initialize() interface has been removed.

And several bugfix are included. This includes chagnes associated with SD drivers, openddir(), signed 8-bit types (int8_t), and USB serial device. See the ChangeLog for details.

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 (apps/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 (apps/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 apps/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. Support for three MCUs and two board configurations are available. MCU support includes: STM32F103ZET6, STM32F103RET6, and STM32F107VC. Board support includes: This port uses the STMicro STM3210E-EVAL development board that features the STM32F103ZET6 MCU. ISOTEL NetClamps VSN V1.2 ready2go sensor network platform based on the STMicro STM32F103RET6. Contributed by Uros Platise. These ports 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. Support for the NetClamps VSN was included in version 5.18 of NuttX. 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 LPC1766 and LPC1768. Configurations are available for three boards: The Nucleus 2G board from 2G Engineering (LPC1768), The mbed board from mbed.org (LPC1768, Contributed by Dave Marples), and The LPC1766-sTK board from Olimex (LPC1766). The Embedded Artists base board with NXP LPCXpresso LPC1768. The Nucleus 2G and the mbed boards feature the NXP LPC1768 MCU; the Olimex LPC1766-STK board features an LPC1766. All use 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 following summarizes the features that has been developed and verified on individual LPC17xx-based boards. These features should, however, be common and available for all LPC17xx-based boards. Nucleus2G LPC1768. 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 (`apps/examples/ostest`). Configurations available include include a verified NuttShell (NSH) configuration (see the NSH User Guide). The NSH configuration supports 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 they have since been verfiied on other platforms; this needs to be revisited on the Nucleus2G). mbed LPC1768. Support for the mbed board was contributed by Dave Marples and released in NuttX-5.11. This port includes a NuttX OS test configuration (see `apps/examples/ostest`). Olimex LPC1766-STK. Support for that Olimex-LPC1766-STK board was added to NuttX 5.13. The NuttX-5.14 release extended that support with an Ethernet driver. The NuttX-5.15 release further extended the support with a functional USB device driver and SPI-based micro-SD. The NuttX-5.16 release added a functional USB host controller driver and USB host mass storage class driver. The NuttX-5.17 released added support for low-speed USB devicers, interrupt endpoints, and a USB host HID keyboard class driver. Embedded Artists base board with NXP LPCXpresso LPC1768. An initial board configuration is included in NuttX-6.1. However, certain Code Red download issues have not yet been resolved and the port has not yet been tested. Verified configurations are now available for the NuttX OS test, for the NuttShell with networking and microSD support(NSH, see the NSH User Guide), for the NuttX network test, for the THTTPD webserver, for USB serial deive and USB storage devices examples, and for the USB host HID keyboard driver. Support for the USB host mass storage device can optionally be configured for the NSH example. A driver for the Nokia 6100 LCD and an NX graphics configuration for the Olimex LPC1766-STK have been added. However, neither the LCD driver nor the NX configuration have been verified as of the the NuttX-5.17 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.
	Intel 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.
	Intel 80486 (i486) Microprocessor
	QEMU/Bifferboard i486. This port uses the QEMU i486 and the native Linux, Cywgin, MinGW the GCC toolchain under Linux or Cygwin. STATUS: The basic port was code-complete in NuttX-5.19 and verifed in NuttX-6.0. The port was verified using the OS and NuttShell (NSH) examples under QEMU. The port is reported to be functional on the Bifferboard as well. This is a great, stable starting point for anyone interest in fleshing out the x86 port!
	Frescale M68HSC12
	MC9S12NE64. Support for the MC9S12NE64 MCU and two boards are included: The Freescale DEMO9S12NE64 Evaluation Board, and The Future Electronics Group NE64 /PoE Badge board. Both use a GNU arm-elf toolchain* under Linux or Cygwin. The NuttX buildroot provides a properly patched GCC 3.4.4 toolchain that is highly optimized for the m9s12x family. STATUS: Coding is complete for the MC9S12NE64 and for the NE64 Badge board. However, testing has not yet begun due to issues with BDMs, Code Warrior, and the paging in the build process. Progress is slow, but I hope to see a fully verified MC9S12NE64 port in the near future.
	Atmel AVR32
	AV32DEV1. This port uses the www.mcuzone.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 has completed all basic development, but there is more that needs to be done. All code is complete for the basic NuttX port including header files for all AT32UC3* peripherals. The untested AVR32 code was present in the 5.12 release of NuttX. Since then, the basic RTOS port has solidified: The port successfully passes the NuttX OS test (apps/examples/ostest). A NuttShell (NSH) configuration is in place (see the NSH User Guide). Testing of that configuration has been postponed (because it got bumped by the Olimex LPC1766-STK port). Current Status: I think I have a hardware problem with my serial port setup. There is a good chance that the NSH port is complete and functional, but I am not yet able to demonstrate that. At present, I get nothing coming in the serial RXD line (probably because the pins are configured wrong or I have the MAX232 connected wrong). The basic, port (including the verified apps/examples/ostest configuration) was be released in NuttX-5.13. A complete port will include drivers for additional AVR32 UC3 devices -- like SPI and USB --- and will be available in a later release, time permitting.
	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 SVN 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 SVN may be accessed in the NuttX SVN.
	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, apps/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, apps/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 SVN 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-6.1 2011-04-10 Gregory Nutt <spudmonkey@racsa.co.cr>

    * arch/arm/include/lpc17xx/irq.h and arch/arm/src/lpc17xx/lpc17_gpio*.c:
      Fix several bugs in the GPIO interrupt logic.  Submited by
      Decio Renno.
    * Initialization for the CONFIG_APPS_DIR is now supported during the
      earlier, 'context' build phase.
    * arch/arm/src/lpc17_gpioint.c: Finish coding of the LPC17xx GPIO
      interrupt logic.
    * net/netdev_unregister.c: Add capability to un-register a network
      device.
    * drivers/mmcsd/mmcsd_sdio.c: extra effort to correctly handle cases
      without the SDcard (but one issue still exists in STM32)
    * arch/arm/src/stm32/stm32_tim.*: Added basic timer support TIM1..TIM8
      with output PWMs and interrupt logic
    * config/vsn/src: added basic support for Sensor Interface (GPIO and
      PWM Power Output, and the sif utility program)
    * fs/: Reorgnize header so that file systems can be built outside
      of the nuttx source tree
    * apps/namedapp/binfs.c: Create a tiny filesystem that can be used
      to show the internal named apps under /bin.
    * fs/fs_opendir.c: Correct an error that occurs when a file system is
      mounted in the root directory.  This was discovered while mounting
      the named app's /bin directory.
    * lib/: Move all source files into a subdirectory of lib/ named after
      the header file in which the library function is prototyped.
    * sched/ and lib/pthread/:  Move pthread attribute-related interfaces
      from sched/ to lib/pthread where they more appropriately belong.
    * sched/ and lib/semaphore/:  Move some semaphore-related interfaces
      from sched/ to lib/pthread where they more appropriately belong.
    * syscall/: The beginnings of an optional syscall kernel interface.
    * tools/mksyscall.c:  Add a tool that will auto-generate syscall proxies
      and stubs from a comma-separated-value (CSV) data file.
    * arch/arm/src/cortexm3/mpu.h: Add a header file describing the Cortex-M3
      MPU registers.
    * Numerous modifications to the build system.  Various people have reported
      build problems since the re-organization and release of NuttX-6.0.  I am
      unable to replicate the build problems in my environment, but the changes
      have be incorporated in hope of correcting the build issues in other
      environments.
    * drivers/i2c/st_lis331dl.c:  I2C-based driver for the LIS331DL MEMS
      motion sensor.  Contributed by Uros Platise.
    * Makefile: The NuttX build system  will now supported building NuttX as two
      separately linked images: (1) a kernel-mode RTOS image, and (2) a user-
      mode application image that communicates to the RTOS kernel via system
      calls.  A lot more still must be done.
    * user_initialize(): Eliminated the user_initialize() initialization hook.
      It is difficult to maintain and redundant:  Board level initialization
      an up_initialize() provide the same kind of capability.
    * arch/*/include/*/type.h: On some compilers, char defaults as unsigned.
      Explicitly add signed to integer types if signed is what is required.
    * arch/*: For all architectures -- Global register state save structure
      (usually called current_regs) should be marked volatile; Added general
      capability to support nested interrupts (not fully realized for all
      architectures).
    * sched/task_create.c: Add support for starting kernel-mode thread.
    * drivers/usbdev/usbdev_serial.c: Fix reported by Sheref Younan.  USB
      was being reset after serial driver was closed.  As a result, you could
      no reopen the serial driver.
    * configs/lpcxpresso-lpc1768: Add a board configuration for the Embedded
      Artists LPCXpresso LPC1768 board.

apps-6.1 2011-04-10 Gregory Nutt <spudmonkey@racsa.co.cr>

    * Creation of auto-generated header files now occurs during the context
      build phase.
    * Added sdcard insert and eject, nsh command '?' and some code remarks
    * Renamed nuttapp to namedapp
    * namedapp/binfs.c -- Create a tiny filesystem that can be used
      to show the internal named apps under /bin.
    * Numerous fixes to build system required to support building with native
      Windows toolchain.

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-1.9 2011-02-10 <spudmonkey@racsa.co.cr>

    * 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 tarbal was released with -Werror enabled and
      the build stops on the first warning.
    * Add support for Freescale m9s12x using binutils 2.18 and gcc 3.3.6 and
      patches available from http://www.msextra.com/tools courtesy of James
      Cortina.  Add configs/m9x12x-defconfig-3.3.6.

Unreleased Changes

nuttx-6.2 2011-xx-xx Gregory Nutt <spudmonkey@racsa.co.cr>

* arch/arm/src/lpc17xx/lpc17_gpioint.c: Correct errors in logic that maps
and IRQ number into a register bit number.
* Makefile: Fix an error introduced in the top-level Makefile in NuttX-6.1.
This error only shows up if you have a /tftpboot directory. Then the
make will fail with an obscure error about not being able to stat pass2.
* configs/lpcxpresso-lpc1768/nsh: Add an NSH configuration for the
LPCXpresso board.
* configs/*/ld.script: Removed 'sh_link not set for section .ARM.edix' for
a few of the builds. In you have this warning, it can be removed with the
following change to the ld.script file:

+ __exidx_start = ABSOLUTE(.);
.ARM.exidx : {
- __exidx_start = ABSOLUTE(.);
*(.ARM.exidx*)
- __exidx_end = ABSOLUTE(.);
} >sram
+ __exidx_end = ABSOLUTE(.);

* arch/arm/src/lpc17xx: Correct some typos/bugs in configuration of LPC17xx
UART2 and UART3.
* nuttx/clock.h: Replace all references to the global variable g_system_timer
with clock_systemtimer() (currently just a macro that that returns g_system_timer).
* lib/string/strrch.c: Would fail if the searched-for character were the first
character in the string.
* tools/version.sh and mkversion.c: Tools to manage a NuttX version number
file
* sched/clock_getutc() and lib/time/lib_time.c: Add support for 1 second UTC
interface.
* net/net_dup2.c and include/nuttx/net.h: The conditional compilation for
'#if CONFIG_NFILE_DESCRIPTOR > 0' was wrong in both of these files. It should
be '#if CONFIG_NFILE_DESCRIPTORS > 0'. This causes a dup2() failure in THTTPD
and a failure to get a CGI page. The consequence can be a very serious bug!
* configs/lpcxpresso-lpc1768/usbstorage, thttpd, and dhcpd: Add an USB storage,
THTTPD web server, and DHCP server configurations for the NXP LPCXpresso board.
* drivers/lcd/ug-9664hswag01.c and ssd1305.h: Add support for Univision UG-9664HSWAG01
OLED with Solomon Systech SD1305 LCD controller.
* configs/lpcxpresso-lpc1668/nx: Add a NX graphics configuration for the LPCXPRESO
board.
* graphics/nxglib/nxglib_nonintersecting.c: Fix some single bit errors in
calculation of non-intersecting regions. This was causing an anomoaly
in examples/nx in column 0.
* drivers/mtd/rammtd.c: Added a RAM based MTD driver. This RAM driver simulates
FLASH and is useful for testing purposes.
* arch/arm/src/arm/up_head.S: Fix backward conditional compilation. This cause
the configs/mx1ads configuration to fail to build but does not appear to affect
any other ARM9 build.
* fs/nxffs: Adding a tiny, wear-leveling FLASH file system for NuttX. This
file system is intended to be small and will have some limitations. The
implementation is incomplete on initial checkin.

apps-6.2 2011-xx-xx Gregory Nutt <spudmonkey@racsa.co.cr>

pascal-2.1 2011-xx-xx Gregory Nutt <spudmonkey@racsa.co.cr>

buildroot-1.10 2011-xx-xx <spudmonkey@racsa.co.cr>

* Add patch submitted by Dimiter Georgiev to work around problems in building
GDB 6.8 with versions of Cygwin > 1.7.
* configs/i486-defconfig-4.3.3 - Builds an i486 cross development toolchain
using gcc 4.3.3. Why would you want such a thing? On Linux, of course,
such a thing is not needed because you can use the installed GCC to build
i486 ELF binaries. But that will not work under Cygwin! The Cygwin
toolchain (and probably MinGW), build DOS MZ format executables (i.e.,
.exe files). That is probably not usable for most NuttX targets.
Instead, you should use this i486-elf-gcc to generate true ELF binaries
under Cygwin.
* Makefile - Alter copy arguments to avoid permissions problems when
copying NuttX header files.
* toolchain/nxflat/nxflat.mk and Makefile - Fix include paths.
* toolchain/gcc/3.3.6 - Added a patch to fixed compilation error on Ubuntu
9.10.
* toolchain/nxflat/Makefile - Correct static library link order.
* configs/arm920t-defconfig-4.3.3 - Enable support for NXFLAT tools.
* toolchain/binutils/2.21 and toolchain/gcc/4.5.2 - Add support for GCC
4.5.2 with binutils 2.21.
* configs/arm920t-eabi-defconfig-4.5.2 - Add a configuration to build a
GCC 4.5.2 EABI ARM toolchain for the ARM920.

Bugs, Issues, Things-To-Do

The current list of NuttX Things-To-Do in SVN here. A snapshot of the To-Do list associated with the current release are available here.

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.

	User Guide
	Porting Guide
	NuttShell (NSH)
	NXFLAT Binary Format
	NX Graphics Subsystem
	Demand Paging
	NuttX README Files
	Change Log
	To-Do List
	USB Device Driver Tracing