# NuttX RTOS Last Updated: July 11, 2011

# 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 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.
| NXFFS. the NuttX wear-leveling FLASH file system.
| 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 server and client, SMTP client, TELNET client, FTP client, TFTP client, HTTP server and client)
| 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.
| NXFFS. the NuttX wear-leveling FLASH file system.
| 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-6.6 Release Notes:

The 735d release of NuttX, Version 6.6, was made on July 11, 2011 and is available for download from the SourceForge website. Note that release consists of two tarballs: `nuttx-6.6.tar.gz` and `apps-6.5.tar.gz`. Both may be needed (see the top-level `nuttx/README.txt` file for build information) The change log associated with the release is available here. Unreleased changes after this release are available in SVN. These unreleased changes are also listed here.

The 6.6 release adds several smaller featurs but is mostly a bugfix release. Bugfixes include

- Fixed several NX Graphics bugs: Rendering fonts at >8 bits-per-pixel, graphics move logic, and display artifacts that appear when a window is closed.
- Corrections to the USB host mass storage class driver
- STM32 bugfixes: serial driver, GPIO interrupt handling
- LPC17xx: Changes for a success compilation with no console.
- Corrections to the Teensy AT90USB SD driver
- Changes for a clean compilation under the ZDS-II toolchain.

Minor features include:

- Add logic to extract AVR `printf` strings from FLASH (but there are still `printf` issues for that target)
- Added a configuration for the Sure Electronics PIC32MX board. However, higher priority tasks have stopped work on that configuration.
- Added several new configurations for the STMicro STM3210E-EVAL board.
- Added support for the STM3210E-EVAL board: (1) LCD in either landscape or portrait mode, and (2) interrupting buttons.
- Added a configuration option to use different serial ports for debug and for the NSH serial console (there are some issues with CR-LF expansion and character echo if NSH is not run on the console).
- Standardized the button press and button interrupt interfaces so that they are common across all boards.
- Added a new graphics example that focuses on placing text on the background while pop-up windows occur. Text should continue to update normally with or without the popup windows present.
- Added ARM stack checking logic.

# Supported Platforms

The short story (Number of ports follow in parentheses. Follow the links for the details):

Linux user mode simulation (1) ARM ARM7TDMI (4) ARM920T (1) ARM926EJS (3) ARM Cortex-M3 (10) Atmel AVR Atmel 8-bit AVR (3) Atmel AVR32 (1) | Freescale M68HCS12 (2) Intel Intel 8052 Microcontroller (1) Intel 80x86 (2) MicroChip PIC32 (MIPS) (2) Renesas/Hitachi: Renesas/Hitachi SuperH (1/2) Renesas M16C/26 (1/2) | Zilog Zilog Z16F (1) Zilog eZ80 Acclaim! (1) Zilog Z8Encore! (2) Zilog Z80 (2)

The details, caveats and fine print follow:

| 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.
| NXP LPC315x. Support for the NXP LPC315x family has been incorporated into the code base as of NuttX-6.4. STATUS: The MCU support logic is present but as of this writing has not been verified on hardware. Because of the high degree of compatibility between the LPC313x and LPC315x family, it is very likely that the support is in place (or at least very close).
| 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 boar, the mbed board, and the LPCXpresso all 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. 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. Embedded Artists base board with NXP LPCXpresso LPC1768 An fully verified board configuration is included in NuttX-6.2. The Code Red toolchain is supported under either Linux or Windows. Verifed configurations include DHCPD, the NuttShell (NSH), NuttX graphis (NX), the NuttX OS test, THTTPD, and USB mass storage device. Development Environments: 1) Linux with native Linux GNU toolchain, 2) Cygwin with Cygwin GNU toolchain, or 3) Cygwin with Windows native toolchain (CodeSourcery devkitARM or Code Red). A DIY toolchain for Linux or Cygwin is provided by the NuttX buildroot package.
| Atmel AVR.
| SoC Robotics ATMega128. This port of NuttX to the Amber Web Server from SoC Robotics is partially completed. The Amber Web Server is based on an Atmel ATMega128. STATUS: Work on this port has stalled due to toolchain issues. Complete, but untested code for this port appears in the NuttX 6.5 release.
| Micropendous 3 AT9USB64x and AT9USB6128x. This port of NuttX to the Opendous Micropendous 3 board. The Micropendous3 is may be populated with an AT90USB646, 647, 1286, or 1287. I have only the AT90USB647 version for testing. This version have very limited memory resources: 64Kb of FLASH and 4Kb of SRAM. STATUS: The basic port was released in NuttX-6.5. This basic port consists only of a "Hello, World!!" example that demonstrates initialization of the OS, creation of a simple task, and serial console output.
| PJRC Teensy++ 2.0 AT9USB1286. This is a port of NuttX to the PJRC Teensy++ 2.0 board. This board was developed by PJRC. The Teensy++ 2.0 is based on an Atmel AT90USB1286 MCU. STATUS: The basic port was released in NuttX-6.5. This basic port consists of a "Hello, World!!" example that demonstrates initialization of the OS, creation of a simple task, and serial console output as well as a somewhat simplified NuttShell (NSH) configuration (see the NSH User Guide). An SPI driver and a USB device driver exist for the AT90USB as well as a USB mass storage configureation. However, this configuration is not fully debugged as of the NuttX-6.5 release.
| AVR-Specific Issues. The basic AVR port is solid and biggest issue for using AVR is its tiny SRAM memory and its Harvard architecture. Because of the Harvard architecture, constant data that resides to flash is inaccessible using "normal" memory reads and writes (only SRAM data can be accessed "normally"). Special AVR instructions are available for accessing data in FLASH, but these have not been integrated into the normal, general purpose OS. Most NuttX test applications are console-oriented with lots of strings used for printf and debug output. These strings are all stored in SRAM now due to these data accessing issues and even the smallest console-oriented applications can quickly fill a 4-8Kb memory. So, in order for the AVR port to be useful, one of two things would need to be done: Don't use console applications that required lots of strings. The basic AVR port is solid and your typical deeply embedded application should work fine. Or, Create a special version of printf that knows how to access strings that reside in FLASH (or EEPROM).
| Development Environments: 1) Linux with native Linux GNU toolchain, 2) Cygwin with Cygwin GNU toolchain, or 3) Cygwin with Windows native toolchain. All testing, however, has been performed using the Nuttx DIY toolchain for Linux or Cygwin is provided by the NuttX buildroot package. As a result, that toolchain is recommended.
| 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.
| Freescale M68HCS12.
| 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.
| 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 80x86.
| 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!
| RGMP. RGMP stands for RTOS and GPOS on Multi-Processor. RGMP is a project for running GPOS and RTOS simultaneously on multi-processor platforms You can port your favorite RTOS to RGMP together with an unmodified Linux to form a hybrid operating system. This makes your application able to use both RTOS and GPOS features. See the RGMP Wiki for further information about RGMP. STATUS: This initial port of NuttX to RGMP was provided in NuttX-6.3. This initial RGP port provides only minimal driver support and does not use the native NuttX interrupt system. This is a great, stable starting point for anyone interest in working with NuttX under RGMP!
| MicroChip PIC32 (MIPS).
| PIC32MX460F512L. A port of NuttX to the PIC32MX460F512L is underway. This port uses the PIC32MX board from PCB Logic Design Co. The board is a very simple -- little more than a carrier for the PIC32 MCU plus voltage regulation, debug interface, and an OTG connector. STATUS: This port is code complete and has begun testing. Testing is, unfortunately, delayed until I obtain some additional test equipment (you can't use PICkit 2 with the PIC32; you need PICkit 3. And, to make things worse, my PICKit3 just hangs when I try to debug).
| PIC32MX440F512H. This port uses the "Advanced USB Storage Demo Board," Model DB-DP11215, from Sure Electronics. This board features the MicroChip PIC32MX440F512H. See the Sure website for further information about the DB-DP11215 board. STATUS: This port is code complete and has begun testing. I hope to use the on-board LEDs to work around the debug problems with the PCL Logic board (see above). Update: Work on this board has stalled due to higher priority tasks.
| Development Environment: These ports uses the LITE version of the PIC32MX toolchain available for download from the MicroChip website.
| 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.

> * 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, Cortex-M3, avr, m68k, m68hc11, m68hc12, m9s12, blackfin, m32c, h8, 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 $(TOPDIR)`. Supported Windows Native Toolchains. At present, only the Zilog Z16F, z8Encore, and eZ80Acclaim ports use a non-GCC native Windows toolchain(the Zilog ZDS-II toolchain). Support for Windows native GCC toolchains (CodeSourcery and devkitARM) is currently implemented for the NXP LPC214x, STMicro STR71x, and Luminary LMS6918 ARM ports. (but could easily be extended to any other GCC-based platform with a small effort).
| Wine + GNU `make` + Windows Native Toolchain
> | I've never tried this one, but I off the following reported by an ez80 user using the ZiLOG ZDS-II Windows-native toolchain: "I've installed ZDS-II 5.1.1 (IDE for ez80-based boards) on wine (windows emulator for UNIX) and to my surprise, not many changes were needed to make SVN snapshot of Nuttx buildable... I've tried nsh profile and build process completed successfully. One remark is necessary: Nuttx makefiles for ez80 are referencing `cygpath` utility. Wine provides similar thing called `winepath` which is compatible and offers compatible syntax. To use that, `winepath` (which itself is a shell script) has to be copied as `cygpath` somewhere in `$PATH`, and edited as in following patch:
>     # diff -u `which winepath` `which cygpath`
>     --- /usr/bin/winepath 2011-05-02 16:00:40.000000000 +0200
>     +++ /usr/bin/cygpath 2011-06-22 20:57:27.199351255 +0200
>     @@ -20,7 +20,7 @@
>     #

>     # determine the app Winelib library name
>     -appname=`basename "$0" .exe`.exe
>     +appname=winepath.exe

>     # first try explicit WINELOADER
>     if [ -x "$WINELOADER" ]; then exec "$WINELOADER" "$appname" "$@"; fi
"Better solution would be replacing all `cygpath` references in `Makefiles` with `$(CONVPATH)` (or `${CONVPATH}` in shell scripts) and setting `CONVPATH` to `cygpath` or `winepath` regarding to currently used environment.
| 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-6.6 2011-07-11 Gregory Nutt <spudmonkey@racsa.co.cr>

        * drivers/mtd/ramtron.c, net/net_checksd.c, fs/fs_fdopen.c, and include/nuttx/mii.h:
          Several structural changes made to get a clean compile under the ez80 ZDS-II
          toolchain (no design changes).
        * drivers/usbhost/usbhost_storage.c: Incorpated bugfixes reported by Sheref H.
          Younan:  (1) Read capacity logic read largest block, not the number of blocks
          and was, therefore, off by one, and (2) Some devices stall of get Max LUN request
          if they support only a single LUN.  Logic now assumes a single LUN if the get
          Max LUN request fails.
        * include/nuttx/arch.h, lib/stdio/lib_libvsprintf.c, lib/stdio/lib_fputs.c: Add
          a new configuration option to support extracting strings from FLASH or EEPROM
          or other memories where the string data cannot be accessed by simply de-referencing
          a string pointer.
        * arch/sim/src/up_romgetc.c: Used to test the basic logic to access strings
          without directly de-referencing a string pointer.
        * arch/avr/src/avr/up_romget.c: Used to access strings that lie in the first
          64Kb of FLASH (But I still haven't figured out how to get strings to reside in
          FLASH without using the PROGMEM attribute).
        * configs/teensy/src/up_spi.c: Correct reading of SD CD and WP pins (was reading
          the wrong register.  AVR SPI now appears to be functional.
        * arch/avr/src/at90usb/at90usb_usbdev.c: Correct USB initialization.  Interrupts
          were being enabled BEFORE the interrupt handler was attached.
        * configs/sure-pic32mx:  Add a configuration for the Sure Electronics, "Advanced USB
          Storage Demo Board," Model DB-DP11215 (http://www.sureelectronics.net/goods.php?id=1168).
          This board features the MicroChip PIC32MX440F512H MCU. (Untested on initial
          check-in).
        * configs/stm3210e-eval/nsh2:  Add another NSH configuration for the STM32 with
          some different properties.
        * CONFIG_NSH_CONDEV:  Add a configuration option to allow using a different character
          device (such a a different UART) for the NSH interface.  This allows, for example,
          debug output to come from the console device while using another device for NSH.
          There are some issues on initial check-in:  NuttX doesn't have termios and the
          console device has special properties that make using NSH awkward.  Examples:
          No CR-LF expansion, no character echoing, no command line editting.
        * arch/arm/src/stm32/stm32_lowputc.c and stm32_serial.c.  Correct seversl bugs
          involving serial port configuration.  These bugs are only critical if you
          are trying to using multiple UARTs on STM32.
        * configs/stm3210e-eval/src/up_lcd.c:  Add a driver for the STM3210E-EVAL's LCD.
        * configs/stm3210e-eval/nx:  Add NX configuration for the STM3210E-EVAL.
        * configs/nuttx/arch.h (and arch/arm/src/stm32, configs/*/src/up_buttons.c):
          Standardize interfaces exported for button support and button interrupts.
        * configs/stm3210e-eval/src/up_buttons.c:  Add interrupting button support.
          Also fixes a few errors in STM3210E-EVAL button decoding.
        * configs/stm3210e-eval/buttons: Add a configuration to exercise STM3210E-EVAL
          buttons.
        * arch/arm/src/stm32/stm32_gpio.c:  GPIO interrupt handling for pin
          numbers were being aliased:  5-9 together and 10-15 together.  Extended
          the logic to peform decoding of GPIO interrupts and unique dispatching
          for all 16 pins.
        * configs/stm3210e-eval/nxtext: Add a configuration for the apps/examples/nxtext
          example.  This example focuses on placing text on the background while
          pop-up windows occur.  Text should continue to update normally with or without
          the popup windows present.
        * arch/arm/src/common/up_checkstack.c:  ARM stack overflow checking submitted
          by Hal Glenn.
        * arch/arm/src/lpc17xx: Changes to compile successfully with no serial console
          (also submitted by Hal Glenn).
        * graphics/nxfonts/nxfonts_convert.c:  Fixed a critical bug that caused
          when renderer some fonts with bits-per-pixel > 8
        * graphics/nxbe/nxbe_move.c: Fixed an error in the graphics move logic (This
          was a previously untested interface).  Basically, there is some confusion
          between use of (x,y) as a relative offset or as an absolute position.
        * graphics/nxbe/nxbe_close.c:  Fixed an important graphics system bug:
          When a window is closed, the display was not being updated.  The old
          window graphic was left on the display for a time.

    apps-6.6 2011-07-11 Gregory Nutt <spudmonkey@racsa.co.cr>

        * Make.defs, namedapp/namedapp.c: Several structural changes made to get a
          clean compile under the ez80 ZDS-II toolchain (no design changes).
        * apps/examples/buttons: Add a test for the new standardized button interfaces
        * apps/examples/nxtext: Add another NX graphics test.  This one focus on
          placing text on the background while pop-up windows occur.  Text should
          continue to update normally with or without the popup windows present.

    pascal-1.0 2011-05-15 Gregory Nutt <spudmonkey@racsa.co.cr>

        * nuttx/:  The Pascal add-on module now installs and builds under the
          apps/interpreters directory.  This means that the pascal-2.1 module is
          incompatible with will all releases of NuttX prior to nuttx-6.0 where the
          apps/ module was introduced.

    buildroot-1.10 2011-05-06 <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 wouldyou 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 ARM920t.

Unreleased Changes

    nuttx-6.7 2011-xx-xx Gregory Nutt <spudmonkey@racsa.co.cr>

    apps-6.7 2011-xx-xx Gregory Nutt <spudmonkey@racsa.co.cr>

    pascal-3.1 2011-xx-xx Gregory Nutt <spudmonkey@racsa.co.cr>

    buildroot-1.11 2011-xx-xx <spudmonkey@racsa.co.cr>

# 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.

# Other Documentation

| 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

# 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.