Nuttx 是一个实时嵌入式操作系统（RTOS），它有一个小巧是在微控制器的环境中使用。这是完全可扩展，从小型（8位）至中型嵌入式（32位）系统。它的目的还在于要完全符合标准，完全实时，并完全开放。
更新日志：
* Incorporate several uIP patches from http://gitweb.aeruder.net/?p=uip.git;a=summary. (1) Lost SYNACK causes connection reset, (2) Fix missing UDP stats for sent/received packets, and (3) Added support for Cygwin as development/test platform.
* configs/demo9s12ne64 - Integrate new buildroot-1.9 m8s12x toolchain.
* 'uname -o' is used throughout the build logic in bash scripts and also in Make.defs files in order to distinguish between Cygwin and Linux. However, the -o option is not standard and is not supported under, for example, OS-X or Solaris. This was solved by changing all 'uname -o' references to the more complex: 'uname -o 2>/dev/null || echo "Other"'
* drivers/usbhost/usbhost_enumerate.c -- Add logic to get the VID and PID. This is necessary in order to support vendor-specific USB devices.
* examplex/wlan, configs/olimex-lpc1766stk/wlan, drivers/usbhost/usbhost_rtl8187.c, Add infrastructure to support RTL18187
wireless USB.
* configs/nucleus2g -- backed out USB host changes... wrong board.
* Renamed arc/hc/include/mc9s12ne64 and src/mc9s12ne64 -- m9s12. That name is shorter and more general.
* The NuttX repository has been converted to SVN and can now be found here http://nuttx.svn.sourceforge.net/viewvc/nuttx/
* configs/mbed/hidkbd -- Added USB host support for the mbed LPC1768 board; add a USB host HID keyboard configuraion.
* drivers/usbhost/hid_parser.c -- Leverages the LUFA HID parser written by Dean Camera.
* examples/nsh -- Correct an usage of getopt(): If you stop calling getopt() before all parameters are parsed, you can leave getopt() in a strange state.
* Rename arch/pjrc-8051 to arch/8051
* configs/ne64badge -- Add a configuration for the Future Electronics Group NE64 Badge development board (Freescale MC9S12NE64)
* Changes contributed by Uros Platise: (1) Add support for the STM32F103RET6, and (2) configs/vsn - Support for the ISOTEL NetClamps VSN V1.2 ready2go sensor network platform
* arch/hc, configs/ne64badge -- Development is complete for the Freescale mc9s12ne64 on the Future Electronics Group NE64 /PoE Badge board. Howeve, this port remains untested until I figure out this BDM / Code Warrior and paged build thing.
该版本主要是bug修复，另外完全支持 Freescala MC9S12NE* 芯片，支持 Cortex-M3 板卡。
下载地址：http://sourceforge.net/projects/nuttx/files/nuttx/nuttx-5.18/nuttx-5.18.tar.gz/download