NuttX RTOS
Last Updated: May 19, 2007
|
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 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 functionaly 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.
|
The seventh release of NuttX (nuttx-0.2.4) is available for download
from the SourceForge
website.
|
Linux User Mode
|
|
A user-mode port of NuttX to the x86 Linux platform is available.
The purpose of this port is primarily to support OS feature developement.
STATUS:
Does not support interrupts but is otherwise fully functional.
|
|
ARM7TDMI.
|
|
TI TMS320C5471 (also called a C5471 or TMS320DM180).
NuttX operates on the ARM7 of this dual core processor.
This port uses the Spectrum Digital
evaluation board with a GNU arm-elf toolchain*.
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-eld toolchain*.
STATUS:
This port is in progress and should be available in the nuttx-0.2.5 release.
|
|
ARM9EJS.
|
|
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*.
STATUS:
This port is code complete but totally untested due to hardware issues with my OSD.
|
|
8052 Microcontroller
|
|
PJRC 87C52 Development Board.
This port uses the PJRC 87C52 development system
and the SDCC toolchain.
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.
|
|
Other ports
|
|
There are partial ports for the TI TMS320DM270 and for MIPS.
|
* A highly modified buildroot
is available that be used to build a NuttX-compatible arm-elf toolchain.
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
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
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.
0.1.0 2007-03-09 Gregory Nutt
* Initial Release
* Support for Linux user mode simulation and TI
TMS320C5471 (Arm7) provided
0.1.1 2007-03-14 Gregory Nutt
* Corrected an error in interrupt level context switching
for C5471
* Added fgets() and gets() logic; verified c5471 console read.
* Corrected error in reading from the C5471 serial port:
Improper use of semaphore can cause deadlock.
* Fixed an error in the memory cleanup: The idle task
cannot take sempahores (because it must always be ready
to run).
* Tasks can now accept a configurable maximum number of
input parameters (argc)
* _task_init() was divided into separate functions that
require fewer parameters. This was necessary to keep
the stack usage down for the 8051/2 (which has only
256 bytes of stack).
* Attempts to use C5471 console from interrupt handlers
can cause errors. Added a special path for this case.
* Refuse calls to sem_wait and sem_trywait from interrupt
handlers. This was happening because interrupt handlers
were calling printf-like functions.
* Added strtok() and strtok_r()
* Added a simple shell called nsh (see examples/nsh).
* Platform support for 8052 is complete but not stable
when the timer interrupt is enabled. Seems to be an
issue when SP enters indirect address space.
* Documentation updates
0.1.2 2007-03-19 Gregory Nutt
* Add dirent.h, opendir(), readdir(), closedir(), etc.
* Add strerror()
* Added 'ls' command to nsh
* Added C5471 watchdog driver
* Fixed another bug where free() is called from IDLE task.
Can't do this; the caller must be able to wait for access
to memory.
* Fixed bugs associated with debug output:
Cannot do dbg() in middle of context switch logic.
because it may require use of semaphores and cause
additional context switches. lldbg() is safe.
* Interrupt must be disabled throughout all context switches.
* Separated C5471 serial driver; a shareable part is
in drivers/. ; the C5471 specific part is in arch/C5471.
serial.h defines the interface.
* Fixed mq_receive() and mq_send() -- bad memcpy()
* Fixed C5471 signal deliver logic: use of dbg() and
other actions by use signal handler can alter errno.
need to protect errno during signal handling.
* Fixed uninitialized variable in filesystem that could
cause various problems
* Added a test for roundrobin scheduler.
0.2.1 2007-03-22 Gregory Nutt
* Fix error in handing signed decimal in vsprintf().
* Major restructuring of header files to get closer to
POSIX compliance.
* Eliminate compilation warnings that that crept into
recent check-ins
* Add kill()
* Added support for POSIX timers
* Some Documentation updates
* Added support for the Neuros OSD / DM320
0.2.2 2007-03-26 Gregory Nutt
* Created the configs/ directory; separated board configuration
from processor architecture logic
* Add memory leak detection test to examples/ostest
* Corrected memory leak in OS pthread join logic
* Corrected memory leaks in examples/ostest due to failures
to join or detach from pthreads.
* Added pthread_once(), pthread_kill(), pthread_sigmask()
* Added pthread_barrierattr_*() APIs
* Added pthread_barrier_init(), pthread_barrier_destroy(), and
pthread_barrier_wait();
* Added pthread barrier test
* Added protection so that errno cannot be modified from
interrupt handling.
* sched_setparam(), sched_setscheduler() now correctly set
errno; pthread_setscheduler() now returns the correct errno.
* Added pthread_setschedprio().
* Added directories to hold board-specific header files
* Added directories to hold board-specific drivers
0.2.3 2007-03-29 Gregory Nutt
* mq_receive and mq_send now return errno's appropriately
* mq_receive and mq_send are now correctly awakened by signals.
* Fixed an unmatched sched_lock/unlock pair in task_delete().
* sched_lock must be called in _exit() because operation of
task_delete() can cause pending tasks to be merged and a
context switch to occur.
* Added mq_timedreceive() and mq_timedsend()
* signal mask is now inherited by both child tasks and threads.
* Improved sharebility of stdout among pthreads (only). Nothing
was broken, but by moving the mutual exclusion logic to a
higher level, the printf output is more readable.
* Fixed a bug in file system cleanup: A list was being deleted
before the buffers contained in the list.
* Fixed a bug in the wait-for-message-queue-not-empty logic.
* Added a test of timed mqueue operations; detected and corrected
some mqueue errors.
* Identified and corrected a race condition associated with
pthread_join. In the failure condition, memory was being
deallocated while still in use.
0.2.4 2007-04-28 Gregory Nutt
* Verfied c5471 build under Cygwin on WinXP
* Makesystem changes to better support different SoCs.
* Made arch/c5471/include and arch/dm320/include identical in
preparation for merging into arch/arm
* Logic from arch/c5471 and arch/dm320 combined into arch/arm.
arch/c5471 and arch/dm320 are deprecated and will be removed
when the new c5471 and dm320 logic is verified.
0.2.5 2007-xx-xx Gregory Nutt
* Corrected some build/configuration issues introduced with the
last release.
* Added support for the NXP 214x processor on the mcu123.com lpc214x
development board (untested)
* Added support for block devices.
* Simulated target now exports a VFAT filesystem
* Begin support for VFAT filesystem (not yet functional)
* Added mount() and umount()
* Fix bug in memcmp return value
* Fix errors in timeslice calculation (several places)
* Added missing irqrestore() in timer_deletall().
* close() was not closing the underlying device.
* Started m68322