ReleaseNotes

development board's display and MicroSD support.  An SPI driver and a DMA support was included
in this 0.4.12 release, but is not yet tested.

This tarball contains a complete CVS snapshot from October 17, 2009

nuttx-0.4.13
^^^^^^^^^^^^

This is the 45th release of NuttX.  The release extends the support for the STMicro
STM32 microcontroller.  Minimal support for the STM3210E-EVAL development board based
around the STM32F103ZET6 MCU was released in NuttX-0.4.12.  This release adds:

    * A simple interface definition to support some FLASH, EEPROM, NVRAM, etc. devices.
    * Verified SPI operation using driver for SPI based FLASH parts M25P64 and M25P128.
    * Improved Cortex-M3 context switching.  This should improve context switching
      performance be 2x in certain cases.
    * Added a USB device-side driver for the STM32.  This is an early release of a
      very complex driver; some bugs are expected.  
    * The USB driver has been verified against the USB serial device class driver.
      There is at least one known outstanding issue (see the full bug description in
      the TODO list).

This release also corrects some important bugs in the early STM32 release:

    * Fixed several errors the prevented operation of NuttX on an STM32 development
      board using USART2 as the serial console.
    * Fixed and optimization-dependent race condition in the clock initialization.
    * Fixed a critical bug in the interrupt control logic that could cause interrupt
      operations to failed used for interrupts in a certain range.

This tarball contains a complete CVS snapshot from November 4, 2009

nuttx-4.14
^^^^^^^^^^

This is the 46th release of NuttX.  The release extends the support for the STMicro
STM32 microcontroller.  Minimal support for the STM3210E-EVAL development board based
around the STM32F103ZET6 MCU was released in NuttX-0.4.12 and extended in Nuttx-0.4.13
to include initial USB support.  This completes the STM32F103ZET6 and adds:

New Generic RTOS Features:

    * Added generic support that can be included in any block driver to provide
      read-ahead buffering and write buffering for improved driver performance.
    * Added a generic worker thread that can used to defer processing from an
      interrupt to a task.
    * Defined a generic SD/SDIO interface can can be bound to a MMC/SD or SDIO
      driver to orovide SDIO support.
    * Implemented a an SDIO-based MMC/SD driver using this new SDIO interface

New STM32 Features:

    * Add support to configure an STM32 input GPIO to generate an EXTI interrupt.
    * Added support for buttons on the STM3210E-EVAL board.
    * Implemented an STM32 version of the common the SDIO interface.
    * Added a configuration to exercise the STM32 with the USB mass storage
      device class example.

This release also corrects some important bugs in the early STM32 release:

    * Correct error handling in the mount() logic.
    * Fixed several STM32 DMA-related issues. Integrated and debugged STM32 DMA
      functionality that was added in 0.4.12.
    * Fixed several bugs in the STM32 USB device-side driver.

NOTE:  This version, 4.14, is equivalent to what would have been called 0.4.14
to follow 0.4.13.  The zero has been eliminated from the front of the version
number to avoid confusion about the state of development:  Some have interpreted
the leading zero to mean that the code is in some way unstable.  That was not
the intent.  Beginning in January 2010, I will switch to the 2010.nn versioning
as many others have done to avoid such confusion.

This tarball contains a complete CVS snapshot from December 2, 2009

nuttx-5.0
^^^^^^^^^

This is 47th release of NuttX and the successor to nuttx-4.14.  This
major revision number has been incremented to indicate that an
incompatibility with previous nuttx releases has been introduced.  This
version adopts standard fixed width integer names as specified by the
ANSII C99 standard.  The core logic of NuttX is older than that
standard and did not conform to it.

If you have applications running on nuttx-4.14, those applications
should continue to build and execute without problem on nuttx-5.0.
However, if you have device drivers or other OS-internal logic, you
will probably have to make some minor changes to your code to use
this version.  Below is a summary of those changes:

o If you include sys/types.h to get the non-standard, fixed width
  integer types (uint32, uint16, ubyte, etc.), that is no longer
  necessary.
o Instead, you will need to include stdint.h where the new fixed width
  integer types are defined (uint32_t, uint16_t, uint8_t, etc.).
o You will have to change all occurrences of the following types:

  uint32 -> uint32_t
  uint16 -> uint16_t
  ubyte  -> uint8_t
  uint8  -> uint8_t
  sint32 -> int32_t
  sint16 -> int16_t
  sint8  -> int8_t

o In addition, the non-standard type 'boolean' must replaced with the
  standard type 'bool'.  The type definition for 'bool' is in stdbool.h

This change in typing caused small changes to many, many files.  It was
verified that all configurations in the release still build correctly
(other than the SDCC-based configurations).  Regression testing was
performed on a few configurations, but it is possible that minor build
issues still exist (if you encounter any, please let me know and I will
help you to fix them).

In the course of the regression testing, several important bugs unrelated
to the type changes were found and corrected.

o Fixed an important error in the RX FIFO handling logic of the LM3S6918
  Ethernet driver.
o Corrected the handling of TCP sequence numbers in the TCP stack.
o And other less important bugs as detailed in the ChangeLog.

The primary focus of this release was standards compatibility, but a
few new features were added including a (1) Flash Translation Layer (FTL)
that will support filesystems on a FLASH device and (2) partial ports
for the STM32F107VC and HCS12 C9S12NE64 MCUs.  Those ports are very
incomplete as of this writing.

This tarball contains a complete CVS snapshot from December 21, 2009

nuttx-5.1
^^^^^^^^^

This is the 48th release of NuttX.  This release adds support for two new
MCU architectures in various states of development:

o AT91SAM3U (http://www.atmel.com/products/at91/sam3landing.asp?family_id=605)

  This release adds support for the SAM3U-EK development board with the
  AT91SAM3U4E MCU (http://www.atmel.com/dyn/products/product_card_mcu.asp?part_id=4562).
  As with most NuttX architecutre releases, the release will be rolled out in
  two parts:  A basic port and an extended port.

  NuttX-5.1 includes the basic port for the SAM3U-EK board.  This release
  passes the NuttX OS test and is proven to have a valid OS implementation.
  It supports the basic boot-up, serial console and timer interrupts.  A
  configuration to support the NuttShell is also included.

  The extended port will also include support for SDIO-based SD cards and
  USB device (and possible LCD support).  These extensions may or may not
  happen by the Nuttx 5.2 release as my plate is kind of full now.

o LPC3131 (http://ics.nxp.com/products/lpc3000/lpc313x.lpc314x.lpc315x/)

  This release also adds the complete implementation of the basic port for
  the NXP LPC3131 MCU on the Embedded Artists EA3131 board
  (http://www.embeddedartists.com/products/kits/lpc3131_kit.php).  That port,
  unfortunately has stalled due to tools issues.  Those tool issues have
  been resolved and I am confident that the verified basic port will be
  available in NuttX-5.2.

  The extended release will follow and should include SDIO-based SD card
  support and device USB.

A few additional features and bugfixes of a minor nature were also incorporated
as detailed in the ChangeLog.

nuttx-5.2
^^^^^^^^^

This is the 49th release of NuttX.  This release completes the verification of
the basic port for the NXP LPC3131 MCU on the Embedded Artists EA3131 board
(http://www.embeddedartists.com/products/kits/lpc3131_kit.php).  This basic
port includes basic boot-up, serial console, and timer interrupts.  This port
has been verified on the using the NuttX OS test and includes a working
implementation of the NuttShell (NSH).

An extended release will follow and should include SDIO-based SD card
support and device USB.

nuttx-5.3
^^^^^^^^^

This is the 50th release of NuttX.  This release suport for one new achitecture:

  * A basic port for the NXP LPC2378 MCU on the Olimex-LPC2378 development board
    was contributed by Rommel Marcelo.

And extensions to two existing architures:

  * David Hewson contributed a dual-speed (full/high) USB device-side driver
    for the NXP LPC3131 on the Embedded Artists EA3131 development board.
  * A DMA driver and a high speed MCI driver for the Atmel AT91SAM3U are
    included (but not fully tested in this release).

Two important bugfix was also included:

  * An important fix to the USB mass storage driver was contributed by
    David Hewson.
  * A serious error in the AT91SAM3U PIO handling was fixed.

nuttx-5.4
^^^^^^^^^

This is the 51st release of NuttX.  This release includes one new, important
extension to th NX graphics system (See http://www.nuttx.org/NXGraphicsSubsystem.html).

NX was develop a couple years back on hardware that supported only framebuffer
devices, that is, video hardware with video memory directly converts the memroy
content to video.  However, most MCUs that NuttX focuses on do not support such
video memory; rather, that typically only support LCDs via parallel or serial
interfaces.

This release of NuttX extends NX so that now renders directly to the LCD device
via its serial or parallel interface.  No in-memory copy of the screen memory
need be maintained so this solution should also work in MCUs with very limited
SRAM.

This initial release of this feature includes the verified NX extensions plus
a driver for the HX8347, 16-bit parallel LCD.  This LCD supports 16-bit RGB
(5:6:5).

nuttx-5.5
^^^^^^^^^

This is the 52nd release of NuttX.  This release includes one new port, some
new drivers and some important bugfixes:

  * NuttX was ported to the Luminary/TI LM3S6965 Ethernet Evaluation Kit.
    At present, that port includes an OS test configuration and a NuttShell
    (NSH) configuration with telnet support.

    MMC/SD and Networking support are provided but not thoroughly verified
    in this release: Current development efforts are focused on porting the
    NuttX window system (NX) to work with the Evaluation Kits OLED display.

  * A NuttX Ethernet driver for the Microchip ENC28J60 SPI Ethernet chip is
    available in the source tree (but has not yet been fully verified because
    I haven't properly connected it to hardware yet).

  * The Olimex STR-P711 NuttX port was extended to support the ENC28J60 and
    some new networking configurations were added.  The ENC28J60 has not
    been tested on the STR-P711, however, because of hardware issues (I don't
    think the USB powered board provides enough power for the ENC28J60 and
    I don't have the right wall wart yet).

    Along the way, external interrupt support (XTI) was added to the STMicro
    STR-P711 port and some important bugs were fixed in the STR-P711 SPI
    driver.

  * Added (optional) floating point support for printf() (contributed by
    Yolande Cates).

  * Corrected an important UDP reference counting error.  It was not a serious
    error, but it trigger an assertion was IS a serious error.

nuttx-5.6
^^^^^^^^^

This is the 53rd release of NuttX.  This release includes one several new drivers
for existing NuttX ports:

  * This port adds support for the RiT displays P14201 4-bpp, greyscale OLED.
    4-bpp greyscale support was integrated into the NX graphics sub-system and
    verified using the TI/Luminary LP3S6965 Ethernet Evaluation Kit.

  * The M25Px driver was extended for the M24P1 FLASH part (see NOTE).

  * An I2C driver and (basic) SPI driver were added for the NXP LPC313x port.
    The I2C interface definition was extended to efficiently handle multiple I2C
    transfers (See NOTE).

    NOTE: Contributed by David Hewson.

As well as a few, important USB-related bugfixes (See the ChangeLog for details).

This release also includes the beginnings of a port for the NXP LPC1768 MCU.  However,
it is too early for that port to be useful (stay tuned for a future announce of the
availability of the LPC1768 port).

nuttx-5.7
^^^^^^^^^

This is the 54th release of NuttX.  This release adds basic support for one new
ARM Cortex-M3 architecture:

  * Added support for NXP LPC1768 MCU as provided on the Nucleus 2G board from
    2G Engineering (http://www.2g-eng.com).
  * 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.
  * That initial basic release included timer interrupts and a serial console and was
    verified using the NuttX OS test.
  * That release includes a verified NuttShell (NSH) configuration
    (see the http://www.nuttx.org/NuttShell.html).
  * Also included are unverified SPI and USB device drivers.

Further efforts include: (1) development of a DMA support library, (2) SPI-based MMC/SD
support, and (3) verification of the USB driver.  Watch for announcement of the completed
LPC1768 port expected in NuttX-5.8.

nuttx-5.8
^^^^^^^^^

This is the 55th release of NuttX.  This includes several important bugfixes:

  * Corrects some interrupt vectoring for the TI/Stellarix LM3S port
  * Correct initialization logic for NXP LPC17xxx NuttX ports:  Power was
    not being provided to the GPIO module!
  * Corrected (but did not verify) implementation of the optional interrupt
    stack feature (all Cortex M3 architectures).
  * Correct a HardFault in the LPC17xx SSP driver.

Additional minor fixes are also included as detailed in the ChangeLog.

Several new features have been fully developed and included in this release, but
full verification of most of these new features has been blocked for a variety
of issues:

  * Added microSD support for the NuttShell (NSH) configuration in the
    Nucleus2G LPC1768 port.  For reasons that have not yet been determined,
    I have not successfully accessed the microSD card as of this writing.
  * Two USB configurations were also added for the Nucleus2G board:  One to
    support the USB serial device and one for the USB mass storage device.
    Some testing of the USB driver was performed, but full verification is
    stalled for an OTG style USB cable.
  * LEDs now work correctly on the Nucleus2G LPC1768 board.
  * The NuttX/uIP networking subsystem now supports IGMPv2 client.  IGMP
    (Internet Group Multicast Protocol) network "appliances" to join into
    multicast groups.  Outbound traffic to enter and leave multicast groups
    has been verified, but full verification will require a switch capable of
    multicast.  Issues associated with the receipt of multicast packets are likely.

nuttx-5.9
^^^^^^^^^

This is the 56th release of NuttX.  This release is difficult to categorize;
NuttX-5.9 was really released because there were too many changes accumulating
in CVS -- a few important, some unfinished implementations, and a couple of
important bugfixes.

  * By far biggest change in this release is the complete implementation
    of on-demand paging support.  This feature will allow you to execute large
    programs on a mass storage device (such as SPI FLASH) in a small RAM.
    All of the core on-demand paging logic was completed (see
    http://www.nuttx.org/NuttXDemandPaging.html) and support was implemented
    for the ARM-9 family.  A test configuration is in place for the NXP
    LPC3131.  It has been verified that this new logic does not interfere
    with normal fixed-page ARM9 operation, but otherwise this new on-demand
    paging feature is untested.
  * Add support for the CodeSourcery toolchain to the Olimex-lpc2378 port
    and for the Neuros OSD port.
  * The Neuros OSD port has been updated to work with the production v1.0
    OSD (previously it only worked with the development board).
  * And some miscellaneous feature enhancements as detailed in the ChangeLog.

This includes several important bugfixes:

  * NXP LPC17xx - Fixed a critical bug in the GPIO configuratino logic:
    When attempting to set no pull-up or pull-down (floating), it would,
    instead, select pull-down.
  * TI/Luminary LM3Sxxxx - Fixed (1) a logic error in an address table
    lookup, (2) GPIO port encoding the limited support to only 8 GPIO
    ports.
  * Corrected the lease time in the DHCPC implementation:  It was not in
    host byte order.
  * And several other less important bugs as documented in the ChangeLog:
    Warnings, cornercase compilation problems, etc.

nuttx-5.10
^^^^^^^^^^

This is the 57th release of NuttX.  This release includes a combination of
some new features as well as several bugfixes.  New features include:

  * TI/Luminary Stellaris LM3S9B96.  Header file changes contributed by
    Tiago Maluta.
  * TI/Luminary Stellaris LM3S8962.  Header file changes and support for
    the Stellaris LM3S8962 Ethernet+CAN Evaluation Board contributed by
    Larry Arnold.
  * On-Demand Paging Support.  The basic logic for the On-Demand Paging
    feature is complete, implemented for the NXP LPC3131, and partially
    tested.  See http://www.nuttx.org/NuttXDemandPaging.html.  Some additional
    test infrastructure will be needed in order to complete the verification.
    See configs/ea3131/README.txt for details.
  * Two Pass Build Support.  The make system now supports a two pass build
    where a relocatable, partially linked object is created on the first
    pass and that object is linked with the NuttX libraris to produce the
    final executable on the second pass.  This two pass build is currently
    only used to support the On-Demand paging feature:  The first pass
    link forces critical logic into the locked text region; the second pass
    builds the NuttX executable more-or-less as normal.
  * CONFIG_APP_DIR. Generalized the way in which applications are built
    and linked with NuttX.  The new configuration CONFIG_APP_DIR replaces
    CONFIG_EXAMPLE.  CONFIG_EXAMPLE used to identify the sub-directory within
    the NuttX examples/ directory that held the example application to be
    built.  That made it awkward to configure to build an application that
    resides outside of the NuttX examples/ directory.  CONFIG_APP_DIR is
    more general; it can be used to refer to any directory containing the
    application to be built.

      For people who have their own configurations and/or Makefiles,
      you will need to make a couple of changes:

      - Replace all occurrences of CONFIG_EXAMPLE=foobar with
        CONFIG_APP_DIR=examples/foobar in all of the configuration
        files.
      - Replace any occurrences of examples/$(CONFIG_EXAMPLE) with
        $(CONFIG_APP_DIR)
      - Replace any occurrences of lib$(CONFIG_EXAMPLE)$(LIBEXT)
        with libapp$(LIBEXT) in your Makefiles.
      - Check any other occurrences of CONFIG_EXAMPLE.

  * Several bugfixes are included as well as code changes to eliminate
    some warnings.  See the ChangeLog for details.

nuttx-5.11
^^^^^^^^^^

This is the 58th release of NuttX.  This is a bugfix release.

  * One very important bug fixes a race condition that can occur using
    semaphores that can be awakened by signals.  Under this particular
    race condition, a task could hang waiting for a semaphore.
  * Corrections to lm3s8962 port contributed by Larry Arnold.  That
    port is purported to work correctly with these changes in place.

Plus less critical bugfixes as detailed in the ChangeLog.  New features
include:

  * A new configuration to support the mbed.org LPC1768 board (Contributed
    by Dave Marples), and
  * A driver for the Atmel AT45DB161D 4Mbit SPI FLASH part,

nuttx-5.12
^^^^^^^^^^

This is the 59th release of NuttX.  This is a critical bugfix release.

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

Other notable changes in NuttX-5.12:

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

nuttx-5.13
^^^^^^^^^^

This is the 60th release of NuttX.  Headlines for this release include:

    * AVR32, www.mcuzone.com AVR32DEV1

      The port for the www.mcuzone.com AVRDEV1 board based on the Atmel
      AT32UC3B0256 MCU was (almost) fully integrated. The port now
      successfully passes the NuttX OS test (examples/ostest).  A
      NuttShell (NSH) configuration is in place (see the NSH User Guide at
      http://www.nuttx.org/NuttShell.html). Testing of that NSH
      configuration, however, has been postponed (because it got bumped
      by the Olimex LPC1766-STK port -- see below)

      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).

      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.

    * LPC1766, Olimex LPC1766-STK

      Support for the Olimex-LPC1766 is newly added to NuttX and is
      still undergoing development, test, and integration. Verified
      configurations for the NuttX OS test and for the NuttShell (NSH,
      see the NSH User Guide at http://www.nuttx.org/NuttShell.html.
      Additional USB configurations are in the release as well, but
      they have not yet been verified.  Goals for NuttX-5.14 include:
      (1) An Ethernet driver, (2) Verified USB support, and (3) SD
      card support.

    * Additional changes and bugfixes as detailed in the ChangeLog.

nuttx-5.14
^^^^^^^^^^

The 61st release of NuttX, nuttx-5.14, was mad on November 27, 2010.  This
release includes multiple, important bugfixes as well as a new driver for
the NXP LPC1766.

Important bugfixes include:

    * Cortex-M3 Hard Fault.  Fixed a hard fault problem that can occur if certain
      types of interrupts are pending at the time another interrupt returns. This
      problem has only been observed on the LPC1766 (returning from a SYSTICK
      interrupt with a pending Ethernet interrupt).  However, it is assumed that
      all Cortex-M3 ports could have this as a latent bug.

    * TCP/IP Sequence Number Bug.  Corrected errors some important logic in the way
      that sequence numbers are managed when send() sends out packets before a
      previous packet has been acknowledged.  Some of that send() logic was incompatible
      with logic in the uIP layer.  Errors seen include: (1) The final final packet
      in a sequence of packets might be too large!  In the THTTPD example, this
      might leave some garbage at the bottom of the display. Or (2) send() might hang
      with outstanding, unacknowledged data (and with no re-transmission requests).
      This was due to differences in sequence number handling in send() and in
      uip_tcpinput.c; uip_tcpinput.c thought (incorrectly) that all of the bytes
      were acknowledged; send.c knew that they were not.

    * One-Shot POSIX Timer Bug. Fixed an error in set-up of a one-shot POSIX timer.
      It was using the repititive timer value (which is zero in the one-shot case),
      always resulting in a 10Ms timer!  Found and fixed by Wilton Tong.

Additional support has been included for the Olimex-LPC1766.  Support for that board
was added to NuttX 5.13.  This release extends that support with an Ethernet driver.
Verified configurations are now available for the NuttX OS test, for the NuttShell
(NSH, see the <a href="ttp://www.nuttx.org/NuttShell.html">NSH User Guide</a>),
for the NuttX network test, and for the THTTPD webserver. (Additional USB
configurations are in the release as well, but those have not yet been verified. 
Goals for NuttX-5.15 (and beyond) include: (1) Verified USB support, (2) SD card
support, and (3) LCD support.

nuttx-5.15
^^^^^^^^^^

The 62nd release of NuttX, nuttx-5.15, was mad on December 12, 2010.  This
release includes several bugfixes as well as feature enhancements, primarily
for the Olimex LPC1766-STK board.

Important bugfxes included:

    * Additional fixes needed with the TCP sequence number problem "fixed" in
      nuttx-5.14.
    * In the send() logic, now checks if the destination IP address is in the
      ARP table before sending the packet; an ARP request will go out instead.
      This improves behavior, for example, on the first on the first GET request
      from a browser
    * All USB class drivers need to call DEV_CONNECT() when they are ready to
      be enumerated.  That is, (1) initially when bound to the USB driver, and
      (2) after a USB reset.
    * The SPI_SETBITS macro was calling the SPI setmode method.
    * And several other bug fixes of lower criticality (see the ChangeLog for
      details).

And feature enhancements:

    * The LPC176x Ethernet driver was using all of AHB SRAM Bank0 for Ethernet
      packet buffers (16Kb).  An option was added to limit the amount of SRAM
      used for packet buffering and to re-use any extra Bank0 memory for heap.
    * Enabled networking and SD/MMC card support in the Olimex LPC1766-STK
      NuttShell (NSH) configuration.
    * The LPC176x USB driver is now fully fully functional.
    * Added an optional cmddata() method to the SPI interface.  Some devices
      require an additional out-of-band bit to specify if the next word sent
      to the device is a command or data. The cmddata method provides selection
      of command or data.
    * A driver for the Nokia 6100 LCD (with either the Phillips PCF8833 LCD
      controller and for the Epson S1D15G10 LCD controller) 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 this release.

nuttx-5.16
^^^^^^^^^^

The 63rd release of NuttX, Version 5.16, was made on January 10, 2010 and is
available for download from the SourceForge website. This release includes
initial support for USB host in NuttX. The USB host infrstruture is new to
NuttX. This initial USB host release is probably only beta quality; it is
expected the some bugs remain in the logic and that the functionality
requires extension.

Below is a summary of the NuttX USB host implementation as extracted from
the NuttX Porting Guide:

  6.3.9 USB Host-Side Drivers
  o include/nuttx/usb/usbhost.h. All structures and APIs needed to work
    with USB host-side drivers are provided in this header file.
  o struct usbhost_driver_s. Each USB host controller driver must
    implement an instance of struct usbhost_driver_s. This structure is
    defined in include/nuttx/usb/usbhost.h.
    Examples: arch/arm/src/lpc17xx/lpc17_usbhost.c.
  o struct usbhost_class_s. Each USB host class driver must implement
    an instance of struct usbhost_class_s. This structure is also defined
    in include/nuttx/usb/usbhost.h.
    Examples: drivers/usbhost/usbhost_storage.c
  o USB Host Class Driver Registry. The NuttX USB host infrastructure
    includes a registry. During its initialization, each USB host class
    driver must call the interface, usbhost_registerclass() in order add
    its interface to the registery. Later, when a USB device is connected,
    the USB host controller will look up the USB host class driver that
    is needed to support the connected device in this registry.
    Examples: drivers/usbhost/usbhost_registry.c,
    drivers/usbhost/usbhost_registerclass.c, and
    drivers/usbhost/usbhost_findclass.c,
  o Detection and Enumeration of Connected Devices. Each USB host device
    controller supports two methods that are used to detect and enumeration
    newly connected devices (and also detect disconnected devices):
    + int (*wait)(FAR struct usbhost_driver_s *drvr, bool connected);
      Wait for a device to be connected or disconnected.
    + int (*enumerate)(FAR struct usbhost_driver_s *drvr);
      Enumerate the connected device. As part of this enumeration process,
      the driver will (1) get the device's configuration descriptor, (2)
      extract the class ID info from the configuration descriptor, (3)
      call usbhost_findclass() to find the class that supports this device,
      (4) call the create() method on the struct usbhost_registry_s
      interface to get a class instance, and finally (5) call the connect()
      method of the struct usbhost_class_s interface. After that, the class
      is in charge of the sequence of operations.
  o Binding USB Host-Side Drivers. USB host-side controller drivers are not
    normally directly accessed by user code, but are usually bound to another,
    higher level USB host class driver. The class driver exports the standard
    NuttX device interface so that the connected USB device can be accessed
    just as with other, similar, on-board devices. For example, the USB host
    mass storage class driver (drivers/usbhost/usbhost_storage.c) will
    register a standard, NuttX block driver interface (like /dev/sda) that
    can be used to mount a file system just as with any other other block
    driver instance. In general, the binding sequence is:

    1. Each USB host class driver includes an intialization entry point
       that is called from the application at initialization time. This
       driver calls usbhost_registerclass() during this initialization in
       order to makes itself available in the event the the device that it
       supports is connected.
       Examples: The function usbhost_storageinit() in the file
       drivers/usbhost/usbhost_storage.c
    2. Each application must include a waiter thread thread that (1) calls
       the USB host controller driver's wait() to detect the connection of a
       device, and then (2) call the USB host controller driver's enumerate
       method to bind the registered USB host class driver to the USB host
       controller driver.
       Examples: The function nsh_waiter() in the file
       configs/nucleus2g/src/up_nsh.c and the function nsh_waiter() in the
       file configs/olimex-lpc1766stk/src/up_nsh.c.
    3. As part of its operation during the binding operation, the USB host
       class driver will register an instances of a standard NuttX driver
       under the /dev directory. To repeat the above example, the USB host
       mass storage class driver (drivers/usbhost/usbhost_storage.c) will
       register a standard, NuttX block driver interface (like /dev/sda)
       that can be used to mount a file system just as with any other other
       block driver instance.
       Examples: See the call to register_blockdriver() in the function
       usbhost_initvolume() in the file drivers/usbhost/usbhost_storage.c.

nuttx-5.17
^^^^^^^^^^

The 64th release of NuttX, Version 5.17, was made on January 19, 2011 and is
available for download from the SourceForge website. This release follows
close on the heels of the 5.16 release and extends the USB host capabilities
first introduced in that version.

    1. The LPC17xx USB host controller driver was extended to (1) add support
       for low-speed devices, (2) handle multiple concurrent transfers on 
       different endpoints (still only one TD per endpoint), and (3) handle
       periodic interrupt endpoint types.
    2. Add a USB host HID keyboard class driver.  Now you can connect a
       standard USB keyboard to NuttX and receive keyboard input for an
       application.

And other changes as detailed in the ChangeLog.

nuttx-5.18
^^^^^^^^^^

The 65th release of NuttX, Version 5.18, was made on February 27, 2011 and is
available for download from the SourceForge website.  This is first release from
the new NuttX SVN repository.  This release is made primarily to keep the release
tarball in synchronization with SVN.  Many smaller changes have been made as
identified in the ChangeLog.  Headlines would include:

    * Incorporate several important uIP patches -- including the well known
      patch to handle missing SYNACK.
    * The Freescale mc8s12ne64 port is code complete but testing has not yet
      begun due to toolchain issues.  Added support for the Future Electronics
      Group NE64 Badge board.
    * Added support for a new STM32 board, the ISOTEL NetClamps VSN V1.2 ready2go
      sensor network platform.  This board is based on a STM32F103RET6 and
      includes some interesting power saving/clock control extensions.
    * USB host support expanded to handle vendor specific USB devices.
    * Incorporated the LUFA HID parser.
    * Various bugfix as detailed in the ChangeLog

nuttx-5.19
^^^^^^^^^^

The 66th release of NuttX, Version 5.19, was made on March 12, 2011 and is
available for download from the SourceForge website.  This release includes
several new features in various states of integration and maturity:

    * 486SX QEMU port.  This port supports the Intel 486SX architecture using
      the QEMU simulator.  Initial functionality is in place a partially
      tested.  There are still some outstanding issues with timer interrupts.
    * Platform specific application support.  A new apps/ directory appears in
      this port.  This apps/ directory provides a mechanism for applications
      using NuttX to have a highly customizable initialization process. It
      supports a set of end-user applications than can be executed (1) standalone
      so you can have a fully customizable application startup, or (2) on top of
      NSH.  Think of it this way:  In a buckled-up embedded application, your
      end-user programs will probably have their own dedicated start-up logic.
      But, during development, you might want to have you applications
      available and executable from the NSH command line.  This apps/ add-on
      (and NSH hooks) was contributed by Uros to accomplish just that.
    * NSH was also extended to support application specific ROMFS
      /etc/init.d/rcS start-up scripts.  This feature, as well, as all of the
      above-mentioned apps/ directory support was contributed by Uros Platise
    * Additional NSH improvements and bug fixes.  See the Changelog for
      details.
    * This release also provides a new SLIP network driver.  This driver
      should support point-to-point network communications to a host using
      TCP/IP or UDP.  This driver is code complete, but not tested in this
      release.
    * New RAMTRON FRAM driver (contributed by Uros Platise)
    * New generic 16550 UART driver.
    * Cortex-M3 Power improvements: Waits for Interrupt (WFI) in idle loop
      for reduced power consumption (LPC17xx and STM32 only - contributed by
      Uros Platise))
    * New waitpid() system interface.
    * Additional bugfixes: pipes, stdint.h, STM32 SDIO and SPI drivers

nuttx-6.0
^^^^^^^^^

The 67th release of NuttX, Version 6.0, was made on March 21, 2011 and is
available for download from the SourceForge website.  The version number of
this release was bumped from 5.19 to 6.0.  A change in the major revision
number is used to reflect an incompatibility with previous versions.  In
this release, the NuttX core OS functionality has been separated from NuttX
application-related functionality.  These are provided as separate tarballs:

    * nuttx-6.0.tar.gz, and
    * apps-6.0.tar.gz

The purpose of this separation is both to better organize and modularize the
NuttX source tree, but also to provide better support for incorporation of
end-user applications with Nuttx.

The incompatibily results from the changes to the board configuration logic
needed to supported the separable application.  The major changes to the
configuration include:

    * CONFIG_APPS_DIR - This should not be set.  The default is ../apps.  This
      should only be set if you have a custom, product-specific application
      directory in some different location.

    * appconfig - Each board configuration now requires a new file called 
      'appconfig.'  As its name suggests, this file provides new configuration
      information needed by the logic in ../apps.

In addition to this major reorganization in the directory structure, this
release also includes some important extensions to existing features and some
important bugfixes.  These include:

    * The SLIP driver was been well debugged and significantly re-designed.
      Now you can have an Ethernet connection to you board even if you have
      no Ethernet hardware.  How cool is that?

    * The QEMU i486 port is now functional.  It has also been reported to
      work on the Bifferboard (see http://bifferos.bizhat.com/).

    * And extensions to the uIP driver interface, and

    * Bug fixes to fopen() and STM32 GPIO configuration

Please see the ChangeLog for details.

nuttx-6.1
^^^^^^^^^

The 68th release of NuttX, Version 6.1, was made on April 10, 2011 and is
available for download from the SourceForge website.  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 associated with SD drivers, openddir(), signed 8-bit types
(int8_t), and USB serial device.  See the ChangeLog for details.

nuttx-6.2
^^^^^^^^^

The 69th release of NuttX, Version 6.2, was made on May 6, 2011 and is
available for download from the SourceForge website.  The 6.2 release
includes several new features:

    * NXFFS: The obvious new feature is NXFFS, the NuttX wear-leveling
      FLASH file system.   This new file system is intended to be
      small for the MCU usage and has some limitations.  No formal
      documentation of NXFFS yet exists.  See the fs/nxffs/README.txt
      file for details (see
      http://nuttx.svn.sourceforge.net/viewvc/nuttx/trunk/nuttx/fs/nxffs/README.txt?view=log)
    * Support for NXP LPCXpresso LPC1768 board on the Embedded
      Artists base board.  The Code Red toolchain is supported under
      either Linux or Windows.   Verifed configurations include dhcpd,
      nsh, nx, ostest, thttpd, and usbstorage.
    * Support for the Univision UG-9664HSWAG01 OLED with Solomon
      Systech SD1305 LCD controller.
    * A new RAM MTD driver with FLASH simulation capability.
    * A version.h file is now automatically generated so that C code
      can now be version-aware.

In addition to these new feature, several important bugfixes are included
in this release correcting problems with dup2(), LPC17xx GPIO interrupts,
LPC17xx UART2/3, the FAT file system, build issues, and strrch(). See the
ChangeLog for more details.

nuttx-6.3
^^^^^^^^^

The 70th release of NuttX follows only a nines days after the release of
version 6.2.  It was released on May 15, 2011.  This special back-to-back
release was made so that the current released version of NuttX will
correspond to the initial release from the RGMP project.

This release adds architecture support and build configuration for RGMP.
RGMP is a project for running GPOS and RTOS simultaneously on multi-
processor platforms. See http://rgmp.sourceforge.net/wiki/index.php/Main_Page
for further information about RGMP.

This release also includes support for STM32 FLASH, build improvements,
and initial, incomplete support for the MicroChip PIC32MX MCU.  Bug fixes
are included for some build problems, USB host class driver error handling,
NX graphics color mapping, and problems with C standard I/O buffer flushing.
See the ChangeLog for further details.

nuttx-6.4
^^^^^^^^^

The 71st release of NuttX, Version 6.4, was made on June 6, 2011 and is
available for download from the SourceForge website.  The 6.4 release
includes several new features:

    * A new, full-featured FTP client.  This client may be used as a library
      for automated FTP or via an FTP client shell.  The FTP shell supports
      the following commands: cd, chmod, get, help, idle, login, ls, quit,
      mkdir, noop, put, pwd, rename, rhelp, rm, rmdir, size, time, and up.
      A configuration is available for the NXP LPC17xx to demonstrate this
      functionality.
    * A functional C1101 wireless driver (contributed by Uros Platise)
    * A PCI-based E1000 Ethernet driver (contributed by Yu Qiang)
    * New C library functions: inet_addr() (contributed by Yu Qiang),
      strndup(), asprintf()
    * Reduced memory allocation overhead for MCUs with small heaps (<64Kb).
    * fdopen() now works with socket descriptors allowing standard buffered
      C functions to be used for network communications.
    * The NSH ifconfig command can now be used to set or change the IP
      address (contributed by Yu Qiang)

This release also includes some completed but untest functionality.

    * The MicroChip PIC32MX port is now code complete and ready to begin
      testing.  Unfortunately, testing will be delayed due to tool issues.
    * Support for the NXP LPC315x MCUs.

Additional miscellaneous enhancements and bug fixes to task_delete(), recvfrom(),
and other changes as noted in the ChangeLog.

nuttx-6.5
^^^^^^^^^

The 72nd release of NuttX, Version 6.5, was made on June 21, 2011 and is
available for download from the SourceForge website.  The 6.5 release
is all about support for the Atmel 8-bit AVR family.  I have been
interested in the AVR family for some time but because of the severe
SRAM constraints and because of the availability of many tiny schedulers
for the AVR, it has not been "on the radar screen."  However, I have
recently become interested because of interest expressed by members of
the forum and because of the availability of newer, larger capacity AVR
parts (that I don't have yet).

This release includes support for the following AVR boards.  As with any
initial support for new architectures, there are some incomplete areas
and a few caveats that need to be stated.  Here they are, ordered from
the least to the most complete:

    * SoC Robotics Amber Web Server (ATMega128).

      This port of NuttX to the Amber Web Server from SoC Robotics
      (http://www.soc-robotics.com/index.htm).  Is only partially in place.
      The Amber Web Server is based on an Atmel ATMega128 (128Kb FLASH
      but only 4Kb of SRAM).

      STATUS: Work on this port has stalled due to toolchain issues.  It
      is complete, but untested.

    * Micropendous 3 AT9USB647

      This port of NuttX to the Opendous Micropendous 3 board. The
      Micropendous3 may be populated with an AT90USB646, 647, 1286, or
      1287.  See http://code.google.com/p/opendous/. I have only the
      AT90USB647 version for testing.  This version has 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.  The tiny SRAM limits what you can do with the
      AT90USB647 (see issues below).

    * PJRC Teensy++ 2.0 AT9USB1286

      This is a port of NuttX to the PJRC Teensy++ 2.0 board.  This board
      was developed by PJRC (http://pjrc.com/teensy/). The Teensy++ 2.0 is
      based on an Atmel AT90USB1286 MCU with 128Kb of FLASH and 8Kb of SRAM;
      a little more room to move than the AT90USB647.

      STATUS:  The basic port was released in NuttX-6.5.  This basic port
      consists of a "Hello, World!!" example and also slightly simplified
      NuttShell (NSH) configuration (see the NSH User Guide at
      http://www.nuttx.org/NuttShell.html).

      An SPI driver and a USB device driver exist for the AT90USB as well
      as a USB mass storage configuration.  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:

1. 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.

2. Create a special version of printf that knows how to access strings that
   reside in FLASH (or EEPROM).