Board-Specific Configurations
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Table of Contents
^^^^^^^^^^^^^^^^^

  o Board-Specific Configurations
  o Summary of Files
  o Supported Architectures
  o Configuring NuttX

Board-Specific Configurations
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The NuttX configuration consists of:

o Processor architecture specific files.  These are the files contained
  in the arch/<arch-name>/ directory.

o Chip/SoC specific files.  Each processor processor architecture
  is embedded in chip or System-on-a-Chip (SoC) architecture.  The
  full chip architecture includes the processor architecture plus
  chip-specific interrupt logic, general purpose I/O (GIO) logic, and
  specialized, internal peripherals (such as UARTs, USB, etc.).

  These chip-specific files are contained within chip-specific
  sub-directories in the arch/<arch-name>/ directory and are selected
  via the CONFIG_ARCH_name selection

o Board specific files.  In order to be usable, the chip must be
  contained in a board environment.  The board configuration defines
  additional properties of the board including such things as
  peripheral LEDs, external peripherals (such as network, USB, etc.).

  These board-specific configuration files can be found in the
  configs/<board-name>/ sub-directories and are discussed in this
  README.  Additional configuration information maybe available in
  board-specific configs/<board-name>/README.txt files.

The configs/ subdirectory contains configuration data for each board.  These
board-specific configurations plus the architecture-specific configurations in
the arch/ subdirectory completely define a customized port of NuttX.

Directory Structure
^^^^^^^^^^^^^^^^^^^

The configs directory contains board specific configurationlogic.  Each
board must provide a subdirectory <board-name> under configs/ with the
following characteristics:


	<board-name>
        |-- README.txt
	|-- include/
	|   `-- (board-specific header files)
	|-- src/
	|   |-- Makefile
	|   `-- (board-specific source files)
        |-- <config1-dir>
	|   |-- Make.defs
	|   |-- defconfig
	|   `-- setenv.sh
        |-- <config2-dir>
	|   |-- Make.defs
	|   |-- defconfig
	|   `-- setenv.sh
	...
Summary of Files
^^^^^^^^^^^^^^^^

README.txt -- This text file provides additional information unique to
  each board configuration sub-directory.

include/ -- This directory contains board specific header files.  This
  directory will be linked as include/arch/board at configuration time and
  can be included via '#include <arch/board/header.h>'.  These header file
  can only be included by files in arch/<arch-name>include/ and
  arch/<arch-name>/src

src/ -- This directory contains board specific drivers.  This
  directory will be linked as arch/<arch-name>/src/board at configuration
  time and will be integrated into the build system.

src/Makefile -- This makefile will be invoked to build the board specific
  drivers.  It must support the following targets:  libext$(LIBEXT), clean,
  and distclean.

A board may have various different configurations using these common source
files.  Each board configuration is described by three files:  Make.defs,
defconfig, and setenv.sh.  Typically, each set of configuration files is
retained in a separate configuration sub-directory (<config1-dir>,
<config2-dir>, .. in the above diagram).

Make.defs -- This makefile fragment provides architecture and
  tool-specific build options.  It will be included by all other
  makefiles in the build (once it is installed).  This make fragment
  should define:

	Tools: CC, LD, AR, NM, OBJCOPY, OBJDUMP
	Tool options: CFLAGS, LDFLAGS
	COMPILE, ASSEMBLE, ARCHIVE, CLEAN, and MKDEP macros

  When this makefile fragment runs, it will be passed TOPDIR which
  is the path to the root directory of the build.  This makefile
  fragment may include ${TOPDIR}/.config to perform configuration
  specific settings.  For example, the CFLAGS will most likely be
  different if CONFIG_DEBUG=y.

defconfig -- This is a configuration file similar to the Linux
  configuration file.  In contains variable/value pairs like:

	CONFIG_VARIABLE=value

  This configuration file will be used at build time:

    (1) as a makefile fragment included in other makefiles, and
    (2) to generate include/nuttx/config.h which is included by
        most C files in the system.

  The following variables are recognized by the build (you may
  also include architecture/board-specific settings).

	Architecture selection:

		CONFIG_ARCH - Identifies the arch/ subdirectory
		CONFIG_ARCH_name - For use in C code
		CONFIG_ARCH_CHIP - Identifies the arch/*/chip subdirectory
		CONFIG_ARCH_CHIP_name - For use in C code
		CONFIG_ARCH_BOARD - Identifies the configs subdirectory and
		   hence, the board that supports the particular chip or SoC.
		CONFIG_ARCH_BOARD_name - For use in C code
		CONFIG_ENDIAN_BIG - define if big endian (default is little
		   endian)
		CONFIG_ARCH_NOINTC - define if the architecture does not
		  support an interrupt controller or otherwise cannot support
		  APIs like up_enable_irq() and up_disable_irq().
		CONFIG_ARCH_IRQPRIO
		  Define if the architecture suports prioritizaton of interrupts
		  and the up_prioritize_irq() API.

	Some architectures require a description of the RAM configuration:

		CONFIG_DRAM_SIZE - Describes the installed DRAM.
		CONFIG_DRAM_START - The start address of DRAM (physical)
		CONFIG_DRAM_VSTART - The start address of DRAM (virtual)

	General build options:

		CONFIG_RRLOAD_BINARY - make the rrload binary format used with
		  BSPs from www.ridgerun.com using the tools/mkimage.sh script.
		CONFIG_INTELHEX_BINARY - make the Intel HEX binary format
		  used with many different loaders using the GNU objcopy program
		  Should not be selected if you are not using the GNU toolchain.
		CONFIG_MOTOROLA_SREC - make the Motorola S-Record binary format
		  used with many different loaders using the GNU objcopy program
		  Should not be selected if you are not using the GNU toolchain.
		CONFIG_RAW_BINARY - make a raw binary format file used with many
		  different loaders using the GNU objcopy program.  This option
		  should not be selected if you are not using the GNU toolchain.
		CONFIG_HAVE_LIBM - toolchain supports libm.a
		CONFIG_HAVE_CXX - toolchain supports C++ and CXX, CXXFLAGS, and
		  COMPILEXX have been defined in the configuratins Make.defs
		  file.

	Building application code:

		CONFIG_APP_DIR - Identifies the directory that builds the
		  application to link with NuttX. This symbol must be assigned
		  to the path to the application build directory *relative* to
		  the NuttX top build direcory. As an an example, there are
		  several example applicatins in the NuttX examples/ sub-directory.
                  To use one of these example applications, say nsh, you would
		  set CONFIG_APP_DIR=examples/nsh. If you had an application
		  directory and the NuttX directory both within another directory
		  like this:

		  build
		   |-nuttx
		   |  |
		   |  `- Makefile
		   `-application
		   |
		   `- Makefile

		  Then you would set CONFIG_APP_DIR=../application.

		  The application direction must contain Makefile and this make
		  file must support the following targets:

		  - libapp$(LIBEXT) (usually libapp.a). libapp.a is a static
		    library ( an archive) that contains all of application object
		    files.
		  - clean. Do whatever is appropriate to clean the application
		    directories for a fresh build.
		  - distclean. Clean everthing -- auto-generated files, symbolic
		    links etc. -- so that the directory contents are the same as
		    the contents in your configuration management system.
		    This is only done when you change the NuttX configuration.
		  - depend. Make or update the application build dependencies.

		  When this application is invoked it will receive the setting TOPDIR< like:

		    $(MAKE) -C $(CONFIG_APP_DIR) TOPDIR="$(TOPDIR)" <target>

		  TOPDIR is the full path to the NuttX directory. It can be used, for
		  example, to include makefile fragments (e.g., .config or Make.defs)
		  or to set up include file paths.

	Two-pass build options.  If the 2 pass build option is selected, then these
	options configure the make system build a extra link object. This link object
	is assumed to be an incremental (relative) link object, but could be a static
	library (archive) (some modification to this Makefile would be required if
	CONFIG_PASS1_OBJECT is an archive). Pass 1 1ncremental (relative) link objects
	should be put into the processor-specific source directory (where other
	link objects will be created).  If the pass1 obect is an archive, it could
	go anywhere.

		CONFIG_BUILD_2PASS - Enables the two pass build options.

	When the two pass build option is enabled, the following also apply:

		CONFIG_PASS1_OBJECT - The name of the first pass object.
		CONFIG_PASS1_BUILDIR - The path, relative to the top NuttX build
		  directory to directory that contains the Makefile to build the
		  first pass object.  The Makefile must support the following targets:
		  - The special target arch/$(CONFIG_ARCH)/src/$(CONFIG_PASS1_OBJECT)
		  - and the usual depend, clean, and distclean targets.

	General OS setup

		CONFIG_DEBUG - enables built-in debug options
		CONFIG_DEBUG_VERBOSE - enables verbose debug output
		CONFIG_DEBUG_SYMBOLS - build without optimization and with
		  debug symbols (needed for use with a debugger).
		CONFIG_DEBUG_SCHED - enable OS debug output (disabled by
		  default)
		CONFIG_DEBUG_MM - enable memory management debug output
		  (disabled by default)
		CONFIG_DEBUG_NET - enable network debug output (disabled
		  by default)
		CONFIG_DEBUG_USB - enable usb debug output (disabled by
		  default)
		CONFIG_DEBUG_FS - enable filesystem debug output (disabled
		  by default)
		CONFIG_DEBUG_LIB - enable C library debug output (disabled
		  by default)
		CONFIG_DEBUG_BINFMT - enable binary loader debug output (disabled
		  by default)
		CONFIG_DEBUG_GRAPHICS - enable NX graphics debug output
		  (disabled by default)
		CONFIG_ARCH_LOWPUTC - architecture supports low-level, boot
		  time console output
		CONFIG_MM_REGIONS - If the architecture includes multiple
		  regions of memory to allocate from, this specifies the
		  number of memory regions that the memory manager must
		  handle and enables the API mm_addregion(start, end);
		CONFIG_TICKS_PER_MSEC - The default system timer is 100Hz
		  or TICKS_PER_MSEC=10.  This setting may be defined to
		  inform NuttX that the processor hardware is providing
		  system timer interrupts at some interrupt interval other
		  than 10 msec.
		CONFIG_RR_INTERVAL - The round robin timeslice will be set
		  this number of milliseconds;  Round robin scheduling can
		  be disabled by setting this value to zero.
		CONFIG_SCHED_INSTRUMENTATION - enables instrumentation in 
		  scheduler to monitor system performance
		CONFIG_TASK_NAME_SIZE - Specifies that maximum size of a
		  task name to save in the TCB.  Useful if scheduler
		  instrumentation is selected.  Set to zero to disable.
		CONFIG_START_YEAR, CONFIG_START_MONTH, CONFIG_START_DAY -
		  Used to initialize the internal time logic.
		CONFIG_GREGORIAN_TIME - Enables Gregorian time conversions.
		  You would only need this if you are concerned about accurate
		  time conversions in the past or in the distant future.
		CONFIG_JULIAN_TIME - Enables Julian time conversions. You
		  would only need this if you are concerned about accurate
		  time conversion in the distand past.  You must also define
		  CONFIG_GREGORIAN_TIME in order to use Julian time.
		CONFIG_DEV_CONSOLE - Set if architecture-specific logic
		  provides /dev/console.  Enables stdout, stderr, stdin.
		CONFIG_MUTEX_TYPES - Set to enable support for recursive and
		  errorcheck mutexes.  Enables pthread_mutexattr_settype().
		CONFIG_PRIORITY_INHERITANCE - Set to enable support for
		  priority inheritance on mutexes and semaphores.
		CONFIG_SEM_PREALLOCHOLDERS: This setting is only used if priority
		  inheritance is enabled.  It defines the maximum number of
		  different threads (minus one) that can take counts on a
		  semaphore with priority inheritance support.  This may be 
		  set to zero if priority inheritance is disabled OR if you
		  are only using semaphores as mutexes (only one holder) OR
		  if no more than two threads participate using a counting
		  semaphore.
		CONFIG_SEM_NNESTPRIO.  If priority inheritance is enabled,
		  then this setting is the maximum number of higher priority
		  threads (minus 1) than can be waiting for another thread
		  to release a count on a semaphore.  This value may be set
		  to zero if no more than one thread is expected to wait for
		  a semaphore.
		CONFIG_FDCLONE_DISABLE. Disable cloning of all file descriptors
		  by task_create() when a new task is started.  If set, all
  		  files/drivers will appear to be closed in the new task.
		CONFIG_FDCLONE_STDIO. Disable cloning of all but the first
		  three file descriptors (stdin, stdout, stderr) by task_create()
		  when a new task is started. If set, all files/drivers will
		  appear to be closed in the new task except for stdin, stdout,
		  and stderr.
		CONFIG_SDCLONE_DISABLE. Disable cloning of all socket
		  desciptors by task_create() when a new task is started. If
		  set, all sockets will appear to be closed in the new task.
		CONFIG_NXFLAT. Enable support for the NXFLAT binary format.
		  This format will support execution of NuttX binaries located
		  in a ROMFS filesystem (see examples/nxflat).
		CONFIG_SCHED_WORKQUEUE.  Create a dedicated "worker" thread to
		  handle delayed processing from interrupt handlers.  This feature
		  is required for some drivers but, if there are not complaints,
		  can be safely disabled.  The worker thread also performs
		  garbage collection -- completing any delayed memory deallocations
		  from interrupt handlers.  If the worker thread is disabled,
		  then that clean will be performed by the IDLE thread instead
		  (which runs at the lowest of priority and may not be appropriate
		  if memory reclamation is of high priority).  If CONFIG_SCHED_WORKQUEUE
		  is enabled, then the following options can also be used:
		CONFIG_SCHED_WORKPRIORITY - The execution priority of the worker
		  thread.  Default: 50
		CONFIG_SCHED_WORKPERIOD - How often the worker thread checks for
		  work in units of microseconds.  Default: 50*1000 (50 MS).
		CONFIG_SCHED_WORKSTACKSIZE - The stack size allocated for the worker
		  thread.  Default: CONFIG_IDLETHREAD_STACKSIZE.
		CONFIG_SIG_SIGWORK - The signal number that will be used to wake-up
		  the worker thread.  Default: 4

    OS setup related to on-demand paging:

		CONFIG_PAGING - If set =y in your configation file, this setting will
		  enable the on-demand paging feature as described in
		  http://www.nuttx.org/NuttXDemandPaging.html.

    If CONFIG_PAGING is selected, then you will probabaly need CONFIG_BUILD_2PASS to
    correctly position the code and the following configuration options also apply:

		CONFIG_PAGING_PAGESIZE - The size of one managed page.  This must
		  be a value supported by the processor's memory management unit.
		CONFIG_PAGING_NLOCKED - This is the number of locked pages in the
		  memory map.  The locked address region will then be from
		  CONFIG_DRAM_VSTART through (CONFIG_DRAM_VSTART +
		  CONFIG_PAGING_PAGESIZE*CONFIG_PAGING_NLOCKED)
		CONFIG_PAGING_LOCKED_PBASE and CONFIG_PAGING_LOCKED_VBASE - These
		  may be defined to determine the base address of the locked page
		  regions.  If neither are defined, the logic will be set the bases
		  to CONFIG_DRAM_START and CONFIG_DRAM_VSTART (i.e., it assumes
		  that the base address of the locked region is at the beginning
		  of RAM).
		  NOTE:  In some architectures, it may be necessary to take some
		  memory from the beginning of this region for vectors or for a
		  page table. In such cases, CONFIG_PAGING_LOCKED_P/VBASE should
		  take that into consideration to prevent overlapping the locked
		  memory region and the system data at the beginning of SRAM.
		CONFIG_PAGING_NPPAGED - This is the number of physical pages
		  available to support the paged text region.  This paged region
		  begins at (CONFIG_PAGING_LOCKED_PBASE + CONFIG_PAGING_PAGESIZE*CONFIG_PAGING_NPPAGED)
		  and continues until (CONFIG_PAGING_LOCKED_PBASE + CONFIG_PAGING_PAGESIZE*(CONFIG_PAGING_NLOCKED +
		  CONFIG_PAGING_NPPAGED)
		CONFIG_PAGING_NVPAGED - This actual size of the paged text region
		  (in pages).  This is also the number of virtual pages required to
		  support the entire paged region. The on-demand paging feature is
		  intended to support only the case where the virtual paged text
		  area is much larger the available physical pages.  Otherwise, why
		  would you enable on-demand paging?
		CONFIG_PAGING_NDATA - This is the number of data pages in the memory
		  map.  The data region will extend to the end of RAM unless overridden
		  by a setting in the configuration file.
		  NOTE:  In some architectures, it may be necessary to take some memory
		  from the end of RAM for page tables or other system usage.  The
		  configuration settings and linker directives must be cognizant of that:
		  CONFIG_PAGING_NDATA should be defined to prevent the data region from
		  extending all the way to the end of memory. 
		CONFIG_PAGING_DEFPRIO - The default, minimum priority of the page fill
		  worker thread.  The priority of the page fill work thread will be boosted
		  boosted dynmically so that it matches the priority of the task on behalf
		  of which it peforms the fill.  This defines the minimum priority that
		  will be used. Default: 50.
		CONFIG_PAGING_STACKSIZE - Defines the size of the allocated stack
		  for the page fill worker thread. Default: 1024.
		CONFIG_PAGING_BLOCKINGFILL - The architecture specific up_fillpage()
		  function may be blocking or non-blocking.  If defined, this setting
		  indicates that the up_fillpage() implementation will block until the
		  transfer is completed. Default:  Undefined (non-blocking).
		CONFIG_PAGING_WORKPERIOD - The page fill worker thread will wake periodically
		  even if there is no mapping to do.  This selection controls that wake-up
		  period (in microseconds).  This wake-up a failsafe that will handle any 
		  cases where a single is lost (that would really be a bug and shouldn't
		  happen!) and also supports timeouts for case of non-blocking, asynchronous
		  fills (see CONFIG_PAGING_TIMEOUT_TICKS).
		CONFIG_PAGING_TIMEOUT_TICKS - If defined, the implementation will monitor
 		  the (asynchronous) page fill logic.  If the fill takes longer than this
		  number if microseconds, then a fatal error will be declared.
		  Default: No timeouts monitored.

	    Some architecture-specific settings.  Defaults are architecture specific.
	    If you don't know what you are doing, it is best to leave these undefined
	    and try the system defaults:
 
		CONFIG_PAGING_VECPPAGE - This the physical address of the page in
		  memory to be mapped to the vector address.
		CONFIG_PAGING_VECL2PADDR - This is the physical address of the L2
		  page table entry to use for the vector mapping.
		CONFIG_PAGING_VECL2VADDR - This is the virtual address of the L2
		  page table entry to use for the vector mapping.
		CONFIG_PAGING_BINPATH - If CONFIG_PAGING_BINPATH is defined, then it
		  is the full path to a file on a mounted file system that contains
		  a binary image of the NuttX executable.  Pages will be filled by
		  reading from offsets into this file that correspond to virtual
		  fault addresses.
		CONFIG_PAGING_MOUNTPT - If CONFIG_PAGING_BINPATH is defined, additional
		  options may be provided to control the initialization of underlying
		  devices. CONFIG_PAGING_MOUNTPT identifies the mountpoint to be used
		  if a device is mounted.
		CONFIG_PAGING_MINOR - Some mount operations require a "minor" number
		  to identify the specific device instance. Default: 0
		CONFIG_PAGING_SDSLOT - If CONFIG_PAGING_BINPATH is defined, additional
		  options may be provided to control the initialization of underlying
		  devices. CONFIG_PAGING_SDSLOT identifies the slot number of the SD
		  device to initialize. This must be undefined if SD is not being used.
		  This should be defined to be zero for the typical device that has
		  only a single slot (See CONFIG_MMCSD_NSLOTS). If defined, 
		  CONFIG_PAGING_SDSLOT will instruct certain board-specific logic to
		  initialize the media in this SD slot.
		CONFIG_PAGING_M25PX - Use the m25px.c FLASH driver.  If this is selected,
		  then the MTD interface to the M25Px device will be used to support
		  paging.
		CONFIG_PAGING_AT45DB - Use the at45db.c FLASH driver.  If this is selected,
		  then the MTD interface to the Atmel AT45DB device will be used to support
		  paging.
		CONFIG_PAGING_BINOFFSET - If CONFIG_PAGING_M25PX or is CONFIG_PAGING_AT45DB
                  defined then CONFIG_PAGING_BINOFFSET will be used to specify the offset
		  in bytes into the FLASH device where the NuttX binary image is located.
		  Default: 0
		CONFIG_PAGING_SPIPORT - If CONFIG_PAGING_M25PX CONFIG_PAGING_AT45DB is
                  defined and the device has multiple SPI busses (ports), then this
                  configuration should be set to indicate which SPI port the device is
                  connected. Default: 0

	The following can be used to disable categories of APIs supported
	by the OS.  If the compiler supports weak functions, then it
	should not be necessary to disable functions unless you want to
	restrict usage of those APIs.

	There are certain dependency relationships in these features.

	o mq_notify logic depends on signals to awaken tasks
	  waiting for queues to become full or empty.
	o pthread_condtimedwait() depends on signals to wake
	  up waiting tasks.

		CONFIG_DISABLE_CLOCK, CONFIG_DISABLE_POSIX_TIMERS, CONFIG_DISABLE_PTHREAD.
		CONFIG_DISABLE_SIGNALS, CONFIG_DISABLE_MQUEUE, CONFIG_DISABLE_MOUNTPOUNT,
		CONFIG_DISABLE_ENVIRON, CONFIG_DISABLE_POLL

	Misc libc settings

		CONFIG_NOPRINTF_FIELDWIDTH - sprintf-related logic is a
		   little smaller if we do not support fieldwidthes
		CONFIG_LIBC_FLOATINGPOINT - By default, floating point
		  support in printf, sscanf, etc. is disabled.

	Allow for architecture optimized implementations

		The architecture can provide optimized versions of the
		following to improve system performance

		CONFIG_ARCH_MEMCPY, CONFIG_ARCH_MEMCMP, CONFIG_ARCH_MEMMOVE
		CONFIG_ARCH_MEMSET, CONFIG_ARCH_STRCMP, CONFIG_ARCH_STRCPY
		CONFIG_ARCH_STRNCPY, CONFIG_ARCH_STRLEN, CONFIG_ARCH_STRNLEN
		CONFIG_ARCH_BZERO, CONFIG_ARCH_KMALLOC, CONFIG_ARCH_KZMALLOC
		CONFIG_ARCH_KFREE

	Sizes of configurable things (0 disables)

		CONFIG_MAX_TASKS - The maximum number of simultaneously
		  active tasks.  This value must be a power of two.
		CONFIG_NPTHREAD_KEYS - The number of items of thread-
		  specific data that can be retained
		CONFIG_NFILE_DESCRIPTORS - The maximum number of file
		  descriptors (one for each open)
		CONFIG_NFILE_STREAMS - The maximum number of streams that
		  can be fopen'ed
		CONFIG_NAME_MAX - The maximum size of a file name.
		CONFIG_STDIO_BUFFER_SIZE - Size of the buffer to allocate
		  on fopen. (Only if CONFIG_NFILE_STREAMS > 0)
		CONFIG_NUNGET_CHARS - Number of characters that can be
		  buffered by ungetc() (Only if CONFIG_NFILE_STREAMS > 0)
		CONFIG_PREALLOC_MQ_MSGS - The number of pre-allocated message
		  structures.  The system manages a pool of preallocated
		  message structures to minimize dynamic allocations
		CONFIG_PREALLOC_IGMPGROUPS - Pre-allocated IGMP groups are used
		  only if needed from interrupt level group created (by the IGMP server).
		  Default: 4.
		CONFIG_MQ_MAXMSGSIZE - Message structures are allocated with
		  a fixed payload size given by this settin (does not include
		  other message structure overhead.
		CONFIG_PREALLOC_WDOGS - The number of pre-allocated watchdog
		  structures.  The system manages a pool of preallocated
		  watchdog structures to minimize dynamic allocations
		CONFIG_DEV_PIPE_SIZE - Size, in bytes, of the buffer to allocated
		  for pipe and FIFO support

	Filesystem configuration
		CONFIG_FS_FAT - Enable FAT filesystem support
		CONFIG_FAT_SECTORSIZE - Max supported sector size
		CONFIG_FS_ROMFS - Enable ROMFS filesystem support

	SPI driver
		CONFIG_SPI_OWNBUS - Set if there is only one active device
		  on the SPI bus.  No locking or SPI configuration will be performed.
		  It is not necessary for clients to lock, re-configure, etc..
		CONFIG_SPI_EXCHANGE - Driver supports a single exchange method
		  (vs a recvblock() and sndblock ()methods)

	SPI-based MMC/SD driver
		CONFIG_MMCSD_NSLOTS - Number of MMC/SD slots supported by the
		  driver. Default is one.
		CONFIG_MMCSD_READONLY -  Provide read-only access.  Default is
		  Read/Write
		CONFIG_MMCSD_SPICLOCK - Maximum SPI clock to drive MMC/SD card.
		  Default is 20MHz.

	SDIO-based MMC/SD driver
		CONFIG_FS_READAHEAD - Enable read-ahead buffering
		CONFIG_FS_WRITEBUFFER - Enable write buffering
		CONFIG_SDIO_DMA - SDIO driver supports DMA
		CONFIG_MMCSD_MMCSUPPORT - Enable support for MMC cards
		CONFIG_MMCSD_HAVECARDDETECT - SDIO driver card detection is
		  100% accurate

	RiT P14201 OLED driver
		CONFIG_LCD_P14201 - Enable P14201 support
		CONFIG_P14201_SPIMODE - Controls the SPI mode
		CONFIG_P14201_FREQUENCY - Define to use a different bus frequency
		CONFIG_P14201_NINTERFACES - Specifies the number of physical P14201
		  devices that will be supported.
		CONFIG_P14201_FRAMEBUFFER - If defined, accesses will be performed
		  using an in-memory copy of the OLEDs GDDRAM.  This cost of this
		  buffer is 128 * 96 / 2 = 6Kb.  If this is defined, then the driver
		  will be fully functional. If not, then it will have the following
		  limitations:
		  - Reading graphics memory cannot be supported, and
		  - All pixel writes must be aligned to byte boundaries.
		  The latter limitation effectively reduces the 128x96 disply to 64x96.

	ENC28J60 Ethernet Driver Configuration Settings:
		CONFIG_NET_ENC28J60 - Enabled ENC28J60 support
		CONFIG_ENC28J60_SPIMODE - Controls the SPI mode
		CONFIG_ENC28J60_FREQUENCY - Define to use a different bus frequency
		CONFIG_ENC28J60_NINTERFACES - Specifies the number of physical ENC28J60
		  devices that will be supported.
		CONFIG_ENC28J60_STATS - Collect network statistics
		CONFIG_ENC28J60_HALFDUPPLEX - Default is full duplex

	TCP/IP and UDP support via uIP
		CONFIG_NET - Enable or disable all network features
		CONFIG_NET_IPv6 - Build in support for IPv6
		CONFIG_NSOCKET_DESCRIPTORS - Maximum number of socket descriptors
		per task/thread.
		CONFIG_NET_NACTIVESOCKETS - Maximum number of concurrent socket
		  operations (recv, send, etc.).  Default: CONFIG_NET_TCP_CONNS+CONFIG_NET_UDP_CONNS
		CONFIG_NET_SOCKOPTS - Enable or disable support for socket options

		CONFIG_NET_BUFSIZE - uIP buffer size
		CONFIG_NET_TCPURGDATA - Determines if support for TCP urgent data
		  notification should be compiled in. Urgent data (out-of-band data)
		  is a rarely used TCP feature that is very seldom would be required.
		CONFIG_NET_TCP - TCP support on or off
		CONFIG_NET_TCP_CONNS - Maximum number of TCP connections (all tasks)
		CONFIG_NET_MAX_LISTENPORTS - Maximum number of listening TCP ports (all tasks)
		CONFIG_NET_TCP_READAHEAD_BUFSIZE - Size of TCP read-ahead buffers
		CONFIG_NET_NTCP_READAHEAD_BUFFERS - Number of TCP read-ahead buffers
		  (may be zero)
		CONFIG_NET_TCPBACKLOG - Incoming connections pend in a backlog until
		  accept() is called. The size of the backlog is selected when listen()
		  is called.
		CONFIG_NET_UDP - UDP support on or off
		CONFIG_NET_UDP_CHECKSUMS - UDP checksums on or off
		CONFIG_NET_UDP_CONNS - The maximum amount of concurrent UDP
		  connections
		CONFIG_NET_ICMP - Enable minimal ICMP support. Includes built-in support
		  for sending replies to received ECHO (ping) requests.
		CONFIG_NET_ICMP_PING - Provide interfaces to support application level
		  support for sending ECHO (ping) requests and associating ECHO
		  replies.
		CONFIG_NET_IGMP - Enable IGMPv2 client support.
		CONFIG_PREALLOC_IGMPGROUPS - Pre-allocated IGMP groups are used
		  only if needed from interrupt level group created (by the IGMP server).
		  Default: 4.
		CONFIG_NET_PINGADDRCONF - Use "ping" packet for setting IP address
		CONFIG_NET_STATISTICS - uIP statistics on or off
		CONFIG_NET_RECEIVE_WINDOW - The size of the advertised receiver's
		  window
		CONFIG_NET_ARPTAB_SIZE - The size of the ARP table
		CONFIG_NET_BROADCAST - Incoming UDP broadcast support
		CONFIG_NET_MULTICAST - Outgoing multi-cast address support
		CONFIG_NET_LLH_LEN - The link level header length
		CONFIG_NET_FWCACHE_SIZE - number of packets to remember when
		  looking for duplicates

	UIP Network Utilities
		CONFIG_NET_DHCP_LIGHT - Reduces size of DHCP
		CONFIG_NET_RESOLV_ENTRIES - Number of resolver entries

	THTTPD:
		CONFIG_THTTPD_PORT - THTTPD Server port number
		CONFIG_THTTPD_IPADDR - Server IP address (no host name)
		CONFIG_THTTPD_SERVER_ADDRESS - SERVER_ADDRESS: response
		CONFIG_THTTPD_SERVER_SOFTWARE - SERVER_SOFTWARE: response
		CONFIG_THTTPD_PATH - Server working directory
		CONFIG_THTTPD_CGI_PATH - Path to CGI executables
		CONFIG_THTTPD_CGI_PATTERN - Only CGI programs matching this
		  pattern will be executed.  In fact, if this value is not defined
		  then no CGI logic will be built.
		CONFIG_THTTPD_CGI_PRIORITY - Provides the priority of CGI child tasks
		CONFIG_THTTPD_CGI_STACKSIZE - Provides the initial stack size of
		  CGI child task (will be overridden by the stack size in the NXFLAT
		  header)
		CONFIG_THTTPD_CGI_BYTECOUNT - Byte output limit for CGI tasks.
		CONFIG_THTTPD_CGI_TIMELIMIT - How many seconds to allow CGI programs
		  to run before killing them.
		CONFIG_THTTPD_CHARSET- The default character set name to use with
		  text MIME types.
		CONFIG_THTTPD_IOBUFFERSIZE - 
		CONFIG_THTTPD_INDEX_NAMES - A list of index filenames to check. The
		  files are searched for in this order.
		CONFIG_AUTH_FILE - The file to use for authentication. If this is
		  defined then thttpd checks for this file in the local directory
		  before every fetch. If the file exists then authentication is done,
		  otherwise the fetch proceeds as usual. If you leave this undefined
		  then thttpd will not implement authentication at all and will not
		  check for auth files, which saves a bit of CPU time. A typical
		  value is ".htpasswd"
		CONFIG_THTTPD_LISTEN_BACKLOG - The listen() backlog queue length.
		CONFIG_THTTPD_LINGER_MSEC - How many milliseconds to leave a connection
		  open while doing a lingering close.
		CONFIG_THTTPD_OCCASIONAL_MSEC - How often to run the occasional
		  cleanup job.
		CONFIG_THTTPD_IDLE_READ_LIMIT_SEC - How many seconds to allow for
		 reading the initial request on a new connection.
		CONFIG_THTTPD_IDLE_SEND_LIMIT_SEC - How many seconds before an
		  idle connection gets closed.
		CONFIG_THTTPD_TILDE_MAP1 and CONFIG_THTTPD_TILDE_MAP2 - Tilde mapping.
		  Many URLs use ~username to indicate a user's home directory. thttpd
 		  provides two options for mapping this construct to an  actual filename.
		  1) Map ~username to <prefix>/username. This is the recommended choice.
		    Each user gets a subdirectory in the main web tree, and the tilde
		    construct points there. The prefix could be something like "users",
		    or it could be empty.
		  2) Map ~username to <user's homedir>/<postfix>. The postfix would be
		    the name of a subdirectory off of the user's actual home dir,
		    something like "public_html".
		  You can also leave both options undefined, and thttpd will not do
		  anything special about tildes. Enabling both options is an error.
		  Typical values, if they're defined, are "users" for
		  CONFIG_THTTPD_TILDE_MAP1 and "public_html"forCONFIG_THTTPD_TILDE_MAP2. 
		CONFIG_THTTPD_GENERATE_INDICES
		CONFIG_THTTPD_URLPATTERN - If defined, then it will be used to match
		  and verify referrers.

	USB device controller driver
		CONFIG_USBDEV - Enables USB device support
		CONFIG_USBDEV_ISOCHRONOUS - Build in extra support for isochronous
		  endpoints
		CONFIG_USBDEV_DUALSPEED -Hardware handles high and full speed
		  operation (USB 2.0)
		CONFIG_USBDEV_SELFPOWERED - Will cause USB features to indicate
		  that the device is self-powered
		CONFIG_USBDEV_MAXPOWER - Maximum power consumption in mA
		CONFIG_USBDEV_TRACE - Enables USB tracing for debug
		CONFIG_USBDEV_TRACE_NRECORDS - Number of trace entries to remember

	USB serial device class driver
		CONFIG_USBSER
		  Enable compilation of the USB serial driver
		CONFIG_USBSER_EPINTIN
		  The logical 7-bit address of a hardware endpoint that supports
		  interrupt IN operation
		CONFIG_USBSER_EPBULKOUT
		  The logical 7-bit address of a hardware endpoint that supports
		  bulk OUT operation
		CONFIG_USBSER_EPBULKIN
		  The logical 7-bit address of a hardware endpoint that supports
		  bulk IN operation
		CONFIG_USBSER_NWRREQS and CONFIG_USBSER_NRDREQS
		  The number of write/read requests that can be in flight
		CONFIG_USBSER_VENDORID and CONFIG_USBSER_VENDORSTR
		  The vendor ID code/string
		CONFIG_USBSER_PRODUCTID and CONFIG_USBSER_PRODUCTSTR
		  The product ID code/string
		CONFIG_USBSER_RXBUFSIZE and CONFIG_USBSER_TXBUFSIZE
		  Size of the serial receive/transmit buffers

	USB Storage Device Configuration
		CONFIG_USBSTRG
		  Enable compilation of the USB storage driver
		CONFIG_USBSTRG_EP0MAXPACKET
		  Max packet size for endpoint 0
		CONFIG_USBSTRGEPBULKOUT and CONFIG_USBSTRG_EPBULKIN
		  The logical 7-bit address of a hardware endpoints that support
		  bulk OUT and IN operations
		CONFIG_USBSTRG_NWRREQS and CONFIG_USBSTRG_NRDREQS
		  The number of write/read requests that can be in flight
		CONFIG_USBSTRG_BULKINREQLEN and CONFIG_USBSTRG_BULKOUTREQLEN
		  The size of the buffer in each write/read request.  This
		  value needs to be at least as large as the endpoint
		  maxpacket and ideally as large as a block device sector.
		CONFIG_USBSTRG_VENDORID and CONFIG_USBSTRG_VENDORSTR
		  The vendor ID code/string
		CONFIG_USBSTRG_PRODUCTID and CONFIG_USBSTRG_PRODUCTSTR
		  The product ID code/string
		CONFIG_USBSTRG_REMOVABLE
		  Select if the media is removable

	Graphics related configuration settings

		CONFIG_NX
		  Enables overall support for graphics library and NX
		CONFIG_NX_MULTIUSER
		  Configures NX in multi-user mode
		CONFIG_NX_NPLANES
		  Some YUV color formats requires support for multiple planes,
		  one for each color component.  Unless you have such special
		  hardware, this value should be undefined or set to 1.
		CONFIG_NX_DISABLE_1BPP, CONFIG_NX_DISABLE_2BPP,
		CONFIG_NX_DISABLE_4BPP, CONFIG_NX_DISABLE_8BPP,
		CONFIG_NX_DISABLE_16BPP, CONFIG_NX_DISABLE_24BPP, and
		CONFIG_NX_DISABLE_32BPP
		  NX supports a variety of pixel depths.  You can save some
		  memory by disabling support for unused color depths.
		CONFIG_NX_PACKEDMSFIRST
		  If a pixel depth of less than 8-bits is used, then NX needs
		  to know if the pixels pack from the MS to LS or from LS to MS
		CONFIG_NX_LCDDRIVER
		  By default, NX builds to use a framebuffer driver (see
		  include/nuttx/fb.h). If this option is defined, NX will
		  build to use an LCD driver (see include/nuttx/lcd.h).
		CONFIG_LCD_MAXPOWER - The full-on power setting for an LCD
		  device.
		CONFIG_LCD_MAXCONTRAST - The maximum contrast value for an
		  LCD device.
		CONFIG_NX_MOUSE
		  Build in support for mouse input.
		CONFIG_NX_KBD
		  Build in support of keypad/keyboard input.
		CONFIG_NXTK_BORDERWIDTH
		  Specifies with with of the border (in pixels) used with
		  framed windows.   The default is 4.
		CONFIG_NXTK_BORDERCOLOR1 and CONFIG_NXTK_BORDERCOLOR2
		  Specify the colors of the border used with framed windows.
		  CONFIG_NXTK_BORDERCOLOR2 is the shadow side color and so
		  is normally darker.  The default is medium and dark grey,
		  respectively
		CONFIG_NXTK_AUTORAISE
		  If set, a window will be raised to the top if the mouse position
		  is over a visible portion of the window.  Default: A mouse
		  button must be clicked over a visible portion of the window.
		CONFIG_NXFONTS_CHARBITS
		  The number of bits in the character set.  Current options are
		  only 7 and 8.  The default is 7.
		CONFIG_NXFONT_SANS
		  At present, there is only one font.  But if there were were more,
		  then this option would select the sans serif font.

	NX Multi-user only options:

		CONFIG_NX_BLOCKING
		  Open the client message queues in blocking mode.  In this case,
		  nx_eventhandler() will never return.
		CONFIG_NX_MXSERVERMSGS and CONFIG_NX_MXCLIENTMSGS
		  Specifies the maximum number of messages that can fit in
		  the message queues.  No additional resources are allocated, but
		  this can be set to prevent flooding of the client or server with
		  too many messages (CONFIG_PREALLOC_MQ_MSGS controls how many
		  messages are pre-allocated).

	Stack and heap information

		CONFIG_BOOT_RUNFROMFLASH - Some configurations support XIP
		  operation from FLASH but must copy initialized .data sections to RAM.
		CONFIG_BOOT_COPYTORAM -  Some configurations boot in FLASH
		  but copy themselves entirely into RAM for better performance.
		CONFIG_STACK_POINTER - The initial stack pointer
		CONFIG_IDLETHREAD_STACKSIZE - The size of the initial stack.
		  This is the thread that (1) performs the inital boot of the system up
		  to the point where user_start() is spawned, and (2) there after is the
		  IDLE thread that executes only when there is no other thread ready to
		  run.
		CONFIG_USERMAIN_STACKSIZE - The size of the stack to allocate
		  for the main user thread that begins at the user_start() entry point.
		CONFIG_PTHREAD_STACK_MIN - Minimum pthread stack size
		CONFIG_PTHREAD_STACK_DEFAULT - Default pthread stack size
		CONFIG_HEAP_BASE - The beginning of the heap
		CONFIG_HEAP_SIZE - The size of the heap

setenv.sh -- This is a script that you can include that will be installed at
  the toplevel of the directory structure and can be sourced to set any
  necessary environment variables.

Supported Boards
^^^^^^^^^^^^^^^^

configs/avr32dev1
    This is a port of NuttX to the Atmel AVR32DEV1 board.  That board is
    based on the Atmel AT32UC3B0256 MCU and uses a specially patched
    version of the GNU toolchain:  The patches provide support for the
    AVR32 family.  That patched GNU toolchain is available only from the
    Atmel website.  STATUS: Under development.

configs/c5471evm
    This is a port to the Spectrum Digital C5471 evaluation board.  The
    TMS320C5471 is a dual core processor from TI with an ARM7TDMI general
    purpose processor and a c54 DSP.  It is also known as TMS320DA180 or just DA180. 
    NuttX runs on the ARM core and is built with a GNU arm-elf toolchain*.
    This port is complete, verified, and included in the NuttX release.

configs/demo9s12ne64
    Feescale DMO9S12NE64 board based on the MC9S12NE64 hcs12 cpu.  This
    port uses the m68hc12 GCC toolchain.  STATUS:  Under development.

configs/ea3131
    Embedded Artists EA3131 Development bard.  This board is based on the 
    an NXP LPC3131 MCU. This OS is built with the arm-elf toolchain*.
    STATUS:  This port is complete and reasonably well tested.

configs/eagle100
    Micromint Eagle-100 Development board.  This board is based on the 
    an ARM Cortex-M3 MCU, the Luminary LM3S6918. This OS is built with the
    arm-elf toolchain*.  STATUS:  This port is complete and mature.

configs/ez80f0910200kitg
    ez80Acclaim! Microcontroller.  This port use the Zilog ez80f0910200kitg
    development kit, eZ80F091 part, and the Zilog ZDS-II Windows command line
    tools.  The development environment is Cygwin under WinXP.

configs/ez80f0910200zco
    ez80Acclaim! Microcontroller.  This port use the Zilog ez80f0910200zco
    development kit, eZ80F091 part, and the Zilog ZDS-II Windows command line
    tools.  The development environment is Cygwin under WinXP.

configs/lm3s6965-ek
    Stellaris LM3S6965 Evaluation Kit.  This board is based on the 
    an ARM Cortex-M3 MCU, the Luminary/TI LM3S6965. This OS is built with the
    arm-elf toolchain*.  STATUS:  This port under development.

configs/m68322evb
    This is a work in progress for the venerable m68322evb board from
    Motorola. This OS is also built with the arm-elf toolchain*.

configs/mbed
    The configurations in this directory support the mbed board (http://mbed.org)
    that features the NXP LPC1768 microcontroller.This OS is also built
    with the arm-elf toolchain*.

configs/mcu123-lpc214x
    This port is for the NXP LPC2148 as provided on the mcu123.com
    lpc214x development board. This OS is also built with the arm-elf
    toolchain*.  The port supports serial, timer0, spi, and usb.

configs/mx1ads
    This is a port to the Motorola MX1ADS development board.  That board
    is based on the Freescale i.MX1 processor.  The i.MX1 is an ARM920T.
    STATUS:  This port is nearly code complete but still under development
    (work is stalled until I devote time to the Micromint Eagle-100)

configs/ntosd-dm320
    This port uses the Neuros OSD v1.0 Dev Board with a GNU arm-elf
    toolchain*: see
    
      http://wiki.neurostechnology.com/index.php/OSD_1.0_Developer_Home
 
    There are some differences between the Dev Board and the currently
    available commercial v1.0 Boards.  See
    
      http://wiki.neurostechnology.com/index.php/OSD_Developer_Board_v1

    NuttX operates on the ARM9EJS of this dual core processor.
    STATUS: This port is code complete, verified, and included in the
    NuttX 0.2.1 release.

configs/nucleus2g
    This port uses the Nucleus 2G board (with Babel CAN board).  This board
    features an NXP LPC1768 processor.  See the 2G website (http://www.2g-eng.com/)
    for more information about the Nucleus 2G.

configs/olimex-lpc2378
    This port uses the Olimex Olimex-lpc2378 board arm-elf toolchain* under
    Linux or Cygwin.  STATUS: ostest and NSH configurations available.

configs/olimex-lpc2378
    This port for the NXP LPC2378 was contributed by Rommel Marcelo.

configs/olimex-strp711
    This port uses the Olimex STR-P711 board arm-elf toolchain* under Linux or Cygwin.
    See the http://www.olimex.com/dev/str-p711.html" for futher information.
    STATUS: Coding for the basic port -- serial console and system timer -- is complete
    but untested to problems I am having using OpenOCD with a wiggler clone JTAG.

configs/pjrc-8051
    8051 Microcontroller.  This port uses the PJRC 87C52 development system
    and the SDCC toolchain.   This port is not quite ready for prime time.

configs/sim
    A user-mode port of NuttX to the x86 Linux platform is available.
    The purpose of this port is primarily to support OS feature development.
    This port does not support interrupts or a real timer (and hence no
    round robin scheduler)  Otherwise, it is complete.

    NOTE: This target will not run on Cygwin probably for many reasons but
    first off because it uses some of the same symbols as does cygwin.dll.

configs/skp16c26
    Renesas M16C processor on the Renesas SKP16C26 StarterKit.  This port
    uses the GNU m32c toolchain.

configs/stm3210e-evel
    STMicrco STM3210E-EVAL development board based on the STMicro STM32F103ZET6
    microcontroller (ARM Cortex-M3).  This port uses the GNU Cortex-M3
    toolchain.

configs/us7032evb1
    This is a port of the Hitachi SH-1 on the Hitachi SH-1/US7032EVB1 board.
    STATUS:  Work has just began on this port.

configs/xtrs
    TRS80 Model 3.  This port uses a vintage computer based on the Z80.
    An emulator for this computer is available to run TRS80 programs on a 
    linux platform (http://www.tim-mann.org/xtrs.html).

configs/z16f2800100zcog
    z16f Microcontroller.  This port use the Zilog z16f2800100zcog
    development kit and the Zilog ZDS-II Windows command line tools.  The
    development environment is Cygwin under WinXP.

configs/z80sim
    z80 Microcontroller.  This port uses a Z80 instruction set simulator.
    That simulator can be found in the NuttX CVS at
    http://nuttx.cvs.sourceforge.net/nuttx/misc/sims/z80sim.
    This port also uses the SDCC toolchain (http://sdcc.sourceforge.net/")
    (verified with version 2.6.0).

configs/z8encore000zco
    z8Encore! Microcontroller.  This port use the Zilog z8encore000zco
    development kit, Z8F6403 part, and the Zilog ZDS-II Windows command line
    tools.  The development environment is Cygwin under WinXP.

configs/z8f64200100kit
    z8Encore! Microcontroller.  This port use the Zilog z8f64200100kit
    development kit, Z8F6423 part, and the Zilog ZDS-II Windows command line
    tools.  The development environment is Cygwin under WinXP.

Other ports for the for the TI TMS320DM270, M683222 and for MIPS are in various
states of progress

Configuring NuttX
^^^^^^^^^^^^^^^^^

Configuring NuttX requires only copying

  configs/<board-name>/<config-dir>/Make.def to ${TOPDIR}/Make.defs
  configs/<board-name>/<config-dir>/setenv.sh to ${TOPDIR}/setenv.sh
  configs/<board-name>/<config-dir>/defconfig to ${TOPDIR}/.config

tools/configure.sh
  There is a script that automates these steps.  The following steps will
  accomplish the same configuration:

  cd tools
  ./configure.sh <board-name>/<config-dir>
