NuttX RTOS Porting Guide

Overview This document provides and overview of the NuttX build and configuration logic and provides hints for the incorporation of new processor/board architectures into the build.

See also arch/README.txt and configs/README.txt.

2.0 Directory Structure

Directory Structure. The general directly layout for NuttX is very similar to the directory structure of the Linux kernel -- at least at the most superficial layers. At the top level is the main makefile and a series of sub-directories identified below and discussed in the following paragraphs:

.
|-- Makefile
|-- Documentation
|   `-- (documentation files)/
|-- arch/
|   |-- <arch-name>/
|   |   |-- include/
|   |   |   |--<chip-name>/
|   |   |   |  `-- (chip-specific header files)
|   |   |   |--<other-chips>/
|   |   |   `-- (architecture-specific header files)
|   |   `-- src/
|   |       |--<chip-name>/
|   |       |  `-- (chip-specific source files)
|   |       |--<other-chips>/
|   |       `-- (architecture-specific source files)
|   `-- <other-architecture directories>/
|-- configs/
|   |-- <board-name>/
|   |   |-- include/
|   |   |   `-- (other board-specific header files)
|   |   |-- src/
|   |   |   `-- (board-specific source files)
|   |   |---<config-name>/
|   |   |   `-- (board configuration-specific source files)
|   |   `---(other configuration sub-directories for this board)/
|   `-- <(other board directories)>/
|-- drivers/
|   |-- Makefile
|   |-- (driver-specific sub-directories)/
|   |   `-- (driver-specific source files)
|   `-- (common driver source files)
|-- examples/
|   `-- (example)/
|       |-- Makefile
|       `-- (example source files)
|-- fs/
|   |-- Makefile
|   |-- (file system-specific sub-directories)/
|   |   `-- (file system-specific source files)
|   `-- (common file system source files)
|-- graphics/
|   |-- Makefile
|   |-- (feature-specific sub-directories)/
|   |   `-- (feature-specific source files library source files)
|   `-- (common graphics-related source files)
|-- include/
|   |-- (standard header files)
|   |-- (standard include sub-directories)
|   |   `-- (more standard header files)
|   |-- (non-standard include sub-directories)
|       `-- (non-standard header files)
|-- lib/
|   |-- Makefile
|   `-- (lib source files)
|-- mm/
|   |-- Makefile
|   `-- (memory management source files)
|-- net/
|   |-- Makefile
|   |-- uip/
|   |   `-- (uip source files)
|   `-- (BSD socket source files)
|-- netutils/
|   |-- Makefile
|   |-- (network feature sub-directories)/
|   |   `-- (network feature source files)
|   `-- (netutils common files)
|-- sched/
|   |-- Makefile
|   `-- (sched source files)
`-- tools/
    `-- (miscellaneous scripts and programs)

Configuration Files. The NuttX configuration consists of:

Processor architecture specific files. These are the files contained in the arch/<arch-name>/ directory and are discussed in a paragraph below.
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, clocking 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.
Board specific configurations. 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 a paragraph below.

2.1 Documentation

General documentation for the NuttX OS resides in this directory.

2.2 arch

2.2.1 Subdirectory Structure

This directory contains several sub-directories, each containing architecture-specific logic. The task of porting NuttX to a new processor consists of add a new subdirectory under arch/ containing logic specific to the new architecture. The complete board port in is defined by the architecture-specific code in this directory (plus the board-specific configurations in the config/ subdirectory). Each architecture must provide a subdirectory, <arch-name> under arch/ with the following characteristics:

<arch-name>/
|-- include/
|   |--<chip-name>/
|   |  `-- (chip-specific header files)
|   |--<other-chips>/
|   |-- arch.h
|   |-- irq.h
|   |-- types.h
|   `-- limits.h
`-- src/
    |--<chip-name>/
    |  `-- (chip-specific source files)
    |--<other-chips>/
    |-- Makefile
    `-- (architecture-specific source files)

2.2.2 Summary of Files

include/<chip-name>/ This sub-directory contains chip-specific header files.
include/arch.h: This is a hook for any architecture specific definitions that may be needed by the system. It is included by include/nuttx/arch.h.
include/types.h: This provides architecture/toolchain-specific definitions for standard types. This file should typedef:
and if the architecture supports 64-bit integers
and finally
Must be defined to the be the size required to hold the interrupt enable/disable state.

This file will be included by include/sys/types.h and be made available to all files.
include/irq.h: This file needs to define some architecture specific functions (usually inline if the compiler supports inlining) and structure. These include:
- struct xcptcontext: This structures represents the saved context of a thread.
- irqstate_t irqsave(void): Used to disable all interrupts.
- void irqrestore(irqstate_t flags): Used to restore interrupt enables to the same state as before irqsave() was called.
This file must also define NR_IRQS, the total number of IRQs supported by the board.


  
    src/<chip-name>/
    This sub-directory contains chip-specific source files.
  
  
    src/Makefile:
    This makefile will be executed to build the targets src/libup.a and
    src/up_head.o.  The up_head.o file holds the entry point into the system
    (power-on reset entry point, for example).  It will be used in
    the final link with libup.a and other system archives to generate the
    final executable.
  
  
    (architecture-specific source files).
    The file include/nuttx/arch.h identifies all of the APIs that must
    be provided by the architecture specific logic.  (It also includes
    arch/<arch-name>/arch.h as described above).



2.2.3 Supported Architectures

   Archictecture- and Chip-Specific Directories.
   All processor architecture-specific directories are maintained in sub-directories of
   the arch/ directory.
   Different chips or SoC's may implement the same processor core.
   Chip-specific logic can be found in sub-directories under the architecture
   directory.
   Current architecture/chip directories are summarized below:


  arch/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 developement.
    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 cygwind.dll.
  

  arch/arm:
    This directory holds common ARM architectures.  At present, this includes
    the following subdirectories:
    
      arch/arm/include and arch/arm/src/common:
          Common ARM logic.
      

      arch/arm/include/c5471 and arch/arm/src/c5471:
        TI TMS320C5471 (also called TMS320DM180 or just C5471).
        NuttX operates on the ARM7 of this dual core processor.
        This port is complete, verified, and included in the NuttX release 0.1.1.
      

      arch/arm/include/dm320 and arch/arm/src/dm320:
        TI TMS320DM320 (also called just DM320).
        NuttX operates on the ARM9EJS of this dual core processor.
        This port complete, verified, and included in the NuttX release 0.2.1.
      

      arch/arm/include/lpc214x and arch/arm/src/lpc214x:
        These directories provide support for NXP LPC214x family of
        processors.
        STATUS: This port is in progress and should be available in the
        nuttx-0.2.5 release.
      

    
  

  configs/mcu123-lpc214x:
    The mcu123.com lpc214x development board.
    This is a work in progress.
  

  arch/m68322
    A work in progress.
  

  arch/pjrc-8051:
    8051 Microcontroller.  This port is not quite ready for prime time.
  

  arch/z16f:
    Zilog z16f Microcontroller.
    This port uses the Zilog z16f2800100zcog Development Kit.
    This port was released with nuttx-0.3.7.
  

    arch/z80:
    This directory holds 8-bit ZiLOG architectures.  At present, this includes the
    Zilog z80, ez80Acclaim! and z8Encore! Microcontrollers.
    
      arch/z80/include and arch/z80/src/common:
          Common logic.
      

      arch/z80/include/z80 and arch/z80/src/z80:
        The Z80 port was released in nuttx-0.3.6 has been verified using only a
        z80 instruction simulator.
        The set 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 and 2.7.0).
      

      arch/z80/include/ez80 and arch/z80/src/ez80:
        The ez80Acclaim! port uses the ZiLOG ez80f0910200kitg development kit, eZ80F091 part,
        with the Zilog ZDS-II Windows command line tools.
        The development environment is Cygwin under WinXP.
        This is a work in progress.  Verified ez80 support will be announced in a future NuttX release.
      

      arch/z80/include/z8 and arch/z80/src/z8:
        The Z8Encore! port uses either the ZiLOG z8encore000zco development kit, Z8F6403 part,
        or the z8f64200100kit development kit, Z8F6423 part with the Zilog ZDS-II Windows command line
        tools.  The development environment is Cygwin under WinXP.
        The initial release, verified only on the ZDS-II ez8 simulator, was released in nuttx-0.3.9.
      
    
    



  Deprecated Architecture Directories.
  The following architecture directories are deprecated.  They have been
  replaced by the logic in arm/arm and will deleted when
  arch/arm is fully verified.


  arch/c5471:
    Replaced with arch/arm/include/c5471 and
    arch/arm/src/c5471.
  


  arch/dm320:
    Replaced with arch/arm/include/dm320 and
    arch/arm/src/dm320.
  



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


2.3 configs

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


2.3.1 Subdirectory Structure

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

<board-name>
|-- include/
|   |-- board.h
|   `-- (board-specific header files)
|-- src/
|   |-- Makefile
|   `-- (board-specific source files)
|-- <config1-dir>
|   |-- Make.defs
|   |-- defconfig
|   `-- setenv.sh
|-- <config2-dir>
|   |-- Make.defs
|   |-- defconfig
|   `-- setenv.sh
|   ...
`-- (other board-specific configuration sub-directories)/


2.3.2 Summary of Files
2.3.2.1 Board Specific Logic

  
    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.
  

2.3.2.2 Board Specific Configuration Sub-Directories

  The configs/<board-name>/ sub-directory holds all of the
  files that are necessary to configure Nuttx for the particular board.
  A board may have various different configurations using the 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).

  The procedure for configuring NuttX is described below,
  This paragraph will describe the contents of these configuration files.


  
    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:
    
    
      As a makefile fragment included in other makefiles, and
      to generate include/nuttx/config.h which is included by
          most C files in the system.
    
  
  
    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.
  


2.3.3 Supported Boards

  All of the specific boards supported by NuttX are identified below.
  These are the specific <board-name>'s that may be used to configure NuttX
  as described below.


  configs/c5471evm:
    This is a port to the Spectrum Digital C5471 evaluation board.  The
    C5471 is a dual core processor from TI with an ARM7TDMI general purpose
    processor and a c54 SDP.  NuttX runs on the ARM core and is built with
    with a GNU arm-elf toolchain* under Linux or Cygwin.
    This port is complete, verified, and included in the NuttX release.
  

  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/m68322evb:
    This is a work in progress for the venerable m68322evb board from
    Motorola.
  

  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* under Linux or Cygwin.
    The port supports serial, timer0, spi, and usb.
  

  configs/ntosd-dm320:
    This port uses the Neuros OSD with a GNU arm-elf toolchain* under Linux or Cygwin.
    See Neuros Wiki
    for futher information.
    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/olimex-strp711:
    This port uses the Olimex STR-P711 board arm-elf toolchain* under Linux or Cygwin.
    See the Olimex web site
    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 under Linux or Cygwin.
    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 developement.
    This port does not support interrupts or a real timer (and hence no
    round robin scheduler)  Otherwise, it is complete.
  

  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
    here.
    This port also the SDCC toolchain
    under Linux or Cygwin(verfied 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/z8encore000zco
    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.
  



  * A customized version of the buildroot
  is available to build these toolchains under Linux or Cygwin.


2.4 drivers


  This directory holds architecture-independent device drivers.

drivers/
|-- Makefile
|-- bch/
|   |-- Make.defs
|   `-- (bch driver source files)
|-- mmcsd/
|   |-- Make.defs
|   `-- (mmcsd driver source files)
|-- net/
|   |-- Make.defs
|   `-- (net driver source files)
|-- usbdev/
|   |-- Make.defs
|   `-- (usbdev driver source files)
`-- (common driver source files)


2.5 examples


  Example and test programs to build against.


2.6 fs


  This directory contains the NuttX file system.
  This file system is described below.

fs/
|-- Makefile
|-- fat/
|   |-- Make.defs
|   `-- (fat file system source files)
|-- romfs/
|   |-- Make.defs
|   `-- (romfs file system source files)
 `-- (common file system source files)


2.7 graphics


  This directory contains files for graphics/video support under NuttX.

graphics/
|-- Makefile
|-- nxglib/
|   |-- Make.defs
|   `-- (NuttX graphics library source files)
|-- nx/
|   |-- Make.defs
|   `-- (Nuttx X-server source files)
`-- (common file system source files)


2.8 include

  This directory holds NuttX header files.
  Standard header files file retained in can be included in the normal fashion:


  include <stdio.h>

  include <sys/types.h>

  etc.


  Directory structure:

include/
|-- (standard header files)
|-- arpa/
|   `-- (standard header files)
|-- net/
|   `-- uip/
|       `-- (uIP specific header files)
|-- netinet/
|   `-- (standard header files)
|-- nuttx/
|   `-- (nuttx specific header files)
`- sys/
    `-- (more standard header files)


2.9 lib

  This directory holds a collection of standard libc-like functions with custom
  interfaces into Nuttx.


2.10 mm

  This is the NuttX memory manager.


2.11 net

  This directory contains the implementation of the socket APIs.
  The subdirectory, uip contians the uIP port.


2.12 netutils

  This directory contains most of the network applications.
  Some of these are original with NuttX (like tftpc and dhcpd) and others were leveraged from the uIP-1.0 apps directory.
  As the uIP apps/README says, these applications "are not all heavily tested."

netutils/
|-- Makefile
|-- dhcp/
|   |-- Make.defs
|   `-- (dhcp source files)
|-- dhcpd/
|   |-- Make.defs
|   `-- (dhcpd source files)
|-- resolv/
|   |-- Make.defs
|   `-- (resolv source files)
|-- smtp/
|   |-- Make.defs
|   `-- (smtp source files)
|-- telnetd/
|   |-- Make.defs
|   `-- (telnetd source files)
|-- tftpc/
|   |-- Make.defs
|   `-- (tftpc source files)
|-- uiplib/
|   |-- Make.defs
|   `-- (uiplib source files)
|-- weblclient/
|   |-- Make.defs
|   `-- (webclient source files)
|-- webserver/
|   |-- Make.defs
|   `-- (webserver source files)
`-- (netutils common files)


2.13 sched

  The files forming core of the NuttX RTOS reside here.


2.14 tools

  This directory holds a collection of tools and scripts to simplify
  configuring, building and maintaining NuttX.

tools/
|-- Makefile.mkconfig
|-- configure.sh
|-- incdir.sh
|-- indent.sh
|-- link.sh
|-- mkconfig.c
|-- mkdeps.sh
|-- mkimage.sh
|-- mknulldeps.sh
|-- unlink.sh
|-- winlink.sh
`-- zipme


2.15 Makefile

  The top-level Makefile in the ${TOPDIR} directory contains all of the top-level control
  logic to build NuttX.
  Use of this Makefile to build NuttX is described below.



  
    
      3.0 Configuring and Building
    
  


3.1 Configuring NuttX

  Manual Configuration.
  Configuring NuttX requires only copying the
  board-specific configuration files into the top level directory which appears in the make files as the make variable, ${TOPDIR}.
  This could be done manually as follows:


  Copy configs/<board-name>/[<config-dir>/]Make.def to ${TOPDIR}/Make.defs,

  
Copy configs/<board-name>/[<config-dir>/]setenv.sh to ${TOPDIR}/setenv.sh, and
  Copy configs/<board-name>/[<config-dir>/]defconfig to ${TOPDIR}/.config


  Where <board-name> is the name of one of the sub-directories of the
  NuttX configs/ directory.
  This sub-directory name corresponds to one of the supported boards
  identified above.
  And <config-dir> is the optional, specific configuration directory for the board.


  Automated Configuration.
  There is a script that automates these steps.  The following steps will
  accomplish the same configuration:

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



  Additional Configuration Steps.
  The remainder of configuration steps will be performed by ${TOPDIR}/Makefile
  the first time the system is built as described below.


3.2 Building NuttX

  Building NuttX.
   Once NuttX has been configured as described above, it may be built as follows:

cd ${TOPDIR}
source ./setenv.sh
make


  The ${TOPDIR} directory holds:


  The top level Makefile that controls the NuttX build.


  That directory also holds:


  The makefile fragment .config that describes the current configuration.
  The makefile fragment Make.defs that provides customized build targers, and
  The shell script setenv.sh that sets up the configuration environment for the build.


The setenv.sh contains Linux/Cygwin environmental settings that are needed for the build.
The specific environmental definitions are unique for each board but should include, as a minimum, updates to the PATH variable to include the full path to the architecture-specific toolchain identified in Make.defs.
The setenv.sh only needs to be source'ed at the beginning of a session.
The system can be re-made subsequently by just typing make.


  First Time Make.
  Additional configuration actions will be taken the first time that system is built.
  These additional steps include:


  Auto-generating the file include/nuttx/config. using the ${TOPDIR}/.config file.
  
Creating a link to ${TOPDIR}/arch/<arch-name>/include at ${TOPDIR}/include/arch.
  
Creating a link to ${TOPDIR}/configs/<board-name>/include at ${TOPDIR}/include/arch/board.
  
Creating a link to ${TOPDIR}/configs/<board-name>/src at ${TOPDIR}/arch/<arch-name>/src/board
  
Creating make dependencies.



  
    
      4.0 Architecture APIs
    
  



  The file include/nuttx/arch.h identifies by prototype all of the APIs that must
  be provided by the architecture specific logic.
  The internal OS APIs that architecture-specific logic must
  interface with also also identified in include/nuttx/arch.h or in
  other header files.


4.1 APIs Exported by Architecture-Specific Logic to NuttX
4.1.1 up_initialize()

Prototype: void up_initialize(void);

Description.
  up_initialize() will be called once during OS
  initialization after the basic OS services have been
  initialized.  The architecture specific details of
  initializing the OS will be handled here.  Such things as
  setting up interrupt service routines, starting the
  clock, and registering device drivers are some of the
  things that are different for each processor and hardware
  platform.


  up_initialize() is called after the OS initialized but
  before the init process has been started and before the
  libraries have been initialized.  OS services and driver
  services are available.


4.1.2 up_idle()
Prototype: void up_idle(void);

Description.
  up_idle() is the logic that will be executed
  when their is no other ready-to-run task.  This is processor
  idle time and will continue until some interrupt occurs to
  cause a context switch from the idle task.


  Processing in this state may be processor-specific. e.g.,
  this is where power management operations might be performed.


4.1.3 up_initial_state()
Prototype: void up_initial_state(FAR _TCB *tcb);

Description.
  A new thread is being started and a new TCB
  has been created. This function is called to initialize
  the processor specific portions of the new TCB.


  This function must setup the intial architecture registers
  and/or  stack so that execution will begin at tcb->start
  on the next context switch.


4.1.4 up_create_stack()
Prototype: STATUS up_create_stack(FAR _TCB *tcb, size_t stack_size);

Description.
  Allocate a stack for a new thread and setup
  up stack-related information in the TCB.


  The following TCB fields must be initialized:


  adj_stack_size: Stack size after adjustment for hardware,
    processor, etc.  This value is retained only for debug
    purposes.
  stack_alloc_ptr: Pointer to allocated stack
  adj_stack_ptr: Adjusted stack_alloc_ptr for HW.  The
    initial value of the stack pointer.


  This API is NOT required if CONFIG_CUSTOM_STACK
  is defined.


Inputs:
  

    tcb: The TCB of new task.
  
  
    stack_size:  The requested stack size.  At least this much
    must be allocated.
  


4.1.5 up_use_stack()
Prototype: 
  STATUS up_use_stack(FAR _TCB *tcb, FAR void *stack, size_t stack_size);


Description.
  Setup up stack-related information in the TCB
  using pre-allocated stack memory.


  The following TCB fields must be initialized:


  adj_stack_size: Stack size after adjustment for hardware,
    processor, etc.  This value is retained only for debug
    purposes.
  stack_alloc_ptr: Pointer to allocated stack
  adj_stack_ptr: Adjusted stack_alloc_ptr for HW.  The
    initial value of the stack pointer.


  This API is NOT required if CONFIG_CUSTOM_STACK
  is defined.


Inputs:

  
    tcb: The TCB of new task.
  
  
    stack_size:  The allocated stack size.
  


4.1.6 up_release_stack()
Prototype: void up_release_stack(FAR _TCB *dtcb);

Description.
  A task has been stopped. Free all stack
  related resources retained int the defunct TCB.


  This API is NOT required if CONFIG_CUSTOM_STACK
  is defined.


4.1.7 up_unblock_task()
Prototype: void up_unblock_task(FAR _TCB *tcb);

Description.
  A task is currently in an inactive task list
  but has been prepped to execute.  Move the TCB to the
  ready-to-run list, restore its context, and start execution.


  This function is called only from the NuttX scheduling
  logic.  Interrupts will always be disabled when this
  function is called.


Inputs:

  tcb: Refers to the tcb to be unblocked.  This tcb is
    in one of the waiting tasks lists.  It must be moved to
    the ready-to-run list and, if it is the highest priority
    ready to run taks, executed.
  


4.1.8 up_block_task()
Prototype: void up_block_task(FAR _TCB *tcb, tstate_t task_state);

Description.
  The currently executing task at the head of
  the ready to run list must be stopped.  Save its context
  and move it to the inactive list specified by task_state.

  This function is called only from the NuttX scheduling
  logic.  Interrupts will always be disabled when this
  function is called.

Inputs:

  tcb: Refers to a task in the ready-to-run list (normally
    the task at the head of the list).  It most be
    stopped, its context saved and moved into one of the
    waiting task lists.  It it was the task at the head
    of the ready-to-run list, then a context to the new
    ready to run task must be performed.
  
  task_state: Specifies which waiting task list should be
    hold the blocked task TCB.
  


4.1.9 up_release_pending()
Prototype: void up_release_pending(void);

Description.
  When tasks become ready-to-run but cannot run because pre-emption
  is disabled, they are placed into a pending task list.
  This function releases and makes ready-to-run all of the tasks that have
  collected in the pending task list.  This can cause a
  context switch if a new task is placed at the head of
  the ready to run list.


  This function is called only from the NuttX scheduling logic when
  pre-emption is re-enabled.  Interrupts will always be disabled when this
  function is called.


4.1.10 up_reprioritize_rtr()
Prototype: void up_reprioritize_rtr(FAR _TCB *tcb, ubyte priority);

Description.
  Called when the priority of a running or
  ready-to-run task changes and the reprioritization will 
  cause a context switch.  Two cases:


  
    The priority of the currently running task drops and the next
    task in the ready to run list has priority.
  
  
    An idle, ready to run task's priority has been raised above the
    the priority of the current, running task and it now has the
    priority.
  


  This function is called only from the NuttX scheduling
  logic.  Interrupts will always be disabled when this
  function is called.


Inputs:

  
    tcb: The TCB of the task that has been reprioritized
  
  
    priority: The new task priority
  


4.1.11 _exit()
Prototype: void _exit(int status) noreturn_function;

Description.
  This function causes the currently executing task to cease
  to exist.  This is a special case of task_delete().


  Unlike other UP APIs, this function may be called
  directly from user programs in various states.  The
  implementation of this function should diable interrupts
  before performing scheduling operations.


4.1.12 up_assert()
Prototype:

  void up_assert(FAR const ubyte *filename, int linenum);

  void up_assert_code(FAR const ubyte *filename, int linenum, int error_code);



Description.
  Assertions may be handled in an architecture-specific
  way.


4.1.13 up_schedule_sigaction()
Prototype:
  void up_schedule_sigaction(FAR _TCB *tcb, sig_deliver_t sigdeliver);


Description.
  This function is called by the OS when one or more
  signal handling actions have been queued for execution.
  The architecture specific code must configure things so
  that the 'igdeliver' callback is executed on the thread
  specified by 'tcb' as soon as possible.


  This function may be called from interrupt handling logic.


  This operation should not cause the task to be unblocked
  nor should it cause any immediate execution of sigdeliver.
  Typically, a few cases need to be considered:


  
    This function may be called from an interrupt handler
    During interrupt processing, all xcptcontext structures
    should be valid for all tasks.  That structure should
    be modified to invoke sigdeliver() either on return
    from (this) interrupt or on some subsequent context
    switch to the recipient task.
  
  
    If not in an interrupt handler and the tcb is NOT
    the currently executing task, then again just modify
    the saved xcptcontext structure for the recipient
    task so it will invoke sigdeliver when that task is
    later resumed.
  
  
    If not in an interrupt handler and the tcb IS the
    currently executing task -- just call the signal
    handler now.
  


  This API is NOT required if CONFIG_DISABLE_SIGNALS
  is defined.


4.1.14 up_allocate_heap()
Prototype: void up_allocate_heap(FAR void **heap_start, size_t *heap_size);

Description.
  The heap may be statically allocated by
  defining CONFIG_HEAP_BASE and CONFIG_HEAP_SIZE.  If these
  are not defined, then this function will be called to
  dynamically set aside the heap region.


  This API is NOT required if CONFIG_HEAP_BASE
  is defined.


4.1.15 up_interrupt_context()
Prototype: boolean up_interrupt_context(void)

Description.
  Return TRUE is we are currently executing in
  the interrupt handler context.


4.1.16 up_disable_irq()
Prototype:
#ifndef CONFIG_ARCH_NOINTC
  void up_disable_irq(int irq);
#endf


Description.
  Disable the IRQ specified by 'irq'
  On many architectures, there are three levels of interrupt enabling: (1)
  at the global level, (2) at the level of the interrupt controller,
  and (3) at the device level.  In order to receive interrupts, they
  must be enabled at all three levels.


  This function implements enabling of the device specified by 'irq'
  at the interrupt controller level if supported by the architecture
  (irqsave() supports the global level, the device level is hardware
  specific).

  If the architecture does not support up_disable_irq,
  CONFIG_ARCH_NOINTC should be defined in the NuttX configuration file.
  Since this API cannot be supported on all architectures, it should be
  avoided in common implementations where possible.


4.1.17 up_enable_irq()
Prototype:
#ifndef CONFIG_ARCH_NOINTC
  void up_enable_irq(int irq);
#endf


Description.
  This function implements disabling of the device specified by 'irq'
  at the interrupt controller level if supported by the architecture
  (irqrestore() supports the global level, the device level is hardware
  specific).


  If the architecture does not support up_disable_irq,
  CONFIG_ARCH_NOINTC should be defined in the NuttX configuration file.
  Since this API cannot be supported on all architectures, it should be
  avoided in common implementations where possible.


4.1.18 up_prioritize_irq()
Prototype:
#ifdef CONFIG_ARCH_IRQPRIO
  void up_enable_irq(int irq);
#endf

Description.
  Set the priority of an IRQ.


  If the architecture supports up_enable_irq,
  CONFIG_ARCH_IRQPRIO should be defined in the NuttX configuration file.
  Since this API cannot be supported on all architectures, it should be
  avoided in common implementations where possible.


4.1.19 up_putc()

Prototype: int up_putc(int ch);
Description.
  This is a debug interface exported by the architecture-specific logic.
  Output one character on the console


4.2 APIs Exported by NuttX to Architecture-Specific Logic

  These are standard interfaces that are exported by the OS
  for use by the architecture specific logic.


4.2.1 os_start()

  To be provided


4.2.2 OS List Management APIs

  To be provided


4.2.3 sched_process_timer()
Prototype: void sched_process_timer(void);

Description.
  This function handles system timer events.
  The timer interrupt logic itself is implemented in the
  architecture specific code, but must call the following OS
  function periodically -- the calling interval must be
  MSEC_PER_TICK.


4.2.4 irq_dispatch()
Prototype: void irq_dispatch(int irq, FAR void *context);

Description.
  This function must be called from the achitecture-
  specific logic in order to dispaly an interrupt to
  the appropriate, registered handling logic.


4.3 LED Support


  A board architecture may or may not have LEDs.
  If the board does have LEDs, then most architectures provide similar LED support that is enabled when CONFIG_ARCH_LEDS
  is selected in the NuttX configuration file.
  This LED support is part of architecture-specific logic and is not managed by the core NuttX logic.
  However, the support provided by each architecture is sufficiently similar that it can be documented here.


4.3.1 Header Files


  LED-related definitions are provided in two header files:
  

    
       LED definitions are provided for each board in the board.h that resides
       in the <board-name>/include/board.h file (which is also
       linked to include/arch/board/board.h when the RTOS is configured).
       Those definitions are discussed below.
    
    
       The board-specific logic provides unique instances of the LED interfaces.
       This is because the implementation of LED support may be very different
       on different boards.
       Prototypes for these board-specific implementations are, however, provided
       in architecture-common header files.
       That header file is usually at <arch-name>/src/common/up_internal.h,
       but could be at other locations in particular architectures.
       These prototypes are discussed below.
    
  


4.3.2 LED Definitions


   The implementation of LED support is very specific to a board architecture. 
   Some boards have several LEDS, others have only one or two. 
   Some have none. 
   Others LED matrices and show alphnumeric data, etc.
   The NuttX logic does not refer to specific LEDS, rather, it refers to an event to be shown on the LEDS
   in whatever manner is appropriate for the board;
   the way that this event is presented depends upon the hardware available on the board.


   The model used by NuttX is that the board can show 8 events defined as follows in <board-name>/include/board.h:

#define LED_STARTED       ??
#define LED_HEAPALLOCATE  ??
#define LED_IRQSENABLED   ??
#define LED_STACKCREATED  ??
#define LED_INIRQ         ??
#define LED_SIGNAL        ??
#define LED_ASSERTION     ??
#define LED_PANIC         ??


  The specific value assigned to each pre-processor variable can be whatever makes the implementation easiest for the board logic.
  The meaning associated with each definition is as follows:


  
    LED_STARTED is the value that describes the setting of the LEDs when the LED logic is first initialized.
    This LED value is set but never cleared.
  
  
    LED_HEAPALLOCATE indicates that the NuttX heap has been configured.
    This is an important place in the boot sequence because if the memory is configured wrong, it will probably crash leaving this LED setting.
    This LED value is set but never cleared.
  
  
    LED_IRQSENABLED indicates that interrupts have been enabled.
    Again, during bring-up (or if there are hardware problems), it is very likely that the system may crash just when interrupts are enabled, leaving this setting on the LEDs.
    This LED value is set but never cleared.
  
  
    LED_STACKCREATED is set each time a new stack is created.
    If set, it means that the system attempted to start at least one new thread.
    This LED value is set but never cleared.
  
  
    LED_INIRQ is set and cleared on entry and exit from each interrupt.
    If interrupts are working okay, this LED will have a dull glow.
  
  
    LED_SIGNAL is set and cleared on entry and exit from a signal handler.
    Signal handlers are tricky so this is especially useful during bring-up or a new architecture.
  
  
    LED_ASSERTION is set if an assertion occurs.
  
  
    LED_PANIC will blink at around 1Hz if the system panics and hangs.
  


4.3.3 Common LED interfaces


  The <arch-name>/src/common/up_internal.h probably has definitions
  like:

/* Defined in board/up_leds.c */

#ifdef CONFIG_ARCH_LEDS
extern void up_ledinit(void);
extern void up_ledon(int led);
extern void up_ledoff(int led);
#else
# define up_ledinit()
# define up_ledon(led)
# define up_ledoff(led)
#endif


   Where:


  
    void up_ledinit(void) is called early in power-up initialization to initialize the LED hardware.
  
  
    up_ledon(int led) is called to instantiate the LED presentation of the event.
    The led argument is one of the definitions provided in <board-name>/include/board.h.
  
  
    up_ledoff(int ledis called to terminate the LED presentation of the event.
    The led argument is one of the definitions provided in <board-name>/include/board.h.
    Note that only LED_INIRQ, LED_SIGNAL, LED_ASSERTION, and LED_PANIC
    indications are terminated.
  



  
    
      5.0 NuttX File System
    
  


Overview.
  NuttX includes an optional, scalable file system.
  This file-system may be omitted altogther; NuttX does not depend on the presence
  of any file system.


Pseudo Root File System.
  Or, a simple in-memory, psuedo file system can be enabled.
  This simple file system can be enabled setting the CONFIG_NFILE_DESCRIPTORS
  option to a non-zero value (see Appendix A).
  This is an in-memory file system because it does not require any
  storage medium or block driver support.
  Rather, file system contents are generated on-the-fly as referenced via
  standard file system operations (open, close, read, write, etc.).
  In this sense, the file system is psuedo file system (in the
  same sense that the Linux /proc file system is also
  referred to as a psuedo file system).



  Any user supplied data or logic can be accessed via the psuedo-file system.
  Built in support is provided for character and block drivers in the
  /dev psuedo file system directory.


Mounted File Systems
  The simple in-memory file system can be extended my mounting block
  devices that provide access to true file systems backed up via some
  mass storage device.
  NuttX supports the standard mount() command that allows
  a block driver to be bound to a mountpoint within the psuedo file system
  and to a file system.
  At present, NuttX supports only the VFAT file system.


Comparison to Linux
  From a programming perspective, the NuttX file system appears very similar
  to a Linux file system.
  However, there is a fundamental difference:
  The NuttX root file system is a psuedo file system and true file systems may be
  mounted in the psuedo file system.
  In the typical Linux installation by comparison, the Linux root file system
  is a true file system and psuedo file systems may be mounted in the true,
  root file system.
  The approach selected by NuttX is intended to support greater scalability
  from the very tiny platform to the moderate platform.



  
    
      6.0 NuttX Device Drivers
    
  



  NuttX supports a variety of device drivers including:
  

    Character Device Drivers,
    Block Device Drivers, and
    Other Specialized Drivers.
  
  These different device driver types are discussed in the following paragraphs.
  Note: device driver support requires that the in-memory, psuedo file system
  is enabled by setting the CONFIG_NFILE_DESCRIPTORS in the NuttX configuration file to a 
  non-zero value.


6.1 Character Device Drivers


  Character device drivers have these properties:


  
    include/nuttx/fs.h.
    All structures and APIs needed to work with character drivers are provided in this header file.
  
  
    struct file_operations.
    Each character device driver must implement an instance of struct file_operations.
    That structure defines a call table with the following methods:
    
     int open(FAR struct file *filp);

     int close(FAR struct file *filp);

     ssize_t read(FAR struct file *filp, FAR char *buffer, size_t buflen);

     ssize_t write(FAR struct file *filp, FAR const char *buffer, size_t buflen);

     off_t seek(FAR struct file *filp, off_t offset, int whence);

     int ioctl(FAR struct file *filp, int cmd, unsigned long arg);

     int poll(FAR struct file *filp, struct pollfd *fds, boolean setup);
    
  
  
    int register_driver(const char *path, const struct file_operations *fops, mode_t mode, void *priv);.
    Each character driver registers itself by calling register_driver(), passing it the
    path where it will appear in the pseudo-file-system and it's
    initialized instance of struct file_operations.
  
  
    User Access.
    After it has been registered, the character driver can be accessed by user code using the standard
    driver operations including
    open(), close(), read(), write(), etc.
  
  
    Examples:
    drivers/dev_null.c, drivers/fifo.c, drivers/serial.c, etc.
  


6.2 Block Device Drivers


  Block device drivers have these properties:


  
    include/nuttx/fs.h.
    All structures and APIs needed to work with block drivers are provided in this header file.
  
  
    struct block_operations.
    Each block device driver must implement an instance of struct block_operations.
    That structure defines a call table with the following methods:
    
     int open(FAR struct inode *inode);

     int close(FAR struct inode *inode);

     ssize_t read(FAR struct inode *inode, FAR unsigned char *buffer, size_t start_sector, unsigned int nsectors);

     ssize_t write(FAR struct inode *inode, FAR const unsigned char *buffer, size_t start_sector, unsigned int nsectors);

     int geometry(FAR struct inode *inode, FAR struct geometry *geometry);

     int ioctl(FAR struct inode *inode, int cmd, unsigned long arg);
    
  
  
    int register_blockdriver(const char *path, const struct block_operations *bops, mode_t mode, void *priv);.
    Each block driver registers itself by calling register_blockdriver(), passing it the
    path where it will appear in the pseudo-file-system and it's
    initialized instance of struct block_operations.
  
  
    User Access.
    Users do not normally access block drivers directly, rather, they access block drivers
    indirectly through the mount() API.
    The mount() API binds a block driver instance with a file system and with a mountpoint.
    Then the user may use the block driver to access the file system on the underlying media.
    Example: See the cmd_mount() implementation in examples/nsh/nsh_fscmds.c.
  
  
    Accessing a Character Driver as a Block Device.
    See the loop device at drivers/loop.c.
    Example: See the cmd_losetup() implementation in examples/nsh/nsh_fscmds.c.
  
  
    Accessing a Block Driver as Character Device.
    See the Block-to-Character (BCH) conversion logic in drivers/bch/.
    Example: See the cmd_dd() implementation in examples/nsh/nsh_ddcmd.c.
  
  
    Examples.
    drivers/loop.c, drivers/mmcds/mmcsd_spi.c, drivers/ramdisk.c, etc.
  


6.3 Specialized Device Drivers

6.3.1 Ethernet Device Drivers


  
    include/net/uip/uip-arch.h.
    All structures and APIs needed to work with Ethernet drivers are provided in this header file.
    The structure struct uip_driver_s defines the interface and is passed to uIP via
    netdev_register().
  
  
    int netdev_register(FAR struct uip_driver_s *dev);.
    Each Eterhenet driver registers itself by calling netdev_register().
  
  
    Examples:
    drivers/net/dm90x0.c, arch/drivers/arm/src/c5471/c5471_ethernet.c, arch/z80/src/ez80/ez80_emac.c, etc.
  


6.3.2 SPI Device Drivers


  
    include/nuttx/spi.h.
    All structures and APIs needed to work with SPI drivers are provided in this header file.
  
  
    struct spi_ops_s.
    Each SPI device driver must implement an instance of struct spi_ops_s.
    That structure defines a call table with the following methods:
    
     void select(FAR struct spi_dev_s *dev, enum spi_dev_e devid, boolean selected);

     uint32 setfrequency(FAR struct spi_dev_s *dev, uint32 frequency);

     void setmode(FAR struct spi_dev_s *dev, enum spi_mode_e mode);

     void setbits(FAR struct spi_dev_s *dev, int nbits);

     ubyte status(FAR struct spi_dev_s *dev, enum spi_dev_e devid);

     uint16 send(FAR struct spi_dev_s *dev, uint16 wd);

     void exchange(FAR struct spi_dev_s *dev, FAR const void *txbuffer, FAR void *rxbuffer, size_t nwords);

     nt registercallback(FAR struct spi_dev_s *dev, mediachange_t callback, void *arg);
  
  

    Binding SPI Drivers.
    SPI drivers are not normally directly accessed by user code, but are usually bound to another,
    higher level device driver.
    See for example, int mmcsd_spislotinitialize(int minor, int slotno, FAR struct spi_dev_s *spi) in drivers/mmcsd/mmcsd_spi.c.
  
  
    Examples:
    drivers/loop.c, drivers/mmcds/mmcsd_spi.c, drivers/ramdisk.c, etc.
  


6.3.3 I2C Device Drivers


  
    include/nuttx/i2c.h.
    All structures and APIs needed to work with I2C drivers are provided in this header file.
  
  
    struct i2c_ops_s.
    Each I2C device driver must implement an instance of struct i2c_ops_s.
    That structure defines a call table with the following methods:
    
     uint32 setfrequency(FAR struct i2c_dev_s *dev, uint32 frequency);

     int setaddress(FAR struct i2c_dev_s *dev, int addr, int nbits);

     int write(FAR struct i2c_dev_s *dev, const ubyte *buffer, int buflen);

     int read(FAR struct i2c_dev_s *dev, ubyte *buffer, int buflen);
  
  

    Binding I2C Drivers.
    SPI drivers are not normally directly accessed by user code, but are usually bound to another,
    higher level device driver.
  
  
    Examples:
    arch/z80/src/ez80/ez80_i2c.c, arch/z80/src/z8/z8_i2c.c, etc.
  


6.3.4 Serial Device Drivers


  
    include/nuttx/serial.h.
    All structures and APIs needed to work with serial drivers are provided in this header file.
  
  
    struct uart_ops_s.
    Each serial device driver must implement an instance of struct uart_ops_s.
    That structure defines a call table with the following methods:
    
     int setup(FAR struct uart_dev_s *dev);

     void shutdown(FAR struct uart_dev_s *dev);

     int attach(FAR struct uart_dev_s *dev);

     void detach(FAR struct uart_dev_s *dev);

     int ioctl(FAR struct file *filep, int cmd, unsigned long arg);

     int receive(FAR struct uart_dev_s *dev, unsigned int *status);

     void rxint(FAR struct uart_dev_s *dev, boolean enable);

     boolean rxavailable(FAR struct uart_dev_s *dev);

     void send(FAR struct uart_dev_s *dev, int ch);

     void txint(FAR struct uart_dev_s *dev, boolean enable);

     boolean txready(FAR struct uart_dev_s *dev);

     boolean txempty(FAR struct uart_dev_s *dev);
    
  
  
    int uart_register(FAR const char *path, FAR uart_dev_t *dev);.
    A serial driver may register itself by calling uart_register(), passing it the
    path where it will appear in the pseudo-file-system and it's
    initialized instance of struct uart_ops_s.
    By convention, serial device drivers are registered at pathes like /dev/ttyS0, /dev/ttyS1, etc.
    See the uart_register() implementation in drivers/serial.c.
  
  
    User Access.
    Serial drivers are, ultimately, normal character drivers and are accessed as other character drivers.
  
  
    Examples:
    arch/arm/src/chip/lm3s_serial.c, arch/arm/src/lpc214x/lpc214x_serial.c, arch/z16/src/z16f/z16f_serial.c, etc.
  



  
    
      Appendix A:  NuttX Configuration Settings
    
  



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


Architecture selection

  The following configuration itemes select the architecture, chip, and
  board configuration for the build.


  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 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
    This option hould 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:
    mmke 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.
  


General OS setup


  
    CONFIG_EXAMPLE: identifies the subdirectory in examples
    that will be used in the build.
  
  
    CONFIG_DEBUG: enables built-in debug options
  
  
    CONFIG_DEBUG_VERBOSE: enables verbose debug output
  
  
    CONFIG_DEBUG_SCHED: enable OS debug output (disabled by default)
  
  
    CONFIG_DEBUG_MM: enable memory management debug output (disabld by default)
  
  
    CONFIG_DEBUG_NET: enable network debug output (disabled by default)
  
  
    CONFIG_DEBUG_FS: enable file system debug output (disabled by default)
  
  
    CONFIG_DEBUG_LIB: enable C library 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: Spcifies 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_JULIAN_TIME: Enables Julian time conversions
  
  
    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.
    Priority inheritance is a strategy of addessing
    priority inversion.
    Details of the NuttX implementation of priority inheritance is
    discussed elsewhere.
  
  
    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.
  



  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.


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



    CONFIG_DISABLE_CLOCK, CONFI_DISABLE_POSIX_TIMERS,
    CONFIG_DISABLE_PTHREAD, CONFIG_DISABLE_SIGNALS,
    CONFIG_DISABLE_MQUEUE, CONFIG_DISABLE_MOUNTPOUNT


Miscellaneous libc settings


  
    CONFIG_NOPRINTF_FIELDWIDTH: sprintf-related logic is a
    little smaller if we do not support fieldwidthes
  


Allow for architecture optimized implementations


  The architecture can provide optimized versions of the
  following to improve sysem 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_BZERO,
  CONFIG_ARCH_KMALLOC, CONFIG_ARCH_KZMALLOC, ONFIG_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_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 (default is 1024).
  


File Systems

  
    CONFIG_FS_FAT: Enable FAT filesystem support.
  
  
    CONFIG_FAT_SECTORSIZE: Max supported sector size.
  
  
    CONFIG_FS_ROMFS: Enable ROMFS filesystem support
  


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
  


Network Support
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_TCP: TCP support on or off
  
  
    CONFIG_NET_TCP_CONNS: Maximum number of TCP connections (all tasks).
  
  
    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_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_MAX_LISTENPORTS: Maximum number of listening TCP ports (all tasks).
  
  
    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_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_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
  


USB Device-Side Support
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
  


NX configuration setting

  
    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_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 not return until a message is received and processed.
  
  
    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
  



  
    
      Appendix B:  Trademarks
    
  


  ARM, ARM7 ARM7TDMI, ARM9, ARM920T, ARM926EJS, Cortex-M3 are trademarks of Advanced RISC Machines, Limited.
  Cygwin is a trademark of Red Hat, Incorporated.
  Linux is a registered trademark of Linus Torvalds.
  Eagle-100 is a trademark of Micromint USA, LLC.
  
LPC2148 is a trademark of NXP Semiconductors.
  TI is a tradename of Texas Instruments Incorporated.
  UNIX is a registered trademark of The Open Group.
  VxWorks is a registered trademark of Wind River Systems, Incorporated.
  ZDS, ZNEO, Z16F, Z80, and Zilog are a registered trademark of Zilog, Inc.


  NOTE: NuttX is not licensed to use the POSIX trademark.  NuttX uses the POSIX
  standard as a development guideline only.

NuttX RTOS Porting Guide

Table of Contents

1.0 Introduction

2.0 Directory Structure

2.1 Documentation

2.2 arch

2.3 configs

2.4 drivers

2.5 examples

2.6 fs

2.7 graphics

2.8 include

2.9 lib

2.10 mm

2.11 net

2.12 netutils

2.13 sched

2.14 tools

2.15 Makefile

3.0 Configuring and Building

4.0 Architecture APIs

Architecture selection

General OS setup

Miscellaneous libc settings

Allow for architecture optimized implementations

Sizes of configurable things (0 disables)

File Systems

SPI-based MMC/SD driver

Network Support

TCP/IP and UDP support via uIP

UIP Network Utilities

USB Device-Side Support

USB Device Controller Driver

USB Serial Device Class Driver

USB Storage Device Configuration

Graphics related configuration settings

NX configuration setting

NX Multi-user only options

Stack and heap information