README.txt
==========

  This README file discuss discusses the port of NuttX to the Texas
  Instruments DK-TM4C129X Connected Development Kit.

  Description
  -----------
  The Tiva™ C Series TM4C129X Connected Development Kit highlights
  the 120-MHz Tiva C Series TM4C129XNCZAD ARM® Cortex™-M4 based
  microcontroller, including an integrated 10/100 Ethernet MAC +
  PHY as well as many other key features.

  Features
  --------

    - Color LCD interface
    - USB 2.0 OTG | Host | Device port
    - TI wireless EM connection
    - BoosterPack and BoosterPack XL interfaces
    - Quad SSI-supported 512-Mbit Flash memory
    - MicroSD slot
    - Expansion interface headers: MCU high-speed USB ULPI port,
      Ethernet RMII and MII ports External peripheral interface for
      memories, parallel peripherals, and other system functions.
    - In-Circuit Debug Interface (ICDI)

Contents
    - Using OpenOCD and GDB with ICDI
    - Buttons and LEDs
    - Serial Console
    - Networking Support
    - Timers
    - Temperature Sensor
    - DK-TM4129X Configuration Options
    - Configurations

Using OpenOCD and GDB with ICDI
===============================

  Building OpenOCD under Cygwin:

    Refer to configs/olimex-lpc1766stk/README.txt

  Installing OpenOCD in Linux:

      sudo apt-get install openocd

    You can also build openocd from its source:

      git clone http://git.code.sf.net/p/openocd/code openocd
      cd openocd

  Helper Scripts:

    I have been using the on-board In-Circuit Debug Interface (ICDI) interface.
    OpenOCD requires a configuration file.  I keep the one I used last here:

      configs/dk-tm4c129x/tools/dk-tm4c129x.cfg

    However, the "correct" configuration script to use with OpenOCD may
    change as the features of OpenOCD evolve.  So you should at least
    compare that dk-tm4c129x.cfg file with configuration files in
    /usr/share/openocd/scripts.  As of this writing, the configuration
    files of interest were:

      /usr/local/share/openocd/scripts/board/dk-tm4c129x.cfg
      /usr/local/share/openocd/scripts/interface/ti-icdi.cfg
      /usr/local/share/openocd/scripts/target/stellaris_icdi.cfg

    There is also a script on the tools/ directory that I use to start
    the OpenOCD daemon on my system called oocd.sh.  That script will
    probably require some modifications to work in another environment:

    - Possibly the value of OPENOCD_PATH and TARGET_PATH
    - It assumes that the correct script to use is the one at
      configs/dk-tm4c129x/tools/dk-tm4c129x.cfg

  Starting OpenOCD

    If you are in the top-level NuttX build directlory then you should
    be able to start the OpenOCD daemon like:

      oocd.sh $PWD

    The relative path to the oocd.sh script is configs/dk-tm4c129x/tools,
    but that should have been added to your PATH variable when you sourced
    the setenv.sh script.

    Note that OpenOCD needs to be run with administrator privileges in
    some environments (sudo).

  Connecting GDB

    Once the OpenOCD daemon has been started, you can connect to it via
    GDB using the following GDB command:

      arm-nuttx-elf-gdb
      (gdb) target remote localhost:3333

    NOTE:  The name of your GDB program may differ.  For example, with the
    CodeSourcery toolchain, the ARM GDB would be called arm-none-eabi-gdb.

    After starting GDB, you can load the NuttX ELF file:

      (gdb) symbol-file nuttx
      (gdb) monitor reset
      (gdb) monitor halt
      (gdb) load nuttx

    NOTES:

    1. Loading the symbol-file is only useful if you have built NuttX to
       include debug symbols (by setting CONFIG_DEBUG_SYMBOLS=y in the
       .config file).
    2. The MCU must be halted prior to loading code using 'mon reset'
       as described below.

    OpenOCD will support several special 'monitor' commands.  These
    GDB commands will send comments to the OpenOCD monitor.  Here
    are a couple that you will need to use:

     (gdb) monitor reset
     (gdb) monitor halt

    NOTES:

    1. The MCU must be halted using 'mon halt' prior to loading code.
    2. Reset will restart the processor after loading code.
    3. The 'monitor' command can be abbreviated as just 'mon'.

Buttons and LEDs
================

  Buttons
  -------
  There are three push buttons on the board.

    --- ------------ -----------------
    Pin Pin Function Jumper
    --- ------------ -----------------
    PP1 Select SW4   J37 pins 1 and 2
    PN3 Up SW2       J37 pins 3 and 4
    PE5 Down SW3     J37 pins 5 and 6
    --- ------------ -----------------

  LEDs
  ----
  The development board has one tri-color user LED.

    --- ------------ -----------------
    Pin Pin Function Jumper
    --- ------------ -----------------
    PN5 Red LED      J36 pins 1 and 2
    PQ4 Blue LED     J36 pins 3 and 4
    PQ7 Green LED    J36 pins 5 and 6
    --- ------------ -----------------

  If CONFIG_ARCH_LEDS is not defined, this LED is not used by the NuttX
  logic.  APIs are provided to support application control of the LED in
  that case (in include/board.h and src/tm4c_userleds.c).

  If CONFIG_ARCH_LEDS is defined then the usage of the LEDs by Nuttx is
  defined in include/board.h and src/tm4c_autoleds.c. The LEDs are used to
  encode OS-related events as follows:

    SYMBOL                Meaning                     LED state
    -------------------  -----------------------  -------- --------
    LED_STARTED          NuttX has been started     Blue
    LED_HEAPALLOCATE     Heap has been allocated    (No change)
    LED_IRQSENABLED      Interrupts enabled         (No change)
    LED_STACKCREATED     Idle stack created         Green
    LED_INIRQ            In an interrupt            (No change)
    LED_SIGNAL           In a signal handler        (No change)
    LED_ASSERTION        An assertion failed        (No change)
    LED_PANIC            The system has crashed     Blinking OFF/RED
    LED_IDLE             MCU is is sleep mode       (Not used)

  Thus if the LED is GREEN then NuttX has successfully booted and is,
  apparently, running normally.  If the LED is flashing OFF/RED at
  approximately 2Hz, then a fatal error has been detected and the
  system has halted.

Serial Console
==============

  By default, all configurations use UART0 which connects to the USB VCOM
  on the DEBUG port on the TM4C123 ICDI interface:

    UART0 RX - PA.0
    UART0 TX - PA.1

  However, if you use an external RS232 driver, then other options are
  available.  If your serial terminal loses connection with the USB serial
  port each time you power cycle the board, the VCOM option can be very
  painful.

  UART0 TTL level signals are also available at J3 (also at J1):

    DEBUG_TX - J3, pin 13.  Labelled PA1
    DEBUG_RX - J3, pin 15.  Labelled PA0

  Remove the jumper between pins 13-14 and 15-16 to disconnect UART0 from
  the TM4C123 ICDI chip; Connect your external RS-232 driver at pins 13
  and 16.  5v, 3.3v, AND GND are arvailable nearby at J10.

Networking Support
==================

  Networking support via the can be added to NSH by selecting the following
  configuration options.

  Selecting the EMAC peripheral
  -----------------------------

  System Type -> SAM34 Peripheral Support
    CONFIG_TIVA_ETHERNET=y              : Enable the EMAC peripheral

  System Type -> EMAC device driver options
    CONFIG_TIVA_EMAC_NRXDESC=8          : Set aside some RX and TX descriptors/buffers
    CONFIG_TIVA_EMAC_NTXDESC=4
    CONFIG_TIVA_AUTONEG=y               : Use autonegotiation
    CONFIG_TIVA_PHY_INTERNAL=y          : Use the internal PHY
    CONFIG_TIVA_BOARDMAC=y              : Use the MAC address in the FLASH USER0/1 registers

  Networking Support
    CONFIG_NET=y                        : Enable Neworking
    CONFIG_NET_ETHERNET=y               : Support Ethernet data link
    CONFIG_NET_NOINTS=y                 : Should operative at non-interrupt level
    CONFIG_NET_SOCKOPTS=y               : Enable socket operations
    CONFIG_NET_MULTIBUFFER=y            : Multi-packet buffer option required
    CONFIG_NET_ETH_MTU=590              : Maximum packet size (MTU) 1518 is more standard
    CONFIG_NET_ETH_TCP_RECVWNDO=536     : Should be the same as CONFIG_NET_ETH_MTU
    CONFIG_NET_ARP=y                    : Enable ARP
    CONFIG_NET_ARPTAB_SIZE=16           : ARP table size
    CONFIG_NET_ARP_IPIN=y               : Enable ARP address harvesting
    CONFIG_NET_ARP_SEND=y               : Send ARP request before sending data
    CONFIG_NET_TCP=y                    : Enable TCP/IP networking
    CONFIG_NET_TCP_READAHEAD=y          : Support TCP read-ahead
    CONFIG_NET_TCP_WRITE_BUFFERS=y      : Support TCP write-buffering
    CONFIG_NET_TCPBACKLOG=y             : Support TCP/IP backlog
    CONFIG_NET_MAX_LISTENPORTS=20       :
    CONFIG_NET_TCP_READAHEAD_BUFSIZE=536  Read-ahead buffer size
    CONFIG_NET_UDP=y                    : Enable UDP networking
    CONFIG_NET_BROADCAST=y              : Needed for DNS name resolution
    CONFIG_NET_ICMP=y                   : Enable ICMP networking
    CONFIG_NET_ICMP_PING=y              : Needed for NSH ping command
                                        : Defaults should be okay for other options
f Application Configuration -> Network Utilities
    CONFIG_NETDB_DNSCLIENT=y               : Enable host address resolution
    CONFIG_NETUTILS_TELNETD=y           : Enable the Telnet daemon
    CONFIG_NETUTILS_TFTPC=y             : Enable TFTP data file transfers for get and put commands
    CONFIG_NETUTILS_NETLIB=y            : Network library support is needed
    CONFIG_NETUTILS_WEBCLIENT=y         : Needed for wget support
                                        : Defaults should be okay for other options
  Application Configuration -> NSH Library
    CONFIG_NSH_TELNET=y                 : Enable NSH session via Telnet
    CONFIG_NSH_IPADDR=0x0a000002        : Select a fixed IP address
    CONFIG_NSH_DRIPADDR=0x0a000001      : IP address of gateway/host PC
    CONFIG_NSH_NETMASK=0xffffff00       : Netmask
    CONFIG_NSH_NOMAC=y                  : Need to make up a bogus MAC address
                                        : Defaults should be okay for other options

  You can also enable enable the DHCPC client for networks that use
  dynamically assigned address:

  Application Configuration -> Network Utilities
    CONFIG_NETUTILS_DHCPC=y             : Enables the DHCP client

  Networking Support
    CONFIG_NET_UDP=y                    : Depends on broadcast UDP

  Application Configuration -> NSH Library
    CONFIG_NET_BROADCAST=y
    CONFIG_NSH_DHCPC=y                  : Tells NSH to use DHCPC, not
                                        : the fixed addresses

  Using the network with NSH
  --------------------------

  So what can you do with this networking support?  First you see that
  NSH has several new network related commands:

    ifconfig, ifdown, ifup:  Commands to help manage your network
    get and put:             TFTP file transfers
    wget:                    HTML file transfers
    ping:                    Check for access to peers on the network
    Telnet console:          You can access the NSH remotely via telnet.

  You can also enable other add on features like full FTP or a Web
  Server or XML RPC and others.  There are also other features that
  you can enable like DHCP client (or server) or network name
  resolution.

  By default, the IP address of the DK-TM4C129X will be 10.0.0.2 and
  it will assume that your host is the gateway and has the IP address
  10.0.0.1.

    nsh> ifconfig
    eth0    HWaddr 00:e0:de:ad:be:ef at UP
            IPaddr:10.0.0.2 DRaddr:10.0.0.1 Mask:255.255.255.0

  You can use ping to test for connectivity to the host (Careful,
  Window firewalls usually block ping-related ICMP traffic).  On the
  target side, you can:

    nsh> ping 10.0.0.1
    PING 10.0.0.1 56 bytes of data
    56 bytes from 10.0.0.1: icmp_seq=1 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=2 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=3 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=4 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=5 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=6 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=7 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=8 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=9 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=10 time=0 ms
    10 packets transmitted, 10 received, 0% packet loss, time 10100 ms

  NOTE: In this configuration is is normal to have packet loss > 0%
  the first time you ping due to the default handling of the ARP
  table.

  On the host side, you should also be able to ping the DK-TM4C129X:

    $ ping 10.0.0.2

  You can also log into the NSH from the host PC like this:

    $ telnet 10.0.0.2
    Trying 10.0.0.2...
    Connected to 10.0.0.2.
    Escape character is '^]'.
    sh_telnetmain: Session [3] Started

    NuttShell (NSH) NuttX-6.31
    nsh> help
    help usage:  help [-v] [<cmd>]

      [           echo        ifconfig    mkdir       mw          sleep
      ?           exec        ifdown      mkfatfs     ping        test
      cat         exit        ifup        mkfifo      ps          umount
      cp          free        kill        mkrd        put         usleep
      cmp         get         losetup     mh          rm          wget
      dd          help        ls          mount       rmdir       xd
      df          hexdump     mb          mv          sh

    Builtin Apps:
    nsh>

  NOTE:  If you enable this networking as described above, you will
  experience a delay on booting NSH.  That is because the start-up logic
  waits for the network connection to be established before starting
  NuttX.  In a real application, you would probably want to do the
  network bringup on a separate thread so that access to the NSH prompt
  is not delayed.

  This delay will be especially long if the board is not connected to
  a network.  On the order of minutes!  You will probably think that
  NuttX has crashed!  And then, when it finally does come up after
  numerous timeouts and retries, the network will not be available --
  even if the network cable is plugged in later.

  The long delays can be eliminated by using a separate the network
  initialization thread discussed below.  Recovering after the network
  becomes available requires the network monitor feature, also discussed
  below.

  Network Initialization Thread
  -----------------------------
  There is a configuration option enabled by CONFIG_NSH_NETINIT_THREAD
  that will do the NSH network bring-up asynchronously in parallel on
  a separate thread.  This eliminates the (visible) networking delay
  altogether.  This current implementation, however, has some limitations:

    - If no network is connected, the network bring-up will fail and
      the network initialization thread will simply exit.  There are no
      retries and no mechanism to know if the network initialization was
      successful (it could perform a network Ioctl to see if the link is
      up and it now, keep trying, but it does not do that now).

    - Furthermore, there is currently no support for detecting loss of
      network connection and recovery of the connection (similarly, this
      thread could poll periodically for network status, but does not).

  Both of these shortcomings could be eliminated by enabling the network
  monitor:

  Network Monitor
  ---------------
  By default the network initialization thread will bring-up the network
  then exit, freeing all of the resources that it required.  This is a
  good behavior for systems with limited memory.

  If the CONFIG_NSH_NETINIT_MONITOR option is selected, however, then the
  network initialization thread will persist forever; it will monitor the
  network status.  In the event that the network goes down (for example, if
  a cable is removed), then the thread will monitor the link status and
  attempt to bring the network back up.  In this case the resources
  required for network initialization are never released.

  Pre-requisites:

    - CONFIG_NSH_NETINIT_THREAD as described above.

    - CONFIG_TIVA_PHY_INTERRUPTS=y.  The TM4C129X EMAC block supports PHY
      interrupts.  This is true whether the TM4C internal PHY is used or
      if an external PHY is used.  If this option is selected, then support
      for the PHY interrupt will be built in and the following additional
      settings will be automatically selected:

        CONFIG_NETDEV_PHY_IOCTL. Enable PHY IOCTL commands in the Ethernet
        device driver. Special IOCTL commands must be provided by the Ethernet
        driver to support certain PHY operations that will be needed for link
        management. There operations are not complex and are implemented for
        the Atmel SAMA5 family.

        CONFIG_ARCH_PHY_INTERRUPT. This is not a user selectable option.
        Rather, it is set when you select a board that supports PHY
        interrupts.  In most architectures, the PHY interrupt is not
        associated with the Ethernet driver at all; the Tiva architecture is
        an exception. For most other architectures, the PHY interrupt is
        provided via some board-specific GPIO.  In any event, the board-
        specific logic must provide support for the PHY interrupt. To do
        this, the board logic must do two things: (1) It must provide the
        function arch_phy_irq() as described and prototyped in the
        nuttx/include/nuttx/arch.h, and (2) it must select
        CONFIG_ARCH_PHY_INTERRUPT in the board configuration file to
        advertise that it supports arch_phy_irq().

        And a few other things: UDP support is required (CONFIG_NET_UDP) and
        signals must not be disabled (CONFIG_DISABLE_SIGNALS).

  Given those prerequisites, the network monitor can be selected with these
  additional settings.

    System Type -> Tiva Ethernet Configuration
      CONFIG_TIVA_PHY_INTERRUPTS=y          : Enable PHY interrupt support
      CONFIG_ARCH_PHY_INTERRUPT=y           : (auto-selected)
      CONFIG_NETDEV_PHY_IOCTL=y             : (auto-selected)

    Application Configuration -> NSH Library -> Networking Configuration
      CONFIG_NSH_NETINIT_THREAD             : Enable the network initialization thread
      CONFIG_NSH_NETINIT_MONITOR=y          : Enable the network monitor
      CONFIG_NSH_NETINIT_RETRYMSEC=2000     : Configure the network monitor as you like
      CONFIG_NSH_NETINIT_SIGNO=18

Timers
======

  Tiva timers may be enbled in 32-bit periodic mode using these settings.

  This settings enables the "upper half" timer driver:

    Devices Drivers -> Timer Support
      CONFIG_TIMER=y

  These settings enable Tiva timer driver support

    System Type -> Tiva/Stellaris Peripheral Support
      CONFIG_TIVA_TIMER1=y     : For timer 1

    System Type -> Tiva Timer Configuration (using Timer 1)
      CONFIG_TIVA_TIMER_32BIT=y
      CONFIG_TIVA_TIMER32_PERIODIC=y

  These setting enable board-specific logic to initialize the timer logic
  (using Timer 1):

    Board Selection -> Timer driver selection
      CONFIG_DK_TM4C129X_TIMER1=y
      CONFIG_DK_TM4C129X_TIMER_DEVNAME="/dev/timer0"
      CONFIG_DK_TM4C129X_TIMER_TIMEOUT=10000

  There is a simple example at apps/examples/timer that can be used to
  exercise the timers.  The following configuration options can be
  selected to enable that example:

    Application Configure -> Examples -> Timer Example
      CONFIG_EXAMPLES_TIMER=y
      CONFIG_EXAMPLE_TIMER_DEVNAME="/dev/timer0"
      CONFIG_EXAMPLE_TIMER_DELAY=100000
      CONFIG_EXAMPLE_TIMER_NSAMPLES=20

Temperature Sensor
==================

  TMP-1000 Temperature Sensor Driver
  ----------------------------------
  Support for the on-board TMP-100 temperature sensor is available.  This
  uses the driver for the compatible LM-75 part.  To set up the temperature
  sensor, add the following to the NuttX configuration file:

    System Type -> Tiva/Stellaris Peripheral Selection
      CONFIG_TIVA_I2C6=y

    Drivers -> I2C Support
      CONFIG_I2C=y

    Drivers -> Sensors
      CONFIG_LM75=y
      CONFIG_I2C_LM75=y

    Applications -> NSH Library
      CONFIG_NSH_ARCHINIT=y

  Then you can implement logic like the following to use the temperature sensor:

    #include <nuttx/sensors/lm75.h>
    #include <arch/board/board.h>

    ret = tiva_tmp100_initialize("/dev/temp");      /* Register the temperature sensor */
    fd  = open("/dev/temp", O_RDONLY);              /* Open the temperature sensor device */
    ret = ioctl(fd, SNIOC_FAHRENHEIT, 0);           /* Select Fahrenheit */
    bytesread = read(fd, buffer, 8*sizeof(b16_t));  /* Read (8) temperature samples */

  More complex temperature sensor operations are also available.  See the IOCTL
  commands enumerated in include/nuttx/sensors/lm75.h.  Also read the descriptions
  of the tiva_tmp100_initialize() and tiva_tmp100_attach() interfaces in the
  arch/board/board.h file (sames as configs/dk-tm4c129x/include/board.h).

  NSH Command Line Application
  ----------------------------
  There is a tiny NSH command line application at examples/system/lm75 that
  will read the current temperature from an LM75 compatible temperature sensor
  and print the temperature on stdout in either units of degrees Fahrenheit or
  Centigrade.  This tiny command line application is enabled with the following
  configuration options:

    Library
      CONFIG_LIBM=y
      CONFIG_LIBC_FLOATINGPOINT=y

    Applications -> NSH Library
      CONFIG_NSH_ARCHINIT=y

    Applications -> System Add-Ons
      CONFIG_SYSTEM_LM75=y
      CONFIG_SYSTEM_LM75_DEVNAME="/dev/temp"
      CONFIG_SYSTEM_LM75_FAHRENHEIT=y  (or CENTIGRADE)
      CONFIG_SYSTEM_LM75_STACKSIZE=1024
      CONFIG_SYSTEM_LM75_PRIORITY=100

DK-TM4129X Configuration Options
================================

    CONFIG_ARCH - Identifies the arch/ subdirectory.  This should
       be set to:

       CONFIG_ARCH=arm

    CONFIG_ARCH_family - For use in C code:

       CONFIG_ARCH_ARM=y

    CONFIG_ARCH_architecture - For use in C code:

       CONFIG_ARCH_CORTEXM4=y

    CONFIG_ARCH_CHIP - Identifies the arch/*/chip subdirectory

       CONFIG_ARCH_CHIP="tiva"

    CONFIG_ARCH_CHIP_name - For use in C code to identify the exact
       chip:

       CONFIG_ARCH_CHIP_TM4C129XNC

    CONFIG_ARCH_BOARD - Identifies the configs subdirectory and
       hence, the board that supports the particular chip or SoC.

       CONFIG_ARCH_BOARD=dk-tm4c129x (for the DK-TM4129X)

    CONFIG_ARCH_BOARD_name - For use in C code

       CONFIG_ARCH_BOARD_DK_TM4C129X

    CONFIG_ARCH_LOOPSPERMSEC - Must be calibrated for correct operation
       of delay loops

    CONFIG_ENDIAN_BIG - define if big endian (default is little
       endian)

    CONFIG_RAM_SIZE - Describes the installed DRAM (SRAM in this case):

       CONFIG_RAM_SIZE=0x00008000 (32Kb)

    CONFIG_RAM_START - The start address of installed DRAM

       CONFIG_RAM_START=0x20000000

    CONFIG_ARCH_LEDS - Use LEDs to show state. Unique to boards that
       have LEDs

    CONFIG_ARCH_INTERRUPTSTACK - This architecture supports an interrupt
       stack. If defined, this symbol is the size of the interrupt
        stack in bytes.  If not defined, the user task stacks will be
      used during interrupt handling.

    CONFIG_ARCH_STACKDUMP - Do stack dumps after assertions

    CONFIG_ARCH_LEDS -  Use LEDs to show state. Unique to board architecture.

    CONFIG_ARCH_CALIBRATION - Enables some build in instrumentation that
       cause a 100 second delay during boot-up.  This 100 second delay
       serves no purpose other than it allows you to calibratre
       CONFIG_ARCH_LOOPSPERMSEC.  You simply use a stop watch to measure
       the 100 second delay then adjust CONFIG_ARCH_LOOPSPERMSEC until
       the delay actually is 100 seconds.

  There are configurations for disabling support for interrupts GPIO ports.
  Only GPIOP and GPIOQ pins can be used as interrupting sources on the
  TM4C129X.  Additional interrupt support can be disabled if desired to
  reduce memory footprint.

    CONFIG_TIVA_GPIOP_IRQS=y
    CONFIG_TIVA_GPIOQ_IRQS=y

  TM4C129X specific device driver settings

    CONFIG_UARTn_SERIAL_CONSOLE - selects the UARTn for the
       console and ttys0 (default is the UART0).
    CONFIG_UARTn_RXBUFSIZE - Characters are buffered as received.
       This specific the size of the receive buffer
    CONFIG_UARTn_TXBUFSIZE - Characters are buffered before
       being sent.  This specific the size of the transmit buffer
    CONFIG_UARTn_BAUD - The configure BAUD of the UART.  Must be
    CONFIG_UARTn_BITS - The number of bits.  Must be either 7 or 8.
    CONFIG_UARTn_PARTIY - 0=no parity, 1=odd parity, 2=even parity
    CONFIG_UARTn_2STOP - Two stop bits

    CONFIG_TIVA_SSI0 - Select to enable support for SSI0
    CONFIG_TIVA_SSI1 - Select to enable support for SSI1
    CONFIG_SSI_POLLWAIT - Select to disable interrupt driven SSI support.
      Poll-waiting is recommended if the interrupt rate would be to
      high in the interrupt driven case.
    CONFIG_SSI_TXLIMIT - Write this many words to the Tx FIFO before
      emptying the Rx FIFO.  If the SPI frequency is high and this
      value is large, then larger values of this setting may cause
      Rx FIFO overrun errors.  Default: half of the Tx FIFO size (4).

    CONFIG_TIVA_ETHERNET - This must be set (along with CONFIG_NET)
      to build the Tiva Ethernet driver
    CONFIG_TIVA_ETHLEDS - Enable to use Ethernet LEDs on the board.
    CONFIG_TIVA_BOARDMAC - If the board-specific logic can provide
      a MAC address (via tiva_ethernetmac()), then this should be selected.
    CONFIG_TIVA_ETHHDUPLEX - Set to force half duplex operation
    CONFIG_TIVA_ETHNOAUTOCRC - Set to suppress auto-CRC generation
    CONFIG_TIVA_ETHNOPAD - Set to suppress Tx padding
    CONFIG_TIVA_MULTICAST - Set to enable multicast frames
    CONFIG_TIVA_PROMISCUOUS - Set to enable promiscuous mode
    CONFIG_TIVA_BADCRC - Set to enable bad CRC rejection.
    CONFIG_TIVA_DUMPPACKET - Dump each packet received/sent to the console.

Configurations
==============

Each DK-TM4C129X configuration is maintained in a
sub-directory and can be selected as follow:

    cd tools
    ./configure.sh dk-tm4c129x/<subdir>
    cd -
    . ./setenv.sh

Where <subdir> is one of the following:

  nsh:
  ---
    Configures the NuttShell (nsh) located at apps/examples/nsh.  The
    configuration enables the serial VCOM interfaces on UART0.  Support for
    builtin applications is enabled, but in the base configuration no
    builtin applications are selected.

    NOTES:

    1. This configuration uses the mconf-based configuration tool.  To
       change this configuration using that tool, you should:

       a. Build and install the kconfig-mconf tool.  See nuttx/README.txt
          see additional README.txt files in the NuttX tools repository.

       b. Execute 'make menuconfig' in nuttx/ in order to start the
          reconfiguration process.

    2. By default, this configuration uses the CodeSourcery toolchain
       for Windows and builds under Cygwin (or probably MSYS).  That
       can easily be reconfigured, of course.

       CONFIG_HOST_WINDOWS=y                   : Windows
       :CONFIG_WINDOWS_CYGWIN=y                : Cygwin under Windows
       CONFIG_ARMV7M_TOOLCHAIN_CODESOURCERYW=y : CodeSourcry fro Windows (arm-none-eabi-gcc)
       CONFIG_RAW_BINARY=y                     : Output formats: ELF and raw binary

    3. Default stack sizes are large and should really be tuned to reduce
       the RAM footprint:

         CONFIG_SCHED_HPWORKSTACKSIZE=2048
         CONFIG_IDLETHREAD_STACKSIZE=1024
         CONFIG_USERMAIN_STACKSIZE=2048
         CONFIG_PTHREAD_STACK_DEFAULT=2048
         CONFIG_POSIX_SPAWN_PROXY_STACKSIZE=1024
         CONFIG_TASK_SPAWN_DEFAULT_STACKSIZE=2048
         CONFIG_BUILTIN_PROXY_STACKSIZE=1024
         CONFIG_NSH_TELNETD_DAEMONSTACKSIZE=2048
         CONFIG_NSH_TELNETD_CLIENTSTACKSIZE=2048

    4. This configuration has the network enabled by default.  See the
       paragraph "Using the network with NSH" above).

       Networking can be easily be disabled or reconfigured (See see the
       network related configuration settings above in the section entitled
       "Networking").

       By default, this configuration assumes a 10.0.0.xx network.  It
       uses a fixed IP address of 10.0.0.2 and assumes that the host is
       at 10.0.0.1 and that the host provides the default router.  The
       network mask is 255.255.255.0.  These address can be changed by
       modifying the settings in the configuration.  DHCPC can be enabled
       be modifying this default configuration (See the "Networking"
       section above).

       The network initialization thread is enabled in this example.  NSH
       will create a separate thread when it starts to initialize the
       network.  This eliminates start-up delays to bring the network.  This
       feature may be disabled by reverting the configuration described above
       under "Network Initialization Thread"

       The persistent network monitor thread is also available in this
       configuration.  The network monitor will monitor changes in the
       link status and gracefully take the network down when the link is
       lost (for example, if the cable is disconnected) and bring the
       network back up when the link becomes available again (for example,
       if the cable is reconnected).  The paragraph "Network Monitor" above
       for additional information.

    5. I2C6 and support for the on-board TMP-100 temperature sensor are
       enabled.  Also enabled is the NSH 'temp' command that will show the
       current temperature on the command line like:

       nsh> temp
       80.60 degrees Fahrenheit

       [80.6 F in January.  I love living in Costa Rica1]

       The default units is degrees Fahrenheit, but that is easily
       reconfigured.  See the discussin above in the paragraph entitled
       "Temperature Sensor".

  ipv6:
  ----
    This is another version of the NuttShell configuration.  It is very
    similar to the nsh configuration except that it has IPv6 enabled and
    IPv4 disabled.  Several network utilities that are not yet available
    under IPv6 are disabled.

    NOTES:

    1. As of 2015-01-23, this configuration was identical to the nsh
       configuration other than using IPv6.  So all of the notes above
       regarding the nsh configuration apply.

       Telnet does not work with IPv6.

    2. This configuration can be modified to that both IPv4 and IPv6
       are support.  Here is a summary of the additional configuration
       settings requird to support both IPv4 and IPv6:

         CONFIG_NET_IPv4=y
         CONFIG_NET_ARP=y
         CONFIG_NET_ARP_SEND=y (optional)
         CONFIG_NET_ICMP=y
         CONFIG_NET_ICMP_PING=y

         CONFIG_NETDB_DNSCLIENT=y
         CONFIG_NETUTILS_TELNETD=y

         CONFIG_NSH_IPADDR=0x0a000002
         CONFIG_NSH_DRIPADDR=0x0a000001
         CONFIG_NSH_NETMASK=0xffffff00
         CONFIG_NSH_TELNET=y

       Then from NSH, you have both ping and ping6 commands:

         nsh> ping 10.0.0.1
         nsh> ping6 fc00::1

       And from the host you can do similar:

         ping 10.0.0.2
         ping6 fc00::2   (Linux)
         ping -6 fc00::2 (Windows cmd)

       and Telnet again works from the host:

         telnet 10.0.0.2

    3. You can enable IPv6 autonomous address configuration with the
       following changes to the configuration:

       + CONFIG_NET_ICMPv6_AUTOCONF=y
       + CONFIG_ICMPv6_AUTOCONF_DELAYMSEC=100
       + CONFIG_ICMPv6_AUTOCONF_MAXTRIES=5

       - CONFIG_NSH_DRIPv6ADDR_1=0xfc00
       - CONFIG_NSH_DRIPv6ADDR_2=0x0000
       - CONFIG_NSH_DRIPv6ADDR_3=0x0000
       - CONFIG_NSH_DRIPv6ADDR_4=0x0000
       - CONFIG_NSH_DRIPv6ADDR_5=0x0000
       - CONFIG_NSH_DRIPv6ADDR_6=0x0000
       - CONFIG_NSH_DRIPv6ADDR_7=0x0000
       - CONFIG_NSH_DRIPv6ADDR_8=0x0001

       - CONFIG_NSH_IPv6ADDR_1=0xfc00
       - CONFIG_NSH_IPv6ADDR_2=0x0000
       - CONFIG_NSH_IPv6ADDR_3=0x0000
       - CONFIG_NSH_IPv6ADDR_4=0x0000
       - CONFIG_NSH_IPv6ADDR_5=0x0000
       - CONFIG_NSH_IPv6ADDR_6=0x0000
       - CONFIG_NSH_IPv6ADDR_7=0x0000
       - CONFIG_NSH_IPv6ADDR_8=0x0002
       - CONFIG_NSH_IPv6NETMASK_1=0xffff
       - CONFIG_NSH_IPv6NETMASK_2=0xffff
       - CONFIG_NSH_IPv6NETMASK_3=0xffff
       - CONFIG_NSH_IPv6NETMASK_4=0xffff
       - CONFIG_NSH_IPv6NETMASK_5=0xffff
       - CONFIG_NSH_IPv6NETMASK_6=0xffff
       - CONFIG_NSH_IPv6NETMASK_7=0xffff
       - CONFIG_NSH_IPv6NETMASK_8=0xff80
