2013-03-01 20:10:02 +01:00
README
^^^^^^
README for NuttX port to the Stellaris LM4F120 LaunchPad. The Stellaris<69> LM4F120 LaunchPad Evaluation Board is a low-cost evaluation platform for ARM<52> Cortex<65> -M4F-based microcontrollers from Texas Instruments.
Contents
^^^^^^^^
Stellaris LM4F120 LaunchPad
On-Board GPIO Usage
2017-11-22 13:54:47 +01:00
Using OpenOCD and GDB with an FT2232 JTAG emulator
2013-03-01 20:10:02 +01:00
LEDs
2013-03-24 21:40:40 +01:00
Serial Console
2013-03-01 20:10:02 +01:00
USB Device Controller Functions
LM4F120 LaunchPad Configuration Options
Configurations
Stellaris LM4F120 LaunchPad
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The Stellaris<69> LM4F120 LaunchPad Evaluation Kit offers these features:
o A Stellaris<69> LaunchPad Evaluation board (EK-LM4F120XL)
o On-board Stellaris<69> In-Circuit Debug Interface (ICDI)
o Programmable user buttons and an RGB LED for custom applications.
o USB Micro-B plug to USB-A plug cable
Features of the LM4F120H5QR Microcontroller
o 32-bit ARM<52> Cortex<65> -M4F 80-MHz processor core.
o On-chip memory, featuring 256 KB single-cycle Flash up to 40 MHz (a
prefetch buffer improves performance above 40 MHz), 32 KB single-cycle
SRAM; internal ROM loaded with StellarisWare<72> software; 2KB EEPROM
o Two Controller Area Network (CAN) modules, using CAN protocol version
2.0 part A/B and with bit rates up to 1 Mbps
o Universal Serial Bus (USB) controller with USB 2.0 full-speed (12 Mbps)
and low-speed (1.5 Mbps) operation, 32 endpoints, and USB OTG/Host/Device
mode
o Advanced serial integration, featuring: eight UARTs with IrDA, 9-bit, and
ISO 7816 support (one UART with modem status and modem flow control); four
Synchronous Serial Interface (SSI) modules, supporting operation for
Freescale SPI, MICROWIRE, or Texas Instruments synchronous serial
interfaces; four Inter-Integrated Circuit (I2C) modules, providing
Standard (100 Kbps) and Fast (400 Kbps) transmission and support for
sending and receiving data as either a master or a slave
o ARM PrimeCell<6C> 32-channel configurable <20> DMA controller, providing a way to
offload data transfer tasks from the Cortex<65> -M4F processor, allowing for
more efficient use of the processor and the available bus bandwidth
o Analog support, featuring: two 12-bit Analog-to-Digital Converters (ADC)
with 12 analog input channels and a sample rate of one million
samples/second; two analog comparators; 16 digital comparators; on-chip
voltage regulator
o Advanced motion control, featuring: eight Pulse Width Modulation (PWM)
generator blocks, each with one 16-bit counter, two PWM comparators, a
PWM signal generator, a dead-band generator, and an interrupt/ADC-trigger
selector; two PWM fault inputs to promote low-latency shutdown; two
2014-04-14 00:22:22 +02:00
Quadrature Encoder Interface (QEI) modules, with position integrator to
2013-03-01 20:10:02 +01:00
rack encoder position and velocity capture using built-in timer
o Two ARM FiRM-compliant watchdog timers; six 32-bit general-purpose timers
(up to twelve 16-bit); six wide 64-bit general-purpose timers (up to twelve
32-bit); 12 16/32-bit and 12 32/64-bit Capture Compare PWM (CCP) pins
o Up to 43 GPIOs (depending on configuration), with programmable control for
GPIO interrupts and pad configuration, and highly flexible pin muxing
o Lower-power battery-backed Hibernation module with Real-Time Clock
o Multiple clock sources for microcontroller system clock: Precision
Oscillator (PIOSC), Main Oscillator (MOSC), 32.768-kHz external oscillator
for the Hibernation Module, and Internal 30-kHz Oscillator
o Full-featured debug solution with debug access via JTAG and Serial Wire
interfaces, and IEEE 1149.1-1990 compliant Test Access Port (TAP) controller
o Industrial-range (-40<34> C to 85<38> C) RoHS-compliant 64-pin LQFP
On-Board GPIO Usage
===================
PIN SIGNAL(S) LanchPad Function
--- ---------------------------------------- ---------------------------------------
17 PA0/U0RX DEBUG/VCOM, Virtual COM port receive
18 PA1/U0TX DEBUG/VCOM, Virtual COM port transmit
19 PA2/SSIOCLK GPIO, J2 pin 10
20 PA3/SSIOFSS GPIO, J2 pin 9
21 PA4/SSIORX GPIO, J2 pin 8
22 PA5/SSIOTX GPIO, J1 pin 8
2014-04-14 00:22:22 +02:00
23 PA6/I2CLSCL GPIO, J1 pin 9
2013-03-01 20:10:02 +01:00
24 PA7/I2CLSDA GPIO, J1 pin 10
45 PB0/T2CCP0/U1Rx GPIO, J1 pin 3
46 PB1/T2CCP1/U1Tx GPIO, J1 pin 4
47 PB2/I2C0SCL/T3CCP0 GPIO, J2, pin 3
48 PB3/I2C0SDA/T3CCP1 GPIO, J4 pin 3
58 PB4/AIN10/CAN0Rx/SSI2CLK/T1CCP0 GPIO, J1 pin 7
57 PB5/AIN11/CAN0Tx/SSI2FSS/T1CCP1 GPIO, J1 pin 2
01 PB6/SSI2RX/T0CCP0 GPIO, J2 pin 7
04 PB7/SSI2TX/T0CCP1 GPIO, J2 pin 6
52 PC0/SWCLK/T4CCP0/TCK DEBUG/VCOM
51 PC1/SWDIO/T4CCP1/TMS DEBUG/VCOM
50 PC2/T5CCP0/TDI DEBUG/VCOM
49 PC3/SWO/T5CCP1/TDO DEBUG/VCOM
16 PC4/C1-/U1RTS/U1RX/U4RX/WT0CCP0 GPIO, J4 pin 4
15 PC5/C1+/U1CTS/U1TX/U4TX/WT0CCP1 GPIO, J4 pin 5
14 PC6/C0+/U3RX/WT1CCP0 GPIO, J4 pin 6
13 PC7/C0-/U3TX/WT1CCP1 GPIO, J4 pin 7
61 PD0/AIN7/I2C3SCL/SSI1CLK/SSI3CLKWT2CCP0 Connects to PB6 via resistor, GPIO, J3 pin 3
62 PD1/AIN6/I2C3SDA/SSI1Fss/SSI3Fss/WT2CCP1 Connects to PB7 via resistor, GPIO, J3 Pin 4
63 PD2/AIN5/SSI1RX/SSI3RX/WT3CCP0 GPIO, J3 pin 5
64 PD3/AIN4/SSI1TX/SSI3TX/WT3CCP1 GPIO, J3 pin 6
43 PD4/U6RX/USB0DM/WT4CCP0 USB_DM
44 PD5/U6TX/USB0DP/WT4CCP1 USB_DP
53 PD6/U2RX/WT5CCP0 GPIO, J4 pin 8
10 PD7/NMI/U2TX/WT5CCP1 +USB_VBUS, GPIO, J4 pin 9
Used for VBUS detection when
configured as a self-powered USB
Device
09 PE0/AIN3/U7RX GPIO, J2 pin 3
08 PE1/AIN2/U7TX GPIO, J3 pin 7
07 PE2/AIN1 GPIO, J3 pin 8
06 PE3/AIN0 GPIO, J3 pin 9
59 PE4/AIN9/CAN0RX/I2C2SCL/U5RX GPIO, J1 pin 5
60 PE5/AIN8/CAN0TX/I2C2SDA/U5TX GPIO, J1 pin 6
28 PF0/C0O/CAN0RX/NMI/SSI1RX/T0CCP0/U1RTS USR_SW2 (Low when pressed), GPIO, J2 pin 4
29 PF1/C1O/SSI1TX/T0CCP1/TRD1/U1CTS LED_R, GPIO, J3 pin 10
30 PF2/SSI1CLK/T1CCP0/TRD0 LED_B, GPIO, J4 pin 1
31 PF3/CAN0TX/SSI1FSS/T1CCP1/TRCLK LED_G, GPIO, J4 pin 2
05 PF4/T2CCP0 USR_SW1 (Low when pressed), GPIO, J4 pin 10
Using OpenOCD and GDB with an FT2232 JTAG emulator
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Building OpenOCD under Cygwin:
2013-03-16 02:57:34 +01:00
Refer to configs/olimex-lpc1766stk/README.txt
2013-03-01 20:10:02 +01:00
Installing OpenOCD in Linux:
2013-03-16 02:57:34 +01:00
sudo apt-get install openocd
As of this writing, there is no support for the lm4f120 in the package
above. You will have to build openocd from its source (as of this writing
the latest commit was b9b4bd1a6410ff1b2885d9c2abe16a4ae7cb885f):
git clone http://git.code.sf.net/p/openocd/code openocd
cd openocd
Then, add the patches provided by http://openocd.zylin.com/922:
git fetch http://openocd.zylin.com/openocd refs/changes/22/922/14 && git checkout FETCH_HEAD
./bootstrap
./configure --enable-maintainer-mode --enable-ti-icdi
2014-04-14 00:22:22 +02:00
make
2013-03-16 02:57:34 +01:00
sudo make install
For additional help, see http://processors.wiki.ti.com/index.php/Stellaris_Launchpad_with_OpenOCD_and_Linux
2013-03-01 20:10:02 +01:00
Helper Scripts.
2013-03-16 02:57:34 +01:00
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:
2014-04-14 00:22:22 +02:00
2013-03-01 20:10:02 +01:00
configs/lm4f120-launchpad/tools/lm4f120-launchpad.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 lm4f120-launchpad.cfg file with configuration files in
/usr/share/openocd/scripts. As of this writing, the configuration
files of interest were:
2013-03-16 02:57:34 +01:00
/usr/local/share/openocd/scripts/board/ek-lm4f120xl.cfg
/usr/local/share/openocd/scripts/interface/ti-icdi.cfg
/usr/local/share/openocd/scripts/target/stellaris_icdi.cfg
2013-03-01 20:10:02 +01:00
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:
2014-04-14 00:22:22 +02:00
2013-03-01 20:10:02 +01:00
- Possibly the value of OPENOCD_PATH and TARGET_PATH
- It assumes that the correct script to use is the one at
configs/lm4f120-launchpad/tools/lm4f120-launchpad.cfg
Starting OpenOCD
2013-03-16 02:57:34 +01:00
If you are in the top-level NuttX build directlory then you should
be able to start the OpenOCD daemon like:
oocd.sh $PWD
2013-03-01 20:10:02 +01:00
2017-04-26 18:12:13 +02:00
provided that you have the path to the oocd.sh script, configs/lm4f120-launchpad/tools,
added to your PATH variable.
2014-04-14 00:22:22 +02:00
2013-03-20 04:39:17 +01:00
Note that OpenOCD needs to be run with administrator privileges in
some environments (sudo).
2013-03-01 20:10:02 +01:00
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.
2014-04-14 00:22:22 +02:00
2013-03-01 20:10:02 +01:00
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:
2014-04-14 00:22:22 +02:00
2013-03-01 20:10:02 +01:00
(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'.
LEDs
^^^^
2013-03-20 04:39:17 +01:00
The LM4F120 has a single RGB LED. If CONFIG_ARCH_LEDS is defined, then
2013-03-01 20:10:02 +01:00
support for the LaunchPad LEDs will be included in the build. See:
- configs/lm4f120-launchpad/include/board.h - Defines LED constants, types and
prototypes the LED interface functions.
- configs/lm4f120-launchpad/src/lm4f120-launchpad.h - GPIO settings for the LEDs.
- configs/lm4f120-launchpad/src/up_leds.c - LED control logic.
OFF:
- OFF means that the OS is still initializing. Initialization is very fast so
if you see this at all, it probably means that the system is hanging up
somewhere in the initialization phases.
GREEN or GREEN-ish
- This means that the OS completed initialization.
Bluish:
- Whenever and interrupt or signal handler is entered, the BLUE LED is
illuminated and extinguished when the interrupt or signal handler exits.
This will add a BLUE-ish tinge to the LED.
Redish:
- If a recovered assertion occurs, the RED component will be illuminated
briefly while the assertion is handled. You will probably never see this.
Flashing RED:
- In the event of a fatal crash, the BLUE and GREEN components will be
extinguished and the RED component will FLASH at a 2Hz rate.
2013-03-24 21:40:40 +01:00
Serial Console
^^^^^^^^^^^^^^
By default, all configurations use UART0 which connects to the USB VCOM
on the DEBUG port on the LM4F120 LaunchPad:
2014-04-07 23:28:04 +02:00
UART0 RX - PA.0
UART0 TX - PA.1
2013-03-24 21:40:40 +01:00
However, if you use an external RS232 driver, then other options are
available. UART1 has option pin settings and flow control capabilities
that are not available with the other UARTS::
2014-04-07 23:28:04 +02:00
UART1 RX - PB.0 or PC.4 (Need disambiguation in board.h)
UART1 TX - PB.1 or PC.5 (" " " " "" " ")
2013-03-24 21:40:40 +01:00
UART1_RTS - PF.0 or PC.4
UART1_CTS - PF.1 or PC.5
NOTE: board.h currently selects PB.0, PB.1, PF.0 and PF.1 for UART1, but
2014-04-07 23:28:04 +02:00
that can be changed by editing board.h
2013-03-24 21:40:40 +01:00
UART2-5, 7 are also available, UART2 is not recommended because it shares
some pin usage with USB device mode. UART6 is not available because its
only RX/TX pin options are dedicated to USB support.
2014-04-07 23:28:04 +02:00
UART2 RX - PD.6
UART2 TX - PD.7 (Also used for USB VBUS detection)
2013-03-24 21:40:40 +01:00
2014-04-07 23:28:04 +02:00
UART3 RX - PC.6
UART3 TX - PC.7
2013-03-24 21:40:40 +01:00
2014-04-07 23:28:04 +02:00
UART4 RX - PC.4
UART4 TX - PC.5
2013-03-24 21:40:40 +01:00
2014-04-07 23:28:04 +02:00
UART5 RX - PE.4
UART5 TX - PE.5
2013-03-24 21:40:40 +01:00
2014-04-07 23:28:04 +02:00
UART6 RX - PD.4, Not available. Dedicated for USB_DM
UART6 TX - PD.5, Not available. Dedicated for USB_DP
2013-03-24 21:40:40 +01:00
2014-04-07 23:28:04 +02:00
UART7 RX - PE.0
UART7 TX - PE.1
2013-03-24 21:40:40 +01:00
2013-03-01 20:10:02 +01:00
USB Device Controller Functions
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Device Overview
An FT2232 device from Future Technology Devices International Ltd manages
USB-to-serial conversion. The FT2232 is factory configured by Luminary
Micro to implement a JTAG/SWD port (synchronous serial) on channel A and
a Virtual COM Port (VCP) on channel B. This feature allows two simultaneous
communications links between the host computer and the target device using
a single USB cable. Separate Windows drivers for each function are provided
on the Documentation and Software CD.
Debugging with JTAG/SWD
2014-04-14 00:22:22 +02:00
The FT2232 USB device performs JTAG/SWD serial operations under the control
2013-03-01 20:10:02 +01:00
of the debugger or the Luminary Flash Programmer. It also operate as an
In-Circuit Debugger Interface (ICDI), allowing debugging of any external
target board. Debugging modes:
MODE DEBUG FUNCTION USE SELECTED BY
1 Internal ICDI Debug on-board LM4F120 Default Mode
microcontroller over USB
interface.
2 ICDI out to JTAG/SWD The EVB is used as a USB Connecting to an external
header to SWD/JTAG interface to target and starting debug
an external target. software. The red Debug Out
LED will be ON.
3 In from JTAG/SWD For users who prefer an Connecting an external
header external debug interface debugger to the JTAG/SWD
(ULINK, JLINK, etc.) with header.
the EVB.
Virtual COM Port
The Virtual COM Port (VCP) allows Windows applications (such as HyperTerminal)
to communicate with UART0 on the LM4F120 over USB. Once the FT2232 VCP
driver is installed, Windows assigns a COM port number to the VCP channel.
LM4F120 LaunchPad 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_CORTEXM3=y
CONFIG_ARCH_CHIP - Identifies the arch/*/chip subdirectory
CONFIG_ARCH_CHIP=lm
CONFIG_ARCH_CHIP_name - For use in C code to identify the exact
chip:
CONFIG_ARCH_CHIP_LM4F120
CONFIG_ARCH_BOARD - Identifies the configs subdirectory and
hence, the board that supports the particular chip or SoC.
CONFIG_ARCH_BOARD=lm4f120-launchpad (for the LM4F120 LaunchPad)
CONFIG_ARCH_BOARD_name - For use in C code
2013-03-01 22:41:29 +01:00
CONFIG_ARCH_BOARD_LM4F120_LAUNCHPAD
2013-03-01 20:10:02 +01:00
CONFIG_ARCH_LOOPSPERMSEC - Must be calibrated for correct operation
of delay loops
CONFIG_ENDIAN_BIG - define if big endian (default is little
endian)
2013-07-26 18:09:17 +02:00
CONFIG_RAM_SIZE - Describes the installed DRAM (SRAM in this case):
2013-03-01 20:10:02 +01:00
2013-07-26 18:09:17 +02:00
CONFIG_RAM_SIZE=0x00010000 (64Kb)
2013-03-01 20:10:02 +01:00
2013-07-26 18:09:17 +02:00
CONFIG_RAM_START - The start address of installed DRAM
2013-03-01 20:10:02 +01:00
2013-07-26 18:09:17 +02:00
CONFIG_RAM_START=0x20000000
2013-03-01 20:10:02 +01:00
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.
There are configurations for disabling support for interrupts GPIO ports.
GPIOJ must be disabled because it does not exist on the LM4F120.
Additional interrupt support can be disabled if desired to reduce memory
footprint.
2014-12-18 22:19:16 +01:00
CONFIG_TIVA_GPIOA_IRQS=y
CONFIG_TIVA_GPIOB_IRQS=y
CONFIG_TIVA_GPIOC_IRQS=y
CONFIG_TIVA_GPIOD_IRQS=y
CONFIG_TIVA_GPIOE_IRQS=y
CONFIG_TIVA_GPIOF_IRQS=y
CONFIG_TIVA_GPIOG_IRQS=y
CONFIG_TIVA_GPIOH_IRQS=y
CONFIG_TIVA_GPIOJ_IRQS=n << Always
2014-04-14 00:22:22 +02:00
2013-03-01 20:10:02 +01:00
LM4F120 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
2014-12-21 22:23:37 +01:00
CONFIG_TIVA_SSI0 - Select to enable support for SSI0
CONFIG_TIVA_SSI1 - Select to enable support for SSI1
2013-03-01 20:10:02 +01:00
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).
2014-03-08 22:50:26 +01:00
CONFIG_TIVA_ETHERNET - This must be set (along with CONFIG_NET)
2013-03-01 20:10:02 +01:00
to build the Stellaris Ethernet driver
2014-03-08 22:50:26 +01:00
CONFIG_TIVA_ETHLEDS - Enable to use Ethernet LEDs on the board.
CONFIG_TIVA_BOARDMAC - If the board-specific logic can provide
2014-03-08 20:29:09 +01:00
a MAC address (via tiva_ethernetmac()), then this should be selected.
2014-03-08 22:50:26 +01:00
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.
2013-03-01 20:10:02 +01:00
Configurations
^^^^^^^^^^^^^^
Each LM4F120 LaunchPad configuration is maintained in a
sub-directory and can be selected as follow:
2018-05-09 19:41:46 +02:00
tools/configure.sh lm4f120-launchpad/<subdir>
2013-03-01 20:10:02 +01:00
Where <subdir> is one of the following:
2013-03-24 22:37:42 +01:00
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:
2014-04-14 00:22:22 +02:00
2013-03-24 22:37:42 +01:00
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
2015-06-28 16:08:57 +02:00
see additional README.txt files in the NuttX tools repository.
2013-03-24 22:37:42 +01:00
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_LINUX=y : Linux (Cygwin under Windows okay too).
CONFIG_ARMV7M_TOOLCHAIN_BUILDROOT=y : Buildroot (arm-nuttx-elf-gcc)
CONFIG_RAW_BINARY=y : Output formats: ELF and raw binary
