README
======
This README discusses issues unique to NuttX configurations for the Shenzhou
IV development board from www.armjishu.com featuring the STMicro STM32F107VCT
MCU. As of this writing, there are five models of the Shenzhou board:
1. Shenzhou I (STM32F103RB)
2. Shenzhou II (STM32F103VC)
3. Shenzhou III (STM32F103ZE)
4. Shenzhou IV (STM32F107VC)
5. Shenzhou king ((STM32F103ZG, core board + IO expansion board)).
Support is currently provided for the Shenzhou IV only. Features of the
Shenzhou IV board include:
- STM32F107VCT
- 10/100M PHY (DM9161AEP)
- TFT LCD Connector
- USB OTG
- CAN (CAN1=2)
- USART connectos (USART1-2)
- RS-485
- SD card slot
- Audio DAC (PCM1770)
- SPI Flash (W25X16)
- (4) LEDs (LED1-4)
- 2.4G Wireless (NRF24L01 SPI module)
- 315MHz Wireless (module)
- (4) Buttons (KEY1-4, USERKEY2, USERKEY, TEMPER, WAKEUP)
- VBUS/external +4V select
- 5V/3.3V power conversion
- Extension connector
- JTAG
Contents
========
- STM32F107VCT Pin Usage
- Shenzhou-specific Configuration Options
- LEDs
- Shenzhou-specific Configuration Options
- Configurations
STM32F107VCT Pin Usage
======================
-- ---- -------------- -------------------------------------------------------------------
PN NAME SIGNAL NOTES
-- ---- -------------- -------------------------------------------------------------------
23 PA0 WAKEUP Connected to KEY4. Active low: Closing KEY4 pulls WAKEUP to ground.
24 PA1 MII_RX_CLK
RMII_REF_CLK
25 PA2 MII_MDIO
26 PA3 315M_VT
29 PA4 DAC_OUT1 To CON5(CN14)
30 PA5 DAC_OUT2 To CON5(CN14). JP10
SPI1_SCK To the SD card, SPI FLASH
31 PA6 SPI1_MISO To the SD card, SPI FLASH
32 PA7 SPI1_MOSI To the SD card, SPI FLASH
67 PA8 MCO To DM9161AEP PHY
68 PA9 USB_VBUS MINI-USB-AB. JP3
USART1_TX MAX3232 to CN5
69 PA10 USB_ID MINI-USB-AB. JP5
USART1_RX MAX3232 to CN5
70 PA11 USB_DM MINI-USB-AB
71 PA12 USB_DP MINI-USB-AB
72 PA13 TMS/SWDIO
76 PA14 TCK/SWCLK
77 PA15 TDI
-- ---- -------------- -------------------------------------------------------------------
PN NAME SIGNAL NOTES
-- ---- -------------- -------------------------------------------------------------------
35 PB0 ADC_IN1 To CON5(CN14)
36 PB1 ADC_IN2 To CON5(CN14)
37 PB2 DATA_LE To TFT LCD (CN13)
BOOT1 JP13
89 PB3 TDO/SWO
90 PB4 TRST
91 PB5 CAN2_RX
92 PB6 CAN2_TX JP11
I2C1_SCL
93 PB7 I2C1_SDA
95 PB8 USB_PWR Drives USB VBUS
96 PB9 F_CS To both the TFT LCD (CN13) and to the W25X16 SPI FLASH
47 PB10 USERKEY Connected to KEY2
48 PB11 MII_TX_EN Ethernet PHY
51 PB12 I2S_WS Audio DAC
MII_TXD0 Ethernet PHY
52 PB13 I2S_CK Audio DAC
MII_TXD1 Ethernet PHY
53 PB14 SD_CD There is confusion here. Schematic is wrong LCD_WR is PB14.
54 PB15 I2S_DIN Audio DAC
-- ---- -------------- -------------------------------------------------------------------
PN NAME SIGNAL NOTES
-- ---- -------------- -------------------------------------------------------------------
15 PC0 POTENTIO_METER
16 PC1 MII_MDC Ethernet PHY
17 PC2 WIRELESS_INT
18 PC3 WIRELESS_CE To the NRF24L01 2.4G wireless module
33 PC4 USERKEY2 Connected to KEY1
34 PC5 TP_INT JP6. To TFT LCD (CN13) module
MII_INT Ethernet PHY
63 PC6 I2S_MCK Audio DAC. Active low: Pulled high
64 PC7 PCM1770_CS Audio DAC. Active low: Pulled high
65 PC8 LCD_CS TFT LCD (CN13). Active low: Pulled high
66 PC9 TP_CS TFT LCD (CN13). Active low: Pulled high
78 PC10 SPI3_SCK To TFT LCD (CN13), the NRF24L01 2.4G wireless module
79 PC11 SPI3_MISO To TFT LCD (CN13), the NRF24L01 2.4G wireless module
80 PC12 SPI3_MOSI To TFT LCD (CN13), the NRF24L01 2.4G wireless module
7 PC13 TAMPER Connected to KEY3
8 PC14 OSC32_IN Y1 32.768Khz XTAL
9 PC15 OSC32_OUT Y1 32.768Khz XTAL
-- ---- -------------- -------------------------------------------------------------------
PN NAME SIGNAL NOTES
-- ---- -------------- -------------------------------------------------------------------
81 PD0 CAN1_RX
82 PD1 CAN1_TX
83 PD2 LED1 Active low: Pulled high
84 PD3 LED2 Active low: Pulled high
85 PD4 LED3 Active low: Pulled high
86 PD5 485_TX Same as USART2_TX but goes to SP3485
USART2_TX MAX3232 to CN6
87 PD6 485_RX Save as USART2_RX but goes to SP3485 (see JP4)
USART2_RX MAX3232 to CN6
88 PD7 LED4 Active low: Pulled high
485_DIR SP3485 read enable (not)
55 PD8 MII_RX_DV Ethernet PHY
RMII_CRSDV Ethernet PHY
56 PD9 MII_RXD0 Ethernet PHY
57 PD10 MII_RXD1 Ethernet PHY
58 PD11 SD_CS Active low: Pulled high (See also TFT LCD CN13, pin 32)
59 PD12 WIRELESS_CS To the NRF24L01 2.4G wireless module
60 PD13 LCD_RS To TFT LCD (CN13)
61 PD14 LCD_WR To TFT LCD (CN13). Schematic is wrong LCD_WR is PB14.
62 PD15 LCD_RD To TFT LCD (CN13)
-- ---- -------------- -------------------------------------------------------------------
PN NAME SIGNAL NOTES
-- ---- -------------- -------------------------------------------------------------------
97 PE0 DB00 To TFT LCD (CN13)
98 PE1 DB01 To TFT LCD (CN13)
1 PE2 DB02 To TFT LCD (CN13)
2 PE3 DB03 To TFT LCD (CN13)
3 PE4 DB04 To TFT LCD (CN13)
4 PE5 DB05 To TFT LCD (CN13)
5 PE6 DB06 To TFT LCD (CN13)
38 PE7 DB07 To TFT LCD (CN13)
39 PE8 DB08 To TFT LCD (CN13)
40 PE9 DB09 To TFT LCD (CN13)
41 PE10 DB10 To TFT LCD (CN13)
42 PE11 DB11 To TFT LCD (CN13)
43 PE12 DB12 To TFT LCD (CN13)
44 PE13 DB13 To TFT LCD (CN13)
45 PE14 DB14 To TFT LCD (CN13)
46 PE15 DB15 To TFT LCD (CN13)
-- ---- -------------- -------------------------------------------------------------------
PN NAME SIGNAL NOTES
-- ---- -------------- -------------------------------------------------------------------
73 N/C
12 OSC_IN Y2 25Mhz XTAL
13 OSC_OUT Y2 25Mhz XTAL
94 BOOT0 JP15 (3.3V or GND)
14 RESET S5
6 VBAT JP14 (3.3V or battery)
49 VSS_1 GND
74 VSS_2 GND
99 VSS_3 GND
27 VSS_4 GND
10 VSS_5 GND
19 VSSA VSSA
20 VREF- VREF-
LEDs
====
The Shenzhou board has four LEDs labeled LED1, LED2, LED3 and LED4 on the
board. These LEDs are not used by the board port unless CONFIG_ARCH_LEDS is
defined. In that case, the usage by the board port is defined in
include/board.h and src/up_leds.c. The LEDs are used to encode OS-related
events as follows:
SYMBOL Meaning LED1* LED2 LED3 LED4****
------------------- ----------------------- ------- ------- ------- ------
LED_STARTED NuttX has been started ON OFF OFF OFF
LED_HEAPALLOCATE Heap has been allocated OFF ON OFF OFF
LED_IRQSENABLED Interrupts enabled ON ON OFF OFF
LED_STACKCREATED Idle stack created OFF OFF ON OFF
LED_INIRQ In an interrupt** ON N/C N/C OFF
LED_SIGNAL In a signal handler*** N/C ON N/C OFF
LED_ASSERTION An assertion failed ON ON N/C OFF
LED_PANIC The system has crashed N/C N/C N/C ON
LED_IDLE STM32 is is sleep mode (Optional, not used)
* If LED1, LED2, LED3 are statically on, then NuttX probably failed to boot
and these LEDs will give you some indication of where the failure was
** The normal state is LED1 ON and LED1 faintly glowing. This faint glow
is because of timer interrupts that result in the LED being illuminated
on a small proportion of the time.
*** LED2 may also flicker normally if signals are processed.
**** LED4 may not be available if RS-485 is also used. For RS-485, it will
then indicate the RS-485 direction.
Shenzhou-specific 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=stm32
CONFIG_ARCH_CHIP_name - For use in C code to identify the exact
chip:
CONFIG_ARCH_CHIP_STM32F107VC=y
CONFIG_ARCH_BOARD_STM32_CUSTOM_CLOCKCONFIG - Enables special STM32 clock
configuration features.
CONFIG_ARCH_BOARD_STM32_CUSTOM_CLOCKCONFIG=n
CONFIG_ARCH_BOARD - Identifies the boards/ subdirectory and
hence, the board that supports the particular chip or SoC.
CONFIG_ARCH_BOARD=shenzhou (for the Shenzhou development board)
CONFIG_ARCH_BOARD_name - For use in C code
CONFIG_ARCH_BOARD_SHENZHOU=y
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=0x00010000 (64Kb)
CONFIG_RAM_START - The start address of installed DRAM
CONFIG_RAM_START=0x20000000
CONFIG_STM32_CCMEXCLUDE - Exclude CCM SRAM from the HEAP
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.
Individual subsystems can be enabled:
AHB
---
CONFIG_STM32_DMA1
CONFIG_STM32_DMA2
CONFIG_STM32_CRC
CONFIG_STM32_ETHMAC
CONFIG_STM32_OTGFS
CONFIG_STM32_IWDG
CONFIG_STM32_PWR -- Required for RTC
APB1 (low speed)
----------------
CONFIG_STM32_BKP
CONFIG_STM32_TIM2
CONFIG_STM32_TIM3
CONFIG_STM32_TIM4
CONFIG_STM32_TIM5
CONFIG_STM32_TIM6
CONFIG_STM32_TIM7
CONFIG_STM32_USART2
CONFIG_STM32_USART3
CONFIG_STM32_UART4
CONFIG_STM32_UART5
CONFIG_STM32_SPI2
CONFIG_STM32_SPI3
CONFIG_STM32_I2C1
CONFIG_STM32_I2C2
CONFIG_STM32_CAN1
CONFIG_STM32_CAN2
CONFIG_STM32_DAC1
CONFIG_STM32_DAC2
CONFIG_STM32_WWDG
APB2 (high speed)
-----------------
CONFIG_STM32_TIM1
CONFIG_STM32_SPI1
CONFIG_STM32_USART1
CONFIG_STM32_ADC1
CONFIG_STM32_ADC2
Timer and I2C devices may need to the following to force power to be applied
unconditionally at power up. (Otherwise, the device is powered when it is
initialized).
CONFIG_STM32_FORCEPOWER
Timer devices may be used for different purposes. One special purpose is
to generate modulated outputs for such things as motor control. If CONFIG_STM32_TIMn
is defined (as above) then the following may also be defined to indicate that
the timer is intended to be used for pulsed output modulation, ADC conversion,
or DAC conversion. Note that ADC/DAC require two definition: Not only do you have
to assign the timer (n) for used by the ADC or DAC, but then you also have to
configure which ADC or DAC (m) it is assigned to.
CONFIG_STM32_TIMn_PWM Reserve timer n for use by PWM, n=1,..,14
CONFIG_STM32_TIMn_ADC Reserve timer n for use by ADC, n=1,..,14
CONFIG_STM32_TIMn_ADCm Reserve timer n to trigger ADCm, n=1,..,14, m=1,..,3
CONFIG_STM32_TIMn_DAC Reserve timer n for use by DAC, n=1,..,14
CONFIG_STM32_TIMn_DACm Reserve timer n to trigger DACm, n=1,..,14, m=1,..,2
For each timer that is enabled for PWM usage, we need the following additional
configuration settings:
CONFIG_STM32_TIMx_CHANNEL - Specifies the timer output channel {1,..,4}
NOTE: The STM32 timers are each capable of generating different signals on
each of the four channels with different duty cycles. That capability is
not supported by this driver: Only one output channel per timer.
JTAG Enable settings (by default JTAG-DP and SW-DP are disabled):
CONFIG_STM32_JTAG_FULL_ENABLE - Enables full SWJ (JTAG-DP + SW-DP)
CONFIG_STM32_JTAG_NOJNTRST_ENABLE - Enables full SWJ (JTAG-DP + SW-DP)
but without JNTRST.
CONFIG_STM32_JTAG_SW_ENABLE - Set JTAG-DP disabled and SW-DP enabled
STM32107xxx specific device driver settings
CONFIG_U[S]ARTn_SERIAL_CONSOLE - selects the USARTn (n=1,2,3) or UART
m (m=4,5) for the console and ttys0 (default is the USART1).
CONFIG_U[S]ARTn_RXBUFSIZE - Characters are buffered as received.
This specific the size of the receive buffer
CONFIG_U[S]ARTn_TXBUFSIZE - Characters are buffered before
being sent. This specific the size of the transmit buffer
CONFIG_U[S]ARTn_BAUD - The configure BAUD of the UART. Must be
CONFIG_U[S]ARTn_BITS - The number of bits. Must be either 7 or 8.
CONFIG_U[S]ARTn_PARTIY - 0=no parity, 1=odd parity, 2=even parity
CONFIG_U[S]ARTn_2STOP - Two stop bits
CONFIG_STM32_SPI_INTERRUPTS - Select to enable interrupt driven SPI
support. Non-interrupt-driven, poll-waiting is recommended if the
interrupt rate would be to high in the interrupt driven case.
CONFIG_STM32_SPI_DMA - Use DMA to improve SPI transfer performance.
Cannot be used with CONFIG_STM32_SPI_INTERRUPT.
CONFIG_STM32_PHYADDR - The 5-bit address of the PHY on the board
CONFIG_STM32_MII - Support Ethernet MII interface
CONFIG_STM32_MII_MCO - Use MCO to clock the MII interface
CONFIG_STM32_RMII - Support Ethernet RMII interface
CONFIG_STM32_RMII_MCO - Use MCO to clock the RMII interface
CONFIG_STM32_AUTONEG - Use PHY autonegotiation to determine speed and mode
CONFIG_STM32_ETHFD - If CONFIG_STM32_AUTONEG is not defined, then this
may be defined to select full duplex mode. Default: half-duplex
CONFIG_STM32_ETH100MBPS - If CONFIG_STM32_AUTONEG is not defined, then this
may be defined to select 100 MBps speed. Default: 10 Mbps
CONFIG_STM32_PHYSR - This must be provided if CONFIG_STM32_AUTONEG is
defined. The PHY status register address may diff from PHY to PHY. This
configuration sets the address of the PHY status register.
CONFIG_STM32_PHYSR_SPEED - This must be provided if CONFIG_STM32_AUTONEG is
defined. This provides bit mask indicating 10 or 100MBps speed.
CONFIG_STM32_PHYSR_100MBPS - This must be provided if CONFIG_STM32_AUTONEG is
defined. This provides the value of the speed bit(s) indicating 100MBps speed.
CONFIG_STM32_PHYSR_MODE - This must be provided if CONFIG_STM32_AUTONEG is
defined. This provide bit mask indicating full or half duplex modes.
CONFIG_STM32_PHYSR_FULLDUPLEX - This must be provided if CONFIG_STM32_AUTONEG is
defined. This provides the value of the mode bits indicating full duplex mode.
CONFIG_STM32_ETH_PTP - Precision Time Protocol (PTP). Not supported
but some hooks are indicated with this condition.
Shenzhou CAN Configuration
CONFIG_CAN - Enables CAN support (one or both of CONFIG_STM32_CAN1 or
CONFIG_STM32_CAN2 must also be defined)
CONFIG_CAN_FIFOSIZE - The size of the circular buffer of CAN messages.
Default: 8
CONFIG_CAN_NPENDINGRTR - The size of the list of pending RTR requests.
Default: 4
CONFIG_CAN_LOOPBACK - A CAN driver may or may not support a loopback
mode for testing. The STM32 CAN driver does support loopback mode.
CONFIG_STM32_CAN1_BAUD - CAN1 BAUD rate. Required if CONFIG_STM32_CAN1
is defined.
CONFIG_STM32_CAN2_BAUD - CAN1 BAUD rate. Required if CONFIG_STM32_CAN2
is defined.
CONFIG_STM32_CAN_TSEG1 - The number of CAN time quanta in segment 1.
Default: 6
CONFIG_STM32_CAN_TSEG2 - the number of CAN time quanta in segment 2.
Default: 7
CONFIG_STM32_CAN_REGDEBUG - If CONFIG_DEBUG_FEATURES is set, this will generate an
dump of all CAN registers.
Shenzhou LCD Hardware Configuration
The LCD driver supports the following LCDs on the STM324xG_EVAL board:
AM-240320L8TNQW00H (LCD_ILI9320 or LCD_ILI9321) OR
AM-240320D5TOQW01H (LCD_ILI9325)
Configuration options.
CONFIG_LCD_LANDSCAPE - Define for 320x240 display "landscape"
support. Default is this 320x240 "landscape" orientation
For the Shenzhou board, the edge opposite from the row of buttons
is used as the top of the display in this orientation.
CONFIG_LCD_RLANDSCAPE - Define for 320x240 display "reverse
landscape" support. Default is this 320x240 "landscape"
orientation
For the Shenzhou board, the edge next to the row of buttons
is used as the top of the display in this orientation.
CONFIG_LCD_PORTRAIT - Define for 240x320 display "portrait"
orientation support.
CONFIG_LCD_RPORTRAIT - Define for 240x320 display "reverse
portrait" orientation support.
CONFIG_LCD_RDSHIFT - When reading 16-bit gram data, there appears
to be a shift in the returned data. This value fixes the offset.
Default 5.
The LCD driver dynamically selects the LCD based on the reported LCD
ID value. However, code size can be reduced by suppressing support for
individual LCDs using:
CONFIG_STM32_ILI9320_DISABLE (includes ILI9321)
CONFIG_STM32_ILI9325_DISABLE
STM32 USB OTG FS Host Driver Support
Pre-requisites
CONFIG_USBHOST - Enable USB host support
CONFIG_STM32_OTGFS - Enable the STM32 USB OTG FS block
CONFIG_STM32_SYSCFG - Needed
CONFIG_SCHED_WORKQUEUE - Worker thread support is required
Options:
CONFIG_STM32_OTGFS_RXFIFO_SIZE - Size of the RX FIFO in 32-bit words.
Default 128 (512 bytes)
CONFIG_STM32_OTGFS_NPTXFIFO_SIZE - Size of the non-periodic Tx FIFO
in 32-bit words. Default 96 (384 bytes)
CONFIG_STM32_OTGFS_PTXFIFO_SIZE - Size of the periodic Tx FIFO in 32-bit
words. Default 96 (384 bytes)
CONFIG_STM32_OTGFS_DESCSIZE - Maximum size of a descriptor. Default: 128
CONFIG_STM32_OTGFS_SOFINTR - Enable SOF interrupts. Why would you ever
want to do that?
CONFIG_STM32_USBHOST_REGDEBUG - Enable very low-level register access
debug. Depends on CONFIG_DEBUG_FEATURES.
CONFIG_STM32_USBHOST_PKTDUMP - Dump all incoming and outgoing USB
packets. Depends on CONFIG_DEBUG_FEATURES.
Configurations
==============
Each Shenzhou configuration is maintained in a sub-directory and
can be selected as follow:
tools/configure.sh shenzhou:<subdir>
Where <subdir> is one of the following:
nsh:
---
Configures the NuttShell (nsh) located at apps/examples/nsh. The
Configuration enables both the serial and telnet NSH interfaces.
CONFIG_ARMV7M_TOOLCHAIN_GNU_EABIW=y : GNU EABI toolchain for Windows
CONFIG_NSH_DHCPC=n : DHCP is disabled
CONFIG_NSH_IPADDR=0x0a000002 : Target IP address 10.0.0.2
CONFIG_NSH_DRIPADDR=0x0a000001 : Host IP address 10.0.0.1
NOTES:
1. This example assumes that a network is connected. During its
initialization, it will try to negotiate the link speed. If you have
no network connected when you reset the board, there will be a long
delay (maybe 30 seconds?) before anything happens. That is the timeout
before the networking finally gives up and decides that no network is
available.
2. Enabling the ADC example:
The only internal signal for ADC testing is the potentiometer input:
ADC1_IN10(PC0) Potentiometer
External signals are also available on CON5 CN14:
ADC_IN8 (PB0) CON5 CN14 Pin2
ADC_IN9 (PB1) CON5 CN14 Pin1
The signal selection is hard-coded in boards/arm/stm32/shenzhou/src/up_adc.c: The
potentiometer input (only) is selected.
These selections will enable sampling the potentiometer input at 100Hz using
Timer 1:
CONFIG_ANALOG=y : Enable analog device support
CONFIG_ADC=y : Enable generic ADC driver support
CONFIG_ADC_DMA=n : ADC DMA is not supported
CONFIG_STM32_ADC1=y : Enable ADC 1
CONFIG_STM32_TIM1=y : Enable Timer 1
CONFIG_STM32_TIM1_ADC=y : Use Timer 1 for ADC
CONFIG_STM32_TIM1_ADC1=y : Allocate Timer 1 to ADC 1
CONFIG_STM32_ADC1_SAMPLE_FREQUENCY=100 : Set sampling frequency to 100Hz
CONFIG_STM32_ADC1_TIMTRIG=0 : Trigger on timer output 0
CONFIG_STM32_FORCEPOWER=y : Apply power to TIM1 a boot up time
CONFIG_EXAMPLES_ADC=y : Enable the apps/examples/adc built-in
nxwm
----
This is a special configuration setup for the NxWM window manager
UnitTest. The NxWM window manager can be found here:
apps/graphics/NxWidgets/nxwm
The NxWM unit test can be found at:
apps/graphics/NxWidgets/UnitTests/nxwm
NOTE: JP6 selects between the touchscreen interrupt and the MII
interrupt. It should be positioned 1-2 to enable the touchscreen
interrupt.
NOTE: Reading from the LCD is not currently supported by this
configuration. The hardware will support reading from the LCD
and drivers/lcd/ssd1289.c also supports reading from the LCD.
This limits some graphics capabilities.
Reading from the LCD is not supported only because it has not
been tested. If you get inspired to test this feature, you can
turn the LCD read functionality on by setting:
-CONFIG_LCD_NOGETRUN=y
+# CONFIG_LCD_NOGETRUN is not set
-CONFIG_NX_WRITEONLY=y
+# CONFIG_NX_WRITEONLY is not set
thttpd
------
This builds the THTTPD web server example using the THTTPD and
the apps/examples/thttpd application.
NOTE: This example can only be built using the older toolchains
due to incompatibilities introduced in later GCC releases.
