README

This README file describes the port of NuttX to the SAMA5D2 Xplained Ulta development board. This board features the Atmel SAMA5D27 microprocessor. See http://www.atmel.com for further information.

Contents

• STATUS
• Loading Code into SRAM with J-Link
• DRAMBOOT, AT25BOOT, SRAMBOOT
• Running NuttX from SDRAM
• Buttons and LEDs
• Serial Console
• SAMA5D2-XULT Configuration Options
• Configurations

STATUS

1. Most of this document is a partially corrected clone of the SAMA5D4-EK README.txt and still contains errors and inconsistencies.

2. Coding is complete for the basic SAMA5D2-XULT NSH configuration, but is completely untested as of this writing (2015-09-15). The primary issue is that I have not yet determine how to load and test code.

Loading Code into SRAM with J-Link

REVISIT: Unverified, cloned text from the SAMA5D4-EK README.txt

Loading code with the Segger tools and GDB

1) Change directories into the directory where you built NuttX.
2) Start the GDB server and wait until it is ready to accept GDB
   connections.
3) Then run GDB like this:

     $ arm-none-eabi-gdb
     (gdb) target remote localhost:2331
     (gdb) mon reset
     (gdb) load nuttx
     (gdb) ... start debugging ...

Loading code using J-Link Commander ----------------------------------

J-Link> r
J-Link> loadbin <file> <address>
J-Link> setpc <address of __start>
J-Link> ... start debugging ...

DRAMBOOT, AT25BOOT, SRAMBOOT

See also boards/arm/sama5/sama5d4-xult/README.txt for a description of the DRAMBOOT program. This is a tiny version of NuttX that can run out of internal SRAM. If you put this program on the HSMCI1 microSD card as boot.bin, then it will boot on power up and you can download NuttX directly into DRAM by sending the nuttx.hex file over the serial connection.

The boards/arm/sama5/sama5d4-xult/README.txt also describes variants AT25BOOT and SRAMBOOT. This have not yet been ported to the SAMA5D2-XULT, but are available if they are useful too you.

Running NuttX from SDRAM

REVISIT: Unverified, cloned text from the SAMA5D4-EK README.txt

NuttX may be executed from SDRAM. But this case means that the NuttX binary must reside on some other media (typically NAND FLASH, Serial FLASH) or transferred over some interface (perhaps a UART or even a TFTP server). In these cases, an intermediate bootloader such as U-Boot or Barebox must be used to configure the SAMA5D2 clocks and SDRAM and then to copy the NuttX binary into SDRAM.

- NuttX Configuration
- Boot sequence
- NAND FLASH Memory Map
- Programming the AT91Boostrap Binary
- Programming U-Boot
- Load NuttX with U-Boot on AT91 boards

TODO: Some drivers may require some adjustments to run from SDRAM. That is because in this case macros like BOARD_MCK_FREQUENCY are not constants but are instead function calls: The MCK clock frequency is not known in advance but instead has to be calculated from the bootloader PLL configuration. See the TODO list at the end of this file for further information.

NuttX Configuration -------------------

In order to run from SDRAM, NuttX must be built at origin 0x20008000 in SDRAM (skipping over SDRAM memory used by the bootloader). The following configuration option is required:

CONFIG_SAMA5_BOOT_SDRAM=y
CONFIG_BOOT_RUNFROMSDRAM=y

These options tell the NuttX code that it will be booting and running from SDRAM. In this case, the start-logic will do to things: (1) it will not configure the SAMA5D2 clocking. Rather, it will use the clock configuration as set up by the bootloader. And (2) it will not attempt to configure the SDRAM. Since NuttX is already running from SDRAM, it must accept the SDRAM configuration as set up by the bootloader.

Boot sequence -------------

Reference: http://www.at91.com/linux4sam/bin/view/Linux4SAM/GettingStarted

Several pieces of software are involved to boot a Nutt5X into SDRAM. First is the primary bootloader in ROM which is in charge to check if a valid application is present on supported media (NOR FLASH, Serial DataFlash, NAND FLASH, SD card).

The boot sequence of linux4SAM is done in several steps :

1. The ROM bootloader checks if a valid application is present in FLASH and if it is the case downloads it into internal SRAM. This program is usually a second level bootloader called AT91BootStrap.

2. AT91Bootstrap is the second level bootloader. It is in charge of the hardware configuration. It downloads U-Boot / Barebox binary from FLASH to SDRAM / DDRAM and starts the third level bootloader (U-Boot / Barebox)

<!-- -->

(see http://www.at91.com/linux4sam/bin/view/Linux4SAM/AT91Bootstrap).

3. The third level bootloader is either U-Boot or Barebox. The third level bootloader is in charge of downloading NuttX binary from FLASH, network, SD card, etc. It then starts NuttX.

4. Then NuttX runs from SDRAM

NAND FLASH Memory Map ---------------------

Reference: http://www.at91.com/linux4sam/bin/view/Linux4SAM/GettingStarted

0x0000:0000 - 0x0003:ffff: AT91BootStrap 0x0004:0000 - 0x000b:ffff: U-Boot 0x000c:0000 - 0x000f:ffff: U-Boot environment 0x0010:0000 - 0x0017:ffff: U-Boot environment redundant 0x0018:0000 - 0x001f:ffff: Device tree (DTB) 0x0020:0000 - 0x007f:ffff: NuttX 0x0080:0000 - end: Available for use as a NAND file system

Programming the AT91Boostrap Binary -----------------------------------

Reference: http://www.at91.com/linux4sam/bin/view/Linux4SAM/AT91Bootstrap

This section describes how to program AT91Bootstrap binary into the boot media with SAM-BA tool using NandFlash as boot media.

1. Get AT91BootStrap binaries. Build instructions are available here:

   http://www.at91.com/linux4sam/bin/view/Linux4SAM/AT91Bootstrap\#Build\_AT91Bootstrap\_from\_sources

   A pre-built AT91BootStrap binary is available here:

   ftp://www.at91.com/pub/at91bootstrap/AT91Bootstrap3.6.1/sama5d3\_xplained-nandflashboot-uboot-3.6.1.bin

2. Start the SAM-BA GUI Application:

   • Connect the USB Device interface to your host machine using the USB Device Cable.
   • Make sure that the chip can execute the SAM-BA Monitor.
   • Start SAM-BA GUI application.
   • Select the board in the drop-down menu and choose the USB connection.

3. In the SAM-BA GUI Application:

   • Choose the "NandFlash" tab in the SAM-BA GUI interface.

   • Initialize the NandFlash by choosing the "Enable NandFlash" action in the Scripts rolling menu, then press "Execute" button.

   • Erase the NandFlash device by choosing the "Erase All" action, then press "Execute" button.

   • Enable the PMECC by choosing the "Enable OS PMECC parameters" action, then press "Execute" button.

     PMECC Number of sectors per page: 4 Spare Size: 64 Number of ECC bits required: 4 Size of the ECC sector: 512 ECC offset: 36

• Choose "Send Boot File" action, then press Execute button to select the at91bootstrap binary file and to program the binary to the NandFlash.
• Close SAM-BA, remove the USB Device cable.

Programming U-Boot -------------------

Reference http://www.at91.com/linux4sam/bin/view/Linux4SAM/U-Boot

1. Get U-Boot Binaries. Build instructions are available here:

   http://www.at91.com/linux4sam/bin/view/Linux4SAM/U-Boot\#Build\_U\_Boot\_from\_sources

   A pre-Built binary image is available here:

   ftp://www.at91.com/pub/uboot/u-boot-v2013.07/u-boot-sama5d3\_xplained-v2013.07-at91-r1.bin

2. Start the SAM-BA GUI Application:

   • Connect the USB Device interface to your host machine using the USB Device Cable.
   • Make sure that the chip can execute the SAM-BA Monitor.
   • Start SAM-BA GUI application.
   • Select the board in the drop-down menu and choose the USB connection.

3. In the SAM-BA GUI Application:

   • Choose the NandFlash tab in the SAM-BA GUI interface.

   • Initialize the NandFlash by choosing the "Enable NandFlash" action in the Scripts rolling menu, then press Execute button.

   • Enable the PMECC by choosing the "Enable OS PMECC parameters" action, then press Execute button.

     PMECC Number of sectors per page: 4 Spare Size: 64 Number of ECC bits required: 4 Size of the ECC sector: 512 ECC offset: 36

   • Press the "Send File Name" Browse button

   • Choose u-boot.bin binary file and press Open

   • Enter the proper address on media in the Address text field: 0x00040000

   • Press the "Send File" button

   • Close SAM-BA, remove the USB Device cable.

You should now be able to interrupt with U-Boot via the DBGU interface.

Load NuttX with U-Boot on AT91 boards

Reference http://www.at91.com/linux4sam/bin/view/Linux4SAM/U-Boot

Preparing NuttX image

U-Boot does not support normal binary images.  Instead you have to
create an uImage file with the mkimage tool which encapsulates kernel
image with header information, CRC32 checksum, etc.

mkimage comes in source code with U-Boot distribution and it is built
during U-Boot compilation (u-boot-source-dir/tools/mkimage).  There
are also sites where you can download pre-built mkimage binaries.  For
example: http://www.trimslice.com/wiki/index.php/U-Boot_images

See the U-Boot README file for more information.  More information is
also available in the mkimage man page (for example,
http://linux.die.net/man/1/mkimage).

Command to generate an uncompressed uImage file (4) :

  mkimage -A arm -O linux -C none -T kernel -a 20008000 -e 20008E20 \
    -n nuttx -d nuttx.bin uImage

Where:

  -A arm: Set architecture to ARM
  -O linux: Select operating system. bootm command of u-boot changes
     boot method by os type.
  -T kernel: Set image type.
  -C none: Set compression type.
  -a 20008000:  Set load address.
  -e 20008E20: Set entry point.
  -n nuttx: Set image name.
  -d nuttx.bin: Use image data from nuttx.bin.

This will generate a binary called uImage.  If you have the path to
mkimage in your PATH variable, then you can automatically build the
uImage file by adding the following to your .config file:

  CONFIG_RAW_BINARY=y
  CONFIG_UBOOT_UIMAGE=y
  CONFIG_UIMAGE_LOAD_ADDRESS=0x20008000
  CONFIG_UIMAGE_ENTRY_POINT=0x20008E20

The uImage file can them be loaded into memory from a variety of sources
(serial, SD card, JFFS2 on NAND, TFTP).

STATUS:
  2014-4-1:  So far, I am unable to get U-Boot to execute the uImage
             file.  I get the following error messages (in this case
             trying to load from an SD card):

    U-Boot> fatload mmc 0 0x22000000 uimage
    reading uimage
    97744 bytes read in 21 ms (4.4 MiB/s)

    U-Boot> bootm 0x22000000
    ## Booting kernel from Legacy Image at 0x22000000 ...
       Image Name:   nuttx
       Image Type:   ARM Linux Kernel Image (uncompressed)
       Data Size:    97680 Bytes = 95.4 KiB
       Load Address: 20008000
       Entry Point:  20008E20
       Verifying Checksum ... OK
       XIP Kernel Image ... OK
    FDT and ATAGS support not compiled in - hanging
    ### ERROR ### Please RESET the board ###

  This, however, appears to be a usable workaround:

    U-Boot> fatload mmc 0 0x20008000 nuttx.bin
    mci: setting clock 257812 Hz, block size 512
    mci: setting clock 257812 Hz, block size 512
    mci: setting clock 257812 Hz, block size 512
    gen_atmel_mci: CMDR 00001048 ( 8) ARGR 000001aa (SR: 0c100025) Command Time Out
    mci: setting clock 257812 Hz, block size 512
    mci: setting clock 22000000 Hz, block size 512
    reading nuttx.bin
    108076 bytes read in 23 ms (4.5 MiB/s)

    U-Boot> go 0x20008E20
    ## Starting application at 0x20008E20 ...

    NuttShell (NSH) NuttX-7.2
    nsh>

Loading through network

On a development system, it is useful to get the kernel and root file
system through the network. U-Boot provides support for loading
binaries from a remote host on the network using the TFTP protocol.

To manage to use TFTP with U-Boot, you will have to configure a TFTP
server on your host machine. Check your distribution manual or Internet
resources to configure a Linux or Windows TFTP server on your host:

  - U-Boot documentation on a Linux host:
    http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.6.

  - Another TFTP configuration reference:
    http://www.linuxhomenetworking.com/wiki/index.php/Quick_HOWTO_:_Ch16_:_Telnet%2C_TFTP%2C_and_xinetd#TFTP

On the U-Boot side, you will have to setup the networking parameters:

 1. Setup an Ethernet address (MAC address)
    Check this U-Boot network BuildRootFAQ entry to choose a proper MAC
    address: http://www.denx.de/wiki/DULG/EthernetDoesNotWork

      setenv ethaddr 00:e0:de:ad:be:ef

 2. Setup IP parameters:
    The board ip address

      setenv ipaddr 10.0.0.2

    The server ip address where the TFTP server is running

      setenv serverip 10.0.0.1

 3. saving Environment to flash

      saveenv

 4. If Ethernet Phy has not been detected during former bootup, reset
    the board to reload U-Boot : the Ethernet address and Phy
    initialization shall be ok, now

 5. Download the NuttX uImage and the root file system to a ram location
   using the U-Boot tftp command (Cf. U-Boot script capability chapter).

 6. Launch NuttX issuing a bootm or boot command.

If the board has both emac and gmac, you can use following to choose
which one to use:

   setenv ethact macb0,gmacb0
   setenv ethprime gmacb0

STATUS: 2014-3-30: These instructions were adapted from the Linux4SAM website but have not yet been used.

Using JTAG ----------

This description assumes that you have a JTAG debugger such as Segger J-Link connected to the SAMA5D3-Xplained.

1. Start the GDB server
2. Start GDB
3. Use the 'target remote localhost:xxxx' command to attach to the GDG server
4. Do 'mon reset' then 'mon go' to start the internal boot loader (maybe U-Boot).
5. Let the boot loader run until it completes SDRAM initialization, then do 'mon halt'.
6. Now you have SDRAM initialized and you use 'load nuttx' to load the ELF file into SDRAM.
7. Use 'file nuttx' to load symbols
8. Set the PC to the NuttX entry point 'mon pc 0x20008E20' and start nuttx using 'mon go'.

Buttons and LEDs

Buttons

A single button, PB_USER1 (PB6), is available on the SAMA5D2-XULT

------------------------------ ------------------- -------------------------
SAMA5D2 PIO                    SIGNAL              USAGE
------------------------------ ------------------- -------------------------
PB6                            USER_PB_PB6         PB_USER push button
------------------------------ ------------------- -------------------------

Closing PB_USER will bring PB6 to ground so 1) PB6 should have a weak pull-up, and 2) when PB_USER is pressed, a low value will be senses.

Support for pollable buttons is enabled with:

CONFIG_ARCH_BUTTONS=y

For interrupt driven buttons, add:

CONFIG_ARCH_IRQBUTTONS=y

Program interfaces for button access are described in nuttx/include/nuttx/arch.h

There is an example that can be enabled to test button interrupts. That example is enabled like:

CONFIG_EXAMPLES_BUTTONS=y
CONFIG_EXAMPLES_BUTTONS_MAX=0
CONFIG_EXAMPLES_BUTTONS_MIN=0
CONFIG_EXAMPLES_BUTTONS_NAME0="PB_USER"
CONFIG_EXAMPLES_IRQBUTTONS_MAX=0
CONFIG_EXAMPLES_IRQBUTTONS_MIN=0

LEDs ----

There is an RGB LED on board the SAMA5D2-XULT. The RED component is driven by the SDHC_CD pin (PA13) and so will not be used. The LEDs are provided VDD_LED and so bringing the LED low will will illuminated the LED.

------------------------------ ------------------- -------------------------
SAMA5D2 PIO                    SIGNAL              USAGE
------------------------------ ------------------- -------------------------
PA13                           SDHC_CD_PA13        Red LED
PB5                            LED_GREEN_PB5       Green LED
PB0                            LED_BLUE_PB0        Blue LED
------------------------------ ------------------- -------------------------

When CONFIG_ARCH_LEDS is defined in the NuttX configuration, NuttX will control the Green LED (only)as follows:

SYMBOL              Meaning                 Green LED
------------------- ----------------------- ---------
LED_STARTED         NuttX has been started  OFF
LED_HEAPALLOCATE    Heap has been allocated OFF
LED_IRQSENABLED     Interrupts enabled      OFF
LED_STACKCREATED    Idle stack created      ON
LED_INIRQ           In an interrupt         N/C
LED_SIGNAL          In a signal handler     N/C
LED_ASSERTION       An assertion failed     N/C
LED_PANIC           The system has crashed  FLASH

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

Serial Console

DEBUG / DBGU Port (J1). There is a TTL serial connection available on pins 2 and 3 of the DEBUG connector. This may be driven by UART1, depending upon the setting of JP2 (DBGU_PE on the schematic, DEBUG_DIS on the board):

---- ------------------------ -------------
J1   SCHEMATIC                   SAMA5D2
PIN  NAME(s)                  PIO  FUNCTION
---- ------------------------ -------------
 2   DBGU_TXD  DBGU_UTXD1_PD3 PD3  UTXD1
 3   DBGU_RXD  DBGU_URXD1_PD2 PD2  URXD1
---- ------------------------ -------------

Standard UART on Arduino connector (J21) is FLEXCOM4. Terminology: FLEXCOM is the same as USART in previous SAMA5D versions.

---- ------- -------------
J21  BOARD      SAMA5D2
PIN  NAME    PIO  FUNCTION
---- ------- -------------
 7   F4_TXD  PD12 FLEXCOM4
 8   F4_RXD  PD13 FLEXCOM4
---- ------- -------------

Other USARTs are available on J22:

---- ------- -------------
J22  BOARD      SAMA5D2
PIN  NAME    PIO  FUNCTION
---- ------- -------------
 3   F0_TXD  PB28 FLEXCOM0
 4   F0_RXD  PB29 FLEXCOM0
 5   F3_TXD  PB23 FLEXCOM3
 6   F3_RXD  PB22 FLEXCOM3
---- ------- -------------

UARTs available of EXT1

---- ------- -------------
EXT1 BOARD      SAMA5D2
PIN  NAME    PIO  FUNCTION
---- ------- -------------
 13  UART_RX PA23 FLEXCOM1
 14  UART_TX PA24 FLEXCOM1
---- ------- ---- --------

UARTs available of EXT2

---- ------- -------------
EXT2 BOARD      SAMA5D2
PIN  NAME    PIO  FUNCTION
---- ------- -------------
 13  UART_RX PB29 FLEXCOM0
 14  UART_TX PB28 FLEXCOM0
---- ------- ---- --------

By default, the standard UART on Arduino connector (J21, FLEXCOM4) is enabled in all of these configurations unless otherwise noted.

REVISIT: UART1 on the DBGU connect might be a better choice for the default serial console

SAMA5D2-XULT 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_CORTEXA5=y

CONFIG_ARCH_CHIP - Identifies the arch/*/chip subdirectory

CONFIG_ARCH_CHIP="sama5"

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

CONFIG_ARCH_CHIP_SAMA5=y
CONFIG_ARCH_CHIP_ATSAMA5D27=y

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

CONFIG_ARCH_BOARD="sama5d2-xult" (for the SAMA5D2-XULT development board)

CONFIG_ARCH_BOARD_name - For use in C code

CONFIG_ARCH_BOARD_SAMA5D2_XULT=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=0x0002000 (128Kb)

CONFIG_RAM_START - The physical start address of installed DRAM

CONFIG_RAM_START=0x20000000

CONFIG_RAM_VSTART - The virtual start address of installed DRAM

CONFIG_RAM_VSTART=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.

Individual subsystems can be enabled: REVISIT: Unverified, cloned text from the SAMA5D4-EK README.txt

CONFIG_SAMA5_DBGU        - Debug Unit
CONFIG_SAMA5_PIT         - Periodic Interval Timer
CONFIG_SAMA5_WDT         - Watchdog timer
CONFIG_SAMA5_HSMC        - Multi-bit ECC
CONFIG_SAMA5_SMD         - SMD Soft Modem
CONFIG_SAMA5_FLEXCOM0    - Flexcom 0
CONFIG_SAMA5_FLEXCOM1    - Flexcom 0
CONFIG_SAMA5_FLEXCOM2    - Flexcom 0
CONFIG_SAMA5_FLEXCOM3    - Flexcom 0
CONFIG_SAMA5_FLEXCOM4    - Flexcom 0
CONFIG_SAMA5_UART0       - UART 0
CONFIG_SAMA5_UART1       - UART 1
CONFIG_SAMA5_UART2       - UART 2
CONFIG_SAMA5_UART3       - UART 3
CONFIG_SAMA5_UART4       - UART 4
CONFIG_SAMA5_TWI0        - Two-Wire Interface 0
CONFIG_SAMA5_TWI1        - Two-Wire Interface 1
CONFIG_SAMA5_SDMMC0      - SD MMC card interface 0
CONFIG_SAMA5_SDMMC1      - SD MMC card interface 1
CONFIG_SAMA5_SPI0        - Serial Peripheral Interface 0
CONFIG_SAMA5_SPI1        - Serial Peripheral Interface 1
CONFIG_SAMA5_TC0         - Timer Counter 0 (ch. 0, 1, 2)
CONFIG_SAMA5_TC1         - Timer Counter 1 (ch. 3, 4, 5)
CONFIG_SAMA5_PWM         - Pulse Width Modulation Controller
CONFIG_SAMA5_ADC         - Touch Screen ADC Controller
CONFIG_SAMA5_XDMAC0      - XDMA Controller 0
CONFIG_SAMA5_XDMAC1      - XDMA Controller 1
CONFIG_SAMA5_UHPHS       - USB Host High Speed
CONFIG_SAMA5_UDPHS       - USB Device High Speed
CONFIG_SAMA5_EMAC0       - Ethernet MAC 0 (GMAC0)
CONFIG_SAMA5_EMAC1       - Ethernet MAC 1 (GMAC1)
CONFIG_SAMA5_LCDC        - LCD Controller
CONFIG_SAMA5_ISI         - Image Sensor Interface
CONFIG_SAMA5_SSC0        - Synchronous Serial Controller 0
CONFIG_SAMA5_SSC1        - Synchronous Serial Controller 1
CONFIG_SAMA5_SHA         - Secure Hash Algorithm
CONFIG_SAMA5_AES         - Advanced Encryption Standard
CONFIG_SAMA5_TDES        - Triple Data Encryption Standard
CONFIG_SAMA5_TRNG        - True Random Number Generator
CONFIG_SAMA5_ARM         - Performance Monitor Unit
CONFIG_SAMA5_FUSE        - Fuse Controller
CONFIG_SAMA5_MPDDRC      - MPDDR controller

Some subsystems can be configured to operate in different ways. The drivers need to know how to configure the subsystem.

CONFIG_SAMA5_PIOA_IRQ    - Support PIOA interrupts
CONFIG_SAMA5_PIOB_IRQ    - Support PIOB interrupts
CONFIG_SAMA5_PIOC_IRQ    - Support PIOD interrupts
CONFIG_SAMA5_PIOD_IRQ    - Support PIOD interrupts

CONFIG_USART0_SERIALDRIVER - Flexcom0 is configured as a UART
CONFIG_USART1_SERIALDRIVER - Flexcom1 is configured as a UART
CONFIG_USART2_SERIALDRIVER - Flexcom2 is configured as a UART
CONFIG_USART3_SERIALDRIVER - Flexcom3 is configured as a UART
CONFIG_USART4_SERIALDRIVER - Flexcom4 is configured as a UART

AT91SAMA5 specific device driver settings

CONFIG_SAMA5_DBGU_SERIAL_CONSOLE - selects the DBGU
  for the console and ttyDBGU
CONFIG_SAMA5_DBGU_RXBUFSIZE - Characters are buffered as received.
   This specific the size of the receive buffer
CONFIG_SAMA5_DBGU_TXBUFSIZE - Characters are buffered before
   being sent.  This specific the size of the transmit buffer
CONFIG_SAMA5_DBGU_BAUD - The configure BAUD of the DBGU.
CONFIG_SAMA5_DBGU_PARITY - 0=no parity, 1=odd parity, 2=even parity

CONFIG_U[S]ARTn_SERIAL_CONSOLE - selects the USARTn (n=0,1,2,3) or UART
       m (m=4,5) for the console and ttys0 (default is the DBGU).
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_PARITY - 0=no parity, 1=odd parity, 2=even parity
CONFIG_U[S]ARTn_2STOP - Two stop bits

AT91SAMA5 USB Host Configuration Pre-requisites

CONFIG_USBDEV          - Enable USB device support
CONFIG_USBHOST         - Enable USB host support
CONFIG_SAMA5_UHPHS     - Needed
CONFIG_SAMA5_OHCI      - Enable the STM32 USB OTG FS block
CONFIG_SCHED_WORKQUEUE - Worker thread support is required

Options:

CONFIG_SAMA5_OHCI_NEDS
  Number of endpoint descriptors
CONFIG_SAMA5_OHCI_NTDS
  Number of transfer descriptors
CONFIG_SAMA5_OHCI_TDBUFFERS
  Number of transfer descriptor buffers
CONFIG_SAMA5_OHCI_TDBUFSIZE
  Size of one transfer descriptor buffer
CONFIG_USBHOST_INT_DISABLE
  Disable interrupt endpoint support
CONFIG_USBHOST_ISOC_DISABLE
  Disable isochronous endpoint support
CONFIG_USBHOST_BULK_DISABLE
  Disable bulk endpoint support

config SAMA5_OHCI_REGDEBUG

Configurations

Information Common to All Configurations

Each SAMA5D2-XULT configuration is maintained in a sub-directory and can be selected as follow:

tools/configure.sh sama5d2-xult:<subdir>

Before building, make sure the PATH environment variable includes the correct path to the directory than holds your toolchain binaries.

And then build NuttX by simply typing the following. At the conclusion of the make, the nuttx binary will reside in an ELF file called, simply, nuttx.

make

The <subdir> that is provided above as an argument to the tools/configure.sh must be is one of the following.

NOTES:

1. These configurations use the mconf-based configuration tool. To change any of these configurations 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. Unless stated otherwise, all configurations generate console output on the DBGU (J23).

3. All of these configurations use the Code Sourcery for Windows toolchain (unless stated otherwise in the description of the configuration). That toolchain selection can easily be reconfigured using 'make menuconfig'. Here are the relevant current settings:

   Build Setup: CONFIG_HOST_WINDOWS=y : Microsoft Windows CONFIG_WINDOWS_CYGWIN=y : Using Cygwin or other POSIX environment

   System Type -> Toolchain: CONFIG_ARM_TOOLCHAIN_GNU_EABI=y : GNU EABI toolchain

4. The SAMA5Dx is running at 528MHz by default in these configurations.

   Board Selection -> CPU Frequency CONFIG_SAMA5D2XULT_528MHZ=y : Enable 528MHz operation CONFIG_BOARD_LOOPSPERMSEC=65775 : Calibrated on SAMA5D3-Xplained at : 528MHz running from SDRAM

Configuration Sub-directories

Summary: Some of the descriptions below are long and wordy. Here is the concise summary of the available SAMA5D2-XULT configurations:

nsh:  This is a basic NuttShell (NSH) configuration.

There may be issues with some of these configurations. See the details for status of individual configurations.

Now for the gory details:

netnsh:

This is a network enabled configuration based on the NuttShell (NSH).
The CDC-ECM driver is enabled, so you can plug a USB cable into the
USB-Micro port (USB-A) and the board will appear as an CDC-ECM
ethernet adapter.

nsh:

This configuration directory provide the NuttShell (NSH).  This is a
very simple NSH configuration upon which you can build further
functionality.

NOTES:

1. This configuration uses the UART1 (PD2 and PD3) for the serial
   console.  USART1 is available at the "DBGU" RS-232 connector (J24).
   This is easily changed by reconfiguring to (1) enable a different
   serial peripheral, and (2) selecting that serial peripheral as the
   console device.

2. By default, this configuration is set up to build on Windows
   under either a Cygwin or MSYS environment using a recent, Windows-
   native, generic ARM EABI GCC toolchain (such as the ARM supported
   toolchain).  Both the build environment and the toolchain
   selection can easily be changed by reconfiguring:

   CONFIG_HOST_WINDOWS=y           : Windows operating system
   CONFIG_WINDOWS_CYGWIN=y         : POSIX environment under windows
   CONFIG_ARMV7A_TOOLCHAIN_EABIW=y : Generic GCC EABI toolchain for Windows

   If you are running on Linux, make *certain* that you have
   CONFIG_HOST_LINUX=y *before* the first make or you will create a
   corrupt configuration that may not be easy to recover from. See
   the warning in the section "Information Common to All Configurations"
   for further information.

4. This configuration supports logging of debug output to a circular
   buffer in RAM.  This feature is discussed fully in this Wiki page:
   https://cwiki.apache.org/confluence/display/NUTTX/SYSLOG . Relevant
   configuration settings are summarized below:

   File System:

   Device Drivers:
   CONFIG_RAMLOG=y             : Enable the RAM-based logging feature.
   CONFIG_RAMLOG_SYSLOG=y      : This enables the RAM-based logger as the
                                 system logger.
   CONFIG_RAMLOG_NONBLOCKING=y : Needs to be non-blocking for dmesg
   CONFIG_RAMLOG_BUFSIZE=16384 : Buffer size is 16KiB

   NOTE: This RAMLOG feature is really only of value if debug output
   is enabled.  But, by default, no debug output is disabled in this
   configuration.  Therefore, there is no logic that will add anything
   to the RAM buffer.  This feature is configured and in place only
   to support any future debugging needs that you may have.

   If you don't plan on using the debug features, then by all means
   disable this feature and save 16KiB of RAM!

   NOTE: There is an issue with capturing data in the RAMLOG:  If
   the system crashes, all of the crash dump information will into
   the RAMLOG and you will be unable to access it!  You can tell that
   the system has crashed because (a) it will be unresponsive and (b)
   the RED LED will be blinking at about 2Hz.

   That is another good reason to disable the RAMLOG!

5. This configuration executes out of SDRAM flash and is loaded into
   SDRAM from NAND, Serial DataFlash, SD card or from a TFTPC sever via
   U-Boot, BareBox, or the DRAMBOOT configuration described above.  Data
   also is positioned in SDRAM.

   The load address is different for the DRAMBOOT program and the Linux
   bootloaders.  This can easily be reconfigured, however:

     CONFIG_SAMA5D2XULT_DRAM_BOOT=y

   See the section above entitled "Creating and Using DRAMBOOT" above
   for more information.  Here is a summary of the steps that I used
   to boot the NSH configuration:

     a. Create the DRAMBOOT program as described above.  It should be
        configured with CONFIG_SAMA5D2XULT_DRAM_START=y so that DRAMBOOT
        will immediately start the program.  You may not want to do
        this is your prefer to break in with GDB.

     b. Write the DRAMBOOT program binary (nuttx.bin) to a microSD
        card as "boot.bin".  Insert the microSD card into the boar;
        The ROM Bootloader should now boot DRAMBOOT on reset and you
        should see this message:

          Send Intel HEX file now

     c. Build the NSH version of NuttX.  Send the Intel HEX of NSH
        at the prompt.  After the file is received, NSH should start
        automatically.

   At times the past, have have tested with nuttx.bin on an SD card and
   booting with U-Boot.  These are the commands that I used to boot NuttX
   from the SD card:

     U-Boot> fatload mmc 0 0x20008000 nuttx.bin
     U-Boot> go 0x20008E20

6. Board LEDs and buttons are supported as described under "Buttons and
   LEDs".  The interrupt button test is also enabled as an NSH built-in
   commands.  To run this test, you simply inter the command:

      nsh>buttons [npresses]

   The interrupt button test will log button press information to the
   syslog.  Since the RAMLOG is enabled, the SYSLOG output will be
   captured to a circular buffer in ram and may be examined using the
   NSH dmesg command:

   nsh> buttons 2
   nsh> dmesg
   maxbuttons: 2
   Attached handler at 200106f0 to button 0 [PB_USER], oldhandler:0
   IRQ:81 Button 0:PB_USER SET:01:
     PB_USER depressed
   IRQ:81 Button 0:PB_USER SET:00:
     PB_USER released
   IRQ:81 Button 0:PB_USER SET:01:
     PB_USER depressed
   IRQ:81 Button 0:PB_USER SET:00:
     PB_USER released

7. This configuration supports /dev/null, /dev/zero, and /dev/random.

     CONFIG_DEV_NULL=y    : Enables /dev/null
     CONFIG_DEV_ZERO=y    : Enabled /dev/zero

   Support for /dev/random is implemented using the SAMA5D2's True
   Random Number Generator (TRNG).  See the section above entitled
   "TRNG and /dev/random" for information about configuring /dev/random.

    CONFIG_SAMA5_TRNG=y   : Enables the TRNG peripheral
    CONFIG_DEV_RANDOM=y   : Enables /dev/random

8. This configuration has support for NSH built-in applications enabled.
   No built-in applications are enabled, however.

9. This configuration has support for the FAT and PROCFS file
   systems built in.

   The FAT file system includes long file name support.  Please be aware
   that Microsoft claims patents against the long file name support (see
   more discussion in the top-level NOTICE file).

     CONFIG_FS_FAT=y        : Enables the FAT file system
     CONFIG_FAT_LCNAMES=y   : Enable lower case 8.3 file names
     CONFIG_FAT_LFN=y       : Enables long file name support
     CONFIG_FAT_MAXFNAME=32 : Arbitrarily limits the size of a path
                              segment name to 32 bytes

   The PROCFS file system is enabled simply with:

     CONFIG_FS_PROCFS=y     : Enable PROCFS file system

10. The Real Time Clock/Calendar (RTC) is enabled in this configuration. See the section entitled "RTC" above for detailed configuration settings.

    The RTC alarm is not enabled by default since there is nothing in this configuration that uses it. The alarm can easily be enabled, however, as described in the "RTC" section.

    The time value from the RTC will be used as the NuttX system time in all timestamp operations. You may use the NSH 'date' command to set or view the RTC as described above in the "RTC" section.

    NOTE: If you want the RTC to preserve time over power cycles, you will need to install a battery in the battery holder (J12) and close the jumper, JP13.

sdmmcnsh:

This is a configuration based on the NuttShell (NSH). The SDMMC
peripheral is enabled, and can read and write to a VFAT filesystem
on the SD Card.