README
======

This README file discusses the port of NuttX to the Atmel SAM E70 Xplained
Evaluation Kit (ATSAME70-XPLD). This board features the ATSAME70Q21 Cortex-M7
microcontroller.

Contents
========

- Status/Open Issues
- Serial Console
- SD card
- Automounter
- LEDs and Buttons
- AT24MAC402 Serial EEPROM
- Program FLASH Access
- Networking
- USBHS Device Controller Driver
- MCAN1 Loopback Test
- SPI Slave
- Click Shield
- Tickless OS
- Debugging
- Using OpenOCD and GDB to flash via the EDBG chip
- Configurations

Status/Open Issues
==================

2015-11-30: The basic NSH configuration is function with serial console
via the EDBG VCOM and LED and buttons support. SDRAM and the HSMCI
SD card slot also appear to be fully functional.

See also configs/samv71-xult/README.txt

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

The SAME70-XPLD has no on-board RS-232 drivers so it will be necessary to
use either the VCOM or an external RS-232 driver. Here are some options.

- Arduino Serial Shield: One option is to use an Arduino-compatible
serial shield. This will use the RXD and TXD signals available at pins
0 an 1, respectively, of the Arduino "Digital Low" connector. On the
SAME70-XPLD board, this corresponds to UART3:

------ ------ ------- ------- --------
Pin on SAME70 Arduino Arduino SAME70
J503 PIO Name Pin Function
------ ------ ------- ------- --------
1 PD28 D0/RX0 0 URXD3
2 PD30 D1/TX0 1 UTXD3
------ ------ ------- ------- --------

In this configuration, an external RS232 driver can also be used
instead of the shield. Simply connext as follows:

--------- -----------
Arduino RS-232
Pin Label Connection
--------- -----------
D0 (RXD) RX
D1 (TXD) TX
GND GND
5VO Vcc
--------- -----------

- Arduino Communications. Additional UART/USART connections are available
on the Arduino Communications connection J505 and J507:

--------- ---------- --------------------------------
Connector SAME70 Pin Description
--------- ---------- --------------------------------
J503 1 URXD3 PD28 Standard Arduino serial (D0/RXD)
J503 2 UTXD3 PD30 Standard Arduino serial (D1/TXD)
--------- ---------- --------------------------------
J505 3 URXD4 PD18 Arduino D19
J505 4 UTXD4 PD19 Arduino D18
J505 5 RXD2 PD15 Arduino D17
J505 6 TXD2 PD16 Arduino D16
J505 7 RXD0 PB0 Arduino D15
J505 8 TXD0 PB1 Arduino D14
--------- ---------- --------------------------------
J507 27 RXD1 PA21 Arduino D46
J507 28 TXD1 PB4 Arduino D47
--------- ---------- --------------------------------

- SAMV7-XULT EXTn connectors. USART pins are also available the EXTn
connectors. The following are labelled in the User Guide for USART
functionality:

SAME70 Xplained Connectors
--------- ---------- --------------------------------
Connector SAME70 Pin Description
--------- ---------- --------------------------------
J401 13 RXD0 PB0 EXT1 UART_RX
J401 14 TXD0 PB1 EXT1 UART_7X
--------- ---------- --------------------------------
J402 13 RXD1 PA21 EXT2 UART_RX
J402 14 TXD1 PB4 EXT2 UART_TX
--------- ---------- --------------------------------

- VCOM. The Virtual Com Port gateway is available on USART1:

EDBG VCOM Interface
---------------- --------- --------------------------
EDBG Singal SAME70
---------------- --------- --------------------------
EDBG_CDC_UART_RX TXD1 PB4
EDBG_CDC_UART_TX RXD1 PA21
---------------- --------- --------------------------

Any of these options can be selected as the serial console by:

1. Enabling the UART/USART peripheral in the
"System Type -> Peripheral Selection" menu, then
2. Configuring the peripheral in the "Drivers -> Serial Configuration"
menu.

NOTE: If USART1 is used (TXD1, RXD1), then PB4 must be reconfigured in the
SUPC. Normally, PB4 is TDI. When it is reconfigured for use with USART1,
the capability to debug is lost! If you plan to debug you should most
certainly not use USART1.

SD Card
=======

Card Slot
---------
The SAM E70 Xplained has one standard SD card connector that is connected to
the High Speed Multimedia Card Interface (HSMCI) of the SAM
E70. SD card connector:

------ ----------------- ---------------------
SAME70 SAME70 Shared functionality
Pin Function
------ ----------------- ---------------------
PA30 MCDA0 (DAT0)
PA31 MCDA1 (DAT1)
PA26 MCDA2 (DAT2)
PA27 MCDA3 (DAT3)
PA25 MCCK (CLK) Shield
PA28 MCCDA (CMD)
PC16 Card Detect (C/D) Shield
------ ----------------- ---------------------

Configuration Settings
----------------------
Enabling HSMCI support. The SAMV7-XULT provides a one, full-size SD memory
card slots. The full size SD card slot connects via HSMCI0. Support for
the SD slots can be enabled with the following settings:

System Type->SAMV7 Peripheral Selection
CONFIG_SAMV7_HSMCI0=y : To enable HSMCI0 support
CONFIG_SAMV7_XDMAC=y : XDMAC is needed by HSMCI0/1

System Type
CONFIG_SAMV7_GPIO_IRQ=y : PIO interrupts needed
CONFIG_SAMV7_GPIOD_IRQ=y : Card detect pin is on PD18

Device Drivers -> MMC/SD Driver Support
CONFIG_MMCSD=y : Enable MMC/SD support
CONFIG_MMSCD_NSLOTS=1 : One slot per driver instance
CONFIG_MMCSD_MULTIBLOCK_DISABLE=y : (REVISIT)
CONFIG_MMCSD_HAVECARDDETECT=y : Supports card-detect PIOs
CONFIG_MMCSD_MMCSUPPORT=n : Interferes with some SD cards
CONFIG_MMCSD_SPI=n : No SPI-based MMC/SD support
CONFIG_MMCSD_SDIO=y : SDIO-based MMC/SD support
CONFIG_SDIO_DMA=y : Use SDIO DMA
CONFIG_SDIO_BLOCKSETUP=y : Needs to know block sizes

RTOS Features -> Work Queue Support
CONFIG_SCHED_WORKQUEUE=y : Driver needs work queue support

Application Configuration -> NSH Library
CONFIG_NSH_ARCHINIT=y : NSH board-initialization, OR
CONFIG_BOARD_INITIALIZE=y

Using the SD card
-----------------

1) After booting, the HSCMI device will appear as /dev/mmcsd0.

2) If you try mounting an SD card with nothing in the slot, the mount will
fail:

nsh> mount -t vfat /dev/mmcsd0 /mnt/sd0
nsh: mount: mount failed: 19

NSH can be configured to provide errors as strings instead of
numbers. But in this case, only the error number is reported. The
error numbers can be found in nuttx/include/errno.h:

#define ENODEV 19
#define ENODEV_STR "No such device"

So the mount command is saying that there is no device or, more
correctly, that there is no card in the SD card slot.

3) Inserted the SD card. Then the mount should succeed.

nsh> mount -t vfat /dev/mmcsd0 /mnt/sd0
nsh> ls /mnt/sd1
/mnt/sd1:
atest.txt
nsh> cat /mnt/sd1/atest.txt
This is a test

NOTE: See the next section entitled "Auto-Mounter" for another way
to mount your SD card.

4) Before removing the card, you must umount the file system. This is
equivalent to "ejecting" or "safely removing" the card on Windows: It
flushes any cached data to an SD card and makes the SD card unavailable
to the applications.

nsh> umount -t /mnt/sd0

It is now safe to remove the card. NuttX provides into callbacks
that can be used by an application to automatically unmount the
volume when it is removed. But those callbacks are not used in
these configurations.

Auto-Mounter
============

NuttX implements an auto-mounter than can make working with SD cards
easier. With the auto-mounter, the file system will be automatically
mounted when the SD card is inserted into the HSMCI slot and automatically
unmounted when the SD card is removed.

Here is a sample configuration for the auto-mounter:

File System Configuration
CONFIG_FS_AUTOMOUNTER=y

Board-Specific Options
CONFIG_SAME70XPLAINED_HSMCI0_AUTOMOUNT=y
CONFIG_SAME70XPLAINED_HSMCI0_AUTOMOUNT_FSTYPE="vfat"
CONFIG_SAME70XPLAINED_HSMCI0_AUTOMOUNT_BLKDEV="/dev/mmcsd0"
CONFIG_SAME70XPLAINED_HSMCI0_AUTOMOUNT_MOUNTPOINT="/mnt/sdcard"
CONFIG_SAME70XPLAINED_HSMCI0_AUTOMOUNT_DDELAY=1000
CONFIG_SAME70XPLAINED_HSMCI0_AUTOMOUNT_UDELAY=2000

WARNING: SD cards should never be removed without first unmounting
them. This is to avoid data and possible corruption of the file
system. Certainly this is the case if you are writing to the SD card
at the time of the removal. If you use the SD card for read-only access,
however, then I cannot think of any reason why removing the card without
mounting would be harmful.

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

LEDs
----
A single LED is available driven by PC8.

This LED is 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/sam_autoleds.c. The LED is used to encode
OS-related events as follows:

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

Buttons
-------
SAM E70 Xplained contains two mechanical buttons. One button is the RESET
button connected to the SAM E70 reset line and the other, PA11, is a generic
user configurable button. When a button is pressed it will drive the I/O
line to GND.

NOTE: There are no pull-up resistors connected to the generic user buttons
so it is necessary to enable the internal pull-up in the SAM E70 to use the
button.

AT24MAC402 Serial EEPROM
========================

Ethernet MAC Address
--------------------
The SAM E70 Xplained features one external AT24MAC402 serial EEPROM with an
EIA-48 MAC address connected to the SAM E70 through I2C. This device
contains a MAC address for use with the Ethernet interface.

Connectivity:

------ -------- --------
SAME70 SAME70 I2C
Pin Function Function
------ -------- --------
PA03 TWID0 SDA
PA04 TWICK0 SCL
------ -------- --------

I2C address:

The 7-bit addresses of the AT24 part are 0b1010AAA for the normal 2Kbit
memory and 0b1011aaa for the "extended memory" where aaa is the state of
the A0, A1, and A3 pins on the part. On the SAME70-XPLD board, these
are all pulled high so the full, 7-bit address is 0x5f.

Configuration
-------------

System Type -> SAMV7 Peripheral Support
CONFIG_SAMV7_TWIHS0=y : Used to access the EEPROM
CONFIG_SAMV7_TWIHS0_FREQUENCY=100000

Device drivers -> Memory Technology Devices
CONFIG_MTD_AT24XX=y : Enable the AT24 device driver
CONFIG_AT24XX_SIZE=2 : Normal EEPROM is 2Kbit (256b)
CONFIG_AT24XX_ADDR=0x57 : Normal EEPROM address */
CONFIG_AT24XX_EXTENDED=y : Supports an extended memory region
CONFIG_AT24XX_EXTSIZE=160 : Extended address up to 0x9f

MTD Configuration Data
----------------------
The AT24 EEPROM can also be used to storage of up to 256 bytes of
configuration data:

Device drivers -> Memory Technology Devices

The configuration data device will appear at /dev/config.

Networking
==========

KSZ8081RNACA Connections
------------------------

------ --------- ---------
SAME70 SAME70 Ethernet
Pin Function Functio
------ --------- ---------
PD0 GTXCK REF_CLK
PD1 GTXEN TXEN
PD2 GTX0 TXD0
PD3 GTX1 TXD1
PD4 GRXDV CRS_DV
PD5 GRX0 RXD0
PD6 GRX1 RXD1
PD7 GRXER RXER
PD8 GMDC MDC
PD9 GMDIO MDIO
PA14 GPIO INTERRUPT
PC10 GPIO RESET
------ --------- ---------

Selecting the GMAC peripheral
-----------------------------

System Type -> SAMV7 Peripheral Support
CONFIG_SAMV7_EMAC0=y : Enable the GMAC peripheral (aka, EMAC0)
CONFIG_SAMV7_TWIHS0=y : We will get the MAC address from the AT24 EEPROM
CONFIG_SAMV7_TWIHS0_FREQUENCY=100000

System Type -> EMAC device driver options
CONFIG_SAMV7_EMAC0_NRXBUFFERS=16 : Set aside some RS and TX buffers
CONFIG_SAMV7_EMAC0_NTXBUFFERS=8
CONFIG_SAMV7_EMAC0_RMII=y : The RMII interfaces is used on the board
CONFIG_SAMV7_EMAC0_AUTONEG=y : Use autonegotiation
CONFIG_SAMV7_EMAC0_PHYADDR=1 : KSZ8061 PHY is at address 1
CONFIG_SAMV7_EMAC0_PHYSR=30 : Address of PHY status register on KSZ8061
CONFIG_SAMV7_EMAC0_PHYSR_ALTCONFIG=y : Needed for KSZ8061
CONFIG_SAMV7_EMAC0_PHYSR_ALTMODE=0x7 : " " " " " "
CONFIG_SAMV7_EMAC0_PHYSR_10HD=0x1 : " " " " " "
CONFIG_SAMV7_EMAC0_PHYSR_100HD=0x2 : " " " " " "
CONFIG_SAMV7_EMAC0_PHYSR_10FD=0x5 : " " " " " "
CONFIG_SAMV7_EMAC0_PHYSR_100FD=0x6 : " " " " " "

PHY selection. Later in the configuration steps, you will need to select
the KSZ8061 PHY for EMAC (See below)

Networking Support
CONFIG_NET=y : Enable Neworking
CONFIG_NET_SOCKOPTS=y : Enable socket operations
CONFIG_NET_ETH_MTU=562 : Maximum packet size (MTU) 1518 is more standard
CONFIG_NET_ETH_TCP_RECVWNDO=562 : Should be the same as CONFIG_NET_ETH_MTU
CONFIG_NET_ARP=y : ARP support should be enabled
CONFIG_NET_ARP_SEND=y : Use ARP to get peer address before sending
CONFIG_NET_TCP=y : Enable TCP/IP networking
CONFIG_NET_TCPBACKLOG=y : Support TCP/IP backlog
CONFIG_NET_TCP_READAHEAD=y : Enable TCP read-ahead buffering
CONFIG_NET_TCP_WRITE_BUFFERS=y : Enable TCP write buffering
CONFIG_NET_UDP=y : Enable UDP networking
CONFIG_NET_BROADCAST=y : Support UDP broadcase packets
CONFIG_NET_ICMP=y : Enable ICMP networking
CONFIG_NET_ICMP_PING=y : Needed for NSH ping command
: Defaults should be okay for other options
Device drivers -> Network Device/PHY Support
CONFIG_NETDEVICES=y : Enabled PHY selection
CONFIG_ETH0_PHY_KSZ8061=y : Select the KSZ8061 PHY used with EMAC0

Device drivers -> Memory Technology Devices
CONFIG_MTD_AT24XX=y : Enable the AT24 device driver
CONFIG_AT24XX_SIZE=2 : Normal EEPROM is 2Kbit (256b)
CONFIG_AT24XX_ADDR=0x57 : Normal EEPROM address */
CONFIG_AT24XX_EXTENDED=y : Supports an extended memory region
CONFIG_AT24XX_EXTSIZE=160 : Extended address up to 0x9f

RTOS Features ->Work Queue Support
CONFIG_SCHED_WORKQUEUE=y : Work queue support is needed
CONFIG_SCHED_HPWORK=y
CONFIG_SCHED_HPWORKSTACKSIZE=2048 : Might need to be increased

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 an IP address
CONFIG_NSH_DRIPADDR=0x0a000001 : IP address of gateway/host PC
CONFIG_NSH_NETMASK=0xffffff00 : Netmask
CONFIG_NSH_NOMAC=n : We will get the IP address from EEPROM
: Defaults should be okay for other options

Cache-Related Issues
--------------------

I- and D-Caches can be enabled but the D-Cache must be enabled in write-
through mode. This is to work around issues with the RX and TX descriptors
with are 8-bytes in size. But the D-Cache cache line size is 32-bytes.
That means that you cannot reload, clean or invalidate a descriptor without
also effecting three neighboring descriptors. Setting write through mode
eliminates the need for cleaning the D-Cache. If only reloading and
invalidating are done, then there is no problem.

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 SAME70-XPLD 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 SAME70-XPLD:

$ 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-7.9
nsh> help
help usage: help [-v] []

[ 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 feature, you experience a delay on booting.
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 a minute! You will probably think that
NuttX has crashed! And then, when it finally does come up, the
network will not be available.

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 networking initialization feature by itself 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.

- Furthermore, there is no support for detecting loss of the network
connection and recovery of networking when the connection is restored.

Both of these shortcomings can 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_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 SAMV7 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. Rather, the PHY interrupt is provided via some
board-specific GPIO and the board-specific logic must provide support
for that GPIO 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(). This logic can be found at
nuttx/configs/same70-xplained/src/sam_ethernet.c.

- 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.

Networking Support -> Networking Device Support
CONFIG_NETDEV_PHY_IOCTL=y : Enable PHY ioctl support

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

USBHS Device Controller Driver
==============================
The USBHS device controller driver is enabled with he following configuration
settings:

Device Drivers -> USB Device Driver Support
CONFIG_USBDEV=y : Enable USB device support
For full-speed/low-power mode:
CONFIG_USBDEV_DUALSPEED=n : Disable High speed support
For high-speed/normal mode:
CONFIG_USBDEV_DUALSPEED=y : Enable High speed support
CONFIG_USBDEV_DMA=y : Enable DMA methods
CONFIG_USBDEV_MAXPOWER=100 : Maximum power consumption
CONFIG_USBDEV_SELFPOWERED=y : Self-powered device

System Type -> SAMV7 Peripheral Selection
CONFIG_SAMV7_USBDEVHS=y

System Type -> SAMV7 USB High Sppeed Device Controller (DCD options
For full-speed/low-power mode:
CONFIG_SAMV7_USBDEVHS_LOWPOWER=y : Select low power mode
For high-speed/normal mode:
CONFIG_SAMV7_USBDEVHS_LOWPOWER=n : Don't select low power mode
CONFIG_SAMV7_USBHS_NDTDS=32 : Number of DMA transfer descriptors
CONFIG_SAMV7_USBHS_PREALLOCATE=y : Pre-allocate descriptors

As discussed in the SAMV71-XULT README, this driver will not work correctly
if the write back data cache is enabled. You must have:

CONFIG_ARMV7M_DCACHE_WRITETHROUGH=y

In order to be usable, you must all enabled some class driver(s) for the
USBHS device controller. Here, for example, is how to configure the CDC/ACM
serial device class:

Device Drivers -> USB Device Driver Support
CONFIG_CDCACM=y : USB Modem (CDC ACM) support
CONFIG_CDCACM_EP0MAXPACKET=64 : Enpoint 0 packet size
CONFIG_CDCACM_EPINTIN=1 : Interrupt IN endpoint number
CONFIG_CDCACM_EPINTIN_FSSIZE=64 : Full speed packet size
CONFIG_CDCACM_EPINTIN_HSSIZE=64 : High speed packet size
CONFIG_CDCACM_EPBULKOUT=3 : Bulk OUT endpoint number
CONFIG_CDCACM_EPBULKOUT_FSSIZE=64 : Full speed packet size
CONFIG_CDCACM_EPBULKOUT_HSSIZE=512 : High speed packet size
CONFIG_CDCACM_EPBULKIN=2 : Bulk IN endpoint number
CONFIG_CDCACM_EPBULKIN_FSSIZE=64 : Full speed packet size
CONFIG_CDCACM_EPBULKIN_HSSIZE=512 : High speed packet size
CONFIG_CDCACM_NWRREQS=4 : Number of write requests
CONFIG_CDCACM_NRDREQS=8 : Number of read requests
CONFIG_CDCACM_BULKIN_REQLEN=96 : Size of write request buffer (for full speed)
CONFIG_CDCACM_BULKIN_REQLEN=768 : Size of write request buffer (for high speed)
CONFIG_CDCACM_RXBUFSIZE=257 : Serial read buffer size
CONFIG_CDCACM_TXBUFSIZE=193 : Serial transmit buffer size (for full speed)
CONFIG_CDCACM_TXBUFSIZE=769 : Serial transmit buffer size (for high speed)
CONFIG_CDCACM_VENDORID=0x0525 : Vendor ID
CONFIG_CDCACM_PRODUCTID=0xa4a7 : Product ID
CONFIG_CDCACM_VENDORSTR="NuttX" : Vendor string
CONFIG_CDCACM_PRODUCTSTR="CDC/ACM Serial" : Product string

Device Drivers -> Serial Driver Support
CONFIG_SERIAL_REMOVABLE=y : Support for removable serial device

The CDC/ACM application provides commands to connect and disconnect the
CDC/ACM serial device:

CONFIG_SYSTEM_CDCACM=y : Enable connect/disconnect support
CONFIG_SYSTEM_CDCACM_DEVMINOR=0 : Use device /dev/ttyACM0
CONFIG_CDCACM_RXBUFSIZE=??? : A large RX may be needed

If you include this CDC/ACM application, then you can connect the CDC/ACM
serial device to the host by entering the command 'sercon' and you detach
the serial device with the command 'serdis'. If you do no use this
application, they you will have to write logic in your board initialization
code to initialize and attach the USB device.

MCAN1 Loopback Test
===================

MCAN1
-----
SAM E70 Xplained has two MCAN modules that performs communication according
to ISO11898-1 (Bosch CAN specification 2.0 part A,B) and Bosch CAN FD
specification V1.0. MCAN1 is connected to an on-board ATA6561 CAN physical-layer
transceiver.

------- -------- -------- -------------
SAM E70 FUNCTION ATA6561 SHARED
PIN FUNCTION FUNCTIONALITY
------- -------- -------- -------------
PC14 CANTX1 TXD Shield
PC12 CANRX1 RXD Shield
------- -------- -------- -------------

Enabling MCAN1
--------------
These modifications may be applied to the same70-xplained/nsh configuration in order
to enable MCAN1:

Device Drivers -> CAN Driver support
CONFIG_CAN=y # Enable the upper-half CAN driver
CONFIG_CAN_FIFOSIZE=8
CONFIG_CAN_NPENDINGRTR=4

System Type -> SAMV7 Peripheral Selections
CONFIG_SAMV7_MCAN1=y # Enable MCAN1 as the lower-half

System Type -> MCAN device driver options
CONFIG_SAMV7_MCAN_CLKSRC_MAIN=y # Use the MAIN clock as the source
CONFIG_SAMV7_MCAN_CLKSRC_PRESCALER=1

System Type ->MCAN device driver options -> MCAN1 device driver options
CONFIG_SAMV7_MCAN1_ISO11899_1=y # Loopback test only support ISO11899-1
CONFIG_SAMV7_MCAN1_LOOPBACK=y # Needed for loopback test
CONFIG_SAMV7_MCAN1_BITRATE=500000 # Not critical for loopback test
CONFIG_SAMV7_MCAN1_PROPSEG=2 # Bit timing setup
CONFIG_SAMV7_MCAN1_PHASESEG1=11 # " " " " " "
CONFIG_SAMV7_MCAN1_PHASESEG2=11 # " " " " " "
CONFIG_SAMV7_MCAN1_FSJW=4 # " " " " " "
CONFIG_SAMV7_MCAN1_FBITRATE=2000000 # CAN_FD BTW mode is not used
CONFIG_SAMV7_MCAN1_FPROPSEG=2 # " " " " " " "" " " " "
CONFIG_SAMV7_MCAN1_FPHASESEG1=4 # " " " " " " "" " " " "
CONFIG_SAMV7_MCAN1_FPHASESEG2=4 # " " " " " " "" " " " "
CONFIG_SAMV7_MCAN1_FFSJW=2 # " " " " " " "" " " " "
CONFIG_SAMV7_MCAN1_NSTDFILTERS=0 # Filters are not used in the loopback test
CONFIG_SAMV7_MCAN1_NEXTFILTERS=0 # " " " " " " " " "" " " " " " "
CONFIG_SAMV7_MCAN1_RXFIFO0_32BYTES=y # Each RX FIFO0 element is 32 bytes
CONFIG_SAMV7_MCAN1_RXFIFO0_SIZE=8 # There are 8 queue elements
CONFIG_SAMV7_MCAN1_RXFIFO0_32BYTES=y # Each RX FIFO1 element is 32 bytes
CONFIG_SAMV7_MCAN1_RXFIFO0_SIZE=8 # There are 8 queue elements
CONFIG_SAMV7_MCAN1_RXBUFFER_32BYTES=y # Each RX BUFFER is 32 bytes
CONFIG_SAMV7_MCAN1_TXBUFFER_32BYTES=y # Each TX BUFFER is 32 bytes
CONFIG_SAMV7_MCAN1_TXFIFOQ_SIZE=8 # There are 8 queue elements
CONFIG_SAMV7_MCAN1_TXEVENTFIFO_SIZE=0 # The event FIFO is not used

Enabling the CAN Loopback Test
------------------------------
Application Configuration -> Examples -> CAN Example
CONFIG_EXAMPLES_CAN=y # Enables the CAN test

Enabling CAN Debug Output
-------------------------
Build Setup -> Debug Options
CONFIG_DEBUG_FEATURES=y # Enables general debug features
CONFIG_DEBUG_INFO=y # Enables verbose output
CONFIG_DEBUG_CAN_INFO=y # Enables debug output from CAN

CONFIG_STACK_COLORATION=y # Monitor stack usage
CONFIG_DEBUG_SYMBOLS=y # Needed only for use with a debugger
CONFIG_DEBUG_NOOPT=y # Disables optimization

System Type -> MCAN device driver options
CONFIG_SAMV7_MCAN_REGDEBUG=y # Super low level register debug output

SPI Slave
=========

An interrutp driven SPI slave driver as added on 2015-08-09 but has not
been verified as of this writing. See discussion in include/nuttx/spi/slave.h
and below.

I do not yet have a design that supports SPI slave DMA. And, under
certain, very limited conditions, I think it can be done. Those
certain conditions are:

a) The master does not tie the chip select to ground. The master must
raise chip select at the end of the transfer. Then I do not need to
know the length of the transfer; I can cancel the DMA when the chip
is de-selected.

b) The protocol includes a dummy read after sending the command. This
is very common in SPI device and should not be an issue if it is
specified. This dummy read time provides time to set up the DMA.
So the protocol would be:

i) Master drops the chip select.
ii) Master sends the command which will indicate whether the master
is reading, writing, or exchanging data. The master discards
the garbage return value.
iii) Slave is interrupted when the command word is received. The
SPI device then decodes the command word and setups up the
subsequent DMA.
iv) Master sends a dummy word and discards the return value.
During the bit times to shift the dummy word, the slave has time
to set up the DMA.
v) Master then reads or writes (or exchanges) the data If the DMA
is in place, the transfer should continue normally.
vi) At the end of the data transfer the master raises the chip
select.

c) There are limitations in the word time, i.e., the time between the
interrupt for each word shifted in from the master.

The controller driver will get events after the receipt of each word in
ii), iv), and v). The time between each word will be:

word-time = nbits * bit time + inter-word-gap

So for an 8 bit interface at 20MHz, the words will be received from the
master a 8 * 50nsec = 400 nsec + inter-word-gap. That is the time
during which the dummy word would be shifted and during which we
receive the interrupt for the command word, interpret the command word,
and to set up the DMA for the remaining word transfer. I don't think
that is possible, at least not at 20 MHz.

That is far too fast even for the interrupt driven solution that I have
in place now. It could not work at 20MHz. If we suppose that interrupt
processing is around 1 usec, then an 8 bit interface could not have bit
times more than 125 nsec or 8 KHz. Interrupt handling should be faster
than 1 usec, but not a lot faster. I have not benchmarked it. NuttX
also supports special, zero latency interrupts that could bring the
interrupt time down even more.

Note that we would also have a little more processing time if you used
16-bit SPI word size.

Note also that the interrupt driven approach would have this same basic
performance limitation with the additional disadvantage that:

a) The driver will receive two interrupts per word exchanged:

i) One interrupt will be received when the word is shifted in from
the master (at the end of 8-bit times). This is a data received
interrupt.

ii) And another interrupt when the next words moved to the shift-out
register, freeing up the transmit holding register. This is the
data sent interrupt.

The ii) event should be very soon after the i) event.

Without DMA, the only way to reduce the interrupt rate would be to add
interrupt-level polling to detect the when transmit holding register
is available. That is not really a good idea.

b) It will hog all of the CPU for the duration of the transfer).

Click Shield
============

In the mrf24j40-starhub configuration, a click shield from
MikroElectronika was used along with a Click "Bee" module. The click
shield supports two click shields and the following tables describe the
relationship between the pins on each click shield, the Arduino
connector and the SAME70 pins.

--------- ---------------------- -------- --------- ------------------ ----------
mikroBUS1 Arduino SAME70 mikroBUS2 Arduino SAME70
--------- ---------------------- -------- --------- ------------------ ----------
AN HD1 A0 AN0 Pin 1 AD0 PD26 AN HD1 A1 AN1 Pin 2 AD1 PC31
RST HD1 A3 Pin 4 AD3 PA19 RST HD1 A2 Pin 3 AD2 PD30
CS HD4 D10 SPI-SS Pin 8 D10 PD25 CS HD4 D9 Pin 9 D9 PC9
SCK HD4 D13 SPI-SCK Pin 5 D13 PD22 SCK Same
MISO HD4 D12 SPI-MISO Pin 6 D12 PD20 MISO Same
MOSI HD4 D11 SPI-MOSI Pin 7 D11 PD21 MOSI Same
3.3V N/A 3.3V N/A
GND N/A GND N/A
PWM HD3 D6 PWMA Pin 2 D6 PC19 PWM HD3 D5 PWMB Pin 5 D5 PD11
INT HD3 D2 INT0 Pin 6 D2 PA5 INT HD3 D3 INT1 Pin 5 D3 PA6
RX HD3 D0 HDR-RX* Pin 8 D0 PD28 RX Same
TX HD3 D1 HDR-TX* Pin 7 D1 PD30 TX Same
SCL HD1 A5 I2C-SCL Pin 5 AD5 PC30 SDA Same
SDA HD1 A4 I2C-SDA Pin 6 AD4 PC13 SCL Same
5V N/A 5V N/A
GND N/A GND N/A
--------- ---------------------- -------- --------- ------------------ ----------

* Depends upon setting of SW1, UART vs PROG.

--- ----- ------------------------------ ---------------------------------
PIN PORT SHIELD FUNCTION SAME70PIN CONFIGURATION
--- ----- ------------------------------ ---------------------------------
AD0 PD26 microBUS2 Analog TD PD26 *** Not an AFE pin ***
AD1 PC31 microBUS2 Analog PC31 AFE1_AD6 GPIO_AFE1_AD6
AD2 PD30 microBUS2 GPIO reset output PD30
AD3 PA19 microBUS1 GPIO reset output PA19
AD4 PC13 (both) I2C-SDA PC13 *** Does not support I2C SDA ***
AD5 PC30 (both) I2C-SCL PC30 *** Does not support I2C SCL ***
AD6 PA17 *** Not used ***
AD7 PC12 *** Not used ***
D0 PD28 (both) HDR_RX PD28 URXD3 GPIO_UART3_RXD
D1 PD30 (both) HDR_TX PD30 UTXD3 GPIO_UART3_TXD_1
D2 PA5 microBUS1 GPIO interrupt input PA5
D3 PA6 microBUS2 GPIO interrupt input PA6
D4 PD27 *** Not used ***
D5 PD11 microBUS2 PWMB PD11 PWMC0_H0
D6 PC19 microBUS1 PWMA PC19 PWMC0_H2
D7 PA2 *** Not used ***
D8 PA17 *** Not used ***
D9 PC9 microBUS2 CS GPIO output PC9
D10 PD25 microBUS1 CS GPIO output PD25 SPI0_NPCS1
D11 PD21 (both) SPI-MOSI PD21 SPI0_MOSI GPIO_SPI0_MOSI
D12 PD20 (both) SPI-MISO PD20 SPI0_MISO GPIO_SPI0_MISO
D13 PD22 (both) SPI-SCK PD22 SPI0_SPCK GPIO_SPI0_SPCK

NOTE: The click shield fits close to the Arduino connect and cannot be
installed directly because it hits the RJ45 connector. You have to get
some extra Arduino connectors to raise the Click shield so that it clears
the RJ45.

This may be a problem only for me because the Arduino connectors that I
soldered onto the SAME70-Xplained are short (around 10mm clearance from
the board). Taller headers might clear the RJ45 connector (around 15mm).

NOTE: Mikroelektronika provides two different click shields: A UNO style
shield with two click mikroBUSes and a larger Mega shield with three
click mikroBUSes. The above discusses on the UNO shield. I know that the
serial ports, at least, differ on the two shields.

UPDATE: And it appears the that Mega shield is *not* compatible with the
SAME70-Xplained. I am told that the SPI in mikroBUS slots does not connect
to pins on the SAME70-Xplained that can support the SPI communications.
Avoid this triple mikroBUS shield!

Tickless OS
===========

Background
----------
By default, a NuttX configuration uses a periodic timer interrupt that
drives all system timing. The timer is provided by architecture-specific
code that calls into NuttX at a rate controlled by CONFIG_USEC_PER_TICK.
The default value of CONFIG_USEC_PER_TICK is 10000 microseconds which
corresponds to a timer interrupt rate of 100 Hz.

An option is to configure NuttX to operation in a "tickless" mode. Some
limitations of default system timer are, in increasing order of
importance:

- Overhead: Although the CPU usage of the system timer interrupt at 100Hz
is really very low, it is still mostly wasted processing time. One most
timer interrupts, there is really nothing that needs be done other than
incrementing the counter.
- Resolution: Resolution of all system timing is also determined by
CONFIG_USEC_PER_TICK. So nothing that be time with resolution finer than
10 milliseconds be default. To increase this resolution,
CONFIG_USEC_PER_TICK an be reduced. However, then the system timer
interrupts use more of the CPU bandwidth processing useless interrupts.
- Power Usage: But the biggest issue is power usage. When the system is
IDLE, it enters a light, low-power mode (for ARMs, this mode is entered
with the wfi or wfe instructions for example). But each interrupt
awakens the system from this low power mode. Therefore, higher rates
of interrupts cause greater power consumption.

The so-called Tickless OS provides one solution to issue. The basic
concept here is that the periodic, timer interrupt is eliminated and
replaced with a one-shot, interval timer. It becomes event driven
instead of polled: The default system timer is a polled design. On
each interrupt, the NuttX logic checks if it needs to do anything
and, if so, it does it.

Using an interval timer, one can anticipate when the next interesting
OS event will occur, program the interval time and wait for it to fire.
When the interval time fires, then the scheduled activity is performed.

Configuration
-------------
The following configuration options will enable support for the Tickless
OS for the SAMV7 platforms using TC0 channels 0-3 (other timers or
timer channels could be used making the obvious substitutions):

RTOS Features -> Clocks and Timers
CONFIG_SCHED_TICKLESS=y : Configures the RTOS in tickless mode
CONFIG_SCHED_TICKLESS_ALARM=n : (option not implemented)
CONFIG_SCHED_TICKLESS_LIMIT_MAX_SLEEP=y

System Type -> SAMV7 Peripheral Support
CONFIG_SAMV7_TC0=y : Enable TC0 (TC channels 0-3

System Type -> Timer/counter Configuration
CONFIG_SAMV7_ONESHOT=y : Enables one-shot timer wrapper
CONFIG_SAMV7_FREERUN=y : Enabled free-running timer wrapper
CONFIG_SAMV7_TICKLESS_ONESHOT=0 : Selects TC0 channel 0 for the one-shot
CONFIG_SAMV7_TICKLESS_FREERUN=1 : Selects TC0 channel 1 for the free-
: running timer

The resolution of the clock is provided by the CONFIG_USEC_PER_TICK
setting in the configuration file.

NOTE: In most cases, the slow clock will be used as the timer/counter
input. The SAME70-Xplained board has pads for a 32.768KHz crystal,
however, the boad ships with that position unpopulated. So, be default
this will probably end up using the slow RC oscillator which will give
you very bad timing.

If you add a crystal to your board, you can select to use it with the
definition BOARD_HAVE_SLOWXTAL in the configs/same70-xplained/board.h
file.

The slow clock has a resolution of about 30.518 microseconds. Ideally,
the value of CONFIG_USEC_PER_TICK should be the exact clock resolution.
Otherwise there will be cumulative timing inaccuracies. But a choice
choice of:

CONFIG_USEC_PER_TICK=31

will have an error of 0.6% and will have inaccuracies that will
effect the time due to long term error build-up.

Using the slow clock clock input, the Tickless support is functional,
however, there are inaccuracies in delays. For example,

nsh> sleep 10

results in a delay of maybe 5.4 seconds. But the timing accuracy is
correct if all competing uses of the interval timer are disabled (mostly
from the high priority work queue). Therefore, I conclude that this
inaccuracy is due to the inaccuracies in the representation of the clock
rate. 30.518 usec cannot be represented accurately. Each timing
calculation results in a small error. When the interval timer is very
busy, long delays will be divided into many small pieces and each small
piece has a large error in the calculation. The cumulative error is the
cause of the problem.

Solution: The same70-xplained/src/sam_boot.c file has additional logic
to enable the programmable clock PCK6 as a clock source for the
timer/counters if the Tickless mode is selected. The ideal frequency
would be:

frequency = 1,000,000 / CONFIG_USEC_PER_TICK

The main crystal is selected as the frequency source. The maximum
prescaler value is 256 so the minimum frequency is 46,875 Hz which
corresponds to a period of 21.3 microseconds. A value of
CONFIG_USEC_PER_TICK=20, or 50KHz, would give an exact solution with
a divider of 240.

SAME70 Timer Usage
------------------
This current implementation uses two timers: A one-shot timer to
provide the timed events and a free running timer to provide the current
time. Since timers are a limited resource, that could be an issue on
some systems.

We could do the job with a single timer if we were to keep the single
timer in a free-running at all times. The SAME70 timer/counters have
16-bit counters with the capability to generate a compare interrupt when
the timer matches a compare value but also to continue counting without
stopping (giving another, different interrupt when the timer rolls over
from 0xffff to zero). So we could potentially just set the compare at
the number of ticks you want PLUS the current value of timer. Then you
could have both with a single timer: An interval timer and a free-
running counter with the same timer! In this case, you would want to
to set CONFIG_SCHED_TICKLESS_ALARM in the NuttX configuration.

Patches are welcome!

Debugging
=========

EDBG
----
The on-board EDBG appears to work only with Atmel Studio. You can however,
simply connect a SAM-ICE or J-Link to the JTAG/SWD connector on the board
and that works great. The only tricky thing is getting the correct
orientation of the JTAG connection.

J-Link/JTAG
-----------
I have been using Atmel Studio to write code to flash then I use the Segger
J-Link GDB server to debug. I have been using the 'Device Programming' I
available under the Atmel Studio 'Tool' menu. I have to disconnect the
SAM-ICE while programming with the EDBG. I am sure that you could come up
with a GDB server-only solution if you wanted.

I run GDB like this from the directory containing the NuttX ELF file:

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

OpenOCD/EDBG
------------
Current OpenOCD also works with SAME70-Xplained via EDBG, but I have not
used OpenOCD with the board.

SAM-BA
------
SAM-BA is another option. With SAM-BA, you can load code into FLASH over
a serial port or USB connection by booting into the ROM bootloader.

CMSIS-DAP Programmer
--------------------
Another useful tool for CMSIS-DAP programmer (formerly Atmel EDBG
programmer) available at:

https://github.com/ataradov/edbg

This is a simple command line utility for programming ARM-based MCUs
(currently only Atmel) though CMSIS-DAP SWD interface. It works on Linux,
Mac OS X and Windows. Very useful to around especially if you have the
following issue:

Booting to FLASH or the ROM Bootloader
--------------------------------------
If you use EDBG or JTAG to load code into FLASH, you may be puzzled why
the code does not run. It may be that you are booting into the ROM
bootloader instead of FLASH. That can be fixed by modifying the SAME70's
GPNVM bits.

If your SAME70 is booting in ROM by default, the GPNVM bits will probably
looking something like:

$ edbg.exe -F r,:, -t atmel_cm7
GPNVM Bits: 0x40

Where bit 1 = 0 boots into the ROM bootloader and bit 1 = 1 boots into
FLASH. You want:

$ edbg.exe -F r,:, -t atmel_cm7
GPNVM Bits: 0x42

If you are trying to use SAM-BA, you might have the opposity problem:
The board might be booting into FLASH when you need it to boot into the
ROM bootloader.

That GPNVM bit can be changed using CMSIS-DAP programmer, Atmel studio, or
using this OpenOCD setup:

atsamv gpnvm [('clr'|'set'|'show') bitnum]
Without arguments, shows all bits in the gpnvm register.
Otherwise, clears, sets, or shows one General Purpose Non-Volatile
Memory (gpnvm) bit.

Perhaps SAM-BA supports a way to do this as well???

Using OpenOCD and GDB to flash via the EDBG chip
================================================

Building OpenOCD under Cygwin:

Refer to configs/olimex-lpc1766stk/README.txt

Installing OpenOCD in Linux (but see note below):

sudo apt-get install openocd

NOTE: At the time of writing installing the above openocd package from
the distribution (Ubuntu 14.04) was not enough to get the latest openocd
version supporting the SAME70 Xplained.

The code was obtained from the OpenOCD git repository, available at
https://github.com/ntfreak/openocd.

git clone https://github.com/ntfreak/openocd.git

Then follow the directions of the "Building OpenOCD" section of their README,
but be sure to configure including the CMSIS-DAP interface:

./bootstrap
./configure --enable-cmsis-dap
make
sudo make install

If your configure step fails, you might be missing some dependencies, i.e.:

sudo apt-get install libhidapi-dev

Helper Scripts.

OpenOCD requires a configuration file. I keep the one I used last here:

configs/same70-xplained/tools/atmel_same70_xplained.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 atmel_same70_xplained.cfg file with configuration files in
/usr/share/openocd/scripts. As of this writing, the configuration
files of interest were:

/usr/share/openocd/scripts/interface/cmsis-dap.cfg
/usr/share/openocd/scripts/board/atmel_same70_xplained.cfg
/usr/share/openocd/scripts/target/atsamv.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/same70-xplained/tools/atmel_same70_xplained.cfg

Starting OpenOCD

Then you should be able to start the OpenOCD daemon like:

configs/same70-xplained/tools/oocd.sh $PWD

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'.

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

Information Common to All Configurations
----------------------------------------
Each SAME70-XPLD configuration is maintained in a sub-directory and
can be selected as follow:

cd tools
./configure.sh same70-xplained/
cd -

Before building, make sure that the PATH environment variable include 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 oldconfig
make

The 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 USART1 (the EDBG VCOM)

NOTE: When USART1 is used, the pin PB4 is reconfigured. Normally, PB4
is TDI. When it is reconfigured for use with USART1, the capability to
debug is lost! If you plan to debug you should most certainly not use
USART1. UART3 might be a good option (the Arduino RXD/TXD):

-CONFIG_SAMV7_USART1=y
-CONFIG_USART1_SERIALDRIVER=y
-CONFIG_USART1_SERIAL_CONSOLE=y
-CONFIG_USART1_RXBUFSIZE=256
-CONFIG_USART1_TXBUFSIZE=256
-CONFIG_USART1_BAUD=115200
-CONFIG_USART1_BITS=8
-CONFIG_USART1_PARITY=0
-CONFIG_USART1_2STOP=0

+CONFIG_SAMV7_UART3=y
+CONFIG_UART3_SERIAL_CONSOLE=y
+CONFIG_UART3_RXBUFSIZE=256
+CONFIG_UART3_TXBUFSIZE=256
+CONFIG_UART3_BAUD=115200
+CONFIG_UART3_BITS=8
+CONFIG_UART3_PARITY=0
+CONFIG_UART3_2STOP=0

UART3 is not the default because (1) the placement of the RJ-45 connector
makes it difficult to install Arduino shield cards and (2) the Arduino
connectors are not populated on the board as it comes from the factory.

3. All of these configurations are set up to build under Windows using the
"GNU Tools for ARM Embedded Processors" that is maintained by ARM
(unless stated otherwise in the description of the configuration).

https://developer.arm.com/open-source/gnu-toolchain/gnu-rm

That toolchain selection can easily be reconfigured using
'make menuconfig'. Here are the relevant current settings:

Build Setup:
CONFIG_HOST_WINDOWS=y : Window environment
CONFIG_WINDOWS_CYGWIN=y : Cywin under Windows

System Type -> Toolchain:
CONFIG_ARMV7M_TOOLCHAIN_GNU_EABIW=y : GNU ARM EABI toolchain

NOTE: As of this writing, there are issues with using this tool at
the -Os level of optimization. This has not been proven to be a
compiler issue (as least not one that might not be fixed with a
well placed volatile qualifier). However, in any event, it is
recommend that you use not more that -O2 optimization.

Configuration sub-directories
-----------------------------

mrf24j40-starhub

This configuration implement a hub node in a 6LoWPAN start network.
It is intended for the us the mrf24j40-starpoint configuration with
the clicker2-stm32 configurations. Essentially, the SAME70 Xplained
plays the roll of the hub in the configuration and the clicker2-stm32
boards are the endpoints in the start.

NOTES:

1. The serial console is configured by default for use with and Arduino
serial shield (UART3). You will need to reconfigure if you will
to use a different U[S]ART.

2. This configuration derives from the netnsh configuration, but adds
support for IPv6, 6LoWPAN, and the MRF24J40 IEEE 802.15.4 radio.

3. This configuration uses the Mikroe BEE MRF24j40 click boards and
connects to the SAMV71-XULT using a click shield as described above.

4. You must must have also have at least two clicker2-stm32 boards each
with an MRF24J40 BEE click board in order to run these tests.

5. The network initialization thread is NOT enabled. As a result, the
startup will hang if the Ethernet cable is not plugged in. For more
information, see the paragraphs above entitled "Network Initialization
Thread" and "Network Monitor".

6. Telnet: The clicker2-stm32 star point configuration supports the
Telnet daemon, but not the Telnet client; the star hub configuration
supports both the Telnet client and the Telnet daemon. Therefore,
the star hub can Telnet to any point in the star, but the star
endpoints cannot initiate telnet sessions. Any host connected via
Ethernet can Telnet to the SAME70 Xplained hub or to any Clicker2
point in the star.

7. TCP and UDP Tests: The same TCP and UDP tests as described for
the clicker2-stm32 mrf24j40-starpoint configuration are supported on
the star endpoints, but NOT on the star hub. Therefore, all network
testing is between endpoints with the hub acting, well, only like a
hub.

The nsh> dmesg command can be use at any time on any endpoint node
to see any debug output that you have selected. Debug output on the
hub will be presented on stdout.

Telenet sessions may be initiated only from the hub to a star
endpoint:

C: nsh> telnet <-- Runs the Telnet client

Where is the IP address of either the E1 or I2 endpoints.

STATUS:
2017-08-16: Configurations added. Initially, I saw hangs i
mrf24j40_reset() before the NSH appears on the serial console.
Unlike the SAMV71-XULT, the SPI looks clean, but was hanging
nevertheless.

Then, on subsequent testing, it "magically" started behaving
properaly and seems quite stable now.. although I did nothing to
solve the problem. Perhaps the radio was in a bad state for awhile;
perhaps something I did masked the problem. However, all is well
for the time being.

No significant functional testing has yet been performed.

netnsh:

Configures the NuttShell (nsh) located at examples/nsh. There are two
very similar NSH configurations:

- nsh. This configuration is focused on low level, command-line
driver testing. It has no network.
- netnsh. This configuration is focused on network testing and
has only limited command support.

NOTES:

1. The serial console is configured by default for use with the EDBG VCOM
(USART1). You will need to reconfigure if you will to use a different
U[S]ART. See "Information Common to All Configurations" above.

2. 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_MIN=256
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

3. NSH built-in applications are supported. There are, however, not
enabled built-in applications.

Binary Formats:
CONFIG_BUILTIN=y : Enable support for built-in programs

Application Configuration:
CONFIG_NSH_BUILTIN_APPS=y : Enable starting apps from NSH command line

4. The network initialization thread and the NSH network montior are
enabled in this configuration. As a result, networking initialization
is performed asynchronously with NSH bring-up. For more information,
see the paragraphs above entitled "Network Initialization Thread" and
"Network Monitor".

5. SDRAM is NOT enabled in this configuration.

6. TWI/I2C

TWIHS0 is enabled in this configuration. The SAM E70 Xplained
supports one devices on the one on-board I2C device on the TWIHS0 bus:
The AT24MAC402 serial EEPROM described above.
Relevant configuration settings:

CONFIG_SAMV7_TWIHS0=y
CONFIG_SAMV7_TWIHS0_FREQUENCY=100000

CONFIG_I2C=y

7. TWIHS0 is used to support 256 byte non-volatile storage. This EEPROM
holds the assigned MAC address which is necessary for networking. The
EEPROM is also available for storage of configuration data using the
MTD configuration as described above under the heading, "MTD
Configuration Data".

8. Support for HSMCI is built-in by default. The SAME70-XPLD provides
one full-size SD memory card slot. Refer to the section entitled
"SD card" for configuration-related information.

See "Open Issues" above for issues related to HSMCI.

The auto-mounter is not enabled. See the section above entitled
"Auto-Mounter".

9. Performance-related Configuration settings:

CONFIG_ARMV7M_ICACHE=y : Instruction cache is enabled
CONFIG_ARMV7M_DCACHE=y : Data cache is enabled
CONFIG_ARMV7M_DCACHE_WRITETHROUGH=y : Write through mode
CONFIG_ARCH_FPU=y : H/W floating point support is enabled
CONFIG_ARCH_DPFPU=y : 64-bit H/W floating point support is enabled

# CONFIG_ARMV7M_ITCM is not set : Support not yet in place
# CONFIG_ARMV7M_DTCM is not set : Support not yet in place

I- and D-Caches are enabled but the D-Cache must be enabled in write-
through mode. This is to work around issues with the RX and TX
descriptors with are 8-bytes in size. But the D-Cache cache line
size is 32-bytes. That means that you cannot reload, clean or
invalidate a descriptor without also effecting three neighboring
descriptors. Setting write through mode eliminates the need for
cleaning the D-Cache. If only reloading and invalidating are done,
then there is no problem.

Stack sizes are also large to simplify the bring-up and should be
tuned for better memory usages.

STATUS:
2015-03-29: I- and D-caches are currently enabled, but as noted
above, the D-Cache must be enabled in write-through mode. Also -Os
optimization is not being used (-O2). If the cache is enabled in
Write-Back mode or if higher levels of optimization are enabled, then
there are failures when trying to ping the target from a host.

nsh:

Configures the NuttShell (nsh) located at examples/nsh. There are two
very similar NSH configurations:

- nsh. This configuration is focused on low level, command-line
driver testing. It has no network.
- netnsh. This configuration is focused on network testing and
has only limited command support.

NOTES:

1. The serial console is configured by default for use with the EDBG VCOM
(USART1). You will need to reconfigure if you will to use a different
U[S]ART. See "Information Common to All Configurations" above.

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

CONFIG_ARCH_INTERRUPTSTACK=2048
CONFIG_IDLETHREAD_STACKSIZE=1024
CONFIG_USERMAIN_STACKSIZE=2048
CONFIG_PTHREAD_STACK_DEFAULT=2048
... and others ...

3. NSH built-in applications are supported.

Binary Formats:
CONFIG_BUILTIN=y : Enable support for built-in programs

Application Configuration:
CONFIG_NSH_BUILTIN_APPS=y : Enable starting apps from NSH command line

4. SDRAM is enabled in this configuration. Here are the relevant
configuration settings:

System Type
CONFIG_SAMV7_SDRAMC=y
CONFIG_SAMV7_SDRAMSIZE=2097152

SDRAM is not added to the heap in this configuration. To do that
you would need to set CONFIG_SAMV7_SDRAMHEAP=y and CONFIG_MM_REGIONS=2.
Instead, the SDRAM is set up so that is can be used with a destructive
RAM test enabled with this option:

Application Configuration:
CONFIG_SYSTEM_RAMTEST=y

The RAM test can be executed as follows:

nsh> ramtest -w 70000000 2097152

NuttShell (NSH) NuttX-7.8
nsh> ramtest -w 70000000 2097152
RAMTest: Marching ones: 70000000 2097152
RAMTest: Marching zeroes: 70000000 2097152
RAMTest: Pattern test: 70000000 2097152 55555555 aaaaaaaa
RAMTest: Pattern test: 70000000 2097152 66666666 99999999
RAMTest: Pattern test: 70000000 2097152 33333333 cccccccc
RAMTest: Address-in-address test: 70000000 2097152
nsh>

5. TWI/I2C

TWIHS0 is enabled in this configuration. The SAM E70 Xplained
supports one device on the one on-board I2C device on the TWIHS0 bus:
The AT24MAC402 serial EEPROM described above.

In this configuration, the I2C tool at apps/system/i2ctool is
enabled. This tools supports interactive access to I2C devices on
the enabled TWIHS bus. Relevant configuration settings:

CONFIG_SAMV7_TWIHS0=y
CONFIG_SAMV7_TWIHS0_FREQUENCY=100000

CONFIG_I2C=y

CONFIG_SYSTEM_I2CTOOL=y
CONFIG_I2CTOOL_MINBUS=0
CONFIG_I2CTOOL_MAXBUS=0
CONFIG_I2CTOOL_MINADDR=0x03
CONFIG_I2CTOOL_MAXADDR=0x77
CONFIG_I2CTOOL_MAXREGADDR=0xff
CONFIG_I2CTOOL_DEFFREQ=400000

Example usage:

nsh> i2c
Usage: i2c [arguments]
Where is one of:

Show help : ?
List busses : bus
List devices : dev [OPTIONS]
Read register : get [OPTIONS] []
Show help : help
Write register: set [OPTIONS] []
Verify access : verf [OPTIONS] [] []

Where common "sticky" OPTIONS include:
[-a addr] is the I2C device address (hex). Default: 03 Current: 03
[-b bus] is the I2C bus number (decimal). Default: 0 Current: 0
[-r regaddr] is the I2C device register address (hex). Default: 00 Current: 00
[-w width] is the data width (8 or 16 decimal). Default: 8 Current: 8
[-s|n], send/don't send start between command and data. Default: -n Current: -n
[-i|j], Auto increment|don't increment regaddr on repititions. Default: NO Current: NO
[-f freq] I2C frequency. Default: 400000 Current: 400000

NOTES:
o An environment variable like $PATH may be used for any argument.
o Arguments are "sticky". For example, once the I2C address is
specified, that address will be re-used until it is changed.

WARNING:
o The I2C dev command may have bad side effects on your I2C devices.
Use only at your own risk.
nsh> i2c bus
BUS EXISTS?
Bus 0: YES
nsh> i2c dev 3 77
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- 28 -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- 37 -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- 57 -- -- -- -- -- -- -- 5f
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

Where 0x28 is the address of TWI interface to the EDBG and 0x57 and
0x5f are the addresses of the AT24 EEPROM (I am not sure what the
other address, 0x37, is as this writing).

6. TWIHS0 is also used to support 256 byte non-volatile storage for
configuration data using the MTD configuration as described above
under the heading, "MTD Configuration Data".

7. Support for HSMCI is built-in by default. The SAME70-XPLD provides
one full-size SD memory card slot. Refer to the section entitled
"SD card" for configuration-related information.

See "Open Issues" above for issues related to HSMCI.

The auto-mounter is not enabled. See the section above entitled
"Auto-Mounter".

8. Performance-related Configuration settings:

CONFIG_ARMV7M_ICACHE=y : Instruction cache is enabled
CONFIG_ARMV7M_DCACHE=y : Data cache is enabled
CONFIG_ARMV7M_DCACHE_WRITETHROUGH=n : Write back mode
CONFIG_ARCH_FPU=y : H/W floating point support is enabled
CONFIG_ARCH_DPFPU=y : 64-bit H/W floating point support is enabled

# CONFIG_ARMV7M_ITCM is not set : Support not yet in place
# CONFIG_ARMV7M_DTCM is not set : Support not yet in place

Stack sizes are also large to simplify the bring-up and should be
tuned for better memory usages.

STATUS:
2015-03-28: HSMCI TX DMA is disabled. There are some issues with the TX
DMA that need to be corrected.