.. _em_starterkit:

DesignWare(R) ARC(R) EM Starter Kit
###################################

Overview
********

The DesignWare(R) ARC(R) EM Starter Kit is a low-cost, versatile solution
enabling rapid software development and software debugging, and profiling
for the ARC EM Family of processors. The EM Family includes the EM4, EM6,
EM5D, EM7D, EM9D, and EM11D cores. The Zephyr RTOS can be used with the
EM Starter Kit.


The ARC EM Starter Kit consists of a hardware platform, including pre-installed
FPGA images of different ARC EM processor configurations with peripherals.
Documentation for this board can be found at the following URL:
https://www.embarc.org.

See also this URL for details about the board:
https://www.synopsys.com/dw/ipdir.php?ds=arc_em_starter_kit

The default configuration for EM Starter Kit boards can be found in
:file:`boards/em_starterkit/em_starterkit_defconfig`.

The default SOC for this board is the EM9D. This configuration is a Harvard
Architecture, with a separate instruction bus and data bus. Instruction memory
is called ICCM and data memory is called DCCM. The configuration file for EM9D
is found in :file:`arch/arc/soc/em9d/Kconfig.defconfig`. If you have a larger
program, you can select the EM11D, which gives access to 128KB DRAM.
The configuration file for EM11D is found in
:file:`arch/arc/soc/em11d/Kconfig.defconfig`.

NOTE: The EM7D SOC choice is currently NOT supported by Zephyr as it requires a fast
interrupt handler that utilizes a single register bank.

Board Layout
************
The ARC EM Starter Kit main board has 6 Pmod connectors. These can be
configured to support attachment of GPIO, I2C, UART or SPI devices.

The board also has a 16MB SPI-FLASH and an SDCard for storage. There are 9 LEDs,
3 buttons, and 4 dip switches that can be used with GPIO.

The Xilinx Spartan(R)-6 LX150 FPGA can auto-load one of 3 FPGA SOC bit files
which have the EM7D, EM9D, or EM11D SOC.

Documentation and general information for the board can be found at the
`embARC-website`_, which also includes some free sample software.

Supported Features
******************
The Zephyr kernel supports multiple hardware features on the EM Starter Kit
through the use of device drivers.

The EM Starter Kit supports 6 Digilent Pmod(TM) Interfaces, which enables the
use of a large variety of pluggable modules for storage, communications,
sensors, displays, etc. With the Pmod interface, you can prototype your
applications using the Zephyr RTOS.

The table below shows which drivers are
supported and which functionality can be found on which architectures:

+-----------+------------+-----+-------+-----------------------+
| Interface | Controller |EM9D | EM11D | Driver/Component      |
+===========+============+=====+=======+=======================+
| INT       | on-chip    | Y   | Y     | interrupt_controller  |
+-----------+------------+-----+-------+-----------------------+
| UART      | usb +      | Y   | Y     | serial port-polling;  |
|           | 2 Pmods    |     |       | serial port-interrupt |
+-----------+------------+-----+-------+-----------------------+
| SPI       | 2 Pmods    | Y   | Y     | spi                   |
+-----------+------------+-----+-------+-----------------------+
| ADC       | n/a        | N   | N     | adc (can add via Pmod)|
+-----------+------------+-----+-------+-----------------------+
| I2C       | 2 Pmods    | Y   | Y     | i2c                   |
+-----------+------------+-----+-------+-----------------------+
| GPIO      | 6 Pmods    | Y   | Y     | gpio                  |
+-----------+------------+-----+-------+-----------------------+
| PWM       | n/a        | N   | N     | pwm                   |
+-----------+------------+-----+-------+-----------------------+
| mailbox   | n/a        | N   | N     | ipm                   |
+-----------+------------+-----+-------+-----------------------+

The board has 3 (debounced and interrupting) buttons for use with GPIO,
4 dip switches, 9 LEDs, SDCard on SPI, and a 16MB SPI-Flash memory.

The SPI-Flash also holds 3 (or 4) separate FPGA CPU bit files, selectable via
dip switch.

The SPI-Flash is also programmed with a bootloader. The booloader can
copy a program image from SPI-Flash into executable memory.
Zephyr initialization will copy the initialized data section to the data memory
if CONFIG_XIP is used.


Required Hardware and Software
==============================

To use Zephyr RTOS applications on the EM Starter Kit board, a few additional
pieces of hardware are required.

* USB Cable (delivered as part of the ARC EM Starter Kit)

* The USB cable provides power to the board; however, if the board is to run
  standalone, the universal switching power adaptor (110-240V AC to 5V DC),
  provided in the package, can be used to power the board.

* :ref:`The Zephyr SDK <zephyr_sdk>`

* Terminal emulator software for use with the USB-UART. Suggestion:
  http://www.putty.org.

* (optional) A collection of Pmods.
  See http://store.digilentinc.com/pmod-peripheral-modules or develop your
  custom interfaces to attach to the Pmod connector.


Building Sample Applications for the EM Starter Kit
***************************************************

You can try many of the sample applications or tests, but let us discuss
the one called hello_world.
It is found in :file:`$ZEPHYR_BASE/samples/hello_world/microkernel`.

You may need to write a prj_arc.conf file if the sample doesn't have one.
Next, you can use the make menuconfig rule to configure the target. By
providing the argument "BOARD=em_starterkit", you can select the ARC
EM Starter Kit board support for Zephyr.

.. code-block:: console

   $ make menuconfig BOARD=em_starterkit

On this board you will also need to consider the "ARC SoC Selection" and set
it either to EM9D or EM11D. To boot up the EM9D on the board, all dip
switches should be UP except for switch 1. Other configuration choices
are made in the normal way. To boot up the EM11D on the board,
all dip switches should be UP except for switch 2. Next press the button
above the letter C in the "ARC" logo on the silkscreen.

To build the application, execute make:

.. code-block:: console

   $ make BOARD=em_starterkit

Connecting Serial Output
************************
In the default configuration, Zephyr's EM Starter Kit images support serial output
via the UART1 on the board.  To enable serial output:

On your development environment, you will need to:

* Open a serial port emulator (i.e. on Linux minicom, putty, screen, etc)

* Specify the tty driver name, for example, on Linux this may be
 :file:`/dev/ttyUSB1`

* Set the communication settings to:

========= =====
Parameter Value
========= =====
Baud:     115200
Data:     8 bits
Parity:    None
Stopbits:  1
========= =====

Debugging on EM Starter Kit
***************************
Before you can debug, you will need to download and install the
Synopsys versions of ARC GNU tools. Unfortunately the Zephyr-SDK versions
of openocd and gdb have some functionality limitations and don't yet
work well with the ARC EM Starter Kit.

The Synopsys tools are found on GITHUB here:

https://github.com/foss-for-synopsys-dwc-arc-processors/toolchain/releases/tag/arc-2016.03

For Linux, you will need:

.. code-block:: console

  arc_gnu_2016.03_ide_linux_install.tar.gz
   arc_gnu_2016.03_prebuilt_elf32_be_linux_install.tar.gz

You can untar these into any directory. Suggestion: /usr/local/arc.
Follow the instructions for how to set up to use these tools.
You will need your path changed to refer to the bin directories for these
so that these cross development tools can be found.

It is also useful to create a bash script to launch openocd, since if you
are like me, you will find it hard to remember the arguments. Here
is the one I use, placed in a file called ocd.

.. code-block:: console

  #!/bin/bash
  openocd -c 'gdb_port 3333' -s $ARCGNU_IDE/share/openocd/scripts -f board/snps_em_sk_v2.2.cfg

  #where the environment variable ARCGNU_IDE refers to the install dir of the
  #openocd IDE

This command to openocd uses port 3333 with gdb client, and provides the board
cfg file for the ARC EM Starter Kit.

I have also found it useful to have a script, named debug.sh, to provide all the arguments to gdb:

.. code-block:: console

  #!/bin/bash
  arc-elf32-gdb \
   -ex "target remote :3333" \
   -ex "load" \
   -ex "break __memory_error" \
   -ex "break _SysFatalErrorHandler" \
   -ex "set remotetimeout 2000" \
   outdir/zephyr.elf

The target remote and load will attach to openocd and load the elf file into
memory. You can also set breakpoints on CPU exception handlers, or fatal
error handlers.

Now to use these two scripts is easy. Boot up the SOC by pressing the "C" button.
Be sure the digilent cable is attached from your host to the EM Starter Kit
board.

In any terminal window, invoke the "ocd" script first. It should establish
contact with the board and output many messages. For example:

.. code-block:: console

  Open On-Chip Debugger 0.9.0-dev-g90a4ff5 (2016-05-04-15:37)
  Licensed under GNU GPL v2
  For bug reports, read
  http://openocd.sourceforge.net/doc/doxygen/bugs.html
  adapter speed: 5000 kHz
  Info : clock speed 5000 kHz
  Info : JTAG tap: arc-em.cpu tap/device found: 0x200044b1 (mfg: 0x258, part: 0x0004, ver: 0x2)
  Info : JTAG tap: arc-em.cpu tap/device found: 0x200044b1 (mfg: 0x258, part: 0x0004, ver: 0x2)
  target state: halted
  target state: halted

In a second console window, navigate to the directory for your sample application,
and invoke the debug.sh script:

.. code-block:: console

  GNU gdb (ARCompact/ARCv2 ISA elf32 toolchain 2016.03) 7.10
  Copyright (C) 2015 Free Software Foundation, Inc.
  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
  This is free software: you are free to change and redistribute it.
  There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
  and "show warranty" for details.
  This GDB was configured as "--host=x86_64-unknown-linux-gnu --target=arc-elf32".
  Type "show configuration" for configuration details.
  For bug reporting instructions, please see:
  <https://github.com/foss-for-synopsys-dwc-arc-processors/toolchain/issues>.
  Find the GDB manual and other documentation resources online at:
  <http://www.gnu.org/software/gdb/documentation/>.
  For help, type "help".
  Type "apropos word" to search for commands related to "word"...
  Reading symbols from outdir/zephyr.elf...done.
  Remote debugging using :3333
  0x000077b4 in ?? ()
  Loading section text, size 0x3714 lma 0x0
  Loading section devconfig, size 0x78 lma 0x3714
  Loading section gpio_compat, size 0x20 lma 0x378c
  Loading section rodata, size 0x244 lma 0x37ac
  Loading section datas, size 0x714 lma 0x80000000
  Loading section initlevel, size 0x78 lma 0x80000714
  Loading section _k_task_list, size 0x58 lma 0x8000078c
  Loading section _k_task_ptr, size 0x8 lma 0x800007e4
  Loading section _k_event_list, size 0x10 lma 0x800007ec
  Start address 0x36f4, load size 16876
  Transfer rate: 122 KB/sec, 1406 bytes/write.
  Breakpoint 1 at 0x3264: file /home/johndoe/repository/zephyr/arch/arc/core/fault_s.S, line 81.
  Breakpoint 2 at 0x3628: file /home/johndoe/repository/zephyr/arch/arc/core/sys_fatal_error_handler.c, line 73.
  (gdb)

At this point you can do your normal debug session. Set breakpoints and then
'c' to continue into the program.

Flashing an Application on the EM Starter Kit
*********************************************

Most of the time you will not be flashing your program but will instead
debug it using openocd and gdb. The program can be download via the USB
cable into the code and data memories.

When you are ready to deploy the program so that it boots up automatically
on reset or power-up, you can follow the steps to place the program on
SPI-FLASH.

For instructions on how to write your program to SPI-FLASH,
refer to the documentation on the ARC EM Starter Kit at the
`embARC-website`_, which includes instructions for how to place an
executable image onto the SPI-FLASH in such a way that it is understood
by the bootloader.


Release Notes
*************

The following is a list of TODO items:

* EM7D not supported. Need 1-register bank, FIRQ support
* cache.h API not yet implemented for EM11D.
* Zephyr needs i-cache API (all targets)
* pinmux driver: Possibly it can be written to configure PMods too.
* Zephyr ARC port doesn't yet support nested regular interrupts.


Bibliography
************
.. _embARC-website: https://www.embarc.org

.. _emstarterkit-website: https://www.synopsys.com/dw/ipdir.php?ds=arc_em_starter_kit

.. _digilent-website: http://store.digilentinc.com

.. _putty-website: http://www.putty.org