.. _v2m_beetle_board:

ARM V2M Beetle
##############

Overview
********

The v2m_beetle board configuration is used by Zephyr applications that run on
the V2M Beetle board. It provides support for the Beetle ARM Cortex-M3 CPU and
the following devices:

- Nested Vectored Interrupt Controller (NVIC)
- System Tick System Clock (SYSTICK)
- Cortex-M System Design Kit GPIO
- Cortex-M System Design Kit UART

.. image:: img/v2m_beetle.png
     :width: 442px
     :align: center
     :height: 335px
     :alt: ARM V2M Beetle

More information about the board can be found at the `V2M Beetle Website`_.

Hardware
********

ARM V2M BEETLE provides the following hardware components:

- ARM Cortex-M3
- ARM IoT Subsystem for Cortex-M
- CORDIO Bluetooth Smart radio
- Memory

  - 256KB of embedded flash
  - 128KB SRAM
  - 2MB of external QSPI flash.

- Debug

  - JTAG, SWD & 4 bit TRACE
  - CMSIS-DAP with a virtual UART port

- Arduino interface

  - GPIO, UART, SPI, I2C
  - Analog signals


Supported Features
===================

The v2m_beetle board configuration supports the following hardware features:

+-----------+------------+-------------------------------------+
| Interface | Controller | Driver/Component                    |
+===========+============+=====================================+
| NVIC      | on-chip    | nested vector interrupt controller  |
+-----------+------------+-------------------------------------+
| SYSTICK   | on-chip    | systick                             |
+-----------+------------+-------------------------------------+
| UART      | on-chip    | serial port-polling;                |
|           |            | serial port-interrupt               |
+-----------+------------+-------------------------------------+
| PINMUX    | on-chip    | pinmux                              |
+-----------+------------+-------------------------------------+
| GPIO      | on-chip    | gpio                                |
+-----------+------------+-------------------------------------+
| WATCHDOG  | on-chip    | watchdog                            |
+-----------+------------+-------------------------------------+
| TIMER     | on-chip    | timer                               |
+-----------+------------+-------------------------------------+

Other hardware features are not currently supported by the port.
See the `V2M Beetle Website`_ for a complete list of V2M Beetle board hardware
features.

The default configuration can be found in the defconfig file:

.. code-block:: console

   boards/arm/v2m_beetle/v2m_beetle_defconfig

Interrupt Controller
====================

Beetle is a Cortex-M3 based SoC and has 15 fixed exceptions and 45 IRQs.

A Cortex-M3/4-based board uses vectored exceptions. This means each exception
calls a handler directly from the vector table.

Handlers are provided for exceptions 1-6, 11-12, and 14-15. The table here
identifies the handlers used for each exception.

+------+------------+----------------+--------------------------+
| Exc# | Name       | Remarks        | Used by Zephyr Kernel    |
+======+============+================+==========================+
| 1    | Reset      |                | system initialization    |
+------+------------+----------------+--------------------------+
| 2    | NMI        |                | system fatal error       |
+------+------------+----------------+--------------------------+
| 3    | Hard fault |                | system fatal error       |
+------+------------+----------------+--------------------------+
| 4    | MemManage  | MPU fault      | system fatal error       |
+------+------------+----------------+--------------------------+
| 5    | Bus        |                | system fatal error       |
+------+------------+----------------+--------------------------+
| 6    | Usage      | undefined      | system fatal error       |
|      | fault      | instruction,   |                          |
|      |            | or switch      |                          |
|      |            | attempt to ARM |                          |
|      |            | mode           |                          |
+------+------------+----------------+--------------------------+
| 11   | SVC        |                | context switch and       |
|      |            |                | software interrupts      |
+------+------------+----------------+--------------------------+
| 12   | Debug      |                | system fatal error       |
|      | monitor    |                |                          |
+------+------------+----------------+--------------------------+
| 14   | PendSV     |                | context switch           |
+------+------------+----------------+--------------------------+
| 15   | SYSTICK    |                | system clock             |
+------+------------+----------------+--------------------------+

Pin Mapping
===========

The ARM V2M Beetle Board has 4 GPIO controllers. These controllers are responsible for pin muxing, input/output, pull-up, etc.

All GPIO controller pins are exposed via the following sequence of pin numbers:

- Pins 0 - 15 are for GPIO 0
- Pins 16 - 31 are for GPIO 1

Mapping from the ARM V2M Beetle Board pins to GPIO controllers:

.. hlist::
   :columns: 3

   - D0 : P0_0
   - D1 : P0_1
   - D2 : P0_2
   - D3 : P0_3
   - D4 : P0_4
   - D5 : P0_5
   - D6 : P0_6
   - D7 : P0_7
   - D8 : P0_8
   - D9 : P0_9
   - D10 : P0_10
   - D11 : P0_11
   - D12 : P0_12
   - D13 : P0_13
   - D14 : P0_14
   - D15 : P0_15
   - D16 : P1_0
   - D17 : P1_1
   - D18 : P1_2
   - D19 : P1_3
   - D20 : P1_4
   - D21 : P1_5
   - D22 : P1_6
   - D23 : P1_7
   - D24 : P1_8
   - D25 : P1_9
   - D26 : P1_10
   - D27 : P1_11
   - D28 : P1_12
   - D29 : P1_13
   - D30 : P1_14
   - D31 : P1_15

Peripheral Mapping:

.. hlist::
   :columns: 3

   - UART_0_RX : D0
   - UART_0_TX : D1
   - SPI_0_CS : D10
   - SPI_0_MOSI : D11
   - SPI_0_MISO : D12
   - SPI_0_SCLK : D13
   - I2C_0_SCL : D14
   - I2C_0_SDA : D15
   - UART_1_RX : D16
   - UART_1_TX : D17
   - SPI_1_CS : D18
   - SPI_1_MOSI : D19
   - SPI_1_MISO : D20
   - SPI_1_SCK : D21
   - I2C_1_SDA : D22
   - I2C_1_SCL : D23

For mode details please refer to `Beetle Technical Reference Manual (TRM)`_.

System Clock
============

V2M Beetle has one external and two on-chip oscillators. The slow clock is
32.768 kHz, and the main clock is 24 MHz. The processor can set up PLL to drive
the master clock.

Serial Port
===========

The ARM Beetle processor has two UARTs. Both the UARTs have only two wires for
RX/TX and no flow control (CTS/RTS) or FIFO. The Zephyr console output, by
default, is utilizing UART1.

Programming and Debugging
*************************

Flashing
========

CMSIS DAP
---------

V2M Beetle provides:

- A USB connection to the host computer, which exposes a Mass Storage and an
  USB Serial Port.
- A Serial Flash device, which implements the USB flash disk file storage.
- A physical UART connection which is relayed over interface USB Serial port.

This interfaces are exposed via CMSIS DAP. For more details please refer
to `CMSIS-DAP Website`_.

Flashing an application to V2M Beetle
-------------------------------------

The sample application :ref:`hello_world` is being used in this tutorial:

.. code-block:: console

   $ZEPHYR_BASE/samples/hello_world

To build the Zephyr kernel and application, enter:

.. code-block:: console

   $ cd $ZEPHYR_BASE
   $ . zephyr-env.sh
   $ cd $ZEPHYR_BASE/samples/hello_world/
   $ make BOARD=v2m_beetle

Connect the V2M Beetle to your host computer using the USB port and you should
see a USB connection which exposes a Mass Storage (MBED) and a USB Serial Port.
Copy the generated zephyr.bin in the MBED drive.
Reset the board and you should be able to see on the corresponding Serial Port
the following message:

.. code-block:: console

   Hello World! arm


.. _V2M Beetle Website:
   https://www.arm.com/products/tools/development-boards/versatile-express/beetle_iot_evaluation_platform.php

.. _Beetle Technical Reference Manual (TRM):
   https://developer.arm.com/-/media/developer/products/system-design-tools/versatile-express-family/V2M-Beetle_TRM_draft.pdf?la=en

.. _CMSIS-DAP Website:
   https://github.com/mbedmicro/CMSIS-DAP