Arduino Due

Overview

The arduino_due board configuration is used by Zephyr applications that run on the Arduino Due board. It provides support for the Atmel SAM3X8E ARM Cortex-M3 CPU and the following devices:

  • Nested Vectored Interrupt Controller (NVIC)
  • System Tick System Clock (SYSTICK)
  • Serial Port over USB (ATMEL_SAM3)

More information about the board can be found at the Arduino Due website. The Atmel SAM3X8E Datasheet has the information and the datasheet about the processor.

Supported Features

The arduino_due board configuration supports the following hardware features:

Interface Controller Driver/Component
NVIC on-chip nested vectored interrupt controller
SYSTICK on-chip system clock
UART on-chip serial port
GPIO on-chip gpio
I2C on-chip i2c

Other hardware features are not currently supported by the Zephyr kernel. See Arduino Due website and Atmel SAM3X8E Datasheet for a complete list of Arduino Due board hardware features.

Note

For I2C, pull-up resistors are required for using SCL1 and SDA1 (near IO13).

Interrupt Controller

There are 15 fixed exceptions including exceptions 12 (debug monitor) and 15 (SYSTICK) that behave more as interrupts than exceptions. In addition, there can be a variable number of IRQs. Exceptions 7-10 and 13 are reserved. They don’t need handlers.

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 fault undefined instruction, or switch attempt to ARM mode system fatal error
11 SVC   context switch and software interrupts
12 Debug monitor   system fatal error
14 PendSV   context switch
15 SYSTICK   system clock

Note

After a reset, all exceptions have a priority of 0. Interrupts cannot run at priority 0 for the interrupt locking mechanism and exception handling to function properly.

System Clock

Arduino Due has two external oscillators/resonators. The slow clock is 32.768 kHz, and the main clock is 12 MHz. The processor can set up PLL to drive the master clock, which can be set as high as 84 MHz.

Serial Port

The Atmel SAM3X8E processor has a single UART that is used by the SAM-BA bootloader. This UART has only two wires for RX/TX and does not have flow control (CTS/RTS) or FIFO. The RX/TX pins are connected to the ATmega16U2, which provides USB-to-TTL serial function. The Zephyr console output, by default, is utilizing this controller.

Flashing Arduino Due for Zephyr

Flashing the Zephyr kernel onto Arduino Due requires the bossa tool. Note that the Arduino specific version is required (branch arduino on GitHub).

The sample application hello_world is being used in this tutorial, which can be found in $ZEPHYR_BASE/samples/hello_world/nanokernel.

  1. To build the Zephyr kernel, enter:

    $ cd $ZEPHYR_BASE
$ make -C samples/hello_world/nanokernel BOARD=arduino_due

  2. Connect the Arduino Due to your host computer using the programming port.

  3. Press the Erase button for more than 220 ms.

  4. Press the Reset button so the board will boot into the SAM-BA bootloader.

  5. To flash the kernel onto Arduino Due, assuming the bossa tool already exists. Using the command line version of bossa, enter:

    $ bossac -p <tty_device> -e -w -v -b outdir/zephyr.bin

    Where <tty_device> is where the Arduino Due can be found. For example, under Linux, <tty_device> should be /dev/ttyACM0.

  6. Run your favorite terminal program to listen for output. For example, under Linux, the terminal should be /dev/ttyACM0.

  7. Press the Reset button and you should see “Hello World!” in your terminal.

Note

Make sure your terminal program is closed before flashing the binary image, or it will interfere with the flashing process.

References