add new board - nRF52840 MDK USB Dongle

[xiongyihui]

support a new nRF52840 board - nRF52840 MDK USB Dongle #3

The board has a builtin bootloader, so the start address of Tock OS is changed to 0x1000

It's a good idea to open an issue first for discussion.

• Tests pass
• Appropriate changes to README are included in PR

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[gendx]

Thanks @xiongyihui for this pull-request, and glad to hear that you're porting OpenSK to another board :) I left a few technical comments on the code.

However, our goal is to upstream as much as possible of the patches/ directory to Tock itself (we already have pull-requests in review - tock/tock#1556 & tock/tock#1467), so the best to move forward would be for you to send a pull-request to add support for the nRF52840 MDK directly in https://github.com/tock/tock. That way we can make sure that this board is properly supported by Tock.

Once that is merged on upstream Tock, we can update the git submodule in third_party/tock to get support for it.

In the meantime, let's keep this pull-request open so that people can experiment with OpenSK on the nRF52840 MDK.

[gendx]

This will definitely need to be discussed upstream.

[xiongyihui]

@gendx Thanks for the comments. I also think adding the board to tock is better, will try that.

[xiongyihui]

To experiment with OpenSK on the nRF52840 MDK USB Dongle with a builtin bootloader , some changes are required:

• change the start address of tock os to 0x1000 at OpenSK/third_party/tock/boards/nordic/nrf52840_dongle/layout.ld
• relocate interrupt vector table (SCB->VTOR = 0x1000)
• change the pins of LEDs and buttons

[markushx]

I have applied the SCB.vtor as well as the linker script change for the original nordic nrf52840-dongle, because i wanted to install without Segger JLink, but with nRF Connect programmer.

Thus I created a hex file, out of the elf file:
arm-none-eabi-objcopy -O ihex ./third_party/tock/boards/nordic/nrf52840_dongle/target/thumbv7em-none-eabi/release/nrf52840_dongle.elf ./third_party/tock/boards/nordic/nrf52840_dongle/target/thumbv7em-none-eabi/release/nrf52840_dongle.hex.

Unfortunately it seems the device does not boot-up.

What is the expected behaviour after boot-up? Should the device show up as a ttyUSB?

[gendx]

I have applied the SCB.vtor as well as the linker script change for the original nordic nrf52840-dongle, because i wanted to install without Segger JLink, but with nRF Connect programmer.

Thus I created a hex file, out of the elf file:
arm-none-eabi-objcopy -O ihex ./third_party/tock/boards/nordic/nrf52840_dongle/target/thumbv7em-none-eabi/release/nrf52840_dongle.elf ./third_party/tock/boards/nordic/nrf52840_dongle/target/thumbv7em-none-eabi/release/nrf52840_dongle.hex.

Unfortunately it seems the device does not boot-up.

I'd recommend discussing kernel support for more boards directly on Tock's repository (https://github.com/tock/tock) for greater visibility.

That said, another way to check whether your flashing method works would be to:

1. Flash the kernel.
2. Compile the blink example from libtock-rs (https://github.com/tock/libtock-rs/blob/master/examples/blink.rs). With this blink app flashed, you should see LEDs blinking as soon as your board boots.

Can you confirm that this works? That'd be helpful to know whether your issue is due to your flashing method (or your board), or specific to OpenSK.

What is the expected behaviour after boot-up? Should the device show up as a ttyUSB?

When plugged on a Linux machine, the OpenSK key should show up in lsusb and you should also see entries in dmesg (example: #3 (comment)). There should also be a /dev/hidrawN device file created for OpenSK.

[jmichelp]

Closing this pull-request as I integrated all your changes as part of a bigger effort to support nordicdfu, locally defined boards, etc. in #78

Thanks a lot @xiongyihui for having done the work of upstreaming the required change and thanks Denis for your work on prototyping flashing over DFU. This made #78 possible and clearly helped improving OpenSK!