RusPiRo kernel w/o custom build target and travis-ci integration

Release notes

This release removes the need of the custom target 'armv8-ruspiro'. It now uses the build in rust build target armv7-unknown-linux-gnueabihf. This release also comes with a working travis-ci integration.

Features:

• showcase usage of the ruspiro-interrupt crate

RusPiRo kernel baseline

Release notes

This new "baseline" version uses the ruspiro-mailbox crate to retrieve the current core clock rate to properly initialize the uart interface. It also uses the ruspiro-console crate to have access to the commonly used macros print! and println usually not available in bare metal no_std environments but known and helpful to have.

RusPiRo kernel utilizing UART for string output

Release notes

This version uses the ruspiro-uart crate to print strings to a connected terminal console. As the ruspiro-uart crate internally depends on the ruspiro-console trait (this would be the proposed way to access the uart), the kernel uses the ruspiro-allocator crate to be linked in.

RusPiRo kernel utilizing GPIO access abstraction

Release notes

This version uses the ruspiro-gpio crate to more conveniently access the GPIO pins.

RusPiRo kernel utilizing MMIO register access for GPIO

Release notes

This version uses the ruspiro-register crate to get access to the MMIO register that allow configuration of the Raspberry Pi GPIO pins. Each core will lit a LED connected to the respective GPIO pin:

• core 0 => pin 17
• core 1 => pin 18
• core 2 => pin 20
• core 3 => pin 21

Initial RusPiRo playground kernel for Raspberry Pi 3

Release Notes

This initial version of the RusPiRo kernel is just a play ground to verify the toolchain to build this crate is configured well and the resulting binary can be deployed to real hardware (Raspberry Pi 3+).
It could be seen as starting point to properly setup all tools and practice the build workflow in the individual environment.
If the deployment to the hardware is successful and all 4 cores are kicked off for stuff to process, this is, however, there is no visible output implemented, neither in form of a blinking LED connected to a GPIO pin nor text written to the UART interface. This will come in the next releases.