cc2540mini: Add upload rule to Makefile

This patch adds "upload" rule to make easier to upload a new firmware
to cc2540mini using CC-Debugger hardware and cc-tool software.

Signed-off-by: Paulo Borges <paulo.borges@openbossa.org>
cc2540mini: Initialize process module

This patch initializes the process module and implements a simple
main loop, which process events and polls.

Signed-off-by: Paulo Borges <paulo.borges@openbossa.org>
cc2540mini: Initialize etimer process

Signed-off-by: Paulo Borges <paulo.borges@openbossa.org>
cc2540mini: Initialize ctimer module

Signed-off-by: Paulo Borges <paulo.borges@openbossa.org>
cc2540mini: Initialize rtimer module

Signed-off-by: Paulo Borges <paulo.borges@openbossa.org>
examples: Add blink example

This patch adds a simple blink example which inverts the green led
each second.

Signed-off-by: Paulo Borges <paulo.borges@openbossa.org>
cc2540mini: Add support for platform buttons

This patch implements support for cc2540mini B3 and B4 buttons using
Contiki sensor feature.

Signed-off-by: Paulo Borges <paulo.borges@openbossa.org>
cc2540mini: Add platform buttons example

This patch adds an example which handles with both buttons present
in the platform.

Signed-off-by: Paulo Borges <paulo.borges@openbossa.org>