lpm_enter() must not enter PM1+ if the UART TX FIFO is not empty. Otherwise, the
UART clock gets disabled, and its TX is broken.
Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
This uses the core/dev/spi.h header and implements the spi_init()
function and the various macros for SPI operation. ssi.h contains all of
the register locations and information.
This implementation is not very versatile, mostly because I don't how to
make it flexible in the contiki system. It supports pin muxing for the
four spi pins, but other than that picks sensible defaults.
The SPI macros (like SPI_READ()) are defined in
cpu/cc2538/spi-arch.h. In order to use the SPI driver, add the following
includes to your project:
#include "spi-arch.h
#include "dev/spi.h"
