get I2C working.  some more work regarding clocking computation is needed, as is some inhertited 'todo's from the basis code.  but it does work with the devices tested so far.

complete logic in 'create stack' and 'use stack' to support stack coloration.  Fix some booboos breaking compatibility with TLS in libc.

altered pin defs for I2C pins; these needed to be specified as open-drain (otherwise they are push-pull)

complete logic in 'create stack' and 'use stack' to support stack coloration.  Fix some booboos breaking compatibility with TLS in libc.

Update Nucleo F303RE and STM32F4Discovery uavcan configurations

*  This driver supports the 'I2C lcd backpack' design that is based on the PCF8574 io expander.  There's a myriad of different vendors of such, but they are principally the same, save wiring and minor features like jumpers for I2C addresses.  This driver supports known and unknown variants.
*  The interface board supports HD44780-based LCD modules up to 4x32, and this driver accommodates all those formats.

This fix removes the disabling of the whole USB peripheral on suspend
interrupt. Its enough to freeze the clock instead.

When disabling the whole peripheral, the next wakeup-interrupt comes
up with an disabled clocking. The unfreeze clock has no effect, because
the master clock is disabled. This makes all registers, including the
IDR unwriteable and the IRQ falls in an endless loop blocking the whole
system.

Furthermore the disabling of the peripheral clock prevents hotplugging
or reconnecting the USB.

sam_systemreset.c edited online with Bitbucket

Add the up_systemreset interface to the samv7 arch.  The approach is slightly different in that: 1) It enables ARCH_HAVE_RESET and allows the user to set if, and for how long, to drive External nRST signal. It also does not contain a default board_reset, as that really should be done in the config's src if CONFIG_BOARDCTL_RESET is defined.

sam_i2cbus_initialize
sam_i2cbus_uninitialize
sam_i2cbus_initialize

Or twi_reset is called.

I found this a while back in the stm32 family, so there may be more arch-es with this sort of bug. I suppose any driver that has the notion of "do not set the freq if it is already set" could be suspect.

Tiva boards:  Fix a naming collision, rename board-specific function from tiva_timer_initialize() to tiva_timer_configure() to remove conflict