Linking the systick and RTC could cause ticks to be lost on some occasions when
the RTC and systick become desync. We don't care about having them synced but
we care about their individual accuracy. Switching to independant timestamps,
using the tasks ones, fixes that and saves space
In the end, priorities are only usefull in preemptive systems. Here, it would
only garentee the execution order, which we don't care about most of the time
zero padding is mostly used with unsiged integers, and is quite difficult to
properly implement for signed integers. Disbaling iti n that case seems like a
good compromise
DMA buffers now work reliably with USART. The DMA api has changed to make it
more efficient code-size-wise. This may, however, complicate things when
implementating powersaving features
The dma buffer should be services that are used on top of peripherals. As such,
the usart driver should'nt directly use them, this is up to the user. The
multi-buffer has also been simplified since I was not satisfied with the
previous implementation
