Due to the RIOT_EPOCH of 2020 this overflow will happen in year 2084. It would be scary if IoT devices are still around then.
We can save RAM and ROM. Furthermore, this overflow handling should block BACKUP power mode in order to keep track of the reference year.
`rtt_get_counter()` already waits for syncbusy before reading the time,
but we also have to do this in RTC mode (`rtc_get_time()`) to avoid
reading old values.
Thus, always wait for syncbusy to clear when accessing the COUNT register.
On SAM L21 only 8 EXTWAKE pins can wake the CPU from Backup sleep.
Handle this analogous to the RTC tamper pins on SAM D5x/E5x where
configuring them as an interrupt will also cause them to wake the
device from Deep Sleep.
Setting up a DMA transfer can take longer than sending out a buffer
byte by byte if the buffer is small.
DMA only shows advantages for large buffers, using it for every transfer
will cause a net slowdown.
Since we did not come up with a good way to determine the treshold based
on the SPI frequency, just use a fixed buffer for now so that DMA can be
used without slowing things down overall.
In Asynchronous Fractional baud rate mode, the baud rate can not be
greater than the source frequency divided by the oversampling (8, 16).
Currently we are always using 16x oversampling.
This makes it impossible to e.g. set a 2 MHz UART baud rate on the 16 MHz
`saml10-xpro`.
With this change, the oversampling is automatically reduced to 8x which
allows us to set 16 MHz / 8 -> 2 MHz baud rate.
SERCOM5 on SAM L21 does not support fractional baud rate mode.
Instead of special-casing it, just use arithmetic baud rate mode
in general on this CPU, as I'm not sure what the advantages of fractional
baud rate mode are.
fixes#16692
In case of network heavy traffic on the Ethernet, interrupts
fire faster than the netdev thread can process them and we
run out of buffers. With this commit, we now check if we
don't have buffers available, so we can flush everything and
restart reception properly even if we did drop a few in the
operation
When using the I2C_NOSTOP flag the bus should remain in control.
The current check assumes it must go to idle when reading.
This adds a condition checks if the nostop flag is active
and expects the bus status to be the owner of the bus.
This reverts commit 585dc15f99d8a89766bb12d064fa2209909a1b6d.
I did misunderstand this feature: This only inverts the data
bits (instead of `c` uart will transmit `~c`), not the whole
line level.
This is not very useful on it's own, so revert it.
This allows to use the sam0 RTT together with the rtt_rtc module.
The idea is to use RTT as a monotonic counter, but still keep track
of the time with the virtual RTC module.
