This implements a basic Real Time Clock based on TIM2.
As the timer is too fast and wraps around after just 8 bits, it is
not used directly. Instead TIM2 is responsible for providing a 1 Hz
tick by generating an alarm every second.
The current time data is kept in the `.noinit` section, so it will survive
a reboot, but the clock will not be updated while the bootloader runs, so
expect inaccuracies.
The reboot process for ATmegas is to enable the watchdog timer and loop until
the wdt reboots this MCU. However, this reboot will keep the wdt configuration,
so that the wdt needs to be disabled during boot. This is done in get_mcusr,
but without the attribute "used" it will be optimized out in LTO builds. This
commits adds the attribute "used" to get_mcusr.
Also simplified the backward compatibility with older ATmegas (currently not
supported by RIOT) on outdated versions of avrlibc.
For atmega boards a TX has not actually completed until UDRn is empty
as well as the Transmit Shift Register.
To avoid resetting an UART before a TX has completed we use the TXCn
flash and ISR to set a variables that indicates TX is ongoing. This
allows not reseting the UART while there are ongoing TX pending.
This fixes an issue where part of the last byte is not shifted out
of the TX shift register causing rubish on the first TX following an
uart_init.
- Using a enum instead of _COUNTER is easier to read
- _COUNTER is also a reserved name; so better not use it to avoid issues
- Split out the pcint code into a static inline function for increased
readability
The bank index and the pin number are not necessarily identical. For all
PCINT banks except for bank 3 bank_idx was used therefore. It was likely
just forgotten to update that for bank 3 as well.
At the end of an ISR, the ATmega code was doing an `thread_yield()` instead of
a `thread_yield_higher()`. This resulted in tests/isr_yield_higher failing.
Fixing this saves a few lines of code, some ROM, and solves the issue.
Names with two leading underscores are reserved in any context of the c
standard, and thus must not be used. This ATmega platform used it however for
defining internal stuff. This commit fixes this.
Moved macros and static inline helper functions needed to access ATmega GPIOs
to cpu/atmega_common/include/atmega_gpio.h in order to reuse them for the
platform specific low level part of the Neopixel driver.
ATmega128RFA1/ATmega256RFR2 do not have a unique CPU ID.
Use the RC oscillator callibration byte as an impromptu CPU ID and rely
on bootlader constants present on all ATmega families for the remaining
bytes.
This way we can provide a faux CPU ID on all ATmega MCUs and typical hobbyists
with no access to JTAG adapters or high voltage programmer capable of writing
the user signature have a good chance that the CPU IDs of their device do not collide.
