Split atmega_common code into avr8_common folder. This moves common
avr8 code to be used for all avr8 variants: tiny, mega and xmega.
Signed-off-by: Gerson Fernando Budke <nandojve@gmail.com>
Split cpu.c file into cpu.c and atmega_cpu.c files. This extract mega
specific code from common code.
Signed-off-by: Gerson Fernando Budke <nandojve@gmail.com>
The module cpu_atmega_common_cxx seems to be non-existing and not used. It is
unclear whether this slipped in by accident or if this was actually useful at
some point in time. In any case, the module is not present (anymore) and cannot
be used, so let's clean up the Makefile.
Split out Gunar Schorcht's clever approach to provide thread safe malloc for
AVR into a system module and make AVR depend on this. This allows other
platforms to also use this.
If a timer triggers while the idle thread is running, previously a stack
overflow was triggered. This commit increases the idle threads stack size if
xtimer is used.
Added a low level implementation of timer_set() that allows setting relative
timeouts as short as 0. This results in tests/periph_timer_short_relative_set
no passing.
The inline assembly implementation was badly in need of improvement.
- irq_disable() took 2 CPU cycles more than needed
- The current interrupt state was stored in a temporary register and
afterwards copied to the target register, rather than storing it in the
target register right away
- The lower bits of the state were cleared (as they have no meaning for the
interrupt status), but the API purposely never required such things from
implementations.
- irq_restore() took 5 CPU cycles. This was reduced to 3 CPU cycles (or 2 CPU
cycles in the best case)
- On pwm_poweron, the PWM resolution was not restored. (A custom resolution was
only usable if, PWM channel 0 is not used. That configuration is not common,
so this bug was likely never triggered)
- Disabled a work around to prevent flickering:
- Previously, PWM was disconnected on level 0% and 100%
- This increases the run time of `pwm_set()`
- It prevents using the PWM for wave form generation via DDS, as the wave
noticeably jumps when reaching 0% or 100%
- Slightly reduces memory requirements: 2 Bytes of RAM, 112 Bytes of ROM
- Tested with avr-gcc 9.2.0 and LTO enabled
Drop `#include "irq.h"` in `cpu.h`, which was there for a legacy work around.
A bunch of missing includes of `irq.h` materialized due to this and were
fixed.
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.
