Functions marked with __atribute__((naked)) may only use basic inline assembly
and must not use any c code. The functions __enter_thread_mode() and
cpu_switch_context_exit() are using C code, so they must not be marked as
naked.
This prevent evaluating `LINKFLAGS` when not needed and when building
in docker so does not produce errors if `avr-ld` is not installed.
```
BUILD_IN_DOCKER=1 BOARD=arduino-mega2560 make --no-print-directory -C examples/hello-world/ clean
/srv/ilab-builds/workspace/git/riot_master/makefiles/toolchain/gnu.inc.mk:18: objcopy not found. Hex file will not be created.
/bin/sh: 1: avr-ld: not found
```
It removes the `/bin/sh: 1: avr-ld: not found`
The brr calculation on the datasheet is different than what is implmented.
This is intentional since it provides better rounding due to truncation.
There was no comment explaining that so this comment should prevent confusion.
- correct number of timers for atmega328p from 2 to 1
- correct number of timer channels for atmega328p from 3 to 2
- adapt atmega periph timer implementation accordingly
cpu.c and startup.c were redundant in most platforms, except for
atmega256rfr2. The common code is now in cpu/atmega_common/cpu.c
and cpu/atmega_common/startup.c. cpu_conf.h is also removed as
it's now in cpu/atmega_common/include thus shared by all atmega
based platforms.
Removes duplicated code for atmega platforms. They were all
basically the same, only with the exception of atmegarfr2,
for which there is an #if statement to use the code in the
same file.
This Patch makes gpio_init precalculate the pin mask once,
This Patch makes gpio_init of atmega_common configure the pin as an input and configure the pullup in the case of GPIO_IN_PU.
GPIO_IN_PU and GPIO_IN need to change pullup so they need to change output (this is coverd by the not touching outputs is not guaranteed statement)
(this is a special case for atmega the pull_up is configured by writing 1 to the port_register which is also the level of the output if the pin is configured to output).
This fix makes it more compliant to comments in periph/gpio.h
A debug pin can be used to probe timer interrupts with an oscilloscope or
other time measurement equipment. Thus, determine when an interrupt occurs
and how long the timer ISR takes.
The pin should be defined in the makefile as follows:
CFLAGS += -DDEBUG_TIMER_PORT=PORTF -DDEBUG_TIMER_DDR=DDRF \
-DDEBUG_TIMER_PIN=PORTF4
fixes the GPIO_LOW interrupt on the atmega platform.
It results from trying to shift GPIO_LOW. Since it is 0, it is not shiftable and will not be set correctly.
There were more issues with the other flanks too, as they are 0b01 or 0b00. If 0b11 was set as a flank before it would not be able to switch to any other mode anymore. Now the bits get cleared before the new flank will be written.
