No, I will try to explain where my problem is. The code I posted before
should turn the LED connected to PB5 on. The code also contains an ISR, but
it is empty and as I never enable interrupts, it should never be called.
The code works without optimizations, but with -Os enabled, the LED does
*not* turn on! If I remove the (empty) ISR and keep everything else the same,
the LED *does* turn on with optimizations enabled!
My problem is not how to toggle the LED, I know how to do that. My problem is
that the code behaves differently when using the optimization option -Os.
8. Mai 2016 14:36 von partha_nay...@yahoo.com:
> Hi,
> "> I do *not* want the ISR to be called". I guess you do not want the
> interrupt to be enabled. If you do not start the timer (as the interrupt is
> timer related) this interrupt will never occur. If you are using the timer
> for something else and need the timer running, then you need not explicitly
> enable timer overflow interrupt (see TIMSK register bits). In the while
> loop, you are always setting the port bit which I guess is connected to the
> LED and the LED will glow when this bit is 1. Suggest toggling the LED
> through a while loop with delays (large enough to be able to see LED
> flashing) inserted.> > Regards,
> Parthasaradhi
> Hyderabad
>
>
> > > > On Sunday, May 8, 2016 3:06 PM, "> a...@tuta.io> " <> a...@tuta.io>
> > wrote:
>
>
> > Thank you for your instant response.
>
> I am sorry if I was unclear about that: I do *not* want the ISR to be
> called. The LED should turn on because I enable it in main(), however, the
> uC goes straight to the ISR!
>
> For example, if I set the LED to high in the ISR and set it to low in
> main(), it will be set to high and the LED will turn on when I flash it.
> Even though I used cli()!
>
> This behavior appears to depend on -Os, so I guess I am either using the
> tools incorrectly, or there is a bug in the optimization code.
>
> 8. Mai 2016 11:22 von > partha_nay...@yahoo.com> :
>
>
>> First off, you are disabling global interrupts (cli ()). You need to
>> enable them (sei ()). I presume you are toggling the LED in ISR, if so the
>> LED will not toggle as interrupts are disabled. >> >> Regards,
>> Parthasaradhi
>> Hyderabad
>>
>>
>> >> >> >> On Sunday, May 8, 2016 2:40 PM, ">> a...@tuta.io>> " <>>
>> a...@tuta.io>> > wrote:
>>
>>
>> >> >> Hello,
>>
>> I have been working on a project for some time and at some point,
>> everything just stopped working. It appears that as soon as I include an
>> ISR in my C code, the main function won't even be called anymore. I
>> reduced my code to this:
>>
>>
>> #include <avr/io.h>
>> #include <avr/interrupt.h>
>>
>> int main (void) {
>> cli();
>> DDRB = 0xff;
>> while(1) PORTB |= (1 << PB5);
>> return 0;
>> }
>>
>> ISR(TIMER0_OVF_vect) {}
>>
>> But the LED just won't turn on. The strange thing is: If I remove the ISR
>> at the bottom without changing anything else, even keeping the include,
>> everything works. If I remove the -Os option from gcc but keep the ISR,
>> everything works.
>>
>> I use these commands to compile, link and flash it:
>>
>> F_CPU=16000000L
>> avr-gcc -Wall -DF_CPU=$F_CPU -c -mmcu=atmega168 -Os main.c -o main.o
>> avr-ld -mavr5 -o led-test.elf main.o
>> avr-objcopy -O ihex led-test.elf led-test.hex
>> sudo avrdude -c avrisp2 -p atmega168 -P usb -b 57600 -U
>> flash:w:led-test.hex
>>
>>
>> I am quite new to the avr tools so I might just have made a silly mistake,
>> so I would appreciate any tips!
>> Thank you!
>>
>>
>> LSB:
>> Distributor ID: Ubuntu
>> Description: Ubuntu 16.04 LTS
>> Release: 16.04
>> Codename: xenial
>>
>> Output of avr-gcc -v:
>> Using built-in specs.
>> Reading specs from /usr/lib/gcc/avr/4.9.2/device-specs/specs-avr2
>> COLLECT_GCC=avr-gcc
>> COLLECT_LTO_WRAPPER=/usr/lib/gcc/avr/4.9.2/lto-wrapper
>> Target: avr
>> Configured with: ../src/configure -v --enable-languages=c,c++
>> --prefix=/usr/lib --infodir=/usr/share/info --mandir=/usr/share/man
>> --bindir=/usr/bin --libexecdir=/usr/lib --libdir=/usr/lib --enable-shared
>> --with-system-zlib --enable-long-long --enable-nls
>> --without-included-gettext --disable-libssp --build=x86_64-linux-gnu
>> --host=x86_64-linux-gnu --target=avr CFLAGS='-g -O2
>> -fstack-protector-strong -Wformat ' CPPFLAGS=-D_FORTIFY_SOURCE=2
>> CXXFLAGS='-g -O2 -fstack-protector-strong -Wformat ' FCFLAGS='-g -O2
>> -fstack-protector-strong' FFLAGS='-g -O2 -fstack-protector-strong'
>> GCJFLAGS='-g -O2 -fstack-protector-strong'
>> LDFLAGS='-Wl,-Bsymbolic-functions -Wl,-z,relro' OBJCFLAGS='-g -O2
>> -fstack-protector-strong -Wformat ' OBJCXXFLAGS='-g -O2
>> -fstack-protector-strong -Wformat '
>> Thread model: single
>> gcc version 4.9.2 (GCC)
>>
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>>
>>
>> >> >>
>
>
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