Hi,
i am playing along with the timer2 in the atmega168 with arduino, and i am searching for a way to put the address of a 'c' function in the interrupt vector!
i would like that each time that the interrupt of the Timer2 arive that my function be call
i need to put the address of that function at location 0x000E (Interrupt Vector for timer2)
Any idea how to make that?
Thanks in advance
Ok i think i found it!
Does ISR stands for Interrupt Sub Routine?
ISR(TIMER1_OVF_vect)
{
TIMSK1 &= ~(1 << TIOE1); // disable timer1 overflow interrupt
sei(); // re-enable global interrupts so that other ISRs can execute
do some stuff;
TCNT1 = 0;
TIFR1 |= 0xFF; // clear any pending timer1 overflow interrupts
TIMSK1 |= 1 << TIOE1; // re-enable timer1 overflow interrupts
// the previous lines make sure that we can now get out of this ISR
// without this ISR interrupting itself
}
Thanks again
Interrupts seem to hold some kind of magic because they seem to enable two things to happen at the same time. But this magic comes at a price – interrupt handlers must get in and out quickly and not rely on other interrupts. Code that runs in interrupt service routines can be difficult to debug if you are not familiar with the low level operation of the chip.
If you really need to run code in interrupts, have a look at the msTimer2 library: Arduino Playground - MsTimer2
Try to keep your code short. By default other interrupts are disabled while in an ISR (interrupt service routine) so some functionality (Serial for example) can miss data.
In fact, the ISR fragment you posted re-enables interrupts – this can cause severe problems such as stack overflows and should be avoided unless you really know what you are doing (or don't mind spending days debugging)
Does ISR stands for Interrupt Sub Routine?
Close. I've usually heard it as Interrupt Service Routine.
I always told my students that an interrupt was just a hardware trigged call to a subroutine.
I always told my students that an interrupt was just a hardware trigged call to a subroutine.
I guess you expected the students would find out the hard way that all the services that needed interrupts for servicing would be disrupted while in that call :o
mem, that may be true for microcontrollers like the ATmega, but it's not true of most larger microprocessors. On other devices, I have seen them prioritized. IRQ0 could interrupt any other ISR. IRQ1 could interrupt all but IRQ0. And so on. This isn't even the only arrangement you could use.
It's really not that hard: if you get an interrupt, start saving current state on the stack; if you are interrupted by a faster IRQ while saving state on the stack, you still start saving your state on the stack and do your ISR; when you're done, you'll quit and restore state from the stack so the interrupted slower IRQ's ISR will resume... saving state on the stack. It just requires the push/pop instructions to be atomic, and enough stack to deal with the nested interruptions.
mem, that may be true for microcontrollers like the ATmega, but it's not true of most larger microprocessors.
I wasn't doubting it can be done. But as this forum is for ATmega microcontrollers; and the Arduino is intended for artists, designers and others that may have very limited low level programming experience, I take the view that re-entrant ISRs shouldn't be encouraged if there are effective and simpler solutions.
Sure, if you understand ISRs, are intimate with the implications of system resource usage in the ISR, and know what atomic instructions are, then it can be done. But I got the impression from patgadgets posts that he could be in over his depth if he ran the code in the second post.
Then again, there is nothing wrong with jumping in the deep end as long as one is fully aware of what they may be getting into.
But it would be a shame to see someone new to the hobby end up frustrated and discouraged by elusive ISR bugs
Perhaps its just me, but I have lost countless days of my (professional)life tracking down bugs in interrupt handlers and would not wish that on anyone not very well paid for the privilege 
BTW i just post that code that i found on the forum, my point was how to address the Interrupt vector with my routine.
And the ISR() seems to be it.
Could not find doc on that in arduino.cc Where should i look
Thanks in advance
did you check out the link on msTimer2 posted in reply #2 above?
Yes i did,
i did not find any help on ISR()
i went to arduino.cc and type ISR in the search box ...
I could only find text in Forum, i can't find any reference?
Is ISR from arduino or is it a ATmega code?
Thanks
MsTimer2 is a small and very easy to use library to interface Timer2. It enables a function to be called on timer2 interrupts. Is there some additional functionality you need that msTimer2 doesn't support?
Thanks for the MStimer,
but can someone help me to find reference or help on ISR();
It seems to be a non documented feature, or i dont know where to search!
There is a lot of Interrupt Vector and there are not only about timer!!!
Table 11-1. Reset and Interrupt Vectors in ATmega48
Vector No. Program Address Source Interrupt Definition
1 0x000 RESET External Pin, Power-on Reset, Brown-out Reset and Watchdog System Reset
2 0x001 INT0 External Interrupt Request 0
3 0x002 INT1 External Interrupt Request 1
4 0x003 PCINT0 Pin Change Interrupt Request 0
5 0x004 PCINT1 Pin Change Interrupt Request 1
6 0x005 PCINT2 Pin Change Interrupt Request 2
7 0x006 WDT Watchdog Time-out Interrupt
8 0x007 TIMER2 COMPA Timer/Counter2 Compare Match A
9 0x008 TIMER2 COMPB Timer/Counter2 Compare Match B
10 0x009 TIMER2 OVF Timer/Counter2 Overflow
11 0x00A TIMER1 CAPT Timer/Counter1 Capture Event
12 0x00B TIMER1 COMPA Timer/Counter1 Compare Match A
13 0x00C TIMER1 COMPB Timer/Coutner1 Compare Match B
14 0x00D TIMER1 OVF Timer/Counter1 Overflow
15 0x00E TIMER0 COMPA Timer/Counter0 Compare Match A
16 0x00F TIMER0 COMPB Timer/Counter0 Compare Match B
17 0x010 TIMER0 OVF Timer/Counter0 Overflow
18 0x011 SPI, STC SPI Serial Transfer Complete
19 0x012 USART, RX USART Rx Complete
20 0x013 USART, UDRE USART, Data Register Empty
21 0x014 USART, TX USART, Tx Complete
Patgadget, could you clarify what you want to do?
I was assuming you had a task in mind for a project that you thought could be best achieved by calling a function in an interrupt handler. But as you don't say why msTimer2 is not a suitable solution, perhaps your interest is primarily in learning about how to use interrupt handlers?
There are lots of threads about interrupts in the avrfreaks forum – that forum is aimed at people more interested in technology at a lower level then that covered here in the Arduino forum. If you have a reasonable grasp of the C language you may be more likely to find the information you want there. If you are a new to C and the ATmega architecture, my advice is to build your knowledge of the language and platform before trying to write ISRs.
I apologize if I am misunderstanding your level of knowledge or goals, please clarify if I have got this wrong.
Sure,
i was searching for a way to call a interrupt subroutine, and i found it on this forum ( ISR(Vector)) but then i ask myself what reference did i not read to have to ask on the forum?
When i have a hardware problem, i read the pdf on the ATmega168
i got some reference on arduino.cc for some code but the rest is documented where???
i play a lot with interrupt, and i found some code using:
interrupts();
noInterrupts();
sei();
cli();
but no description of sei and cli on arduino site?
is there a lot of function like that, that exist and i could use but don't know about?
where is the complete list?
is there another site that i should know about? another pdf files that i should know?
You are talking about a specialize site for interrupts? fine i will read on it.
but what about all the other function that i can find about?
i just would like to know if the only way to find is asking on this forum?
i would prefer to search a bit on myself and don't disturb every body! but i don't know where.
And sorry if i was not clear at the first time, could be a language issue (i am french Canadian)
Thanks for your quick response.
The avrfreaks forum http://www.avrfreaks.net/index.php?name=PNphpBB2&file=index covers all aspects of the underlying technology used by the arduino, its not specific to interrupts nor to just the Arduino chip. Have a look around, there is lots of information for people that want to understand whats under the covers. But be prepared for much steeper learning curve – the Arduino tends to hide the low level stuff because its complicated and not usually necessary for most people. But there are lots of tutorials on the avrfreaks site if you are motivated to learn.
Good luck!