Re: [avr-gcc-list] altering array variable and interrupts

[Philipp Burch]

Hi,

ok, if you need to modify the characters, then you can just declare the 
mentioned array volatile and not PROGMEM.
What do you mean with "I don't think this really completely stops 
execution"? Have you tested it, or are you just guessing? What's the 
interval of the interrupt, how is F_CPU defined and do you use 
optimization? There's an easy way to check if the program continues: 
Place a cli(); instruction right before your mainloop. If it doesn't 
hang in the interrupt, the program should then just run inside the 
infinite loop and hence not do anything with the controllers pins, so 
you can easy check.

btw: You should reply to "address@hidden", or I'm the only 
recipient of the mail.

Philipp
> Hi,
>  
> Thanks for reply. I do want to modify that array of char not to 
> prevent changing them. Basicaly each time interrupt occurs it should 
> read the array and output values, and I will change values often. I 
> know delay inside interrupt is not a good tactic but I just didn't 
> have time to compute the right low-to-high transaction time in CPU 
> clocks to match the 74hc161 4-bit counter logical diagaram I clock 
> from interrupt; hence I used a delay. I don't think this really 
> completely stops execution of the program so the value never change.
>  
> Cornel
>
> ----- Original Message ----
> From: Philipp Burch <address@hidden>
> To: address@hidden
> Sent: Tuesday, January 15, 2008 8:24:17 PM
> Subject: Re: [avr-gcc-list] altering array variable and interrupts
>
> Hi,
>
> I guess, your ISR takes too long. Delayloops in ISRs are very, very bad
> style, because they block the whole CPU. I suppose, the Interrupt comes
> more often than every 3ms, so there is no way for the AVR to execute any
> code outside the ISR. You should rewrite the complete program, there are
> many unnecessary things, such as character generation at runtime. Just
> declare a PROGMEM array with all your digits and read from it with
> pgm_read_byte() (From avr/pgmspace.h, check the manual of avr-libc),
> that saves RAM and initialization work. And it prevents the characters
> from getting modified (Or do you really need this "feature"?).
>
> Philipp
> > sorry I forgot to put url: http://rafb.net/p/fxrljj42.html
> > 
> >