Yep, this is the way that I ended up doing it in my ATTiny2313 clocks.
It works better than CTC timer, but it still had the same kinds of
problems for me. (to a lesser severity)
-Adam
On 11/4/2013 4:57 PM, NeonJohn wrote:
On 11/04/2013 07:00 PM, Frank Bemelman wrote:
Assume you have an interrupt every 57 uS.
[untested code]
int timervalue = 0;
int msektimer = 0;
.
.
.
timer_int()
{ timervalue += 57; // add the uS that have passed since previous interrupt
if(timervalue>1000) // a millisecond + some extra uS have past
{ timervalue -= 1000; // keep the remaining uS
msektimer++; // keep track of total milliseconds
}
}
Keeping track of seconds can be done in a similar way, just expand code.
Sure there is some jitter on the timervalues, but a jitter of 57uS
is usually not a problem for household purposes.
Clever. I have been thinking about slowing the interrupts down
dramatically but I can't generate a precise decimal time interval that
way. I'd been thinking about an algorithm but yours just solved it for
me. Thanks much
John
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