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Izolator
Joined: 10 Feb 2004
Posts: 12
Location: Denmark, (Scandinavia-Europe)
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| setup_timer_2(??,??,??) with Neoton zero drift RTC |
 Posted: Mon Feb 23, 2004 3:29 pm |
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Hi Guys,
I'm using a slightly minimized version of Neotone's old code, cutting out month, years and leapyears.
| Code: |
//RTC variables
int32 const xtl = 19660800;
int32 clock = xtl;
int8 days=0,hours=0,minutes=0,seconds=0;
int1 leapyear=0,tick=0;
// 0.83mS resolution with my xtl value
// -=Process Zero Drift Real Time Clock Information=-
// Decrement cycles per interupt
// Increment seconds counter, Set 1 second flag, Add number of ticks per second to clock
// Increment minutes counter
// Increment hours counter
// Increment days counter
#int_TIMER2
void TIMER2_isr() { clock -= 16384;
if(clock < 16384) {seconds++;clock += xtl;Tick= 1;
if(seconds == 60) {minutes++;seconds = 0;
if(minutes == 60) {hours++;minutes = 0;
if(hours == 24) {days++;hours= 0;
}}}}}
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Problem:
As I am a total newbie with Timers & Interrupt I just recently discovered that the interrupt needs to be setup and enabled. I dont understand the math of it ?!?!?
I'm using:
20Mhz osc. quartz
Pic16F877
PCM 3.173
...what do I do to make the routine work as intended, with my crystal ?
I tried with:
setup_timer_2(T2_DIV_BY_16,0xff,1);
but that makes it count a little too fast: some 30sec in 20 min, hmm.
Keep in mind that to me the 3 variables are just numbers and I guessed at random to test it....not the correct way I know.
| Code: |
main() {
setup_timer_2(??,??,??); // what do I put instead of the ??'s to make Neotrons code behave as intended, a RTC that puts secs, mins, hours....
enable_interrupts(int_timer2);
enable_interrupts(global);
while(1) {
}
} |
side question:
what does the dear mr. Neotone mean by the following:
1) // 0.83mS resolution with my xtl value
2) int32 const xtl = 19660800; => do I need to change this to 20000000 ?
Thanks for you assistance guys, this is making my head hurt 
BR
Rasmus 'Izolator'
Last edited by Izolator on Mon Feb 23, 2004 4:45 pm; edited 2 times in total |
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Neutone
Joined: 08 Sep 2003
Posts: 839
Location: Houston
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| Posted: Mon Feb 23, 2004 4:40 pm |
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I think this has better comments. 19660800 is a frequency that can be divided to get the most common baud rates. It's the frequency of the crystle I use.
| Code: |
/*********************************************
* Initialize RTC *
*********************************************/
void Initialize_RTC(void)
{ Ticker = XTAL_FREQUENCY;
setup_timer_2 ( T2_DIV_BY_4, 0xff, 4 ); // initialize 8 bit counter/timer 2 to interupt every 16384 clock cycles
enable_interrupts( INT_TIMER2 ); // Start RTC
}
// Global Real Time Clock Information
#int_TIMER2 // Clock interrupt adjusted to occurs ~ 1ms
void TIMER2_isr() // -=Process Zero Drift Real Time Clock Information=-
{ tickmSec = 1; // set each MS very approximately
Ticker -= 16384; // Decrement ticker by clocks per interupt
if ( Ticker < 16384 ) // If second has expired
{ Ticker += XTAL_FREQUENCY; // Increment ticker by clocks per second
second++; // Increment number of seconds
tickSec = 1; // set each Second very accuratly
}
}
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Last edited by Neutone on Mon Feb 23, 2004 4:43 pm; edited 1 time in total |
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Izolator
Joined: 10 Feb 2004
Posts: 12
Location: Denmark, (Scandinavia-Europe)
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| Posted: Mon Feb 23, 2004 4:43 pm |
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Thankyou good Sir,
It seems to work right out of the box.
Bless you, I might still pass my exam 
BR
Rasmus 'Izolator' |
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