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adi1133
Joined: 30 Dec 2010
Posts: 6
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| What is the best way to trigger an interrupt after X ms ? |
 Posted: Thu Dec 30, 2010 5:55 pm |
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I want to trigger an interrupt after X ms.
I currently use this code, is there a better or "proper" way to do it ?
| Code: |
int16 time; //ms
int t1count=0;
int t1count_end;
int16 t1time;
int1 flag=0;
#INT_TIMER1
void timer1()
{
if (t1count>=t1count_end)
{
Flag=1;
disable_interrupts(INT_TIMER1);
}
else t1count++;
}
void main(void)
{
setup_oscillator(OSC_4MHZ);
SETUP_TIMER_1(T1_INTERNAL | T1_DIV_BY_8);
enable_interrupts(GLOBAL);
time=1000; //set time in ms , this can be changed
t1count_end=(125*time)>>16; //calculate the no of times t1 int is done
t1time=~((125*time)&65535); //enhance precision
set_timer1(t1time);
t1count=0;
enable_interrupts(INT_TIMER1);
while(1); //flag becomes 1 in X time
}
//125*time converts ms into timer value (for T1_DIV_BY_8 )
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temtronic
Joined: 01 Jul 2010
Posts: 9165
Location: Greensville,Ontario
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| Posted: Thu Dec 30, 2010 8:18 pm |
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Better and 'proper' are subjective terms..
Better.. How ?? perhaps you can cut code that is more efficient in code space used, number of variables(RAM) used, etc.
'proper'..by whose 'standards' ! In my case, I remember cutting code in just 8Kbytes of 1702 EPROM. The system (still in use today) scans 512 remote devices via single wire, corrects for line loss, controls these remotes and retrieves data on a scheduled basis with several layers of alarms as well as printer and keyboard functions. For me 'proper' requires very, very tight code maximizing every byte.
'proper' for others might mean very wordy code(takes up space) but easier to understand, Some feel only interrupt driven code is 'proper'.
Every program ever made can be 'tweaked' to be 'better' and 'proper', at the cost of time and energy, yet still does the original procedure.
The bottom line is, it if works for you and you're happy, leave it alone. |
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adi1133
Joined: 30 Dec 2010
Posts: 6
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| Posted: Thu Dec 30, 2010 8:27 pm |
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Is there a better built-in function or some other alternative to this ?
I just think my code is too bulky for such a simple feature |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Dec 30, 2010 8:41 pm |
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What is your overall purpose for doing this ? This information will help
us to give you advice. |
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jecottrell
Joined: 16 Jan 2005
Posts: 559
Location: Tucson, AZ
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| Posted: Thu Dec 30, 2010 8:47 pm |
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Do you want to change the interrupt timing at runtime?
Do you want to wake the processor with the interrupt?
Do you want it only to interrupt once or EVERY x period of time?
Start here and see if this helps:
http://www.ccsinfo.com/forum/viewtopic.php?t=22467 |
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adi1133
Joined: 30 Dec 2010
Posts: 6
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| Posted: Thu Dec 30, 2010 8:51 pm |
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| I use this to stop a motor, I want to change the interrupt timing during runtime, I do not use sleep and I only want to interrupt once, not every x period of time. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19350
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| Posted: Fri Dec 31, 2010 3:33 am |
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As 'comments', a couple of things come to mind:
1) What resolution is needed?.
2) Is the interrupt going to do anything more than setting the flag?.
If (for instance), you were 'happy' with a 10mSec resolution, then a simpler long term solution, is to use timer2, and set this up to interrupt every 10mSec. Then the timer2 code, becomes:
| Code: |
int16 counter;
#INT_TIMER2
void tick(void) {
if (counter) --counter;
}
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Then all you need do, is set 'counter' to the number of 10mSec 'ticks' you want, and it'll go to zero, when this time has completed.
If the second is 'false', then it is worth realising that the timer interrupt 'flag', is just that, a flag, which can be used just like any other variable (after a bit definition).
So if you set the interrupt counter to a value which will set the interrupt flag the required time in the future, clear the interrupt flag, and leave interrupts _disabled_, you can test the interrupt flag, just like your 'flag' variable, and it'll go 'true' when the time expires. No need for an interrupt handler at all...
Best Wishes |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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