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start/stop interrupt rountine

 
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ariza



Joined: 16 Mar 2005
Posts: 13

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start/stop interrupt rountine
PostPosted: Tue Mar 22, 2005 3:51 pm     Reply with quote
Hi all.
I am having some serious trouble with a very simple problem abut using interrupts.
In my program I use ext,ext1,ext2,timer0 interrupts and i want to enable and disable interrupts with ext2. In ext2 routine, if my program is working(a/d conversion in timer0 interrupt), it closes all interrupts. Also if my program is not working, it activates the program. Something like start/stop A/D conversion.
Firstly i use a variable in main part like "a" and give an initial value of a=1 and also in my other interrupt routines the value of "a" is "1". When program enters ext2 routine i write:

Code:
#int_EXT2
EXT2_isr()
{ if(a==1)
  {output_high(PIN_C1);   //control led
  a=0;
  disable_interrupts(global);
  delay_ms(100);
  pc=0;   
  }

  if(a==0){
  output_high(PIN_C2);      //control led
  enable_interrupts(global);
  a=1;
  delay_ms(100);
  enable_interrupts(global);
  pc=0;
  }
}


And in main part
Code:
   for(;;)
{ output_high(PIN_C7);  // control led
   delay_ms(100);
   output_low(PIN_C7);
   delay_ms(100);}


Now is this the correct way??
Because when it enters ext2, program does not return to main part. There is no change in C7 led. Do I need to put break at the end of if parts.
And i want to cut other interrupts when Ext2 is active but also at the end of a==0 part in ext2 i want to activate forexample ext interrupt, so how can i set High/Low interrupt for ext2.
I know that if I set it high i can not activate another interrupt, is it correct ??
Note: in ext i take channel information
in
Code:
ext1
i set sample rate
in timer0 A/D conversion
in ext2 start/stop my interrupts

Thanks : Wink

Emrah
ariza



Joined: 16 Mar 2005
Posts: 13

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PostPosted: Tue Mar 22, 2005 4:04 pm     Reply with quote
Hi all..


A correction : in notes part

Quote:
in ext1 i set sample rate



thanks Embarassed

Emrah
Ttelmah
Guest
PostPosted: Tue Mar 22, 2005 4:37 pm     Reply with quote
You must _never_ use enable_interrupts(global), inside an interrupt handler.
The interrupt hardware on the PIC, automatically disables the interrupts, when one is being responded to, _and re enables then, when the return from the handler code is executed_. By re enabling the interrupts before this point, you raise the possibility that an interrupt could interrupt an interrupt. The system can only save the registers once (which is done in the global interrupt handler), so if this happens, the original values will be lost, and the program will probably crash.
If you want to disable/enable the interrupts, set a flag in the handler, and have the main code do the disabling. You can quite happily disable/enable any individual handler inside the interrupts without problems (so 'disable_interrupts(INT_EXT', is fine).

Best Wishes
Guest
PostPosted: Wed Mar 23, 2005 12:53 am     Reply with quote
OK!! thanks for advice. But my program main part(A/D conversion) is executed in timer0 interrupt nad I want to interrupt it and after Ext2 interrupt i don't need to return where the interrupt comes. The program starts to wait another ext2 to start the program again. How can i do this?

Best regards
Mark



Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA

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PostPosted: Wed Mar 23, 2005 10:43 am     Reply with quote
Not clear on what you are trying to do but you should set flags with the interrupts and handle your tasks in the main.

If you need to enable\disable global interrupts via a pin, then you will need to monitor those pins in the main loop.
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