[51] led on off using interrupt

[vikun]

sir, i want ,
1) if i press switch first time the LED will b ON until delay ends and LED OFF when Delay ends.
also,
2)if i press switch before delay Ends LED should be OFF immediately.

i have tried this but, first if i press switch first 1st is ok but 2nd is not.

please tell me logic and code.

 

[KlausST]

Hi,

Where is your code?
Best if you could show your schematic, too.

Klaus

 

[vikun]

Hi,

Where is your code?
Best if you could show your schematic, too.

Klaus

---

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#include<REG51.h>
 
sbit in   = P1^2;
 
sbit out  = P1^7;
 
 
 void Delay( unsigned int msDelay )
{                     
        
    unsigned int i, j;
    for( i = msDelay; i > 0; --i)
    {
        for( j = 57600; j > 0; --j );
        {
            if(in==0)
            out=0;
            break;
         }   
     }
}
 
void main()
{
 
   in=1;
   out=0;
   
    while(1)
      {
         if(in==0)
           {
             out  =  1,
             
             Delay(3000);
             
             out =  0;
           }
      }
}

---

 

[KlausST]

Hi,

General rule for ISRs:
They should be as short as possible in time.
--> No loops, no busy_waits.

I assume
* you didn't draw a flow chart
* you didn't do a step-by-step trave (either with software or with paper and pencil)

Issues*
* you need some debouncing technique. Either hardware or software
* you need to detect key_press
* and additionally you need to detect key_release.

******
My recommended solution.
* don't use an input_pin_ISR
* use a fixed 5...50ms timer ISR. (Let's say 20ms)

Within the ISRpseudo code)

* key_actual = key
* if LED is ON
*    If (key_actual = active) AND (key_before = inactive): --> switch LED OFF
*    Else: decrement delay_counter; if delay_counter=0, then switch LED OFF

* ELSE (LED = OFF)
*   If (key_actual = active) AND (key_before = inactive): --> switch LED ON, set delay_counter to the desired value

* key_before = key_actual
* exit ISR

...not tested.

Klaus

 

[vikun]

Hi,

General rule for ISRs:
They should be as short as possible in time.
--> No loops, no busy_waits.

I assume
* you didn't draw a flow chart
* you didn't do a step-by-step trave (either with software or with paper and pencil)

Issues*
* you need some debouncing technique. Either hardware or software
* you need to detect key_press
* and additionally you need to detect key_release.

******
My recommended solution.
* don't use an input_pin_ISR
* use a fixed 5...50ms timer ISR. (Let's say 20ms)

Within the ISRpseudo code)

* key_actual = key
* if LED is ON
*    If (key_actual = active) AND (key_before = inactive): --> switch LED OFF
*    Else: decrement delay_counter; if delay_counter=0, then switch LED OFF

* ELSE (LED = OFF)
*   If (key_actual = active) AND (key_before = inactive): --> switch LED ON, set delay_counter to the desired value

* key_before = key_actual
* exit ISR

...not tested.

Klaus

could you plz send me code .. i am using AT89C2051 controller ic.

 

[KlausST]

Hi,

No.
* I'm not familiar with the used microcontroller
* I don't know which compiler you use
* there are a lot of specifications missing
* maybe you find one if you pay him
* it's your job to do the work. We will only support you to solve problems

Klaus

 

[swapan]

Which MCU do you use?

2)if i press switch before delay Ends LED should be OFF immediately.

then what? will it remain in OFF for ever or will ON again?

Clarify your requirement. Do you want a continuous loop or a single shot?

 

[baileychic]

Try this code.

You have to add debounce delay at two places.

#include <REG51.h>
 
sbit in  = P1^2; 
sbit out = P1^7;
 
 
 void Delay( unsigned int msDelay )
{       
    unsigned int i, j;

    for( i = msDelay; i > 0; --i)
    {
        for( j = 57600; j > 0; --j )
        {
            if(in == 0) {
		//debounce delay required here
		if(in == 0) 
			{
                    		out = 0;
                    		break;
			}
	    }
        }   
     }
}
 
void main()
{
 
   in = 1;
   out = 0;
   
    while(1)
      {
         if(in == 0)
           {
	   //debounce delay required here
	   if(in == 0)
		{
             		out  =  1,
             
             		Delay(3000);
             
             		out =  0;
	   	}
           }
      }
}

 

[KlausST]

Hi,

the above code won´t work:
* it doesn`t follow the rule: "* and additionally you need to detect key_release." from post#4
* the OP wants it to be interrupt driven.
I assume (but don´t know for sure) not because he just wants to use "interrupt", but because the function should operate independently of other tasks running in main loop.

Klaus