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8051 hardware input switch reading problem

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aliraza786

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hello i wana ask i have intefaced two switches with 8051 when one switch is on relay on and when other switch is on relay will be off..every thing works fine in protious and hardwre but it is ok for a short interval of time almost 5 minute but i have to off the relay after 12 hours ...after a long time 8051 doesnot read the pin i dnt know what is the problem.....this is the simple code here. 8051 read switch for a small interval of time but after a long time interval 8051 doesnot read the pin.........
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#include<reg51.h>
sbit sw=P2^0;
sbit sw1=P2^1;
unsigned int x,g;
sbit relay=P1^6;
void delay(x)
{
    for(g=0; g<x; g++)
    {
        TMOD=0x01;
        TH0=0xFC;
        TL0=0x67;
        TR0=1;
        while(TF0==0);
        TR0=0;
        TF0=0;
    }
}
void main()
{   P2=0xFF;
    sw=1;
    sw1=1;
 
    while(1)
    {
        if(sw==0)
        {
            delay(800);
            if(sw==0)
            {
                relay=0;
                delay(300);
            }
        }
        if(sw1==0)
        {
            delay(800);
            if(sw1==0)
            {
                relay=1;
                delay(300);
            }
        }
    }
}

my mcu is 89s51
 
Last edited by a moderator:

I suggest you to
1. share the circuit diagram, so we can look into h/w problem as well, if any.
2. If possible use EXT INTR (INT0 and INT1) instead of P2.0, P2.1.
 
i dont know how to use external intrupt please suggest me the article where i can learn how to use external intrupts ans sample code too....thnkyou very much for this help....!
 

aliraza786 said:
i dont know how to use external intrupt please suggest me the article where i can learn how to use external intrupts ans sample code too....
Click to expand...

Here are a few tutorials discussing external interrupts:





INTERRUPT PROGRAMMING IN 8051

Appnote 103 - 8051 Interrupt Vectors

To define an interrupt function using the Keil C51 Compiler, an interrupt number and register bank is specified where the interrupt number corresponds to a specific interrupt vector address.
Click to expand...

void my_external_interrupt_0_routine(void) interrupt 0 using 2
{
/* do something */
}
Click to expand...



8051_EX0.ZIP Keil Example

While each C compiler has its own Interrupt Service Routine (ISR) syntax, it appears you are using Keil, if not reference the appropriate compiler docs for the proper ISR syntax.



BigDog
 
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#include<reg51.h>
sbit sw=P2^0;
sbit sw1=P2^1;
unsigned int x,g;
sbit relay=P1^6;

void init(void)
{
TMOD=0x01;
P2=0xFF;
sw=1;
sw1=1;



}
void delay(x)
{
for(g=0; g<x; g++)
{
TH0=0xFC;
TL0=0x67;
TR0=1;
while(TF0==0);
TR0=0;
TF0=0;
}
}
void main()
{
init();
while(1)
{
if(sw==0)
{
delay(10);
if(sw==0);
{
while(!sw);
relay=0;
delay(10);
}
}

if(sw1==0)
{
delay(10);
if(sw1==0)
{
while(!sw1);
relay=1;
delay(10);
}
}
}
}
 

welove8051 i try ur code but still it is good for short time i can on the system but cant make it off.....becuse system have to remain on for almost 12 hours...
 

aliraza786 said:
8051 read switch for a small interval of time but after a long time interval 8051 doesnot read the pin.........
Click to expand...

It sounds like there maybe another issue besides your code. Especially if the system works for a period of time and then sudden fails.

Can you provide a schematic of your circuit?

BigDog
 
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@aliraza,

As I foretold...please share your hardware circuit design.
 

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