Delay problem

dear friends,

i have written program send digital value input pin output pin. objective " read status of sensor connected input pin , write status output pin. if input pin high, wish set output pin high , keep high 2 seconds. then, turn output pin pin off after 2 seconds , wait 5 minutes. again, check status of input pin.  if high, set output pin high again , keep high 2 seconds..." repeat procedure on , on again.

the problem is:
for few times (once or twice), 5 minutes delay caccurate. after few time, five-minutes delay longer , longer. checked one-minute long delay. there same problem five-minutes delay. first few times, one-minute delay works fine. after several time, accuracy goes down , delay time gets longer. program follows:

code: [select]

const int inputpin = 12;
const int outputpin = 13;

void setup(){
 pinmode(inputpin,input);
 pinmode(outputpin,output);
 
 digitalwrite(outputpin,low);
 digitalwrite(inputpin,low);
 
 
}

void loop(){
 if(digitalread(inputpin)==high){
   digitalwrite(outputpin,high);
   delay(1000l*2l); // 2 sec
   digitalwrite(outputpin,low);
   delay(1000l*60l*1l); // 1 min
 }
}

you don't enable pullups on output pins. fix or remove faulty comment.

evidence? don't see evidence of claim.

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