Counter Interrupt not working

[anilson002]

Hello,

I am trying a simple project to count how many times a PushButton has been pressed.
I searched a couple of post but could not figure out how to make it work.

version 1

Code: Select all

/*
 * Project name:
     MyProject_3a (Using Timer0 to obtain count interrupts)

 * Description:
     - This code demonstrates how to use Timer0 and it's interrupt.
     - Program counts how many times PushButton on PORTA.RA4 has been pressed
     - Each count increment turns ON a LED (PORTB.RB1, PORTB.RB2, PORTB.RB3)
     - The count resets to Zero after 3 presses and turns OFF all LEDs
*/


unsigned cnt_pb;

void initialize()
{
   ANSEL = 0;

   TRISA = 0xFF;
   TRISB = 0x00;

   PORTB = 0x01;             //0b00000001

   cnt_pb = 0;
   
   OPTION_REG = 0x20;        //0b00100000
   TMR0 = 155;
   INTCON = 0xA0;            //0b10100000
}


void interrupt()
{
    cnt_pb++;
    TMR0 = 155;
    INTCON.TMR0IF = 0;
    
    switch(cnt_pb)
    {
       case 1:
            PORTB.RB1 = 1; break;
       case 2:
            PORTB.RB2 = 1; break;
       case 3:
            PORTB.RB3 = 1; break;
       default:
            PORTB.RB1 = 0;
            PORTB.RB2 = 0;
            PORTB.RB3 = 0;
            cnt_pb = 0;
    }
}


void main()
{
   initialize();
   while(1){}
}

version 2

Code: Select all

/*
 * Project name:
     MyProject_3a (Using Timer0 to obtain count interrupts)

 * Description:
     - This code demonstrates how to use Timer0 and it's interrupt.
     - Program counts how many times PushButton on PORTA.RA4 has been pressed
     - Each count increment turns ON a LED (PORTB.RB1, PORTB.RB2, PORTB.RB3)
     - The count resets to Zero after 3 presses and turns OFF all LEDs
*/


char cnt, old_cnt;


void initialize()
{
   ANSEL = 0;

   TRISA = 0xFF;
   TRISB = 0x00;

   PORTB = 0x01;             //0b00000001

   cnt = 0;

   OPTION_REG = 0x20;        //0b00100000
   TMR0 = 155;
   INTCON = 0xA0;            //0b10100000
}


void interrupt()
{
   if(INTCON.TMR0IF)
   {
      cnt++;
      TMR0 = 155;
      INTCON.TMR0IF = 0;
   }
}


void display()
{
    switch(cnt)
    {
       case 1:
            PORTB.RB1 = 1; break;
       case 2:
            PORTB.RB2 = 1; break;
       case 3:
            PORTB.RB3 = 1; break;
       default:
            PORTB.RB1 = 0;
            PORTB.RB2 = 0;
            PORTB.RB3 = 0;
            cnt = 0;
    }
}


void main()
{
   initialize();

   while(1)
   {
      if (old_cnt != cnt)
      {
         display();
         old_cnt = cnt;
      }
   }
}

Circuit_MyProject_3.JPG (53.29 KiB) Viewed 2012 times

[hexreader]

Your code works, but 1:2 prescaler is enabled, so timer 0 rolls over every 200 button presses.
Set PSA bit to bypass the prescaler. Now you only need 100 button presses to light an LED

Set TMR0 register to 255, not 155, so that only one button push is required to roll Timer 0 over to 0 and light the next LED

Code: Select all

/*
 * Project name:
     MyProject_3a (Using Timer0 to obtain count interrupts)

 * Description:
     - This code demonstrates how to use Timer0 and it's interrupt.
     - Program counts how many times PushButton on PORTA.RA4 has been pressed
     - Each count increment turns ON a LED (PORTB.RB1, PORTB.RB2, PORTB.RB3)
     - The count resets to Zero after 3 presses and turns OFF all LEDs
*/

char cnt, old_cnt;

void initialize()
{
   ANSEL = 0;                // disable analogue

   TRISA = 0xFF;             // all input
   TRISB = 0x00;             // all output

   PORTB = 0x01;             // 0b00000001

   cnt = 0;

   OPTION_REG = 0x28;        // 0b00100000 no pull-up, T0 clk RA4, rising edge, 1:2, PSA set (no prescaler)
   TMR0 = 255;               // a single button press will cause rollover
   INTCON = 0xA0;            // 0b10100000 GIE, TMR0IE,
}

void interrupt()
{
   if(INTCON.TMR0IF)
   {
      cnt++;
      TMR0 = 255;            // a single button press will cause rollover
      INTCON.TMR0IF = 0;
   }
}


void display()
{
    switch(cnt)
    {
       case 1:
            PORTB.RB1 = 1; break;
       case 2:
            PORTB.RB2 = 1; break;
       case 3:
            PORTB.RB3 = 1; break;
       default:
            PORTB.RB1 = 0;
            PORTB.RB2 = 0;
            PORTB.RB3 = 0;
            cnt = 0;
    }
}


void main()
{
   initialize();

   while(1)
   {
      if (old_cnt != cnt)
      {
         display();
         old_cnt = cnt;
      }
   }
}