Start a timer with an button interrupt (MSP432)

There are button debonunce surce code all over internet. Why are you trying to invent The Wheel? ;)

Code for "LED on" while button pressed (wrote from scratch, could be buggy):

volatile unsigned char button_pressed, button_debounce_counter;

while (1) {
  if (button_pressed) {
    LED_on();
  } else {
    LED_off();
  }
  sleep_till_next_ISR();
}

timer_ISR() {
  if ( !(BUTTON_INPORT & BUTTON_PIN) ) { // logical "0" when button pressed, "1" when released
    if (button_debounce_counter > DEBOUCE_TRESHOLD)  // set treshold count to be equal ~ 50..100 ms
      button_pressed = 1;
    else
      button_debounce_counter++;
  } else {
    button_pressed = 0;
  }
}

Ilmars said:

Don't use port IRQ but polling from timer/tick ISR running at 100 to 1000Hz.

This comes from my post here.

But as I said, I do prefer the timer method without interrupts as well. An interrupt for a button is a little bit exaggerated.

This threshold depends on your individual timer settings. If your timer invokes an interrupt every 1ms and you want a debounce time of 10ms, then define it as 10. For 500µs timer interval and 50ms debounce time, define it as 100.

Why did you comment out the pull-up resistor?

And you have to reset your button_debounce_counter somewhere.

Christoph Marko said:

The ISR was called but the comparison of the value didn't work and I don't know why.

Hi Christoph!

Which comparison are you talking about?

Dennis

There is a major fault in your code - you inittialize your port 1 here:

P1DIR |= BIT0;
P1OUT |= BIT1;
P1REN |= BIT1;

This sets P1.0 to output direction, sets P1.1 high and enables the resistor for P1.1, which results in a pull-up. Correct so far, but your next line

P1OUT = 0x00;

overrides the previous made setting and sets the resistor to pull-down. I guess you simply wanted the LED at P1.0 to be off, right? You have to use bitwise operations. To only set P1.0 low, write

P1OUT &= ~BIT0;

Or for high write

P1OUT |= BIT0;

This is also wrong here:

if( button_pressed )
{
  P1OUT = 0xFF;
}
else
{
  P1OUT = 0x00;
}

Again, you also change the setting of the resistor. Another time in your ISR:

if( P1IN & BIT1 )
{
  if( button_debounce_counter > 10 )
  {
    button_pressed = 1 ;
    P1OUT = 0xFF;                  // <- HERE
  }
  else
  {
    button_debounce_counter++;
  }
}
else
{
  button_debounce_counter = 0;
  button_pressed = 0;
  P1OUT = 0x00;                    // <- HERE
}

Dennis

P.S.: Please use the syntax highlighter for inserting code which is available in rich formatting mode that appears on the lower right when replying.

I just saw another thing:

if( P1IN & BIT1 )
{
  ...
}

This checks if the input pin is high, so NOT pressed. You want

if( !(P1IN & BIT1) )
{
  ...
}

Dennis