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keymatrix debounce example

Mahmood Elnasser

Hi all
Does any one have keymatrix debounce example on keil c.
Thanx

  • 0

    Hi Mahmood!

    I usually do that in an timer interrupt routine.

    if (--tsec_counter == 0) {
    tsec_counter = DEF_10TH;
    if (t0_10thcnt > 0) {
      --t0_10thcnt;
    }
    if (((~INPORT) | 0xc0) != input_new_state) {
       input_new_state = (~INPORT) | 0xc0;
       t0_bounce = bounce_time;
    }
    if (t0_bounce != 0) {
      --t0_bounce;
    }
    if ((input_new_state != input_old_state) && (t0_bounce == 0)) {
      input_active |= input_pedge & (input_old_state ^ input_new_state) & (input_new_state & ~input_old_state);
      input_active |= input_nedge & (input_old_state ^ input_new_state) & (input_old_state & ~input_new_state);
      input_old_state = input_new_state;
      input_triggered |= input_active;
    }
  }

    This is from a very slow input (debounce time 0.3sec).

    It is part of the interrupt service routine of timer 0. It is called every 1/1024 second. If a tenth second is reached, I will check the INPORT for it's state and when it is the same for 0.3 secs it triggers some action.

    If you ahve something like a real keyboard, I would suggest a stack of key codes that is processed outside the timer ISR.

    Take care,
    Sven