Faris Hajdarpasic

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5 years ago.

How to use only one button to display different things on nokia display?

My question is simple, but I dont know how to realize it? So I can use only one button(on LPC1114).

If button is pressed , I need to do one thing, and if same button is pressed again I need to do another thing. And over and over again like that. So to understand me better I will explain you like this:

Press button -> do thing 1 Press button -> do thing 2 Press button -> do thing 1(again) Press button -> do thing 2 Press button -> do thing 1 Press button -> do thing 2

and so on. So I dont realize how to do this if I am using only one button. Thanks!

2 Answers

Jan Kamidra
5 years ago.

Hi, you can add a simple counter into your "button pressed" check statement or something else.

Great example is from Graham S. https://os.mbed.com/questions/74042/Multi-Function-PUSH-button/

Best regards J.

Andy A
5 years ago.

What you are describing is a simple state machine. You use a variable to track the current state of the system and depending on the value of that variable act appropriately.

// define an enum to track what to do next.
// since there are only 2 states we could use a bool variable
// but that then doesn't allow adding more modes
// or we could use an integer with different values for each
//  state but then we need a set of defines or constants
// to track which value is for which state.
// an enum is effectively an int and set of defines combined.
enum state_e { action1 , action2 } nextButtonAction;

void doNextButtonAction (void) {
  switch (nextButtonAction) { 
    case action1:
    default: // default should never be hit but include it to be safe.
      doAction1();
      nextButtonAction = action2;
      break;
    case action2:
      doAction2();
      nextButtonAction = action1;
      break;
  }
}

main () {
  // initalise 
  nextButtonAction = action1;

  while (true) {

    if (button) {  // button is pressed
      doNextButtonAction();  
      while (button)  // wait for button to be released
         wait_us(10);
    }

  }
}