Operation control of 4 button circuits

When connecting 4 buttons to Arduino, I connected them by pull-down. At this time, I would like to know the code that stops the operation if more than 2 buttons are pressed. Also, the code below is the code I made. At the top, I wrote down the basic pin settings, setup, and operation of each button.

 if ((button1State == HIGH && button2State == HIGH) || 
 (button1State == HIGH && button3State == HIGH) ||
 (button1State == HIGH && button4State == HIGH) ||
 (button2State == HIGH && button3State == HIGH) ||
 (button2State == HIGH && button4State == HIGH) ||
 (button3State == HIGH && button4State == HIGH))
 {
  Serial.print("Two or more buttons were pressed");
 }

The problem with this code is that when you press two buttons, button 1 works, then button 2 works, and then it recognizes that 2 buttons are pressed and the text is output. What I want to do is, when two or more buttons are pressed, I shouldn't do anything, but I'm worried because they keep working.

If you know the code that stops the operation when two or more buttons are pressed, please reply.

For flexibility, here is what you can do:

• De-bounce the buttons like usual. Place the de-bounced result in a bit-field variable.
• Create a function pointer jump table. This can be done by providing a function to all supported combinations of buttons and ignoring the rest (setting them to null).
• Use the de-bounced bit-field as array index in the jump table.
• If the function address found is NULL, optionally do some error handling, otherwise execute the function.

For example lets assume for simplicity that all buttons are connected to pins 0 to 3 in PORTA. We could then create a variable for the de-bounced result uint8_t debounced_PORTA which can then hold all button combinations, equavilent to values 0 to 15.

We'd then define a function template: typedef void action_func (void); then declare a jump table by using this template, supporting up to 16 combinations:

action_func* action [0x0F]

We will initialize this one to point at various functions:

action_func* action [0x0F] =
{
  [PTA0]        = do_something,
  [PTA1 | PTA2] = do_something_else
};

Here PTA0 etc are the pin names provided by your register map (I don't remember exact names) - they are integer constants. In the above example the function void do_something (void) will get called when PTA0 and only PTA0 is pressed. Whereas the function do_something_else will get called when PTA1 and PTA2 and nothing else is pressed. And so on - this design is easy to maintain and scales well.

Indices not mentioned in the above jump table will get automatically set to null since that's required by C.

We can then use this jump table with the debounced port value as index:

if( action[debounced_PORTA] == NULL )
{
  /* optional error handling */
}
else
{
  action[debounced_PORTA]();
}