One out of four LEDs not responding to button switches

Using Arduino Programming Questions
1

Can't seem to control the LED on pin 3, using any of the four button switches. Only using 4 out of the 10 LED pins at the moment. Any ideas to why pin 3 is not responding would be greatly appreciated. The other LEDs and switches work.

// constants won't change. They're used here to 
// set pin numbers:
const int ledPin[] = {3,4,5,6,7,8,9,10,11,12}; // the number of the LED pin
const int buttonPin[] = {14,15,16,13};    // pin A0,A1,A2,13  

// Variables will change:
int ledState[] = {HIGH,HIGH,HIGH,HIGH};         // the current state of the output pin
int buttonState;             // the current reading from the input pin
int lastButtonState[] = {LOW,LOW,LOW,LOW};   // the previous reading from the input pin
int c = 0;

int reading[]={0,1,2,3};  
int state[] = {LOW,LOW,LOW,LOW};
int previous[] = {HIGH,HIGH,HIGH,HIGH};

// the following variables are long's because the time, measured in miliseconds,
// will quickly become a bigger number than can be stored in an int.
long lastDebounceTime = 0;  // the last time the output pin was toggled
long debounceDelay = 50;    // the debounce time; increase if the output flickers

void setup() {
  for(int x=0; x<4;x++){
  pinMode(buttonPin[x], INPUT);
  }
 for(int i=0; i<4;i++){
  pinMode(ledPin[i], OUTPUT);
 }
}

void loop() {
  // read the state of the switch into a local variable:
                        
                        if(c > 4){
                          c = 0;
                        }
                          
  reading[c] = digitalRead(buttonPin[c]);

  // check to see if you just pressed the button 
  // (i.e. the input went from LOW to HIGH),  and you've waited 
  // long enough since the last press to ignore any noise:  

  // If the switch changed, due to noise or pressing:
  if (reading[c] != lastButtonState[c]) {
    // reset the debouncing timer
    lastDebounceTime = millis();
  } 
  
  if ((millis() - lastDebounceTime) > debounceDelay) {
    // whatever the reading is at, it's been there for longer
    // than the debounce delay, so take it as the actual current state:

    // if the button state has changed:
    if (reading[c] != buttonState) {
      buttonState = reading[c];

      // only toggle the LED if the new button state is HIGH
      if (buttonState == HIGH) {
        ledState[c] = !ledState[c];
      }
    }
  }
  
  // set the LED:
  digitalWrite(ledPin[c], ledState[c]);

  // save the reading.  Next time through the loop,
  // it'll be the lastButtonState:
  lastButtonState[c] = reading[c];
  
                              c++;
}
2

harrybst:
Can't seem to control the LED on pin 3, using any of the four button switches. Only using 4 out of the 10 LED pins at the moment. Any ideas to why pin 3 is not responding would be greatly appreciated.

You are coding a "buffer overflow" and do RAM-write outside the bounds of an array that you defined:

int reading[]={0,1,2,3};  
...
  if(c > 4){
    c = 0;
  }
                          
  reading[c] = digitalRead(buttonPin[c]);

You defined a 'reading' and a 'buttonPin' array with 4 elements, indexed 0,1,2,3 = 4 Elements

But your 'c' variable can become 4 and then you set

reading[4] = digitalRead(buttonPin[4]);

Both arrays are accessed outside of their range, so you access some other variables from RAM, that do not belong to your array.

Typical 'buffer overflow'.
You never can say what happens when doing random write to the RAM.

The correct 'c' resetting logic would be '>=':

int reading[]={0,1,2,3};  
...
  if(c >= 4){
    c = 0;
  }

That way the may. array index stays 3 or less, which is correct.

3

I thought I tried that. Thank you very much for your input. It works fine now.

4