I have the project to build a robot for my school. It will record button pushes then move according to this record.

Before usig motors, i'm trying to do this using leds.

Thanks from posts from this community, I've succeed in recording button pushes in an array.

Now I'm trying to light the leds according to this array. I have 4 buttons with 4 leds and one button tu run the recording when it's ready.

I'm stuck in lighting the leds when I push the play_button.

I hope someone can help me...

Here's my script :

int arr[10];
boolean previous = LOW;
unsigned long time1 = 0;
int debounce = 200;
unsigned long time2 = 0;
int index_state = 0;

int play_button = 13; //define pin # for play button

int button[4] = {2,4,6,8}; //store button pins in an array
int leds[4] = {3,5,7,9}; //store led pins in an array

void setup()
  for(int n=0;n<10;n++) arr[n] = 0;//initialisition

void loop(){
 boolean mode = digitalRead(2) || digitalRead(4) || digitalRead(6) || digitalRead (8);
 while(mode == LOW) mode = digitalRead(2) || digitalRead(4) || digitalRead(6) || digitalRead (8);//wait here till one of the pushbutton goes high;
 if( mode == HIGH && previous == LOW && millis() - time1 > debounce) {
 //find out which one is high and store that value in array;
 if(digitalRead(2)) arr[index_state] = 2;
 else if(digitalRead(4)) arr[index_state] = 4;
 else if(digitalRead(6)) arr[index_state] = 6;
 else if(digitalRead(8)) arr[index_state] = 8;
 else ;

 //print the value and the index;
 Serial.print(" Stored in index: ");
 index_state = (index_state + 1) % 10;
 //update value of time1 for button debouncing
 time1 =  millis();

  //update the value of previous button state
  previous = digitalRead(2) || digitalRead(4) || digitalRead(6) || digitalRead(8);


Thank you

1 Answer 1


You have problems in including the further functionality (the playback), since your loop() function is solely written for providing the first part of functionality (the recording). You need an overall structure, that will execute the correct functionality at the correct time/logic order.

For this, an Finite State Machine (FSM) is the best way. It will help you to structure your code and the logic. It is an important principle to learn.

First you would have to divide your program logic into different states and transitions between them (don't look too close at the actual code at this point, but with a higher abstraction). Currently I see 2 states in your project: A state, where you are recording the button presses in an array, just like you already did. And a state, where the array is used for playback. The transition from the first to the second state happens, when the playback button is pressed. The transition back happens, when the playback is finished. It helps to draw a graph for this, to visualize the the states and their transitions. In my answer to this question I explained this further including an example of such a graph.

When you are finished creating the states and transitions, you can create the necessary code structure. The easiest way for a beginner is to use a simple state variable (simply an integer, or - if you want to use names for the states - an enum) in a switch()-case statement. You can also see this in the linked answer. Your code then goes into the case statements. The switch statement will only execute the code for the current state. To do a transition to another state, you simply change the state variable. So in the case statement of the first state, you put the code that you already have for reading the buttons, and an if statement, that checks the playback button. If the playback button was pressed, change the state variable to the second state.

You could also solve this problem without an FSM, but the structure won't be that good and easy to expand. Also you might get some extra points for implementing an FSM :D

Currently your code is blocking. That means, that it will block any further operation, until something happened, in this case, that one of the 4 buttons gets pressed. Often this is only a hindrance, when adding functionalities. It is better to use do-maybe code, means code, that will only do something, if some condition is met (like time). You are already doing this in the if statement

if( mode == HIGH && previous == LOW && millis() - time1 > debounce) {

(it only triggers the recording of a new button, if a button was pressed and the debounce time has passed) so why are you blocking before this with the while loop? You could just write to mode without the while loop.

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