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Arduino 2 Digit 7 Segment Display Sketch (with Buttons) | Part 5

* This is a multi-part post. Here are links to all parts:

Part 1: Intro, bill of materials and simple sketch
Part 2: The circuit for the 2-digit 7-segment counter
Part 3: Sketch broken down in sections, explained
Part 4: Added two buttons, and modified sketch
Part 5: Code for buttons, explained; this post

As you could see from last week’s full Arduino sketch listing, the source code for the 2-digit 7-segment display project using buttons is strikingly similar to the one without the buttons; praise for ‘copy and paste‘! (It is worth noting, though, that ‘copy and paste‘ can be responsible for a higher percentage of bugs than I’d care to admit).

There are just a couple of snippets that I would like to comment on:

2 Digit 7 Segment Display Sketch

The first part of the loop() function checks whether either button has been pressed and increments the value of each digit.

  // check button1
  int val1 = digitalRead(BTN1);
  if (val1 == HIGH) {
    digit1 %= 10;

  // check button2
  int val2 = digitalRead(BTN2);
  if (val2 == HIGH) {
    digit2 %= 10;

The line

digit1 %= 10;

which is shorthand for

digit1 = digit1 % 10;

accomplishes the same as the line

if (count == 10) count = 0;

that was used on the sketch for the single-digit 7-segment project a couple of months ago. It updates digit1 with the remainder of the division of itself by 10, which will be zero when digit1 is 10. The latter code looks a bit more obvious for beginner programmers.

The last part of the loop() function refreshes the display, and is very similar to the sketch for the 2-digit 7-segment display counter.

  // display number
  unsigned long startTime = millis();
  for (unsigned long elapsed=0; elapsed < 600; elapsed = millis() - startTime) {
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