From Tinkercad Circuits to Arduino Code

If you have built circuits in Tinkercad Circuits, you already know the hard part: how a breadboard works, why an LED needs a resistor, and what a button does. This post is for the next step. You will build a small Arduino Uno circuit with an LED and a button, write the code as plain text the way real Arduino projects do, read the serial monitor, and learn how saving and libraries work in Mokxi. Tinkercad Circuits is a good beginner tool, and nothing here is meant to talk you out of it.

What carries over

Most of what you learned still applies. An Uno is an Uno. A breadboard has the same strips. An LED still has a long leg and a short leg. A pin set as an output still gives 5 volts or 0 volts. Even the serial monitor is an old friend: the Uno prints text, and you read it in a panel.

What changes

Three things feel different when you move to real code.

The code is text. Tinkercad Circuits has a Code panel with a Text mode, and if you have used that, you have already written C++ like this. If you have only used Blocks, text will be new. Mokxi is text only: there is no block coding. If your students or you need blocks to get started, Tinkercad's blocks are the better first step, and Mokxi is a good place to come next.

Libraries use #include. In real Arduino code you add a library with a line at the top. In Mokxi the common ones such as Servo.h, Wire.h, LiquidCrystal_I2C.h and DHT.h are built in under their usual names, so the line compiles as it stands. For any other library, the Arduino Library Manager search under the code finds it in the official index and installs it in one tap. For comparison, one Arduino Forum thread describes adding a library to Tinkercad by pasting its .h and .cpp files into the sketch by hand.

Saving is a choice. More on that below.

What you need

An Arduino Uno
One LED and one 220 ohm resistor
One pushbutton
Jumper wires

Wire it up

From	To	What it does
Uno pin 8	220 ohm resistor	Limits the LED current.
Resistor, other end	LED anode (long leg)	Positive side of the LED.
LED cathode (short leg)	Uno GND	Completes the loop.
Uno pin 2	Button, one side	The input.
Button, other side	Uno GND	Pulls the pin low when pressed.

In many beginner circuits the button gets a 10 k resistor to ground. Here there is none. The sketch turns on the Uno's built-in pull-up resistor, which keeps the pin high until you press the button. A pull-up resistor holds a pin at a known high level when nothing else is driving it. With it on, a pressed button reads LOW, not HIGH.

The complete sketch

const int BUTTON_PIN = 2;
const int LED_PIN = 8;
const unsigned long DEBOUNCE_MS = 25;

bool ledOn = false;
int presses = 0;
int lastReading = HIGH;
int stableState = HIGH;
unsigned long lastChange = 0;

void setup() {
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  Serial.begin(9600);
  Serial.println("Ready. Press the button.");
}

void loop() {
  int reading = digitalRead(BUTTON_PIN);
  if (reading != lastReading) {
    lastChange = millis();
    lastReading = reading;
  }

  if (millis() - lastChange >= DEBOUNCE_MS && reading != stableState) {
    stableState = reading;
    if (stableState == LOW) {
      presses++;
      ledOn = !ledOn;
      digitalWrite(LED_PIN, ledOn);
      Serial.print("Press number ");
      Serial.print(presses);
      Serial.print(": LED is ");
      Serial.println(ledOn ? "on" : "off");
    }
  }
}

I compiled this sketch for the Uno with Mokxi's own build path and ran it in the simulator. With three presses it printed Press number 1: LED is on, then Press number 2: LED is off, then Press number 3: LED is on.

Line by line

const int BUTTON_PIN = 2; gives the pin a name. A name in capitals is a habit for values that never change.
ledOn, presses and the last... variables live outside every function, so they remember their values between loops.
pinMode(LED_PIN, OUTPUT); says pin 8 sends signals out.
pinMode(BUTTON_PIN, INPUT_PULLUP); says pin 2 listens, with the pull-up on.
Serial.begin(9600); opens the serial monitor at 9600 baud. That is the speed the Uno and the monitor agree to talk at.
loop() runs over and over, forever. This is the part you would build with a "repeat forever" block.
digitalRead(BUTTON_PIN) reads the pin: HIGH or LOW.
The millis() lines are a debounce. A button's metal contacts chatter for a few thousandths of a second when pressed, and the Uno is fast enough to see each flicker. The sketch only trusts a reading once it has stayed the same for 25 milliseconds. millis() is the number of milliseconds since the board started.
if (stableState == LOW) runs once per real press.
presses++; adds one. ledOn = !ledOn; flips on to off and off to on.
digitalWrite(LED_PIN, ledOn); sets the LED.
The four Serial lines build one message. print stays on the same line and println ends it. The ? : inside is a short if-else that picks the word "on" or "off".

Open the serial monitor

Press Run, then look at the strip along the bottom of the editor. That is the serial monitor. Click the button part with the mouse and hold it, and a line appears for each press. The monitor also has a box to type text back to the board, which you will use when you write sketches that read Serial.read().

Saving your work

While you work, Mokxi writes your project into your browser automatically, so closing a tab loses nothing. Pressing Save (or Ctrl/Cmd+S) puts it on that browser's shelf of projects. If you sign in, Save also stores the project in your account, and you get a link that stays the same. The free plan keeps five private or link-only projects on your account, and public projects are unlimited. The saving guide has every detail, including version history.

A signed-out project lives in one browser only. Clear your site data or switch laptops, and it is gone, so save to an account when the project matters.

Bringing a Tinkercad project over

Tinkercad keeps a circuit on its own servers and does not give you a file that says how it is wired, so no tool can bring the wiring across whole. What you can bring is the code and the parts list. Copy the code from the Code panel in Text mode and the Component List, paste both on the import page, and Mokxi places the parts it has and puts the code on the Uno. You wire them the way your original circuit was. Most Uno sketches compile unchanged.

Try next

Add a second LED on pin 9 and make it light only when the first is off.
Count presses to 10, then print "Ten!" and reset the count.
Change DEBOUNCE_MS to 0. Press quickly and watch whether the count jumps.
Move the LED to pin 13 and drop the resistor from your wiring. Then read what the Circuit Doctor says.

Try it on Mokxi

If you want the full picture of what moves and what does not, the switching from Tinkercad guide maps each Tinkercad habit to its Mokxi name, and the comparison with Tinkercad says where each tool is the better answer. For a first sketch, the blink an LED guide is a gentle start, and the Arduino simulator is where you will build this circuit.

Ready to build it yourself? Create your free Mokxi account and open the editor in your browser. No installs, no parts to buy.