How to Reset Arduino Uno: A Complete Step-by-Step Guide

In the world of electronics and embedded systems, the Arduino Uno is a popular go-to board for hobbyists, students, and professionals alike. Like any microcontroller, it may require a reset to restart a sketch, troubleshoot code, or fix operational glitches. In this blog, we'll take a deep dive into the different ways on how to reset Arduino Uno, what happens during a reset, and best practices to ensure smooth functioning.

What Does Resetting Arduino Uno Do?

When you reset an Arduino Uno, it stops executing the current program and starts from the beginning of the sketch loaded onto the board. It doesn’t delete your code or configuration. Resetting is helpful in cases such as:

• Restarting a malfunctioning program

• Syncing Arduino with a connected device

• Reinitializing sensors

• Preparing the board before uploading new code

Common Reasons to Reset Arduino Uno

Here are a few scenarios where resetting is necessary:

• Code Errors: Infinite loops or delays

• Hardware Changes: After modifying connected sensors or modules

• Data Sync Issues: Mismatch with serial communication

• Manual Testing: When checking how the system behaves on startup

Methods to Reset Arduino Uno

There are several ways to reset your Arduino Uno, both manually and programmatically. Let’s go through them one by one.

1. Using the Reset Button

This is the easiest and most commonly used method.

Steps:

• Locate the small round Reset button on the Arduino Uno board (usually near the USB port).

• Press and hold the button for 1-2 seconds.

• Release it, and the board will restart.

Tip: Useful for quick debugging or restarting your code after changes.

2. Unplugging and Replugging USB Cable

When the board is powered via USB, removing and reconnecting the USB cable resets it.

Steps:

• Unplug the USB cable connected to your computer.

• Wait for 2-3 seconds.

• Plug it back in.

This method is often used when the board becomes unresponsive.

3. Reset via Software (Sketch Code)

You can trigger a reset by writing code within the sketch using the Watchdog Timer (WDT).

Sample Code:

#include <avr/wdt.h>

void setup() {

  wdt_enable(WDTO_15MS); // Set watchdog timer to 15ms

  while(1);              // Infinite loop to trigger reset

}

void loop() {}

Warning: Use cautiously. Improper use can lead to a continuous reset loop.

4. Using External Reset Pin

Arduino Uno has a dedicated RESET pin that you can use for external control.

Steps:

• Connect a momentary push-button between the RESET pin and GND.

• Pressing the button connects RESET to GND and initiates a board reset.

Use Case: Ideal for embedded systems where the Arduino is housed in an enclosure.

5. Via Serial Communication (DTR/RTS Pins)

If you're using the Serial Monitor or programming via USB, Arduino Uno resets automatically due to the DTR (Data Terminal Ready) signal.

Behind the Scenes:

• The USB-to-Serial chip on the Uno sends a reset pulse when you open the serial port.

• This is useful for auto-resetting before uploading sketches.

Best Practices While Resetting Arduino Uno

To avoid damage or confusion, keep these tips in mind:

• Avoid frequent resets during uploads

• Don’t reset while writing to EEPROM

• Monitor the serial port status when troubleshooting

• Use external reset only with proper debounce circuitry

Troubleshooting Reset Issues

Sometimes, the Arduino Uno may not reset as expected. Here’s how you can troubleshoot:

Board Doesn’t Reset via Button

• Check if the reset button is physically damaged

• Ensure the board is not drawing excessive current

Software Reset Not Working

• Confirm Watchdog Timer library is correctly included

• Check for conflicting code in setup()

External Reset Not Responding

• Inspect your circuit for proper connections

• Add a pull-up resistor (~10k ohm) if needed

Conclusion

Resetting the Arduino Uno is a basic yet crucial skill when working with microcontroller projects. Whether you're debugging, syncing with sensors, or preparing the board for a fresh upload, understanding different reset methods gives you greater control. From pressing the onboard button to using watchdog timers and external pins, each method has its place.

By following this guide, you can now confidently reset your Arduino Uno and keep your projects running smoothly.

FAQs

1. Will resetting Arduino Uno delete my uploaded code?

No. Resetting only restarts the current sketch; your uploaded code remains intact.

2. Can I reset Arduino Uno with a smartphone?

Yes, if you use Bluetooth modules like HC-05 with an app that sends a reset command via serial communication.

3. Is there a way to auto-reset Arduino Uno on power-up?

Yes. Use a simple capacitor circuit between the RESET pin and GND or rely on the board's default auto-reset behavior.

4. Why does Arduino Uno reset when I open the Serial Monitor?

The board resets because the USB-to-Serial chip sends a DTR signal that triggers a soft reset.

5. Can a faulty sketch prevent resetting the Arduino Uno?

In rare cases, code that disables the watchdog timer or corrupts memory can interfere with resets. A double-tap on the reset button or bootloader reflashing may help.