Troubleshooting Guide: How to Fix the 'avrdude: ser_open(): can't open device "\\.\com5"' Error and Locate Missing File Specified in the System

This guide will provide you with a step-by-step solution to fix the 'avrdude: ser_open(): can't open device "\.\com5"' error, which occurs when attempting to upload code to an Arduino or other microcontroller using the Arduino IDE.

Table of Contents

  1. Understanding the Error
  2. Locating the Missing File
  3. Step-by-Step Solution
  4. FAQs
  5. Related Links

Understanding the Error

The 'avrdude: ser_open(): can't open device "\.\com5"' error message indicates that a communication problem exists between your computer and the microcontroller. This issue typically arises due to one or more of the following reasons:

  1. A wrong or non-existent COM port is selected in the Arduino IDE.
  2. The microcontroller is not properly connected to the computer.
  3. Incorrect board or processor is selected in the Arduino IDE.

Locating the Missing File

To resolve the error, you must first locate the missing file specified in the system. To do this, follow these steps:

  1. Open the Arduino IDE and click on File > Preferences.
  2. In the Settings tab, locate the Show verbose output during section and check the box for upload.
  3. Click OK to save the changes.

Now, when you attempt to upload code to your microcontroller, the Arduino IDE will generate a detailed output, which will help you identify the missing file or any other issues related to the error.

Step-by-Step Solution

Here's a step-by-step guide to resolving the 'avrdude: ser_open(): can't open device "\.\com5"' error:

Step 1: Check the USB Connection

Ensure that the microcontroller is properly connected to your computer with a functioning USB cable. Also, try connecting the microcontroller to a different USB port on your computer.

Step 2: Select the Correct COM Port

  1. In the Arduino IDE, navigate to Tools > Port.
  2. Check if the correct COM port is selected (e.g., COM5). If not, select the appropriate port.

Step 3: Select the Correct Board and Processor

  1. In the Arduino IDE, navigate to Tools > Board.
  2. Ensure that the correct board (e.g., Arduino Uno) is selected.
  3. If applicable, navigate to Tools > Processor and ensure the correct processor is selected.

Step 4: Restart the Arduino IDE

After verifying the USB connection, COM port, board, and processor settings, close the Arduino IDE and reopen it. Attempt to upload the code again.

If the error persists, it's possible that the issue lies with the microcontroller itself or the USB driver. In such cases, consider reinstalling the USB driver for the microcontroller or using a different microcontroller to further troubleshoot the problem.


Q1. How do I find the correct COM port for my microcontroller?

To find the correct COM port for your microcontroller:

  1. Connect your microcontroller to your computer.
  2. Open Device Manager (Windows) or System Information (macOS).
  3. Look for your microcontroller in the list of connected devices. The COM port number should be displayed next to the device name.

Q2. Can a faulty USB cable cause the 'avrdude: ser_open(): can't open device "\.\com5"' error?

Yes, a faulty USB cable can lead to communication issues between your computer and the microcontroller, resulting in the error.

Q3. How do I reinstall the USB driver for my microcontroller?

To reinstall the USB driver for your microcontroller:

  1. Disconnect your microcontroller from your computer.
  2. Uninstall the existing driver from your computer.
  3. Download the latest driver from the microcontroller manufacturer's website.
  4. Install the new driver and reconnect your microcontroller.

Q4. Can the error be caused by incorrect board or processor settings in the Arduino IDE?

Yes, selecting the wrong board or processor in the Arduino IDE can lead to the 'avrdude: ser_open(): can't open device "\.\com5"' error. Always ensure that you have selected the correct board and processor before attempting to upload code.

Q5. What should I do if the error persists even after following the step-by-step solution?

If the error persists, consider using a different microcontroller to further troubleshoot the problem. If the issue still remains, contact the microcontroller manufacturer for additional support.

  1. Arduino IDE Download
  2. Arduino Troubleshooting Guide
  3. AVRDUDE User Manual
  4. Arduino Forum
  5. Arduino Stack Exchange

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