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1 vote

Problem :

Currently I am using a Arduino API  with the Uno board and it was working fine until few days.
Recently I was working with the interrupt timers and somehow my board went into a mode where I am unable to upload the app.
I have the app which blinks the LED light.
I am trying to upload the very simple loop app but now I am facing below error:

“Avrdude: ser_open(): can't open device "\\.\COM3": Access is denied.”

I have also tried to reboot my PC but still it is not working for me. How to fix above error?

8 5 2
3,230 points

3 Answers

1 vote

Solution :

I can help you in fixing your error. Just follow below procedure.

First you must go to your device manager. Now you should select the required ports.
Please select the port of the Arduino board for example : com1 , com2 , com3 according to the need
Now you should right click on your com port and then you need to select the properties.
kindly press tab port settings and then click on advanced option.
After that on the com port number you must select the new port number which is currently not in use
Now you need to just confirm your selection and then click on save it. Finally you should click on continue and your problem will be resolved.

8 4
5,680 points
0 votes


Follw these steps:

1 - Unplug the Arduino

2 - Upload code with no Arduino connected to PC

3 - Reconnect Arduino

4 - Upload code to the Arduino

You should do a few checks in order to jump to a conclusion, your Arduino may be just fine. As far as I know, Code cannot destroy a controller.

  1. Check if any other software is using the same serial port. Two softwares cannot use the same serial port at the same time

  2. Reset your PC and then try again

  3. Remove the Microcontroller form the board, connect it to the PC and try to open the com port. If it opens then connect your Tx pin with the Rx pin, send some data and check if you are getting the data back. This way you will enusre your USB-TTL converter is fine

  4. If this goes successful, then insert your microcontroller in some other board and check if it is getting programmed

I am sure after these checks you will find out the reason of failure of your board/microcontroller..

If it is not solved yet try this way

Open Arduino application > Tools > Port > Change to the target Port
If you are unsure which port to choose from: (on Windows) Open Device Manager > Connections (COM & LPT) > Usb Serial Port (COM[x]) where "[x]" is the index you are looking for.
10 6 4
31,120 points
0 votes
USB may need CH340 driver.
Some Arduinos use the CH340 controller
Find and install the CH34X_Driver_V3.4_Windows.zip
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