Arduino Uno R3 Stopped uploading

Official Hardware UNO Family UNO R3
1

I've my arduino uno r3 it was working successfully and I've updated it using IDE for many times but one day I tried to update it once again but IDE stucked on updating with any actual update on the board.
noting that arduino was working on COM4 and now I can't find except COM6&7 and when I reconnect the board to PC or press reset button the L led blinks then holds to be on.
I've a really important project to be done and need this issue to be solved

2

We will need to see more information.

3

Have you tried to analyze the root cause?

  • another PC?
  • another UNO board?
  • does the last program uploaded send some output perhaps?
  • another USB cable?
4

I tried to use another PC and different cable but still the same.

5

I am assuming you are talking about updating your code and not the firmware. I will also assume the TX LED is the one stuck on. If my assumptions are correct you have a serial flood:

Steps to Recover Your Arduino Board from Serial Flood:

  1. Power Off the Board: Completely turn off your Arduino board by removing the power source.
  2. Disconnect the USB Cable: Unplug the USB cable from the board.
  3. Hold the Reset Button: Press and hold down the Reset button on the board.
  • Alternatively, you can run a jumper wire from the RESET pin to the GND pin.
  1. Reconnect the USB Cable: While still holding the Reset button, reconnect the USB cable to the board.
  2. Start Uploading a New Sketch: Begin uploading a sketch that does not produce the same problem (e.g., the Blink sketch).
  3. Release the Reset Button: When you see the Receive light blink, release the Reset button.
  4. Modify Your Code: To prevent the issue from recurring, add a delay(3000); or a longer delay in the setup() function of your sketch. This delay allows you to recover easily from a serial flood.

Note: This problem often occurs when the serial output is flooded, indicated by the TX light being stuck on. A quick fix is to put a delay(3000); in the startup code. The lower the baud rate the more susceptible to serial flood your code is.

6

the issue is not related with L led, the issue that PC can't detect the arduino on device manager nor IDE, it was being detected on COM4 before but now I can only see COM6 & COM7 that not detected as arduino thus when I choose COM6 and try to upload the uploading process lasts to forever without uploading my code to the board.

7

It should flash three times in quick succession and next do what the last uploaded code tells it to do.

Is your Uno R3 an original or a clone? If it's an original or faithful clone the board would be identified as Arduino Uno in Windows device manager, else it will be identified as something else. You can usually also recognise an original or faithful clone because it has a 6-pin header close to the USB port.

Disconnect the board.
Check which COM ports you have Windows device manager.
Connect the board.
Check which (new) COM port(s) you have.

If you get two new COM ports (as I understand from your post), something is not right and I would re-install the driver.

If you don't get anything, I suspect that your serial-to-usb converter (16U2 for originals or faithful clone, CH340 for most cheap clones) is malfunctioning or your cable is bad.
For an original or faithful clone you can try to burn the 16U2 firmware using the 6-pin header closest to the USB port.

What was the project that you last uploaded successfully? Anything involving voltages different from 5V or motors or solenoids or relays?