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[on:]

Hi,

I have Arduino Mega 2560 running on Windows XP. Previously, I have succesfully uploaded a program to drive the motor into my Arduino and the program running succesfully.

Now I am trying to reupload a new program to my Arduino but the software does not detect the COM port of arduino. I have checked the device manager and the device manager does not detect any arduino hardware. However, my previous program still able to run.

Does anyone know what is the problem with my arduino?

PS: When I plug the USB cable to the arduino, the power LED and pin 13 LED is on. The LED for Tx and RX are not blinking

[Reply #1 on:]

It seems that the ATmega16U2 chip to handle the communication between the USB and the 2560 microcontroller is blown.
http://arduino.cc/en/Main/arduinoBoardMega2560

If the sketch is running, you could program your sketch using a programmer and the ISCP header. That si a way to program the 2560 microcontroller without the USB communication.

[Reply #2 on:]

Two possibilities for you based on my own recent experience.
a)  Are you using a USB port extender hub.  Sometimes these do not allow certain devices to enumerate. If you do, make sure you run it with external power.
b) Make sure you are using a good USB cable.  Some of the cables are a little flimsy and wires break in the cable.

[Reply #3 on:]

It seems that the ATmega16U2 chip to handle the communication between the USB and the 2560 microcontroller is blown.
http://arduino.cc/en/Main/arduinoBoardMega2560

If the sketch is running, you could program your sketch using a programmer and the ISCP header. That si a way to program the 2560 microcontroller without the USB communication.

How to check if the connection is blown?

Do you have a reference to program with the ISCP header?

I have try different USB cable and different computer and it seems, all the computer do not able to detect the arduino.