I've tried different USB cables, computers, ports and none of them can detect my possibly bricked Mega 2560 R3. Nothing shows up at all in the Device Manager, not even "Unknown Device".

When the board is plugged in via USB, the "L" LED is constantly lit as well as the "ON" LED next the reset button.

I came up on this article here and I gave it a try, which I believe is putting it in DFU mode. However I'm not having any luck with this. http://www.wayneandlayne.com/blog/2011/02/16/fixing-linux-firmware-issues-on-arduino-mega-2560/

Any one have any ideas on where to go from here? I'm very new with Arduino.

  • Have you tried a different computer and cord? When did it stop working (and what did you do differently)? Aug 5, 2014 at 22:54
  • I recently purchased a clone Mega 2560, and could not get the USB port to work. Check the USB chip marking. If its a CH340G, it is not compatible with the Arduino drivers for PC USB ports. You need to find a file called ch341ser.zip, and install this on the PC, not the Arduino.
    – kiwiron
    Dec 9, 2014 at 8:43
  • I have the same issue with an Arduino Mega ADK (same as Mega 2560 but with additional USB Host port) and only get gibberish as serial output
    – KaitoCross
    Feb 21, 2018 at 7:35

4 Answers 4


If your Mega has an ICSP header for the USB chip (circled below) then you can test that chip.

Mega2560 ICSP header

You can use another Arduino (eg. a Uno) to detect the signature on that chip, as per my sketch on Sketch to detect Atmega chip types.

All you need is 6 hookup wires to connect your testing board (the known good one with the sketch on it) to the ICSP header on the Mega. Note the pin orientation. I have circled the correct header pins, and pointed to pin 1. On the board pin 1, has a small white dot.

Below are the ICSP pin names, seen from above (component side).

ICSP pins

Wire the Uno to the chip being tested as follows:

Arduino Uno      Target chip

D10 (SS)            /RESET
D11 (MOSI)          MOSI
D12 (MISO)          MISO
D13 (SCK)           SCK

Gnd                 GND
+5V                 VCC

Check your wiring! If you wire things around the wrong way you can turn a good chip into a bad one.

Important! Only attempt this process if you can see that you have an ATmega8U2 or ATmega16U2 chip on your board (see below). If you have something totally different this will not work. In that case you probably have a cheap clone board.

Atmega16U2 chip

Using the Serial Monitor on your Uno, you should then see something like this:

Atmega chip detector.
Written by Nick Gammon.
Version 1.17
Compiled on Jul  7 2015 at 10:47:47 with Arduino IDE 106.
Attempting to enter ICSP programming mode ...
Entered programming mode OK.
Signature = 0x1E 0x93 0x89 
Processor = ATmega8U2
Flash memory size = 8192 bytes.
LFuse = 0xEF 
HFuse = 0xD9 
EFuse = 0xF4 
Lock byte = 0xFF 
Clock calibration = 0xAB 
Bootloader in use: No
EEPROM preserved through erase: No
Watchdog timer always on: No
Bootloader is 4096 bytes starting at 1000


1000: 0x4B 0xC0 0x00 0x00 0x64 0xC0 0x00 0x00 0x62 0xC0 0x00 0x00 0x60 0xC0 0x00 0x00 
1010: 0x5E 0xC0 0x00 0x00 0x5C 0xC0 0x00 0x00 0x5A 0xC0 0x00 0x00 0x58 0xC0 0x00 0x00 
1020: 0x56 0xC0 0x00 0x00 0x54 0xC0 0x00 0x00 0x52 0xC0 0x00 0x00 0xCB 0xC4 0x00 0x00 
1030: 0x4E 0xC0 0x00 0x00 0x4C 0xC0 0x00 0x00 0x4A 0xC0 0x00 0x00 0x48 0xC0 0x00 0x00 

My board had a ATmega8U2 on it, yours might have a ATmega16U2. However the concept is the same. If you see something like that, the chip is (probably) good. At least it responds to programming commands.

If you see something like

Atmega chip detector.
Written by Nick Gammon.
Version 1.17
Compiled on Jul  7 2015 at 10:47:47 with Arduino IDE 106.
Attempting to enter ICSP programming mode ......................................................
Failed to enter programming mode. Double-check wiring!
Programming mode off.

Then either you made a wiring error, or the chip is bad.


I have had the same symptom with a Arduino Decimilia.

In that case had the USB to Serial chip failed. I used a USB to Serial device to verify the problem


Check the Chips for any solder mistake, I found that my serial chip had two pins soldered together, probably cause i bought it for cheap :D


It sounds like the USB to serial chip has failed. You could test this by using another arduino or a programmer like the AVRISP mkII to load a program that way and see if it's your whole board or just the serial chip.

If the board and main chip are still good, you could just get used to uploading with this new method, or you could try to reprogram the other chip used for serial. I know it I'd possible but ever time I've burned one this hadn't help so YMMV.

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