UNO R3 not recognized by PC, executes last uploaded sketch, can't switch to DFU

Using Arduino IDE 1.x
1

Hi,

I've started having this issue after doing a few tutorials. Upon plugging in the Uno, it's not recognized by the PC (tried on my Linux PC and Linux netbook), the TX/RX LEDs never flash as they normally do, the red L LED flashes briefly and remains lit, then the Uno executes the last uploaded sketch.
I've read somewhere that this may be a bug in the earlier firmware versions when using Serial.begin(9600); and suggested firmware upgrade. Not being able to even check the firmware version at this point, I decided to give it a go, however I can't reset the Uno to DFU mode by jumping the reset/gnd pins as suggested in numerous tutorials, as simply nothing changes when I do.

What am I missing and what else can I try?

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First check on device manager Whether port being detected or not. Check Whether port Being detected with yellow mark. if yes then you need to Upload serial library.
Please share us screen shot of it.

have you tested the board with High current application ??
Also check when you connect the board Serial IC gets heats up or not?? if it gets heating up. definitely your IC got damaged & its time to replace it

3

I just posted a similar issue. However, My computer recognizes my Arduinos and I've successfully used the serial examples.

http://forum.arduino.cc/index.php?topic=251810.0

What Tutorials have you used for reprogramming the atmega16u2?

4

AMPS-N:
First check on device manager Whether port being detected or not. Check Whether port Being detected with yellow mark. if yes then you need to Upload serial library.
Please share us screen shot of it.

have you tested the board with High current application ??
Also check when you connect the board Serial IC gets heats up or not?? if it gets heating up. definitely your IC got damaged & its time to replace it

I'm using Linux, and the device is not detected at all now. Also, there is no anomalous heating and I generally don't think anything is busted.

Phobos123:
I just posted a similar issue. However, My computer recognizes my Arduinos and I've successfully used the serial examples.

DFU Mode - Issues - Installation & Troubleshooting - Arduino Forum

What Tutorials have you used for reprogramming the atmega16u2?

I'm fairly sure the version I have doesn't need the resistor soldered to reset it to DFU mode. As all tutorials that I found (dealing with this model) suggest, I tried countless times bridging the two pins, to no avail.

5

I am in the same vote. I can't seem to get it into DFU mode. I've contacted Atmel, but because Arduino isn't supported by Atmel they won't help.

6

@Mwgg: have you gotten your arduino into DFU mode?

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