My Arduino is quite old, and I had to upgrade the firmware to address some issues that arose with serial.
Basically I used Windows XP and those resources:
http://arduino.cc/en/Hacking/DFUProgramming8U2
but it’s no so verbose, it’s useful as a general introduction.
I soldered a 10K resistor like advised, but then I decided to rely on this one[thanks a lot, Ant_b] without compiling myself the firmware which I got here:
Arduino Uno updated firmware (contains also others versions, so I had to check that the hex file is sound, and could’t just right click and save)
and using the resistor instead of the jumper.
Ant_b gives two VERY important bits of information: where to find drivers for Arduino’s Atmel once in DFU mode (Arduino Uno DFU, drivers are inside Atmel flip programmer installation directory in Atmel\Flip 3.x.x\usb) and which Device I ad to use for a successful update (selected the device AT90USB82 and not the ATmega8u2 as advised!!).
To avoid soldering here I found some other stuff:
[Untested]This Forum post [Thanks Pluggy]
[Untested, I soldered]http://ossnotebook.blogspot.it/2011/06/dfu-mode-arduino-uno-without-soldering.html which can be a good idea because the pad is small and it’s easy to burn it. Now Arduino shows firmware ID in windows control panel – hardware devices 000.001 instead of 000.000.
Thanks guys!