I have a question about the updating the 8U2 chip on my arduino uno. According the the directions here: http://arduino.cc/en/Hacking/DFUProgramming8U2 I need to solder on a 10k ohm resistor to the back. What is the purpose of that resistor and does it need to be removed after updating the 8u2 for the uno to work correctly or can I just leave it?
From looking at my rev 1 Uno it holds the HWB line low for the 8U2 as far as I can tell - it seems later Uno revision have this held down so it looks like it can be left in place - you can double check against the schematics for the Uno boards (they are public domain!)