Hello,
I have a working Arduino board again. It seems that the device at some point went into DFU mode and never returned back to normal. At least that's what I think because all I got from my board when plugging it into a Linux box was as described on CJ Davies after going into DFU mode. Hence I had to install the original firmware again. For completeness' sake, here are the relevant steps:
1 - download dfu-programmer from Atmel USB DFU Programmer download | SourceForge.net (v0.5.4)
2 - add a line to src/arguments.c, according to http://academic.cleardefinition.com/2012/07/31/using-dfu-programmer-with-an-arduino-uno-r3:
--- src/arguments.c (revision 105)
+++ src/arguments.c (working copy)
@@ -72,6 +72,7 @@
{ "at90usb647", tar_at90usb647, adc_AVR, 0x2FF9, 0x03eb, 0x10000, 0x2000, true, 128, true, false, 128, 0x0800 },
{ "at90usb646", tar_at90usb646, adc_AVR, 0x2FF9, 0x03eb, 0x10000, 0x2000, true, 128, true, false, 128, 0x0800 },
{ "at90usb162", tar_at90usb162, adc_AVR, 0x2FFA, 0x03eb, 0x04000, 0x1000, true, 128, true, false, 128, 0x0200 },
- { "at90usb162unor3",tar_at90usb162, adc_AVR, 0x2FEF, 0x03eb, 0x04000, 0x1000, true, 128, true, false, 128, 0x0200 },
{ "at90usb82", tar_at90usb82, adc_AVR, 0x2FF7, 0x03eb, 0x02000, 0x1000, true, 128, true, false, 128, 0x0200 },
{ "atmega32u6", tar_atmega32u6, adc_AVR, 0x2FF2, 0x03eb, 0x08000, 0x1000, true, 128, true, false, 128, 0x0400 },
{ "atmega32u4", tar_atmega32u4, adc_AVR, 0x2FF4, 0x03eb, 0x08000, 0x1000, true, 128, true, false, 128, 0x0400 },
3 - compile
4 - get the firmware from the Arduino IDE sources: Arduino-COMBINED-dfu-usbserial-atmega16u2-Uno-Rev3.hex
5 - plug in the board and (for completeness) shorten two pins in a group of six (the group being close to the USB port). The two pins are those closest to the reset button. This should turn the board into DFU mode
6 - then reflash the firmware:
dfu-programmer at90usb162unor3 erase
dfu-programmer at90usb162unor3 flash Arduino-COMBINED-dfu-usbserial-atmega16u2-Uno-Rev3.hex --suppress-bootloader-mem
dfu-programmer at90usb162unor3 reset
7 - Plug out, plug in, done.
Cheers,
Enno