Step by step testing inside a Linux Terminal usage for the USB Arduino Diecimila Board... Issued as completely Public Domain by B.Walker, G0LCU, Circa 30-03-2011. 1) Boot up to your Linux flavour as root, (or run in a root Terminal). 2) Temporarily disable any net access or use a stand-alone machine. 3) Plug in the USB Arduino board. 4) Open up a, (root), Terminal and clear the screen. 5) clear 6) Check that you have a device as ttyUSB? 7) ls /dev NOTE:- ? above will probably be 0. 8) If ttyUSB0, (to 7), appears then carry on; otherwise ignore the remainder of this text. NOTE:- Assuming the device is ttyUSB0 from now on, change below if needed to your ttyUSBx device. 9) Place a wire link between ANALOG 0 and the 3.3 V terminals. NOTE:- 'chmod' is not really needed but added for fullness! 10) chmod 666 /dev/ttyUSB0 11) Set up the on board serial I/O to 1200bps and RAW data transfer. 12) stty -F /dev/ttyUSB0 1200 13) stty -F /dev/ttyUSB0 raw 14) Now start printing characters to the screen... 15) cat < /dev/ttyUSB0 NOTE:- The characters will be from about 168 to 174 decimal allowing for bit error of the Arduino ADC. 16) Remove and replace the wire link from ANALOG 0 and GND or ANALOG 0 and 5 V too. 17) Press 'Ctrl-C' to stop any characters being printed to the Terminal. 18) Unplug the USB Arduino board. 19) Power down the computer IF REQUIRED. Enjoy finding simple solutions to often very difficult problems... ;o)