please be aware that the serial console connection gets killed in minutes
if the /mnt/us/DO_NOT_KILL_UART file doesn't exist
See
/etc/init.d/power
and
/etc/rc5.d/S90power
for details.
The above is true for the DXG unit running the 2.5.5 firmware...
Similar technique is used to generate an idle timeout in uBoot on kindle.
Don't know how to cure it -- too boring
HTH,
h1uke