I tried to access the serial port but was not successful.
First of all the 1.8V were not able to supply my level shifter (74AVC4T245 which requires about 2mA@1.8V).
This I solved by using the 3.3V Volt from my usb to serial adapter to generate the 1.8V (using Zener diode and a resistor).
There is no communication on the serial port, I also checked with an osziloscope.
Do I have to enable something to see the boot log and access the device?
I am using a Kindle 3 3G (non US) with firmware version 3.1.