Still have the pins and little jumper cables on the adapter?
If so -
remove jumper cables on adapter Tx & Rx -
now use one of the jumpers to connect Tx & Rx on the adapter together -
bring up the terminal emulator and type at it.
Do you get back the same character that you type?
(I expect that you will.)
If that seems to work -
remove the geekmaster level shifter from the connections -
set the adapter for 3.3 volt -
hook it back up to the Kindle (without the geekmaster circuit) -
Are the trash characters still gone?
If so - we will use it that way - others have without problems.
Note:
Unlike the hyperterminal/windows combination - the minicom/linux combination will not "lose" the connection when rebooting the Kindle.
So you can bring up minicom and let it go through its start-up before you have the Kindle running.
(which I suspect you have noticed)
So don't try to hit the 'type a character to stop auto boot' prompt exactly -
Reboot the Kindle -
Now hold down one of the keyboard keys, let it auto-repeat until the boot process stops -
I.E: a big stick works as well as a single character.
When you see the u-boot> prompt, just hit return -
u-boot will not do anything with a bunch of (for instance) j 's
Although your logs show that the update has successfully re-loaded the (main, 5.6.x) kernel image we will try the (old) diags kernel image.
Enter:
bootm 0xE41000
That should boot the (old) diags system.
I don't recall if the diags kernel trys to auto-update -
(That answer can be found in the logs attached to the recent fastboot recovery thread - I am too lazy to look it up.)
If it does try to auto-update, let it and hope it works.
OR
You might be looking at the 'recovery menu' now.
Let me know where we stand at this point.