Quote:
Originally Posted by wlaf
Thanks...
Is using 3.3v safe? I mean if it doesn't work, I can create a custom board, but is there any chance of breaking the Kindle hardware using 3.3v?
Btw, it seems that the root of the problem is now obvious. I have changed inittab to include usbnetworking, and maybe I had mistakes there, but it is really strange, because I have rebooted the device several times and I had no problem, 2 exceptions was rebooting through the shell. The first time I could be able to repair using updates, but this time, no.
Does rebooting through Kindle shell actually reboot the device? If it's true, I should have this problem with the first reboot through Kindle menus.
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The K4 and K5 have a 1K series resistor on both the Tx and Rx lines. I and other have successfully connected them to 3.3v, but depending on which 3.3v serial you use, you may have to use part (or all) of the level-shifter circuit linked in the hardware index. Also, on my adapter, I needed to remove an LED from it that drew more current than the kindle could sink to ground for a logic zero, and I added a 20K pullup resistor to 3.3v on the adapter side of the diode. It works great.
Some people reported that their adapter just worked with not modification or level shifting. Also, the ground on the serial connector is often NOT enough. It helps to connect a USB cable between the kindle and the computer using the serial adapter, for a better ground connection.
There have been reports of the serial I/O changing its settings, working during u-boot then failing when loading the linux kernel, until a level shifter was used...