[WaseemAlkurdi]

Originally Posted by Yorker

Couldn't find a straight answer for the 3.3 - 1.8 question just as you said some said it worked some said it didn't as a general rule it's recommended to stick with original design and even the "level shifter circuit" uses resistors for this reason.

I myself believe that it's 3.3v-tolerant. However, I do understand your concern.

I honestly don't mind soldering it in the problem is i don't have any parts and have to order and wait a few weeks for them :/

Why order parts? Why not simply solder in the resistors as per the level-shifter circuit? It's literally two resistors and a diode. Beats waiting for parts.

Following this nice guide i found:
http://ebookrepairs.com/kindle-tips/...t-to-a-kindle/
seems like the LM1117 1.8V mentioned there should do the trick.

I guess he has the resistor connected to the jumper but where should i connect mine if i don't have one? if i solder to the ping would need to solder the other end to the kindle? or maybe i should just make a Y shaped jumper head?
Attachment 173601

You mean the AMS1117 LDO regulator. Never used it myself, nor I ever saw it being used on this forum. Theoretically, it would work, but how is it different to using a simple resistor?
And since you're buying parts, wouldn't it be better to just buy a new serial cable that provides 1.8 volts out of the box with no modifications?

As for the picture, it's definitely odd. In my setup, I never touched the jumper pins, except to set the jumper to 3.3 volts. I guess that the owner of the picture used the jumper pins as a 3.3v source either out of ignorance of the jumper's use, or deliberately, possibly because they had lost the actual jumper itself. But there's no need for a 3.3v source. The 3.3v are provided over Tx and Rx.
Edit: After having re-read the article, he's using that to supply the 1.8 volts to the Tx and Rx pins. That 1.8v comes out of that black box, the LDO regulator, on the backside of the board.
Again, why not buy something that provides 1.8v out of the box?

To recap, you only need three cables going out of that board:
1. Board Rx -> Kindle Tx
2. Board Tx -> Kindle Rx
3. Board Ground -> Ground.
Not a single cable is needed on top of that.

Looking for my kindle board i stumbled upon this image and now i'm not sure about the connections, TX,RX,GND but what is the 4th?
I'm taking about the red wire in this img:
https://www.mobileread.com/forums/attachment.php?attachmentid=145410&d=1452450964[/IMG]

Whatever that extra cable is, it definitely isn't connected to the Kindle's serial port pad. It seems to be going to a screw on the Kindle's board, probably taped over the screw instead of wrapping it round the screw the way it's supposed to be done. If that's what happened, it would be another ground cable, but there's already another ground cable soldered to the RF shields (the metallic boxes on the board).

Regarding your setup i'm wondering why you didn't just make a hole in the case for the jumpers thus avoiding opening the kindle every time? Also curios you used a female to male jumper wire to bridge the soldered cables and the serial board?

I'd rather open up my Kindle every time (and how many times is that going to be?) rather than permanently disfigure it with a hole to the outside. I thought of sticking the cables out as a compromise, but even that is ugly.

Lastly i should have said so but my kindle was never hooked to an AP so it never had any connection and was only used offline so no OTA was possible, no idea how it got messed up on it's but obviously not ruling out HW failure so you're right about taking it slow.
Just to be clear tho, you are saying that while using serial it's impossible to ruing the device with a bad\improper image?

With serial, you are going to flash the individual partitions. Even if you flash your Kindle with the wrong partitions, it's not going to do the Kindle any harm, because you can always flash them again with the correct image via fastboot.
A word of caution though: Modifying the bootloader (U-Boot), which is located outside of user-accessible flash storage, is risky. But IIRC, an Amazon stock update package won't touch that.