Kindle Paperwhite Died - Can't figure problem

[Yorker]

Used a Kindle Paperwhite 3 from 2014 until a few weeks ago, it died while using,
Tried to charge it with socket connection

Tried to charge it with usb cable and a PC

Left it connected for days

Drained Battery tried to charge it again

Tried a soft reset (8 secs power button)

Tried a hard reset (40 secs power button)

Was pretty sure it was the battery then took it apart, no loose cables no swollen battery no signs of any damage or anything looking bad.

Checked battery with a multimeter seems good, checked the battery connection with a multimeter while connected to a power source also looks good.

No idea what else could it be.

[WaseemAlkurdi]

Originally Posted by Yorker

Used a Kindle Paperwhite 3 from 2014 until a few weeks ago, it died while using,
Tried to charge it with socket connection

Tried to charge it with usb cable and a PC

Left it connected for days

Drained Battery tried to charge it again

Tried a soft reset (8 secs power button)

Tried a hard reset (40 secs power button)

Was pretty sure it was the battery then took it apart, no loose cables no swollen battery no signs of any damage or anything looking bad.

Checked battery with a multimeter seems good, checked the battery connection with a multimeter while connected to a power source also looks good.

No idea what else could it be.

- Is there any voltage on the serial port pads? If the Kindle is alive, it should be sending its kernel log over serial, and the voltage should read 1.8 volts. Don't forget to connect the other end of the multimeter to ground. You can use the RF shields if there's no space left on the Kindle's serial port pad.

- And is the light turning on at all?

If there's no voltage, then poke around the board with a multimeter to see if any electricity is flowing, especially to the CPU.

Keep us updated.

[Yorker]

Originally Posted by WaseemAlkurdi

- Is there any voltage on the serial port pads? If the Kindle is alive, it should be sending its kernel log over serial, and the voltage should read 1.8 volts. Don't forget to connect the other end of the multimeter to ground. You can use the RF shields if there's no space left on the Kindle's serial port pad.

- And is the light turning on at all?

If there's no voltage, then poke around the board with a multimeter to see if any electricity is flowing, especially to the CPU.

Keep us updated.

I got 1.735 on the serial pads

The light turns on but only if i connect the kindle to a power source otherwise only if i hold it for 8 secs in blinks 3 times, maybe it's the battery after all? i got a 3.9v from it and also checked the pads on the battery connection to see it charges it.

[WaseemAlkurdi]

Originally Posted by Yorker

I got 1.735 on the serial pads

The light turns on but only if i connect the kindle to a power source otherwise only if i hold it for 8 secs in blinks 3 times, maybe it's the battery after all? i got a 3.9v from it and also checked the pads on the battery connection to see it charges it.

Good!
Getting a signal on the serial debug pins means that the Kindle is actually on and is sending its kernel output over serial.
You need to get a 1.8 V or 3.3 V USB to TTL converter board (see the numerous serial cable jailbreak tutorials on this forum for the recommended board). I personally use a Chinese part that consists of a red board with six pins sticking out of the bottom. It's a clone of the FTDI FT232RL, and is available for pocket change on eBay and (for a little more) at electronics stores. If you use that board, make sure you set the jumper to 3.3 V.

You need to "read" the output of the serial port to see what's causing the error. Actually, you're lucky to have a signal on the pins on that board ... it's going to be of great help.

[Yorker]

Originally Posted by WaseemAlkurdi

Good!
Getting a signal on the serial debug pins means that the Kindle is actually on and is sending its kernel output over serial.
You need to get a 1.8 V or 3.3 V USB to TTL converter board (see the numerous serial cable jailbreak tutorials on this forum for the recommended board). I personally use a Chinese part that consists of a red board with six pins sticking out of the bottom. It's a clone of the FTDI FT232RL, and is available for pocket change on eBay and (for a little more) at electronics stores. If you use that board, make sure you set the jumper to 3.3 V.

You need to "read" the output of the serial port to see what's causing the error. Actually, you're lucky to have a signal on the pins on that board ... it's going to be of great help.

I have something i got some time back, it's a red board with 5 pins sticking out and no jumper, so i guess i need to solder RX TX GND?

This is the guide i found
https://www.mobileread.com/forums/sh...90&postcount=1
I only have the adapter no serial cable, i'm assuming if i connect the adapter to a usb port and solder the pins to the kindle board it should work but what bothers me is the voltage you mentioned since my board doesn't have a jumper just pins, here is a link

https://www.ebay.com/itm/New-USB-2-0...0AAOSwUBJdEMK6

[WaseemAlkurdi]

Originally Posted by Yorker

I have something i got some time back, it's a red board with 5 pins sticking out and no jumper, so i guess i need to solder RX TX GND?

This is the guide i found
https://www.mobileread.com/forums/sh...90&postcount=1
I only have the adapter no serial cable, i'm assuming if i connect the adapter to a usb port and solder the pins to the kindle board it should work but what bothers me is the voltage you mentioned since my board doesn't have a jumper just pins, here is a link

https://www.ebay.com/itm/New-USB-2-0...0AAOSwUBJdEMK6

This is the one indeed, except that it doesn't have the jumper, as you noted. You only need to connect three pins:
1. Board Rx to Kindle Tx
2. Board Tx to Kindle Rx
3. Board Ground to Kindle Ground (or to a bare cable squeezed under a screw on the Kindle board).

Note that ground is NOT optional - there will be no serial output until you connect it.

To make sure that the adapter is the right voltage, connect one terminal of your multimeter to the Tx pin of the board and the other to the board's ground. If the board gives out 1.8 - 3.3 volts, you're good to go. Otherwise, buy a new one with a jumper, or solder resistors and electronic magic until the voltage goes down to 1.8 or 3.3 volts. Late Geekmaster has left us the schematic for such a "logic level shifter circuit if you have to build one.

Edit: Looking at the product description, you do have both 5 V and 3.3 V, but they are on separate pins, where Tx is 3.3 volts. Doesn't hurt to check it with the multimeter though.
And your adapter is different because it's based on a different chip, the CP2102. But people have reported success with this adapter too. Search this forum if it doesn't work out of the box (but it should).

[Yorker]

Originally Posted by WaseemAlkurdi

This is the one indeed, except that it doesn't have the jumper, as you noted. You only need to connect three pins:
1. Board Rx to Kindle Tx
2. Board Tx to Kindle Rx
3. Board Ground to Kindle Ground (or to a bare cable squeezed under a screw on the Kindle board).

Note that ground is NOT optional - there will be no serial output until you connect it.

To make sure that the adapter is the right voltage, connect one terminal of your multimeter to the Tx pin of the board and the other to the board's ground. If the board gives out 1.8 - 3.3 volts, you're good to go. Otherwise, buy a new one with a jumper, or solder resistors and electronic magic until the voltage goes down to 1.8 or 3.3 volts. Late Geekmaster has left us the schematic for such a "logic level shifter circuit if you have to build one.

Edit: Looking at the product description, you do have both 5 V and 3.3 V, but they are on separate pins, where Tx is 3.3 volts. Doesn't hurt to check it with the multimeter though.
And your adapter is different because it's based on a different chip, the CP2102. But people have reported success with this adapter too. Search this forum if it doesn't work out of the box (but it should).

Great i"ll test it out but 3 questions to go

1. I saw someone solder a resistor to scale down 3.3v to 1.8v i thought it's mandatory otherwise it won't work or fry

2. i'm wondering how to connect this as i only have jumper cables with this adapter so i guess cut one end of one cable and solder the points while keeping the jumper on the other end and connect to the pins?

3. Assuming it works the next step would be to get and copy the correct image? i need that exact one? i didn't update the kindle ever if that matters

[WaseemAlkurdi]

Originally Posted by Yorker

Great i"ll test it out but 3 questions to go

1. I saw someone solder a resistor to scale down 3.3v to 1.8v i thought it's mandatory otherwise it won't work or fry

2. i'm wondering how to connect this as i only have jumper cables with this adapter so i guess cut one end of one cable and solder the points while keeping the jumper on the other end and connect to the pins?

3. Assuming it works the next step would be to get and copy the correct image? i need that exact one? i didn't update the kindle ever if that matters

1. It depends on the Kindle model concerned.
I have a Kindle Touch (two of them, one dead) and a Kindle 7th generation (KT2).
The Kindle Touch wouldn't accept 3.3 volts (and I tried), requiring Geekmaster's level-shifter circuit, or at least a resistor (and I don't have one, so I left them without serial port access). It didn't burn out or anything when I connected the 3.3v adapter, but didn't send any output either.
But the 7th gen Kindle happily accepted the 3.3v adapter without an issue. Check around here to see if your Kindle Paperwhite model is 3.3v-tolerant. I'd guess that it is indeed. But is it really difficult to wire a resistor? You don't even have to solder it, you just wrap the cables around its pins.

2. That's like my setup. In the picture below from my 7th generation Kindle, I took another jumper cable from an old ATX case (had to settle for two-pin, more on that later) and soldered it to the Kindle to create a permanent serial port, then glued it to the sides so it won't move around when the Kindle is closed.
Then, when I need serial access, I would connect Tx and Rx to these two, and ground is from a third, bare-ended jumper cable wrapped around a Kindle motherboard screw.

3. No, not that fast. You first need to read the serial output to find out what's the issue. If it's eMMC failure, then what good would copying a new image be? But on the other hand, and since you never updated that Kindle before, it might just be a borked OTA update, done behind your back and interrupted for some reason.

i need that exact one?

You need the image for your Kindle model. But since you're on the serial port, it isn't really a mortal sin to copy the wrong image.

[Yorker]

Originally Posted by WaseemAlkurdi

1. It depends on the Kindle model concerned.
I have a Kindle Touch (two of them, one dead) and a Kindle 7th generation (KT2).
The Kindle Touch wouldn't accept 3.3 volts (and I tried), requiring Geekmaster's level-shifter circuit, or at least a resistor (and I don't have one, so I left them without serial port access). It didn't burn out or anything when I connected the 3.3v adapter, but didn't send any output either.
But the 7th gen Kindle happily accepted the 3.3v adapter without an issue. Check around here to see if your Kindle Paperwhite model is 3.3v-tolerant. I'd guess that it is indeed. But is it really difficult to wire a resistor? You don't even have to solder it, you just wrap the cables around its pins.

2. That's like my setup. In the picture below from my 7th generation Kindle, I took another jumper cable from an old ATX case (had to settle for two-pin, more on that later) and soldered it to the Kindle to create a permanent serial port, then glued it to the sides so it won't move around when the Kindle is closed.
Then, when I need serial access, I would connect Tx and Rx to these two, and ground is from a third, bare-ended jumper cable wrapped around a Kindle motherboard screw.

3. No, not that fast. You first need to read the serial output to find out what's the issue. If it's eMMC failure, then what good would copying a new image be? But on the other hand, and since you never updated that Kindle before, it might just be a borked OTA update, done behind your back and interrupted for some reason.


You need the image for your Kindle model. But since you're on the serial port, it isn't really a mortal sin to copy the wrong image.

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 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 :/

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?


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]

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?

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?

[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.

[Yorker]

Originally Posted by WaseemAlkurdi

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

I'm still wondering whether i should take the chance or not, it would save me the time waiting for parts...

Originally Posted by WaseemAlkurdi

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.

That's the thing, where am i supposed to get the resistors and diode, whichever way i take i need parts, i got nothing at the moment as i don't do this often.

Originally Posted by WaseemAlkurdi

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?

I just googled regulator vs resistor that's how much i know about this stuff lol , i guess a resistor does makes more send at the point but the price for a regulator is a very small margin and it's 1 part instead of 2 resistors right?

Regarding the serial cable:
1. those are expensive
2. i honestly like to improve my skills and this job fits perfectly for this as there is low risk to mess something up

Originally Posted by WaseemAlkurdi

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?

i would if it was cheap

Originally Posted by WaseemAlkurdi

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.

Originally Posted by WaseemAlkurdi

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).

Why would anyone need 2 ground connections?

Originally Posted by WaseemAlkurdi

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.

I can relate to this but opening every time can also be bad and annoying i guess it really does depend on how often it happens to justify.

Originally Posted by WaseemAlkurdi

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.

I've seen some people erase all and then could not recover from it , i thought i'd ask

[WaseemAlkurdi]

Originally Posted by Yorker

I'm still wondering whether i should take the chance or not, it would save me the time waiting for parts...

On the one hand, fixed Kindle ...
But on the other hand, fried Kindle. Your call.

That's the thing, where am i supposed to get the resistors and diode, whichever way i take i need parts, i got nothing at the moment as i don't do this often.

Local mobile phone and general electronics repair stores have a good supply of these parts.

I just googled regulator vs resistor that's how much i know about this stuff lol , i guess a resistor does makes more send at the point but the price for a regulator is a very small margin and it's 1 part instead of 2 resistors right?

It's about whatever you find easier to get. If you (locally shopping around) find somebody who has a regulator in stock, then by all means get one.

Regarding the serial cable:
1. those are expensive

What? They are around $2 - $4 in price.
From eBay: https://www.ebay.com/itm/TXD-1-8v-PL...e/142006114032

2. i honestly like to improve my skills and this job fits perfectly for this as there is low risk to mess something up

Ah, that's a good point.

Why would anyone need 2 ground connections?

I can't think of any other explanation given the point where the cable seems to run to, a point in which a screw is there on my own Kindle.

I can relate to this but opening every time can also be bad and annoying i guess it really does depend on how often it happens to justify.

If I were to use the Kindle primarily as a small ARM board, then I'd leave them sticking out of the bezel or charging port. A compromise.
But since I'm getting the Kindle as a purposely distraction-free study aid for my failing eyesight, and to hack around when I have free time, I decided that leaving the cable in there would turn of that "urge to hack"

I've seen some people erase all and then could not recover from it , i thought i'd ask

Can you point me to such an instance? It's pretty much impossible to do.
I initially thought that said people have been wiping /dev/mmcblk0 completely, perhaps by a wrong dd command where of=/dev/mmcblk0.
But if you (1) do a complete image of the eMMC, using this dd command:

# dd if=/dev/mmcblk0 of=/path/to/image.bin bs=4096

then a second image with @knc1's image backup script, and
(2) stick to the Kindle's partitions when flashing!!
then you're safe. Nothing can then go wrong.

After second thoughts however, look at this tutorial:
https://www.mobileread.com/forums/sh...d.php?t=271750
It starts out with a blank eMMC and from there, writes the bootloader and all.
So really, it's virtually impossible to brick a Kindle by wiping it when you have serial port access.

[Yorker]

Originally Posted by WaseemAlkurdi

Local mobile phone and general electronics repair stores have a good supply of these parts.


It's about whatever you find easier to get. If you (locally shopping around) find somebody who has a regulator in stock, then by all means get one..

It's actually a lot more expensive in my country compared to online at least 5-10X depending on the part. it doesn't mean much could still be 5$ instead of 0.25 but still i would rather spend 2$ to get a few pieces of that instead of paying for their overpriced parts

Originally Posted by WaseemAlkurdi

What? They are around $2 - $4 in price.
From eBay: https://www.ebay.com/itm/TXD-1-8v-PL...e/142006114032.

Wow that is cheap, i got the idea from some guide, maybe this
https://www.mobileread.com/forums/sh...90&postcount=1
"I used the FTDI TTL-232RG-VREG1V8-WE (from Farnell for 23€ + shipping)"
And i remember another thread stating those are expensive maybe in the WIKI

But i would need to strip the jumpers and solder the cables to the board right?

Originally Posted by WaseemAlkurdi

Can you point me to such an instance? It's pretty much impossible to do.
I initially thought that said people have been wiping /dev/mmcblk0 completely, perhaps by a wrong dd command where of=/dev/mmcblk0.
But if you (1) do a complete image of the eMMC, using this dd command:

# dd if=/dev/mmcblk0 of=/path/to/image.bin bs=4096

then a second image with @knc1's image backup script, and
(2) stick to the Kindle's partitions when flashing!!
then you're safe. Nothing can then go wrong.

After second thoughts however, look at this tutorial:
https://www.mobileread.com/forums/sh...d.php?t=271750
It starts out with a blank eMMC and from there, writes the bootloader and all.
So really, it's virtually impossible to brick a Kindle by wiping it when you have serial port access.

Thanks for the details it did help me understand the process better and also added some reassurance now i feel more confident doing the process
The thread i was talking about was this:
https://www.mobileread.com/forums/sh...unbrick+kindle

Originally Posted by WaseemAlkurdi

I can't think of any other explanation given the point where the cable seems to run to, a point in which a screw is there on my own Kindle.

I think this thread
https://www.mobileread.com/forums/sh...d.php?t=267541
Shows what is the 4th conenction

Originally Posted by WaseemAlkurdi

If I were to use the Kindle primarily as a small ARM board, then I'd leave them sticking out of the bezel or charging port. A compromise.
But since I'm getting the Kindle as a purposely distraction-free study aid for my failing eyesight, and to hack around when I have free time, I decided that leaving the cable in there would turn of that "urge to hack"

BTW you could do a wireless solution like this:
https://darron.typepad.com/not-nearl...dx-part-1.html

[Yorker]

I decided to try and solder what i have to the kindle, very tiny points it was a mess....

Eventually i think i succeeded since i checked the voltage with the multimeter.

For some reason the USB\TTL adapter didn't light up on TX but RX and GND were fine.
GND was wrapped around a screw so that is sold while TX and RX were soldered so it's strange.

I checked the voltages and TX was getting 0.9 while RX got 3.3 so i guess based on experiments if its less than 1 it doesn't light up

Also on the dmesg it showed as follows:

[    0.850853] 00:05: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A

But after disconnecting it still shows that so it's not related to the adapter


Does this mean i need 1.8?

Also i found this if it relevant

[WaseemAlkurdi]

Originally Posted by Yorker

I decided to try and solder what i have to the kindle, very tiny points it was a mess....

Yeah, it is indeed messy. But look at my setup ... don't solder stuff directly to the Kindle. Solder a cable like I did, then solder stuff to the cable as not disfigure the Kindle itself.

Eventually i think i succeeded since i checked the voltage with the multimeter.

For some reason the USB\TTL adapter didn't light up on TX but RX and GND were fine.

GND was wrapped around a screw so that is sold while TX and RX were soldered so it's strange.

I checked the voltages and TX was getting 0.9 while RX got 3.3 so i guess based on experiments if its less than 1 it doesn't light up

At which point did you check the voltages? At the adapter or at the Kindle?

Also on the dmesg it showed as follows:

[    0.850853] 00:05: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A

But after disconnecting it still shows that so it's not related to the adapter

Why are you expecting that dmesg entry to disappear? dmesg is a log ... plug events don't disappear from there when unplugged. Try with a USB drive and see the entries for yourself.
By the way, the adapter is usually ttyUSB0.

Does this mean i need 1.8?

If Tx were to read 1.8 volts, then yeah, but reading 0.8 volts is strange. Unless you weren't reading from the Kindle, or you have something causing an inaccuracy.

Also i found this if it relevant
Attachment 173667

These are good. I'm not an electrician, but I do remember Ohm's Law being useful for these. Not sure of the exact calculation needed.