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Old 12-23-2020, 04:48 AM   #1
themasterandmat
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Unhappy KT4 Bricked

Hi all,

It took me less than a week to get sick of the screensaver on my brand new KT4 and I asked myself surely there must be a way to change it.

Days of research on this forum later and I thought I had it all sorted. I lined up all the downloads in order and started with the diags update to allow downgrading.

I copied it to the root of my kindle and rebooted it. It took much longer than expected to reboot, so I waited, and waited. Eventually I realised something must be wrong. I went back and double checked everything and realised my terrible mistake:
I'd accidently selected the PW4 diag instead of the KT4 diag file, and now my kindle is stuck on the boy under the tree and "Please wait a moment while your kindle starts up"
When I plug it into my computer I don't get a USB drive at all.

I spent another day hunting for unbricking options, but they all need the kindle to be placed into usb recovery mode, which involves holding the power button and then pressing the Magic key. but the KT4 doesn't have any other buttons except the power button.

Pressing the power button on the bottom turns the power LED on green for a couple of seconds and then it goes off.
Holding the power button the LED will stay on for a while, and then flash green a couple of times, then turn off for a few seconds and then it'll flash orange 5 times.


In the words of the great Leeloominaï Lekatariba Lamina-Tchaï Ekbat De Sebat : "Please Help"
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Old 12-26-2020, 11:50 AM   #2
dhdurgee
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I don't know if there is anything to be done at this point, but the only possibility I can see of any kind would involve opening up the KT4 and accessing the serial port. You would need the proper equipment, tools and ability to deal with tiny easy to damage contacts on the mainboard of the KT4. If you can interrupt the boot process and export the partition you should be able to put the correct firmware in place and then install it.

Dave
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Old 12-28-2020, 06:10 AM   #3
themasterandmat
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Thanks so much for the reply Dave.

I'm pretty handy with a soldering iron, so that's definitely an option I'd be happy to pursue. I'm happy to hunt around for teardown images for the KT4, I believe I've already seen a few, but I'm a bit hazy on what serial commands to actually run, do you have a link to a post somewhere that talks about serial commands on the KT4

Again, thank you very much
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Old 12-28-2020, 06:31 AM   #4
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Nobody has reported on the KT4 serial port debricking or jailbreaking so far.
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Old 12-28-2020, 04:13 PM   #5
themasterandmat
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That's why I can't find anything

I'll keep researching and post my results here.
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Old 12-30-2020, 12:31 PM   #6
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Quote:
Originally Posted by themasterandmat View Post
That's why I can't find anything

I'll keep researching and post my results here.
This thread appears to be sbout a similar bricking:

https://www.mobileread.com/forums/sh...d.php?t=336042

Opinions there are that the Oasis is closest to your model, so that is likely a good thread for you to study.

I wish you success in your attempt so we can add another model to the serial jailbreak list.

Dave

Last edited by dhdurgee; 12-30-2020 at 12:33 PM. Reason: correct link formatting
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Old 01-09-2021, 05:59 AM   #7
themasterandmat
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Sad news for those playing at home.

I opened up my KT4, hooked up a modified USB to Serial adapter to allow 1.8V comms, and tried to talk to it at 115200 with no joy. I took some pictures, but I'm too new to attach files.

Basically I soldered wires to the port that looks like a serial port in this thread: https://www.mobileread.com/forums/sh...d.php?t=267541
It's at the bottom right corner of the KT4

I tried swapping the TX and RX lines, that didn't work either. There was no communication at all, I tried disconnecting and reconnecting the battery while it was all hooked up to see if I could get something when it first started up. Also nothing.

Reading that thread Dave suggested, and a bit more digging, I might have to wire directly to the processor, but it's under some EMI shielding, so I'll have to get a heat gun to it or something.

There's also a chance that my voltage step down converter isn't connected correctly, so it's back to the drawing board. I do have a cheap oscilliscope, I'm just waiting on a replacement probe for it, so I'll try again when that arrives and see if I can see any blips on either of the lines
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Old 01-10-2021, 09:37 PM   #8
branislavbane
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Couple days ago I had success with serial port communication on same device, but my success was only partial. Don't worry serial communication worked but I was not able to stop boot process by pressing a button.

You'll need to solder only three wires to use serial communication: GND (left), RX (middle), TX (right).
Click image for larger version

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Do not get confused RX on source device is connected to TX on destination device and reverse.
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For power source use battery or power device through usb port.

Best luck. I am really curries to see will you succeed to prevent boot by pressing a button.

Last edited by pdurrant; 01-11-2021 at 02:31 AM.
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Old 01-17-2021, 09:51 PM   #9
comer
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with the PW4 diag ,your KT4 uboot lost,so bricked,and also no uboot running infomation with USB to Serial adapter.
in the device manager ,if can find a new HID-compliant device ,
or you can try use mgftool to reload uboot on KT4.
that is the way to unbrick a kindle with uboot lost,even replace an new blank MMC chip.
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