K3 using serial port problem

BusterBrown · 06-03-2012, 10:49 PM

Hello, This is my first post and hopefully someone can help me with my problem. I bought a couple of broken Kindle's B006 and B008's to just play around with. I have managed to brick one of the units and have a working serial port working with linux and Minicom 2.5. I can watch the boot process in my computer terminal and can interrupt the boot and see the U-boot prompt. If I just let the Kindle boot-up, it goes to: Starting Kernel.... Uncompressing Linux but, I am unable to see any more text after the uncompressing .............. I never see the "Welcome to Kindle" screen. What am I doing wrong?
Thanks in Advance,

hawhill · 06-04-2012, 07:29 AM

I guess you're doing nothing wrong, but either the kernel does not use the serial interface (might be because the kernel image is broken, or the bootloader isn't passing the right kernel command line), or it switched to different connection settings (baud rate).

geekmaster · 06-04-2012, 08:08 AM

You *SHOULD* see all the messages from the kernel that end up in the log files you can view with "dmesg", and you should even get a login prompt at the serial port.

The "simple debricking" sticky has a link to the K3 debricking thread, which contains this video that shows what you should see during a restart (including output from the kernel):

Also, on some kindles, it helps to keep the USB cable connected to the same host PC that the serial adapter connects to, to supply a better ground connection. This seems to be more important on the K4 and K5 though...

knc1 · 06-04-2012, 08:17 AM

Quote:

Originally Posted by BusterBrown

I can watch the boot process in my computer terminal and can interrupt the boot and see the U-boot prompt. If I just let the Kindle boot-up, it goes to: Starting Kernel.... Uncompressing Linux but, I am unable to see any more text after the uncompressing ..............

Your doing nothing wrong (other than attempting to run a broken or missing kernel) if that is the last message you see.

Replace the kernel image with a known good one and try again.

hawhill · 06-04-2012, 08:24 AM

...which won't be easy on a K3 (I think the OP is talking about K3s, or do the more recent Kindles share the serial number prefixes?), I think nobody really went that way. Writing the root partition is a known fix for broken K3s, but it requires a working kernel (plus initramfs) - so it would not help with the OPs problem. There is the Freescale toolkit (ATK) for the iMX35, I played with it for a few minutes, but didn't really get anywhere. Aside from that, I never saw reports from someone who went further.

knc1 · 06-04-2012, 08:28 AM

Quote:

Originally Posted by hawhill

...which won't be easy on a K3 (I think the OP is talking about K3s, or do the more recent Kindles share the serial number prefixes?), I think nobody really went that way. Writing the root partition is a known fix for broken K3s, but it requires a working kernel (plus initramfs) - so it would not help with the OPs problem. There is the Freescale toolkit (ATK) for the iMX35, I played with it for a few minutes, but didn't really get anywhere. Aside from that, I never saw reports from someone who went further.

Perhaps you noticed I did not say: "How" to do that?

I only know it can be done, but like you, have not learned (yet) how to do it.
O.P. reports that u-boot is working, that should be enough working firmware on the kindle to get the job done.
Just don't ask me how (yet).
I do own a K3, and am certain I will brick it sometime (probably RSN, just any day).

geekmaster · 06-04-2012, 08:34 AM

u-boot is loaded before the kernel. Doesn't it provide a recovery menu that you can access even with a bad kernel?

Here is a thread that shows how to get to recovery mode:
https://www.mobileread.com/forums/sho...d.php?t=124861

One of the posts in that thread says this:

Quote:

Have you tried running the recovery mode on reboot? Hold the power slider for about 15-20 seconds and then once you let go, immediately hold down the "Home" button before the screen even has a chance to flicker back on. This should Hard Reset the kindle and holding down the "Home" key while it's starting back up, you should be presented with a Recovery Mode. It will ask you to type in "RESET", which it will then run I suppose a factory reset on the kindle. You'll have to re-register and all of your books will be in the archived folder, instead of organized as you had it, because it's formatted your kindle obviously...but this is what it took to fix mine when I was having issues with the screen not changing.

There are also posts in other threads that say you only have a few seconds to select a recovery menu item, so you may have to try this a few times before you can read all the menu options...

hawhill · 06-04-2012, 09:01 AM

I must admit that I did not consider that it might be part of u-boot. I was always under the impression that this "rescue menu" is done in an initramfs run by a (working...) Linux kernel. Well, so the suggestion for the OP is: see if the rescue menu appears :-)

geekmaster · 06-04-2012, 09:03 AM

There are other rescue menu options besides RESET. That is just the option used in that quote. You need to be careful to NOT select an option that can make things worse than they already are...

The rescue menu shown in seaniko7's video is after the kernel loads, but there is a more primitive menu with fewer options that can be accessed as shown in the quote.

P.S. I cannot test this on my k3 right now. The battery has been completely draining lately when it is not connected to a USB cable (even when a screensaver is showing), and it is dead now. I do not know why it started this behavior, and it is dead everytime I want to use it. I did not install anything new on it. Must be a bad OTA update or something. Annoying...

BusterBrown · 06-04-2012, 11:11 AM

Hi to all replies,
I have watched Seaniko7's video many times to no avail. I have tried my serial connection on good working units with the same result. One thing I haven't done is try the Chown uucp /dev/ttyUSB0 thing. This can't be anything to do with a bad kernel.
Thanks for all the responses.

BusterBrown · 06-04-2012, 11:22 AM

This was I get on a good working unit:

S/N: B006A0A0xxxxxxx
DRAM: 256 MB
Using default environment

In: serial
Out: serial
Err: serial
No ethernet found.
i.MX35 CPU board version 2.0
Net: No ethernet found.
Hit any key to stop autoboot: 0
## Booting image at 87f40400 ...
Image Name: Linux-2.6.26-rt-lab126
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 2150760 Bytes = 2.1 MB
Load Address: 80008000
Entry Point: 80008000
Verifying Checksum ... OK
Loading Kernel Image ... OK

Starting kernel ...

Uncompressing Linux............................................( no more output to screen after this)

hawhill · 06-04-2012, 11:28 AM

So what you are saying is that the output is the same for the working unit you refer in this (#11) post and the broken unit you refer to in the OP (#1)? Or are you referring to the same unit?

If so: The working unit should show more output, I think.

The "Hit any key to stop autoboot" indeed indicates that at that point, you could make appear a menu or similar means within uboot. Did you hit a key at that point and looked what happens? Of course I mean for the blocked unit you refer to in #1.

As a side note: That this looks the same on the bricked kindle and working kindles still does not prove that the kernel of the bricked unit is OK. It's just a hint that it might be.

Ownership of the tty device on the host machine certainly isn't the culprit here. You wouldn't see anything if that were the case, and facing a permission error instead.

geekmaster · 06-04-2012, 11:33 AM

You could try connecting the USB cable as I suggested, to provide a better ground. The only other thing I can think is that your u-boot and kernel images are using different serial baud rates, but that is not "normal"...

How is your kindle and host PC different from what seaniko7 used in his video, when he DID get a root login prompt at his serial port?

BusterBrown · 06-04-2012, 11:49 AM

All of my testing is being done with good working units. I can hit return on my computer and stop the boot process and see the U-boot prompt. So, that tells me that I have two way communications with the Kindle. I have also tried this while the USB was connected. I have one good Kindle screen and several units with broken screens so, I would prefer to use the serial connection for my experimenting and would sure like to get the 'Log-in' screen.

geekmaster · 06-04-2012, 11:53 AM

The display cable on a K3 is near the edge. I have successfully "borrowed" a screen from another kindle without removing it, but just removing the back covers and swapping the eink cable connection. With the kindles back-to-back, there is enough room to get in between them and plug in the cable with a needle-nosed pliers (or tweezers). You may be able to see what is on the eink display during startup that way... If you can turn on the voice guide in the settings menu, a kindle with a broken screen is quite usable...

You may also want to turn on USB networking all the time (using the AUTO file).

What firmware version are you running? Perhaps your version (and patch level) does not output to the serial port after the kernel loads...

06-04-2012, 08:08 AM	#3
geekmaster Carpe diem, c'est la vie. Posts: 6,433 Karma: 10773668 Join Date: Nov 2011 Location: Multiverse 6627A Device: K1 to PW3	You SHOULD see all the messages from the kernel that end up in the log files you can view with "dmesg", and you should even get a login prompt at the serial port. The "simple debricking" sticky has a link to the K3 debricking thread, which contains this video that shows what you should see during a restart (including output from the kernel): Also, on some kindles, it helps to keep the USB cable connected to the same host PC that the serial adapter connects to, to supply a better ground connection. This seems to be more important on the K4 and K5 though... Last edited by geekmaster; 06-04-2012 at 08:15 AM.

06-04-2012, 09:03 AM	#9
geekmaster Carpe diem, c'est la vie. Posts: 6,433 Karma: 10773668 Join Date: Nov 2011 Location: Multiverse 6627A Device: K1 to PW3	There are other rescue menu options besides RESET. That is just the option used in that quote. You need to be careful to NOT select an option that can make things worse than they already are... The rescue menu shown in seaniko7's video is after the kernel loads, but there is a more primitive menu with fewer options that can be accessed as shown in the quote. P.S. I cannot test this on my k3 right now. The battery has been completely draining lately when it is not connected to a USB cable (even when a screensaver is showing), and it is dead now. I do not know why it started this behavior, and it is dead everytime I want to use it. I did not install anything new on it. Must be a bad OTA update or something. Annoying... Last edited by geekmaster; 04-14-2016 at 09:28 AM.

06-04-2012, 11:53 AM	#15
geekmaster Carpe diem, c'est la vie. Posts: 6,433 Karma: 10773668 Join Date: Nov 2011 Location: Multiverse 6627A Device: K1 to PW3	The display cable on a K3 is near the edge. I have successfully "borrowed" a screen from another kindle without removing it, but just removing the back covers and swapping the eink cable connection. With the kindles back-to-back, there is enough room to get in between them and plug in the cable with a needle-nosed pliers (or tweezers). You may be able to see what is on the eink display during startup that way... If you can turn on the voice guide in the settings menu, a kindle with a broken screen is quite usable... You may also want to turn on USB networking all the time (using the AUTO file). What firmware version are you running? Perhaps your version (and patch level) does not output to the serial port after the kernel loads... Last edited by geekmaster; 06-04-2012 at 11:57 AM.

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06-03-2012, 10:49 PM	#1
BusterBrown Kindle Expirmenter Posts: 25 Karma: 10 Join Date: May 2012 Location: Washington State, USA Device: k2k3k4	K3 using serial port problem Hello, This is my first post and hopefully someone can help me with my problem. I bought a couple of broken Kindle's B006 and B008's to just play around with. I have managed to brick one of the units and have a working serial port working with linux and Minicom 2.5. I can watch the boot process in my computer terminal and can interrupt the boot and see the U-boot prompt. If I just let the Kindle boot-up, it goes to: Starting Kernel.... Uncompressing Linux but, I am unable to see any more text after the uncompressing .............. I never see the "Welcome to Kindle" screen. What am I doing wrong? Thanks in Advance,

06-04-2012, 07:29 AM	#2
hawhill Wizard Posts: 1,379 Karma: 2155307 Join Date: Nov 2010 Location: Goettingen, Germany Device: Kindle Paperwhite, Kobo Mini	I guess you're doing nothing wrong, but either the kernel does not use the serial interface (might be because the kernel image is broken, or the bootloader isn't passing the right kernel command line), or it switched to different connection settings (baud rate).

06-04-2012, 08:24 AM	#5
hawhill Wizard Posts: 1,379 Karma: 2155307 Join Date: Nov 2010 Location: Goettingen, Germany Device: Kindle Paperwhite, Kobo Mini	...which won't be easy on a K3 (I think the OP is talking about K3s, or do the more recent Kindles share the serial number prefixes?), I think nobody really went that way. Writing the root partition is a known fix for broken K3s, but it requires a working kernel (plus initramfs) - so it would not help with the OPs problem. There is the Freescale toolkit (ATK) for the iMX35, I played with it for a few minutes, but didn't really get anywhere. Aside from that, I never saw reports from someone who went further.

06-04-2012, 09:01 AM	#8
hawhill Wizard Posts: 1,379 Karma: 2155307 Join Date: Nov 2010 Location: Goettingen, Germany Device: Kindle Paperwhite, Kobo Mini	I must admit that I did not consider that it might be part of u-boot. I was always under the impression that this "rescue menu" is done in an initramfs run by a (working...) Linux kernel. Well, so the suggestion for the OP is: see if the rescue menu appears :-)

06-04-2012, 11:11 AM	#10
BusterBrown Kindle Expirmenter Posts: 25 Karma: 10 Join Date: May 2012 Location: Washington State, USA Device: k2k3k4	Hi to all replies, I have watched Seaniko7's video many times to no avail. I have tried my serial connection on good working units with the same result. One thing I haven't done is try the Chown uucp /dev/ttyUSB0 thing. This can't be anything to do with a bad kernel. Thanks for all the responses.

06-04-2012, 11:22 AM	#11
BusterBrown Kindle Expirmenter Posts: 25 Karma: 10 Join Date: May 2012 Location: Washington State, USA Device: k2k3k4	This was I get on a good working unit: S/N: B006A0A0xxxxxxx DRAM: 256 MB Using default environment In: serial Out: serial Err: serial No ethernet found. i.MX35 CPU board version 2.0 Net: No ethernet found. Hit any key to stop autoboot: 0 ## Booting image at 87f40400 ... Image Name: Linux-2.6.26-rt-lab126 Image Type: ARM Linux Kernel Image (uncompressed) Data Size: 2150760 Bytes = 2.1 MB Load Address: 80008000 Entry Point: 80008000 Verifying Checksum ... OK Loading Kernel Image ... OK Starting kernel ... Uncompressing Linux............................................( no more output to screen after this)

06-04-2012, 11:28 AM	#12
hawhill Wizard Posts: 1,379 Karma: 2155307 Join Date: Nov 2010 Location: Goettingen, Germany Device: Kindle Paperwhite, Kobo Mini	So what you are saying is that the output is the same for the working unit you refer in this (#11) post and the broken unit you refer to in the OP (#1)? Or are you referring to the same unit? If so: The working unit should show more output, I think. The "Hit any key to stop autoboot" indeed indicates that at that point, you could make appear a menu or similar means within uboot. Did you hit a key at that point and looked what happens? Of course I mean for the blocked unit you refer to in #1. As a side note: That this looks the same on the bricked kindle and working kindles still does not prove that the kernel of the bricked unit is OK. It's just a hint that it might be. Ownership of the tty device on the host machine certainly isn't the culprit here. You wouldn't see anything if that were the case, and facing a permission error instead.

06-04-2012, 11:33 AM	#13
geekmaster Carpe diem, c'est la vie. Posts: 6,433 Karma: 10773668 Join Date: Nov 2011 Location: Multiverse 6627A Device: K1 to PW3	You could try connecting the USB cable as I suggested, to provide a better ground. The only other thing I can think is that your u-boot and kernel images are using different serial baud rates, but that is not "normal"... How is your kindle and host PC different from what seaniko7 used in his video, when he DID get a root login prompt at his serial port?

06-04-2012, 11:49 AM	#14
BusterBrown Kindle Expirmenter Posts: 25 Karma: 10 Join Date: May 2012 Location: Washington State, USA Device: k2k3k4	All of my testing is being done with good working units. I can hit return on my computer and stop the boot process and see the U-boot prompt. So, that tells me that I have two way communications with the Kindle. I have also tried this while the USB was connected. I have one good Kindle screen and several units with broken screens so, I would prefer to use the serial connection for my experimenting and would sure like to get the 'Log-in' screen.

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