Kobo Touch N905 - need external sd boot

[NoPro]

Hi,

I bricked my Kobo Touch n905 (not the one with internal sd-card)

bricking was succesfuy done by installing xcsoar and changing usb-otg settings in the xcsoar menue (xcsoar is a great , in my opinion the best soaring navigation software and the kobo touch n905 (a) works with it as long as usb-otg setting is not changed).

before bricking i made a backup.img
now the blue light is blinking, by pressing the home button when sliding the powerbutton the led lights constant blue. when i press the reset button home button and powerbutton in all possibe combinations, blue light changes to red light.

i want to made the kobo boot from an external sdcard by holding the home button when sliding the power button.
when some system is working i can write the backup.img on the internal memory via usb cable.
i dont knwo how to make the sd card with some linux distribution.
according to a thread in this forum (link below) i have to make a partition on the sd card with ext2 filesystem and then copy (?) debian there..
can someone give me a hint how to start?
https://www.mobileread.com/forums/sh...d.php?t=289206

[davidfor]

If you have an image, you might be able to put that on a card and boot from that. This works with the Aura using an image from the Aura H2O. If that works, you can try to restore the image from the card.

But, how did you create the image in the first place? I haven't seen one for the N905 Touch. I would think the only way to produce one is to boot from the SD card. I suppose producing one when booted normally might work. I don't know if that would produce a a usable image or not.

[pazos]

The external sd boot mentioned in the link still relies on a working bootloader on the internal storage. That bootloader (u-boot) will load the kernel in memory (again from the internal storage) and jump at it. What changes is the root cmdline argument passed to the kernel.

That means that you'll need a working bootloader/kernel on the internal partiton. If that's your case you can follow @davidfor suggestion: flash your backup to an external sdcard and try to boot from it.

Some things won't work at all in this config (ie: the "user" partition is hardcoded at mmcblk0p3 in the firmware) but you'll see -at least- the bootlogo and you can tweak the 1st partition of your external sdcard to get a working FW.

[NiMa]

Originally Posted by pazos

The external sd boot mentioned in the link still relies on a working bootloader on the internal storage. That bootloader (u-boot) will load the kernel in memory (again from the internal storage) and jump at it. What changes is the root cmdline argument passed to the kernel.

That means that you'll need a working bootloader/kernel on the internal partiton. If that's your case you can follow @davidfor suggestion: flash your backup to an external sdcard and try to boot from it.

Some things won't work at all in this config (ie: the "user" partition is hardcoded at mmcblk0p3 in the firmware) but you'll see -at least- the bootlogo and you can tweak the 1st partition of your external sdcard to get a working FW.

The fact that the light turned red when key combinations were pressed is a good sign that U-Boot works.

[pazos]

Originally Posted by NiMa

The fact that the light turned red when key combinations were pressed is a good sign that U-Boot works.

Indeed. I didn't think about it

[NoPro]

thanks for your answers. im still in hope that there is someone alive in the kobo giving me rescue signs by the red light sigals

i created the image of the briked kobo with win32diskimager.
i tried to boot this image from the external sd by powerup+home btn - blue led blinking slow.
i tried the "external sd boot method" with an other good kobo touch. copied the 1,4gb partition with HDDRawCopyTool and tried powerup+home btn - blue led blinking slow... doesnt work

can you give me some advice how to boot?
is there a way to the serial output from the kobo with a serial-usb adapter.. soldering the cable to the kobo is no problem.

[davidfor]

Originally Posted by NoPro

thanks for your answers. im still in hope that there is someone alive in the kobo giving me rescue signs by the red light sigals

i created the image of the briked kobo with win32diskimager.

In that case, I don't think it is a valid image. When you connect a working Kobo ereader by USB, it only presents one partition. That is the partition with the books. It doesn't have the root or kernel or anything. Trying to boot from that would not work. And the size mentioned below agrees with this.

i tried to boot this image from the external sd by powerup+home btn - blue led blinking slow.
i tried the "external sd boot method" with an other good kobo touch. copied the 1,4gb partition with HDDRawCopyTool and tried powerup+home btn - blue led blinking slow... doesnt work

can you give me some advice how to boot?
is there a way to the serial output from the kobo with a serial-usb adapter.. soldering the cable to the kobo is no problem.

There is some discussion in the forums about using the headers on the PCB to connect to it. I don't remember if they got it to work or not.

If you have a working N905 Touch, you might be able to create an image using that. You should be able to telnet into the working device and us the dd command to create an image of the device on the SD card. Then use that to create the bootable SD car for the non-working device. I think this would work, but, I am not sure. And I don't know the dd command well enough to suggest what the parameters should be. Telnet is turned on when you turn on the developer mode. And that has an option to force WiFi on so it won't go to sleep when executing the commands needed.

As possible test of this is using the image from the N905B Touch. I think this might be close enough to the N905 to boot. I'm not sure of that, but, something in the back of my brain suggests it is. I don't think it will work completely, but, might get further than you currently have. I have sent you a PM with the link to the image if you want to try it.

[NiMa]

Originally Posted by davidfor

In that case, I don't think it is a valid image. When you connect a working Kobo ereader by USB, it only presents one partition. That is the partition with the books. It doesn't have the root or kernel or anything. Trying to boot from that would not work. And the size mentioned below agrees with this.


There is some discussion in the forums about using the headers on the PCB to connect to it. I don't remember if they got it to work or not.

If you have a working N905 Touch, you might be able to create an image using that. You should be able to telnet into the working device and us the dd command to create an image of the device on the SD card. Then use that to create the bootable SD car for the non-working device. I think this would work, but, I am not sure. And I don't know the dd command well enough to suggest what the parameters should be. Telnet is turned on when you turn on the developer mode. And that has an option to force WiFi on so it won't go to sleep when executing the commands needed.

As possible test of this is using the image from the N905B Touch. I think this might be close enough to the N905 to boot. I'm not sure of that, but, something in the back of my brain suggests it is. I don't think it will work completely, but, might get further than you currently have. I have sent you a PM with the link to the image if you want to try it.

IIRC, the N905B uses a different CPU/SoC (imx508) than the N905 and N905C (imx507). I think it has more chances to work with the N905C image.
Actually, if you can, you could debrick it with a serial connection. U-Boot is normally locked up on those devices (bootdelay=0), but if it can't find a kernel, it will let you type in a command prompt. From there, you can loady/loadx/loadb a kernel uImage from the serial port containing a minimal initrd and reflash the device manually, recovering old partitions as possible (especially recoveryfs).

[NoPro]

its great to get your time and support.
step by step it makes some progress
soldered rx and tx to an arduino and tried the 905b image
seems that it dosnt work with the *b image. i tried the *c image as well with same results.

[NiMa]

Originally Posted by NoPro

its great to get your time and support.
step by step it makes some progress
soldered rx and tx to an arduino and tried the 905b image
seems that it dosnt work with the *b image. i tried the *c image as well with same results.

So you can't "Hit any key to stop autoboot"?
Probably not, all those old Kobos have bootdelay set to 0. You might still try. If you get to the U-Boot command line, then debricking is possible.

[croofec]

I have just successfully unbricked kobo n905 with internal MMC.
For unbrick, you need a connection with uart and sdcard.

For uart:




For the preparation of the card you can use the latest firmware from https://pgaskin.net/KoboStuff/kobofirmware.html (Kobo Touch A/B and feescale upload folder) or you can use uImage.

for Linux (or for windows use to some image tool)

dd if=./uImage of=/dev/disk2 bs=512

after that put sdcard into the slot.

The first goal is to interrupt the kernel boot process. For this, you need to shorten the MMC line to the ground.

More or less place of this line



and the line under the microscope (it’s some data line for MMC - I don’t know which one)



you need to do it after start booting but before the kernel load (try a reset, short to ground for success). If you succeed you’ll see the prompt:



then just change boot delay:



after that let’s try recovery your kobo:




The first-line disabled quite mode for kernel, the second read kernel from your sdcard and run recovery mode.

now just run



after that, you will see a lot of debugging information from the kernel and blinking blue led on the kobo device.

Restart and enjoy!



After that of course you need to hack again kobo for custom installation.

Happy New Year!

[NiMa]

Impressive walkthrough! Thanks for diving in and finding a way to un-brick a locked device at firmware level.