Kobo Libra H2O (kobo-librah2o)

Features
Flashing
USB Networking	Works
Internal storage
SD card
Battery
Screen
Touchscreen	Works
Multimedia
Camera Flash
IR TX
Connectivity
WiFi	Works
NFC
Miscellaneous
FDE
USB OTG
HDMI/DP
Sensors
Accelerometer	Broken
Magnetometer
Ambient Light
Proximity
Hall Effect
Haptics
Barometer

Kobo Libra H2O N873
	; insides
Manufacturer	Kobo
Name	Libra H2O N873
Codename	kobo-librah2o
Released	2019
Type	ebook reader
Hardware
Chipset	Freescale i.MX6 SLL
CPU	1x 1 GHz Cortex-A9
GPU	PXP + EPDC
Display	1680x1264 eink/epaper
Storage	8GB eMMC
Memory	512M
Architecture	armv7
Software
Original software	Kobo Firmware
postmarketOS
Category	testing
Pre-built images	no
Mainline	yes

Contributors

Andi (has only a device with a broken screen)

Users owning this device

Andi (Notes: broken screen)
Lostnet (Notes: ereader)
M0Rf30
Minosimo
Omni

Mainlining status

A basic devicetree is upstream, display waits for testing

Accessing the internal storage

Contrary to non-waterproof eBook readers, the Libra H2O does not have an internal replaceable µSD but an internal eMMC, so things have to be flashed on the device.

With the factory uboot, the command to enable mass storage mode is

 ums 0 mmc 0

This can be run in a serial console with the help of a usb debugger, or we can flash a bootenv using fastboot. The needed binary is at: https://misc.andi.de1.cc/ums-env.bin

Flashing this bootenv will cause the following command to run at boot:

 bootcmd=ricoh_watchdog disable; ums 0 mmc 0

Enter fastboot by pressing pagedown while powering on the device, and flash the bootenv using

 fastboot flash bootenv ums-env.bin

after the flash succeeds, do

 fastboot reboot

The emmc will appear as /dev/sdX on your host. It is probably a good idea to do a full backup at this stage.

 sudo dd if=/dev/sdX of=kobo.img status=progress

Alternately, you can download a stock image from here: https://archive.org/details/kobo_librah2o_N873_factory

With this bootenv, the kobo will always boot to mass storage mode. To restore the original bootenv, write back the u-boot.mmc which is located in the rootfs. To do this directly, you can use:

 mount /dev/sdX1 /mnt
 dd if=/mnt/etc/u-boot/mx6sll-ntx/u-boot.mmc bs=128K seek=6 of=/dev/sdX
 umount /mnt

You can also download u-boot.mmc from here: https://archive.org/details/mx6sll-ntx_u-boot_mmc

Installation

Enable mass storage access in U-Boot (see above) and install using pmbootstrap --sdcard

If the flash fails with an error like "Partitions have been written, but we have been unable to inform the kernel of the change", unmount all partitions on /dev/sdX, reboot the kobo, make sure no partitions are auto-mounted, and try again.

With the pmOS-installed bootloader, you can enter mass storage by Page*Up* while powering on

Recovery

If nothing which looks like a bootloader is found on startup, the following device

hid-generic 0003:1FC9:0128.001B: hiddev1,hidraw1: USB HID v1.10 Device [   NXP    SemiConductor Inc  SE Blank 6SLL] on usb-0000:00:14.0-6.1/input0

appears. It can be accessed using a tool called uuu from a package mfgtools. This allows the device to be restored if the eMMC is inaccessible (corrupted MBR, formatted partitions).

You will need:

A USB serial debugger
Stock uboot image
mfgtools

Serial debuggers are cheap and easy to come by, check an electronics store or search for a hackerspace near you.

The stock boot image can be extracted from the full eMMC image using:

 dd if=kobo.img of=uboot.img bs=128k count=4

To connect the debugger, pry off the back of the kobo and solder or otherwise connect the Rx, Tx, and Ground pads to the debugger. Do not connect the power lead.

Note that the Rx from the debugger needs to be connected to the Tx on the kobo, and vice versa.

The goal is to use uuu from mfgtools to send the stock uboot image to the kobo over usb, which will load it from RAM. You can then interact with the loaded bootloader using the serial console.

It is useful to keep dmesg open in the background to follow the device state.

 sudo dmesg --follow

Open a serial console in a separate terminal:

 sudo bt /dev/tty0
 or
 sudo screen /dev/tty0

Now plug in and power on the kobo via the usual usb connection. Check that uuu sees your device:

 sudo uuu -lsusb

Send and boot the stock uboot image:

 sudo uuu -v -b spl uboot.img

This command will appear to hang, but you should see output in the serial console to confirm that uboot is working. If there is no console output, check whether the RX light on your debugger blinks. If not, there is probably something wrong with your debugger or your hookup. The kobo uses a default baud rate of 115200, there is no need to change it.

Now that you have access to the serial console, there are a few useful commands.

boot the device:

 boot

enable fastboot:

 fastboot 0

enable mass storage mode:

 ums 0 mmc 0

The console may appear garbled, react slowly or partially to key input, but that's ok. Just type the command normally and press enter.

With mass storage mode enabled, we can restore the factory image using:

 sudo dd if=kobo.img of=/dev/sdX status=progress

This will take several hours to complete. Keep in mind that if you imaged your kobo after flashing the bootenv to enable mass storage mode, you will need to restore the bootenv as described above.

You should now have a working kobo!