Mobile devices from the inside. Study of YB1-X90L Tablet Boot Modes

1. Introduction

Let's continue to consider the YB1-X90L tablet, which I started exploring in a previous post:


Figure 1 . General view of the tablet

Google search revealed that the tablet was created on an Intel Atom x5-Z8550 processor with 4 cores [1,2]. For the user, as always, there are 2 external controls for standard use:

• Power button - turn on / off the tablet;
• rocker Vol + / Vol- - volume control of the built-in speakers, which, by the way, are two.

Well, after experimenting with them, I found that there are 4 options for downloading. So this article appeared ...

2. Tablet boot modes

The YB1-X90L fully turned off tablet can be turned on in four ways, i.e. run it in one of four operating modes:

1. BOOT - loading the OS;
2. FASTBOOT - FASTBOOT mode;
3. TEST - test mode;
4. DNX FASTBOOT - FASTBOOT for DNX.

Let's look at them one at a time.

2.1. BOOT mode (OS boot)

This mode is used most often because Allows you to download the tablet for the average user. At the same time, the standard MU firmware download is performed : BOOTLOADER-> BOOT-> SYSTEM .

To load into this mode, you need to press the Power button on the turned off tablet and hold it until a sound signal appears (approximately 1 second). After 3-5 seconds, the manufacturer’s logo will appear on the screen:


Fig. 2. Lenovo logo

Your further actions are determined only by desires and imagination as a user.

Let's move on to the next mode.

2.2. FASTBOOT mode

This mode is used to perform special actions to restore the tablet. This loads FASTBOOT and awaits further instructions from the user.

To enter it on the off tablet, you need to hold down the Vol + volume up button and then press the Power button . Hold them together until a beep sounds. Then the power button can be released (this is about 1 second after the start of the download), but continue to hold down the Vol + button until the manufacturer’s logo appears on the screen (about 3-5 seconds more). A few seconds after the manufacturer’s logo appears, a window appears saying FASTBOOT MODE, in which you can select one of the operating modes indicated in the selection window, highlighted in yellow by a yellow line in Figure 3:


Figure 3. Operating modes from FASTBOOT

This window also additionally displays some auxiliary information: serial number, bootloader lock status, protection mode status, etc. From this mode, you can execute any fastboot command yourself. If a tablet in this mode is connected to a PC, then using any terminal it is possible, for example, to flashing a tablet or any one partition, remove or set the bootloader lock, etc.

If you change the state of the selection window, you can run the following commands:

• boot into recovery mode ( RECOVERY MODE );
• reboot into OS ( REBOOT );
• restart bootloader ( RESTART BOOTLOADER );
• turn off the power of the tablet ( POWER OFF );
• booting the OS ( NORMAL BOOT ).

The command is selected using the volume control buttons Vol + and Vol- , and the selected command is launched by the Power button . Exiting this mode is possible either using the above FASTBOOT commands , or by turning off the tablet, i.e. holding the POWER button for 5-10 seconds.

Let's look at each of the modes individually.

2.2.1. RECOVERY MODE

When you select this command, the tablet will boot into recovery mode, i.e. RECOVERY . Availability via ADB and the availability of ROOT access in this mode is determined only by the settings of the recovery mode itself. The stock option is not rich in possibilities, so many users as recovery sets custom-recovery , such as TWRP.

2.2.2. REBOOT mode

When this command is selected, the tablet will completely reboot into OS boot mode, similar to BOOT mode ( see section 2.1 ).

2.2.3. RESTART BOOTLOADER mode

When this command is selected, it will reboot again into BOOTLOADER mode .

2.2.4. POWER OFF mode

Selecting this command will completely turn off the tablet power.

2.2.5. NORMAL BOOT mode

Selecting this command will continue loading the OS without rebooting.

2.3. Download to TEST mode

To enter the test mode with the tablet turned off, hold down the Vol- volume down button and press the Power button . Hold them until a beep sounds. Then you can release the power button (this is about 1 second from the start of the download), but continue to hold down the Vol- button until the manufacturer’s logo appears on the screen (about another 3-5 seconds). About 5 seconds will elapse before fully loading into TEST mode : Fig. 4. TEST Command Menu In this mode, the following test commands can be executed:

1. Board Test - a choice of tablet tests.
2. Current Test - execution of previously selected (current) tests.
3. RF Antena Test - RF Antenna Test .
4. Test Info - test data.
5. Reboot - restart the tablet (exit test mode).
6. Droidboot
7. RF calibration & IMEI write - RF calibration and recording IMEI values.
8. Factory Reset - Reset to factory settings.
9. Erase Userdata - clear (delete) the contents of Userdata .
10. Security Boot - boot in Security Boot mode .
11. PMIC FW Update - Install PMIC updates .

Navigation by commands is carried out by the volume control buttons Vol + and Vol- , and the selected command is launched by the Power button .

To exit this mode, run the Reboot command - the OS will boot, or hold down the Power button for about 10 seconds. until completely turned off.

2.4. Download to DNX FASTBOOT mode

This mode is designed to restore tablet loaders.

To enter this mode with the tablet turned off, hold down both of the volume rocker buttons Vol + and Vol- simultaneously and press the Power button . Hold them until a beep sounds. Then you can release the power button (this is about 1 second from the start of the download), but continue to hold down the Vol + and Vol- buttons until the manufacturer’s logo appears on the screen (about 3-5 seconds more). DNX FASTBOOT MODE appears on the screen under the logo :


Fig . 5 DNX mode

and the tablet freezes, waiting for commands to work with DNX .

You can exit this mode only by turning off the tablet, i.e. holding the POWER button for 5-10 seconds.

3. Conclusion

We studied the boot modes and the layout of the tablet’s memory, in the next publication we will continue to perform practical actions and try, for example, unlock the bootloader to install custom-recovery and get ROOT access.

4. Sources of information

1. Lenovo Yoga Book review: a guest from the future .
2. Review of the tablet laptop Lenovo Yoga Book Android .