I've bought a no-brand tablet based on Allwinner A33 CPU running Android 4.4.2 to be put as a media system in a car. This tablet has few specific features which makes it suitable for the task but the most important one is "Quick boot" mode which keeps tablet running while powered off and then booting it in a matter of seconds (4-5 seconds) so I don't have to wait for the whole system to boot (something similar to hibernation).
I'd also like to mention that I have a lot of knowledge working with the hardware and software but my question is purely software-related.
Since I want to keep tablet charged at all times (to power RTC and to enable quick boot feature) via 5V DC in plug, when I turn off the tablet normally or via quick boot it displays the charging animation.
What I have noticed is that there are two different animations:
- When tablet is powered down normally it displays animation from the
bootpartition and it seems it's handled by the
chargerapplication which is also found in the same partition
- When tablet is powered down via quick boot it displays similar animation but I'm unable to find where this is called from.
At first I thought it fetches animation images from the
bootloader partition but when I remove those images animation is still playing. Then when browsing through the U-Boot code I've seen it also handles charging animation but I've recompiled and updated the U-boot but animation is still playing.
I've also noticed when tablet is turned off via quick boot option, it keeps Android system running because
dmesg gets filled with messages from the
healthd application regarding the status of the battery without interrupting even when the tablet is turned off.
Ideally, I'd like to completely avoid powering on screen while tablet is turned off (car is turned off) but I'm running out of options and thought to look for a help here.
Anyone has any idea regarding this matter?