YESS! IT'S ALIVE! |
I've openend the tablet again, removed the heat spreader (or EM shield ?) to have easier access to the NOR-flash SPI chip containing the firmware
connected ch341a chip programmer + 1.8V level converter + SOIC8 clip and after flashing the latest firmware
it booted up like nothing happened.
So at the source of the problem it's likely there was some ACPI firmware fuckup!
The last time it was working correctly BEFORE not being able to boot anymore with led OFF happened the following:
I running Android with charger and external keyboard connected (I have the latest metallic one),
then i turner off the tablet (shutdown, not suspend) leaving the keyboard and charger connected
and closed the tabled+keyboard like you do wth a notebook computer.
Later I disconnected the keyboard FIRST and then the charger to move it to another place in the house, reconnected the charger, tried to turn the tablet on and ...nothing.
I guess that by having the external keyboard connected the firmware must be in some low-power ACPI mode, non a complete shutdown, not suddenly at least.
(while I tried to bring it back to life with the triple quick pressure + long pressure of the power button I noticed it didn't shut down completely after the long pressure if the
keyboard was connected).
I guess that while powering down the ACPI firmware stores some status data in the NOR-flash and if the (supposedly) "fixed" hardware configuration at the next boot changes suddenly, the initial bootloader
goes into some sort of panic mode and stays there until the NOR-flash chip is rewritten completely (rewritting the bios and writing "safe" dfault parameters for ACPI/hardware status data).
Usually on PC/notebook devices there's a special "emergency recovery" or "panic mode recovery" sequence to tell the device to boot using "safe" parameter for everything
exactly for situations when something like this happens, maybe Insyde (those that provided the bootloader, IIRC) didn't tell Chuwi what is the sequence of actions to activate it or it kicks in only AFTER the initial bootloader
(the one that allows to choose between booting Android or Windows) selects the successive bootloader to execute ?
Anyway, a NOR-flash rewrite seems to do the trick ... if you have the right tool and know how to do it properly.