Cube U25GT-C4W USB OTG and Charging Weirdness

[mmkarim]

Hi All,

I have a U25GT-C4W running Android 4.4.2 KitKat. I have managed to root the tablet.

The tablet has a separate charging DC 5V in jack as well as a USB Micro OTG connector. It connects to PC fine and I am able to detect it through adb.

It is also able to detect OTG devices connected to it such as a Keyboard, Mouse and a USB Stick/Flash Drive.

Out of all the China tablet clones that I have tested, this one has a peculiar behavior. See picture attached to understand this behavior.

If I connect DC 5V plug to tablet, tablet starts charging.
Then when I connect a USB Mouse, the tablet STOPS charging after 5 seconds (Not normal behavior).
Then when I remove the USB Mouse, tablet starts charging again (after 10 seconds).

I have tested other tablets with separate DC 5V jack and they do not show this behavior. This is not normal.

Tablets I have tested:
ValuePad VP112
King's Hong Kong H704A

When these above tablets are charging with DC 5V, and then I connect USB Mouse, these tablets do not stop charging like the Cube U25GT is doing.

Has anyone else experienced this type of issue? Has anyone solved it? Are there any custom kernels/system that I could use for this to solve the problem? I don't usually post questions on the forum because I usually find the answers I need after searching for a while, but this has been a baffling situation.

Hopefully someone will answer. Let me know if you have any questions about my issue.

Thanks.

[rrileypm]

It all really depends on how the charging circuit is designed.

USB provides 5v...correct. Many, but not all tablets have the option of charging through the USB port. I have a Pipo M7 Pro, U8, P9 and an iFive Mini 3GS...all designed to charge from a USB cable. They all work just fine using the USB plug from a standard phone charger...but not as well from a PC USB because of lower voltage. I've never had the notion to even try charging with another external device plugged in.

When you plug in multiple devices via USB, there are fluctuations in the voltage. If there is an LED on the mouse or keyboard...for instance...some voltage must be diverted to operate that external device.

These tablets are designed to run/charge in a very narrow margin of error with regard to voltage. So in order to keep circuits from failing...there must be some type of protection that kicks in that will turn off charging while an external device is connected. It's actually a pretty good idea...just in case the external device could suffer damage if exposed to an external 5 volt circuit that it isn't designed to deal with it.

I've heard of several people trying a powered USB hub to charge and run other devices...but again, it works on some units...but not on others....but if you are going to go that route...you might as well just use the regular charger. That would involve a less complicated setup.

If it's important for the operation of your device to always have an external input device while you are charging....a bluetooth device might be a better alternative.

[mmkarim]

Thanks

Thanks for the input Riley. Really appreciate it.

It all really depends on how the charging circuit is designed.

USB provides 5v...correct. Many, but not all tablets have the option of charging through the USB port. I have a Pipo M7 Pro, U8, P9 and an iFive Mini 3GS...all designed to charge from a USB cable. They all work just fine using the USB plug from a standard phone charger...but not as well from a PC USB because of lower voltage. I've never had the notion to even try charging with another external device plugged in.

When you plug in multiple devices via USB, there are fluctuations in the voltage. If there is an LED on the mouse or keyboard...for instance...some voltage must be diverted to operate that external device.

These tablets are designed to run/charge in a very narrow margin of error with regard to voltage. So in order to keep circuits from failing...there must be some type of protection that kicks in that will turn off charging while an external device is connected. It's actually a pretty good idea...just in case the external device could suffer damage if exposed to an external 5 volt circuit that it isn't designed to deal with it.

I've heard of several people trying a powered USB hub to charge and run other devices...but again, it works on some units...but not on others....but if you are going to go that route...you might as well just use the regular charger. That would involve a less complicated setup.

If it's important for the operation of your device to always have an external input device while you are charging....a bluetooth device might be a better alternative.