Android OTG questions

[#1]

I`m trying to set up a Lenovo A3000 7" tablet...

I have a OTG cable, to a USB 4 port.  In the ports, I plug a keyboard, a mouse and can use the other two slots for USB memory stick, etc.

If I set it up with all that plugged in.. it works fine...  but I can`t find a way to "eject" the USB stick, using the mouse or keyboard command as on my laptop...  any offers on this.... ? ? ? 

When I do unplug the USB stick... it renders the USB 4 port useless, and I have to re-boot for to use the keyboard and mouse again.. likewise, if there is no USB inserted... when I plug one in...it causes the 4 port to stop working and a reboot WITH the USB plugged in to make it all work again..

Moving on ... Obviously, when I am using the OTG with the USB 4 Port, mouse and keyboard, the Tablet is running on Battery... ok.. it runs for a couple of hours..( can`t remember how long though )... when it gets low, there is a warning message, and I have to plug in a OTG /USB cable to either the laptop, or a mains charger unit... and then can only use the touch screen for activity.

I have bought a USB to OTG converter ....  https://www.ebay.co.uk/itm/Mini-Type-C-to-Adapter-3-0-USB-C-3-1-Male-OTG-A-Female-Data-Connector-Con...

I also bought one of these,,....... https://www.ebay.co.uk/itm/Micro-USB-Type-C-to-USB-SD-TF-OTG-Connection-Adapter-Cable-for-Android-Ph...

Which has an adapter from Type c to OTG...

wondering if.... going back to the first configuration above,.. I have a spare USB slot on the 4 port ....

could I put this USB to OTG converter in there... and then plug the OTG/USB cable and mains adapter into that. to keep the Tablet charging,

while I am working on it, using the mouse, keyboard, and USB memory stick, ????

[#2]

Is this on your Linux OS, @shutter ? If so does it not show in the connected devices on there?

[#3]

@shutter 

Probably of no help but looking at the list of stuff that you have plugged in to this single port makes me question whether this is a power availability/power regulator  problem, or a small surge on the power supply when you unplug a USB stick. unless of course you are using a powered four port hub?

[#4]

@shutter 

.  but I can`t find a way to "eject" the USB stick, using the mouse or keyboard command as on my laptop...  any offers on this.... ? ? ? 

https://www.technologyhint.com/safely-remove-otg-from-android/

[#5]

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@jab1 wrote:

Is this on your Linux OS, @shutter ? If so does it not show in the connected devices on there?

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No... this is a "proper" Android 4.2 ( I think the version is) ... o.s. on this tablet....

Linux remove USB is no problem.... !

[#6]

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@Baldrick1 wrote:

@shutter 

Probably of no help but looking at the list of stuff that you have plugged in to this single port makes me question whether this is a power availability/power regulator  problem, or a small surge on the power supply when you unplug a USB stick. unless of course you are using a powered four port hub?

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No it`s not a "Powered" USB 4 port ....  so.. yes, it may well be a power surge on removing that causes it to revert to "normal" .  thanks for that suggestion...

[#7]

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@MisterW wrote:

@shutter 

.  but I can`t find a way to "eject" the USB stick, using the mouse or keyboard command as on my laptop...  any offers on this.... ? ? ? 

https://www.technologyhint.com/safely-remove-otg-from-android/

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Thanks for the linky... have read it.. and will read again later.....

cheers

[#8]

Thanks to all for the input.... how about the main question about mains powering the Tablet through the adapters in the USB 4 port ? while still using the tablet, with mouse and keyboard, etc.... ?

Am I going to cause damage, ?  or will it work.... ??     or  not ? ?? 

[#9]

@shutter 

My assumption, backed up a bit by your photos of the tracks on a PCB a couple of days ago is that the power supply pins are all connected in parallel, with no other circuitry involved.

 I guess that the risk is that the power supply kicks out more than 5V, which is regulated down at the battery and that this damages your other external devices. It might be worth checking this with a meter. From memory it's pins 1 and 4 on a Type A USB connector.

[#10]

@Baldrick1 

So .. in effect... pins 1 & 4 .. are the power lines, and they do not affect the "signal" lines 2 & 3, during any input/output operations to the usb memory stick, or the keyboard /mouse operations...

In other words.... YES !... it should charge up/keep it charged,  using the configuration that I suggested in the original post  ? ? ? ? ?

Would you agree????

[#11]

@Baldrick1  Just checked the output of the Mains psu... it shows 5v 2a on the label... running the Multimeter across the red and black wires.. it shows a variable 5.07 to 5.10 on the DC volt scale... So.. I would think that was "within tolerance"

[#12]

@shutter 

What I am saying, based on assumptions only, is that a 5V USB charger depending on its make might put out more than 5V and that this is stabilised within the tablet. If, and it is if, this is the case then it's possible that if it is connected into a passive hub that this excessive voltage could be applied to other devices plugged into that hub. Hence my suggestion that the output of the power supply should be measured. It would also be interesting to see what sort of ripple is being generated but that would need an oscilloscope.

So there might be risk of damage to the other external devices through overvoltage. There are also connections from the power lines  through resistor networks to the data pins but I would doubt this causing a problem.

EDIT

Crossed with previous one from @shutter 

At this voltage I would not expect a problem.

[#13]

@Baldrick1  OK... thanks for the techy info there... understood... just going to plug it all up and see what happens ! ..

cheers

OK...   Plugged it all up as described... not charging... so... just using a short OTG to USB cable... only... plugged in the mains charge lead,  with the adapters described... not charging.... so... either the idea does not work... or the  adapters are non functional... ..

not sure how to test the functionablity of the two adapters in use... between the OTG/USB cable and the Mains charger cable..( yes that does show "charging" as soon as it is plugged in on the OTG socket on the tablet. 

I did try another OTG/USB cable... both definitely OK...

[#14]

@shutter 

OK with every other idea failing I have given in and read the instructions, https://content.etilize.com/user-manual/1025667111.pdf If you look at page 21 (25 of the download) you will note that the 'pins' used to charge the tablet (it seems to use the shroud of the connector for one connection) are not those that you might expect. I assume that this is why this cunning idea of back charging through the normal USB power pins does not work.

[#15]

@Baldrick1  (almost cross posted just now... )   ..... OK   seen your post about pin locations....

Been looking further into this on Ebay... and find this item

https://www.ebay.co.uk/itm/4-In-1-USB-2-0-OTG-Host-Cable-Cord-Connector-with-Power-Powered-Charging/...

which,.... seems to fit the bill.... however a "similar" device mentioned that it was not a "through" power supply for charging the phone/tablet.   so I have asked the seller for clarification.