Nexus 2012 in my car, help with OTG charging and waking up. - Nexus 7 Q&A, Help & Troubleshooting

First: How do I get my Nexus 7 to charge from the OTG cable? I can connect USB devices to it but connecting the power cable of the Y doesn't seem to do anything.
Second: Is it possible to wake from tapping?
Related threads:
http://forum.xda-developers.com/showthread.php?t=2776308
(references using the Nexus 2013)
All other threads I've found relating to the OTG cable charging reference Timur's ROM which is no longer available. Is there another solution?
I've got a Nexus 2012 Wifi and all the hardware (USB DAC, amp, wiring, etc) to install this in my car. My last 2 hurdles before ripping the dash apart is the charging while connected to a USB hub and how to wake the tablet up. I was afraid of leaving the screen on all the time would burn it out and drain the battery. I wanted the ability to turn the tablet on without having the keys in the ignition. I guess I could forego that requirement and just have the tablet always on and only turn on in the ACC position.
For the wake I am thinking of creating a mechanical switch that activates the button. The power button on the tablet now will be concealed by the bezel once installed in the dash. There is an app that works but it doesn't really wake from sleep but rather creates a black screen that is tappable. I really wanted the thing to go to sleep and then wake with a tap.
I also wanted the newer android version, 6 or greater. I flashed with CM 7.1 and it works great save the two issues I'm having. Even if I had access to Timur's ROM it hasn't been updated since 4.something so I would want it newer anyway.
Any ideas or suggestions?
Thanks in advance.

I installed the BeanStalk 6.19 and I am now able to OTG charge and double-tap to wake device (no extra settings as it was included with the ROM).
My problem now is it seems to only want to OTG charge when I first plug in the OTG cable to the tablet. If it's charging and I turn off the power to the OTG (like disconnect the charging cable connected to the OTG) and then plug that charging cable back in it will not charge until I reconnect the OTG cable to the tablet. I wanted to hide the cable behind the bezel of the dashboard.
I was hoping to switch the power to the USB hub that is connected to the OTG charge cable with the ACC line from the ignition. This way I wouldn't be draining the battery at all when the keys are not in the ignition. It's only 12.5 watts so I guess I could leave it on all the time. It's getting cold here this time of year so I didn't want any type of extra drain on the battery when I didn't need it.
Any suggestions?

Related

[Q] Battery Connection Voltage/Amperage

ok here's what I want to do.
Permanently integrate a nexus 7 in my car dashboard in the double din radio opening
Remove the battery from the nexus 7 and hardwire to always on power from the car battery
Hardwire the power button to a button installed in the dash
Dashmount a usb port connected via otg for hotswapping media
Hardwire a potentiometer into the dash for volume control
all of the above is fairly simple except for power supply, otg+charging is a possible solution but a car battery wired solution is far better so what i need is information on what the battery pins supply in terms voltage/amperage so i can create a 12v to direct power converter or a device that already does this. any help is appreciated TIA
bump, if someone knows i could really use this info
b22ri22an said:
ok here's what I want to do.
Permanently integrate a nexus 7 in my car dashboard in the double din radio opening
Remove the battery from the nexus 7 and hardwire to always on power from the car battery
Hardwire the power button to a button installed in the dash
Dashmount a usb port connected via otg for hotswapping media
Hardwire a potentiometer into the dash for volume control
all of the above is fairly simple except for power supply, otg+charging is a possible solution but a car battery wired solution is far better so what i need is information on what the battery pins supply in terms voltage/amperage so i can create a 12v to direct power converter or a device that already does this. any help is appreciated TIA
Click to expand...
Click to collapse
Can't you just use the USB port to charge it? it takes 5V, and 2A. With a car battery it should have enough amps, the voltage is what you'd need to regulate.
But if you really want to take out the battery instead...can't you just use a volt meter to see what the N7 draws from the battery? I'd guess it's 3.7v lithium ion but I'm not positive. I couldn't find the specs on google either..
As far as I have read there are some major difficulties getting otg+charging to work at the same time and I need the storage space provided by external storage. Having the car power source replacing the nexus 7 battery would eliminate that problem altogether.
I was hoping that someone here had known the voltages since I don't currently own or have access to a multimeter to test for myself. Knowing the voltages in advance would give me the opportunity to see what would be entailed financially to build the project and determine if its its financially acceptable to me, if the project isn't viable the money spent on the multimeter to do the tests would be wasted as it's not something I need for anything other than this particular project. So in the interest of trying to save $20 I figured I would ask here first and that there was a good chance that someone might have the information I needed.
b22ri22an said:
As far as I have read there are some major difficulties getting otg+charging to work at the same time and I need the storage space provided by external storage. Having the car power source replacing the nexus 7 battery would eliminate that problem altogether.
I was hoping that someone here had known the voltages since I don't currently own or have access to a multimeter to test for myself. Knowing the voltages in advance would give me the opportunity to see what would be entailed financially to build the project and determine if its its financially acceptable to me, if the project isn't viable the money spent on the multimeter to do the tests would be wasted as it's not something I need for anything other than this particular project. So in the interest of trying to save $20 I figured I would ask here first and that there was a good chance that someone might have the information I needed.
Click to expand...
Click to collapse
oh ok..well have you taken a look at the battery? It should just be 3.7v, I don't think it would be too hard to find which pins it is. Maybe take a LED and test it across the pins?
Also, I have heard reports OTG + charging is working fine on CM10 with a patched kernel. you might want to check this thread: http://forum.xda-developers.com/showthread.php?t=1934722
mvmacd said:
oh ok..well have you taken a look at the battery? It should just be 3.7v, I don't think it would be too hard to find which pins it is. Maybe take a LED and test it across the pins?
Also, I have heard reports OTG + charging is working fine on CM10 with a patched kernel. you might want to check this thread: http://forum.xda-developers.com/showthread.php?t=1934722
Click to expand...
Click to collapse
I've been participating heavily in the arena of OTG + charging simultaneously, as well as using USB audio.
To answer the OP's question directly: I have demonstrated (to myself) that I can power down my Nexus 7, disconnect the battery connector, plug in my y-splitting OTG cable with power in one plug, and an unpowered USB hub in the other plug. [Plugged into the USB hub is a flash drive, USB DAC, and I'm sure a keyboard would also be an option.] Then I turn on my Nexus 7, and in the OS it shows the battery at 0%, but charging (obviously it's not actually charging without the battery present...).
I even booted up the Nexus 7 normally, with all the same stuff connected to USB, and then disconnected the battery connector... and the Nexus 7 remained on!
I've thought about integrating some sort of tactile switch that essentially disconnects the battery whenever the switch is depressed. So then part of the car mount could be a little protrusion that presses this switch whenever the tablet is inserted into the car mount. That way whenever the tablet is removed from the car mount, the battery will take over without removing power from the motherboard.
MetalMan2 said:
I've been participating heavily in the arena of OTG + charging simultaneously, as well as using USB audio.
To answer the OP's question directly: I have demonstrated (to myself) that I can power down my Nexus 7, disconnect the battery connector, plug in my y-splitting OTG cable with power in one plug, and an unpowered USB hub in the other plug. [Plugged into the USB hub is a flash drive, USB DAC, and I'm sure a keyboard would also be an option.] Then I turn on my Nexus 7, and in the OS it shows the battery at 0%, but charging (obviously it's not actually charging without the battery present...).
I even booted up the Nexus 7 normally, with all the same stuff connected to USB, and then disconnected the battery connector... and the Nexus 7 remained on!
I've thought about integrating some sort of tactile switch that essentially disconnects the battery whenever the switch is depressed. So then part of the car mount could be a little protrusion that presses this switch whenever the tablet is inserted into the car mount. That way whenever the tablet is removed from the car mount, the battery will take over without removing power from the motherboard.
Click to expand...
Click to collapse
Lol, yes, I think I had you in mind when I said that.. I'm still waiting for my Y cable. I won't get it till at least 1.5 weeks..
MetalMan2 said:
I've been participating heavily in the arena of OTG + charging simultaneously, as well as using USB audio.
To answer the OP's question directly: I have demonstrated (to myself) that I can power down my Nexus 7, disconnect the battery connector, plug in my y-splitting OTG cable with power in one plug, and an unpowered USB hub in the other plug. [Plugged into the USB hub is a flash drive, USB DAC, and I'm sure a keyboard would also be an option.] Then I turn on my Nexus 7, and in the OS it shows the battery at 0%, but charging (obviously it's not actually charging without the battery present...).
I even booted up the Nexus 7 normally, with all the same stuff connected to USB, and then disconnected the battery connector... and the Nexus 7 remained on!
I've thought about integrating some sort of tactile switch that essentially disconnects the battery whenever the switch is depressed. So then part of the car mount could be a little protrusion that presses this switch whenever the tablet is inserted into the car mount. That way whenever the tablet is removed from the car mount, the battery will take over without removing power from the motherboard.
Click to expand...
Click to collapse
Am i understanding you correctly? If i unplug the battery, and just have the OTG cable plug into the charger, it would be able to power on and off and run just fine?
ho9984 said:
Am i understanding you correctly? If i unplug the battery, and just have the OTG cable plug into the charger, it would be able to power on and off and run just fine?
Click to expand...
Click to collapse
This was how it worked while the N7 was running Jelly Bean 4.1.2. I can't guarantee it would operate the same on 4.2.2.
MetalMan2 said:
This was how it worked while the N7 was running Jelly Bean 4.1.2. I can't guarantee it would operate the same on 4.2.2.
Click to expand...
Click to collapse
Someone tried it on Reddit. Removed the battery and tried powering it on with only OEM charger. The screen just flickered. They were on 4.2.2
I am curious about removing the battery and hardwiring as well as I am gathering parts to put my Nexus 7 in my car dash. The problem w/ the OTG route - it gets pretty hot down here and I'm afraid the battery will have some long term issues (ie...could leak/explode). So, hardwiring it would be preferred.
Any ideas for hardwiring?
with the new nexus 7 coming out I am just going to mount the wireless charger behind the tablet dock, now I just hope otg is supported with the slimport on the new nexus 7

The ultimate solution for In-car entertainment, but how ?

Hi folks.
I am looking into installing my Nexus 7 permanently in the car, needing the use of being able to charge it, and use an USB DAC at the same time.
This page promises to have an ROM that is able to do that, but I have been unable to get that to work at all. I do not want to upgrade to 4.2.x due to the known bugs, so it's 4.1.2 for me at the moment.
http://goo.gl/fQ2LL
Using a stock ROM i am able to start/stop playback with Tasker registering "AC charge" - How do i go about this when using an OTG-Charge ROM ?
I do not want to charge the tablet when i'm not driving the car, what happens to the USB DAC when the power is cut, does it lose sync with the Nexus 7, and requires a reboot to function again?
So in short this is what I had in mind:
Ignition on -> Tasker registering AC power, starts playing music.
Ignition off -> Tasker registering power is off, pauses music, tablet go to sleep after at set amount of time.
I am realising that this may not even be possible, I can't see how the USB connection should survive, when the power is being cut, but maybe some of you more experienced guys can chime in on this subject.
I would rather not make any modifications to the tablet, but if this is neccessary to make it work, i'll have to do it (e.g. feed power directly to the battery with Li-Ion charging circuit.
Any other ideas of letting Tasker know that the car is started ? I have a bluetooth handsfree in the car, but that is connected to my iPhone, so I cannot use that as a wakeup function when that connects as Tasker do not have any "Blutooth Near" functions...
I've tried to connect 5V to the POGO pins on the side, but it won't charge the battery this way (it's enabled in the 4,2,x ROM afaik)
I've wired up my USB OTG cable like this: http://goo.gl/vqc3F
Any ideas is very welcome, as I cannot see how to do this.
Regards,
// Per.
I'm looking at doing the same thing but also a USB flash drive and also a Joycon EX Steering Wheel Control PC Interface via USB.
What I'm debating on doing is instead of hooking the charger to the ignition to turn on n off with he car I'm thinking about using constant power and hooking up an input on the joy on to the ignition 12V and setting the screen to come on n off with the car.
Unfortunately this means the tablet will be on the charger 24/7 but not sure how else to make sure everything reconnects as it should.
Anyone else have any ideas?
Sent from my Nexus 7 using xda app-developers app
I'm planning on doing a car install with all the bells and whistles also:
Joycon Ex
USB DAC (E10 or Behringer?)
USB Hard drive
Powered USB Hub
From what I've read of other threads, some people have trouble getting the DAC to reconnect after power changes, and some don't. In general, the rule of thumb is as long as the N7 is booted with the DAC attached, you should be able to unplug (or stop powering it), and then start again. There seem to be some behavioral exceptions with this (e.g. if you don't stop audio playback before putting the tablet to sleep with tasker, when it wakes up, you may need to fiddle with it before it starts working again).
It's a long thread, but I'd recommend reading this:
rootzwiki.com/topic/30615-can-you-charge-usb-host-mode-simultaneously/page__st__140
Timur has provided multiple patches that are trying to satisfy everyone's exceptions in trying to get this working.

[Q] Nexus 7 short circut damage help, please.

So, I apparently did something very stupid with my new Nexus 7.
I have a few 1 TB external hard drives, which don't get enough power via an OTG adapter from the Nexus 7 to run. So, I purchased a two into one cable -- that is, a cable that combines two male USB A plugs into one Micro USB B plug so that a USB 3.0 hard drive can use two USB 2.0 ports to have enough power. I had planned to use this to enable use of the hard drives with the Nexus 7 while traveling by plugging one cable in the tablet and the other into a charger.
When I got the cable I tested it by plugging one of the USB A plugs into my Nexus 7, and then I plugged the other into my computer's USB port. The Nexus 7 promptly shut down, the computer complained of a power surge on the USB port, and a distinct smell of melted plastic came from the computer's USB port. I guess the combining cable didn't combine so much as it just acted like a double headed male A USB cable and shorted things out?
The Nexus 7 refused to restart afterwards until I it plugged it into its charger. It works now, mostly. However, if its battery charge is above about eighty-seven percent then it always reports that it is charging, regardless if it is plugged in or not. And if I plug it into a computer while it is reporting that it is charging I have to restart the tablet to get it to connect to the computer -- I guess it thinks it is connected to a charger and doesn't bother checking for a data connection unless restarted.
The level where it stops thinking it's charging varies somewhat -- I've had it still claim to be charging all the way down to eighty-two percent charge, and by repeatedly opening the battery app over and over again I have been able to get it to notice that it's really not charging all the way up to ninety-one percent, but no higher, and I have to open and close the battery app an increasing number of times for every percent that it goes up over eighty-seven before it will notice it's not charging.
Any idea what kind of damage I'm looking at? How to fix it? Whether I can get the warranty people to fix it free of charge? If yes, whether they will send me a new one or just fix the one I have? Whether it's worth getting fixed since it mostly still works, and doesn't really bother me as long as it doesn't get worse?
Nothing?
Nothing from anyone?
Try replacing the internal USB plug? About $25. Easy to do your self.

Nexus 10 battery draining faster than charging when in use - fixable?

Hi,
I just picked up a used Nexus 10 for an app I'm building. I specifically needed this tablet as it an NFC reader both on the front and back of the device. Everything was great until I realized that the battery drains faster than it charges with the screen on and in use. I am using the POGO charger with what I believe is the stock Samsung plug (output 2A).
I've done some searching and it seems that this is a known issue with this tablet. Are there any known solutions?
Will buying and installing a new battery remedy this? I don't even necessarily need it to charge back up, I just need it to hold steady at its current charge while the screen is on and in use. Thank you!
OK, I realized this is because I simultaneously have a micro USB cable plugged in to a serial device and am using the Nexus 10 as an OTG host device - so even though it shows charging, it's actually not charging at all it appears hence the draining. If I unplug the micro USB device (which supplies its own power, even), the Nexus 10 begins incrementing battery %, slowly but surely.
I will try getting a Y cable for the micro USB portion per a thread I found on androidcentral.

Nexus 7 wiring??

Hello all,
First thread here and hoping you guys and girls with more experience can help.
Basically I am fitting my nexus 7 2012 in my car but its got the common charging problem where my battery drains faster than I can charge it.
I have ordered a new USB port strip as I've read that can fix it and fingers crossed with that.
My problem/requirement:
1. I want to charge the tablet via the usb port using a hardwired 5V 2A device this will be plugged into a otg y splitter which is then plugged into the tablet.
2. The USB A side of the splitter I want to connect to my cars ECU (it has a USB port) so I can read the data on that (basically a very expensive memory stick)
I wanted to confirm that this would work and id be able to read data at the same time as charging it.
I also wanted to double check I'm not somehow going to send my 5v 2a power down into my ECU and set it on fire
On a side note, if my new USB port replacement doesn't solve the issue of charging the tablet i will have to remove the battery and hardwire it in, will i still be ok with using the USB port for the ecu while charging hardwired with no battery?
Kind Regards
Tim
Getting any USB 2.0 device to take current while hosting is tricky.
Usually it involves talking directly to the PMIC (power management IC).
If it's a fixed installation, why not remove the battery?
It will avoid the grief of the battery swelling up, which is not too unusual for things plugged in all the time.
I've been using a Nexus 7 (2013) for a few years, but just charging on USB.
It started falling out of its nice holder.
That's when I realized that the battery was all puffed up making the back convex.
I cut off the battery cell itself on the metal tabs and soldered in wires to a 4 V 2 A supply.
I found out that the BMS is a bit balky, it refused to turn on.
So I connected it to USB to "charge" it for about 10 seconds.
Then I could turn it on (without the USB).
Ok, I could have bypassed the BMS entirely but that can be a whole 'nother can of worms too.

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