# Nexus 7: The Ultimate Car Stereo



## jmcguire525

I know a few people here are considering using the N7 as a head unit. There's a professional install in a Ram on youtube that was done well but IMO far from perfect...

The ideal way to do this is have the audio output digitally through USB and use an external DAC, you are also going to want to be able to charge at the same time... These can both be achieved with a simple flash of an .img file by Timur. The only thing remaining is to choose an amp to drive your speakers and add a volume control or sound processor. I'm personally using a Turtle Beach Micro II DAC with optical output and pairing it with a Audison BitOne and 5k amp that accepts optical to keep the whole stream digital (yes its overboard but makes things simple)

What you need:
-Nexus 7 with https://github.com/mehrvarz/files/raw/master/boot-cm10-grouper-host-mode-power-2012-10-22.img flashed
-USB OTG Y cable with Micro Power http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=110965743382
-Your choice of USB DAC
-Amplifier

I have my N7 setup with a 15 screen cutoff and I turned on screen awake while charging in dev options, this forces the tablet screen to turn on and off in sync with the cars ignition (and will hopefully be enough charge while driving to keep it running throughout the week)

I will be tethering my phone to the tablet for internet, TuneIn radio gets all the stations I listen to and allows me to rewind, pause, and record, Google music for everything else, and Torque Pro for some cool widgets to see what kind times my Trailblazer SS can put down.

I'll add pictures and video once the install starts and try to help anyone else that decides to do something similar


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## CaucasianAsian

Subbed! I might get another N7 for Christmas and I would really love to install my extra in my car.

Sent from my Nexus 7 using Tapatalk 2


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## SkyBehind

I've been doing the same thing, though streaming through bluetooth. But in addition to internet streaming, I wanted to be able to play off a hard drive. So I got that working, only problem is that when I kill the power to the HDD, you have to reboot before you can remount. Also, it's read only.

Faux123 kernel has write NTFS and can remount without reboot, but his OTG + Charge flag resets on reboot. I've heard that he added Timur's Patch #2 in his latest beta, so we'll see.


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## jmcguire525

Puffmais just brought something to my attention. I mentioned having the screen turning off with the ignition and that it happens when the tablet no longer has AC power, this will be a problem because once the power source is cut off the tablet will need to reboot to work with the DAC again. This may be fixed in Faux123 kernel mentioned above, if not we may need some help from a kernel dev getting the DAC to remount after charging is restored.


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## jmcguire525

Adding to the post above, Faux123 kernel didn't help with the problem, every now and then it will reconnect with the DAC but I haven't been able to figure out any pattern on why it does one time but not the other 10. Hopefully this can be fixed


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## sledge3n8

jmcguire525 said:


> Puffmais just brought something to my attention. I mentioned having the screen turning off with the ignition and that it happens when the tablet no longer has AC power, this will be a problem because once the power source is cut off the tablet will need to reboot to work with the DAC again. This may be fixed in Faux123 kernel mentioned above, if not we may need some help from a kernel dev getting the DAC to remount after charging is restored.


Sent from my Nexus 7 using Tapatalk 2

Why don't you just tie the power to the N7 into the HOT side of the ignition circuit? There is always power there. The only downside is your Nexus will always be "on". This would still require weeks to drain the battery if the car was off and the N7 was left turned on.

There is also a hot wire in the harness for your stereo. This is the connection that keeps your clock running so you don't need to reset the time whenever you turn your car back on.


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## puffmais

do you think it would last weeks to drain the battery??

and than the display is always on, thats not so cool...or you must hit a button to turn it on/off, and hit another button to start play music. every time! also stop the music and turn display off when you leave the car...


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## jmcguire525

the problem then is there is no way to make the screen turn on and off without keeping a magnet around which would get very annoying. I want my install to be somewhat permanent where you only see the screen and do not have access to the power and volume buttons.


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## Turdbogls

jmcguire525 said:


> the problem then is there is no way to make the screen turn on and off without keeping a magnet around which would get very annoying. I want my install to be somewhat permanent where you only see the screen and do not have access to the power and volume buttons.


maybe use tasker. set up profiles for when you are using certain apps. like music and tunein ect you could have screen off set to like 20 minutes. but when no apps open, set it to 15 seconds.

and maybe use some gesture proximity sensor thing to turn the screen on. i am pretty sure there is an app that does that.


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## jmcguire525

Turdbogls said:


> maybe use tasker. set up profiles for when you are using certain apps. like music and tunein ect you could have screen off set to like 20 minutes. but when no apps open, set it to 15 seconds.
> 
> and maybe use some gesture proximity sensor thing to turn the screen on. i am pretty sure there is an app that does that.


That could work, but it still requires closing out of apps before I get out of the car to make sure the screen turns off, hopefully I can find out what is causing the inconsistentcy when it comes to reconnecting with the DAC and sending the audio thru USB


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## EniGmA1987

jmcguire525 said:


> the problem then is there is no way to make the screen turn on and off without keeping a magnet around which would get very annoying. I want my install to be somewhat permanent where you only see the screen and do not have access to the power and volume buttons.


Why not use an NFC setup and make it so when you get in the car you swipe your phone in front of the N7, that would turn the screen on and start playing music. Swipe phone on the way out to stop playing music and turn the screen off


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## happypizza

EniGmA1987 said:


> Why not use an NFC setup and make it so when you get in the car you swipe your phone in front of the N7, that would turn the screen on and start playing music. Swipe phone on the way out to stop playing music and turn the screen off


I dont think NFC would respond from being swiped by the screen. It usually only works over the "Nexus 7" on the back of the unit for me. Plus would scratch over time.


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## TheTyler0013

I will be watching this thread I an wanting to do this in my explorer. Since the N7 is a perfect fit where my current radio is.

Sent from my Galaxy Nexus using RootzWiki


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## monk2413

You could try to split the USB going to the DAC into two ends. One with just the data wires and the other with just the power wires. Then plug the one with the data wires into the N7 and the one with the power wires into a constant source from the car. This would allow the N7 to be on a switched source and have the screen turn on and off with the ignition without losing power to the DAC. Not sure if the tablet will still recognize the DAC without the power wires but there's only one way to find out. Great thread tho. Before I read this I was planning on getting my audio through the 3.5mm jack and splitting it to RCAs to my EQ.


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## railroad

This guy has done it, said he'd do a writeup. Not sure how he dealt with screen on/off but you could send him a message on YT and see what he did..

I'm thinking of doing the same thing in my car.


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## jmcguire525

[background=rgb(245, 245, 245)]I think I have a solution that will work on the hardware side. The picture should be self explanatory, V&G are your power and ground +&- are your data wires. This should allow the DAC to stay on at all times by being connected to the hot wire in the car and the tablet will be connected so that it only has power when the car is running.[/background]


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## tallnerd1985

There is also a DIY Arduino project that uses ADK to turn the tablet from sleep to on with ignition+power along with a DAC for the audio. This would be the cleanest and most ideal way of using a N7 as a HU. Then, with the audio out, just connect to a EQ/Crossover for Front/Rear/Sub control.

Sent from my Galaxy Nexus using Tapatalk 2


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## jmcguire525

tallnerd1985 said:


> There is also a DIY Arduino project that uses ADK to turn the tablet from sleep to on with ignition+power along with a DAC for the audio. This would be the cleanest and most ideal way of using a N7 as a HU. Then, with the audio out, just connect to a EQ/Crossover for Front/Rear/Sub control.
> 
> Sent from my Galaxy Nexus using Tapatalk 2


Do you have more info or a link to where this is being discussed?


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## tallnerd1985

Your best bet is to Google "USB DAC ADK". There are some documentation on how to do it but it all just needs to be pieced together.

Sent from my Galaxy Nexus using Tapatalk 2


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## jmcguire525

I switched out the Micro II for a Behringer UCA202 and have been getting better results when reconnecting the DAC. I've tested a good bit and as long as you pause audio before or right after unplugging the power source it will return once you reconnect power and press play. If anyone is good with tasker could you suggest a way to set up a profile telling the N7 to stop audio, no matter what app it is coming from, when the device is not being charged and to restart audio when charging is restored.


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## jmcguire525

Actually this thread pretty much answers the rest of my questions.... http://forum.xda-developers.com/showthread.php?t=1852202&page=3

Basically I just need to tell tasker to turn off the screen and either pause audio or stop the open app when charging is not present, and then resume when charging is reconnected!


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## puffmais

i made such a tasker profile, but with reboot the Nexus 7 after turn on the ignition. with only pause and resume music it wont work with my dac when the Nexus was in sleepmode. so now its not Perfect, but these few seconds for waiting reeboot is okay for me. better than replug a cable or turn a switch. here a picture, Hope it works:

__
https://flic.kr/p/8226651310


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## jmcguire525

Good news, I haven't been able to test it yet but there are some flashable zip files that should make the DAC plug and play without the need to reboot. Check it out here http://rootzwiki.com/topic/37176-mod-cm10-usb-audio-support/


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## wave_is

How do you turn on the tablet? I can not make my Nexus 7 turned on together with ACC.


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## wave_is

If I hold the tablet constantly? A screen is turned on and off with a magnet? How long live the tablet battery?


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## puffmais

when you turn on the ignition the tablet became power to usb--> set up a tasker profile to turn lock screen off/on. tablet battery live is very long when tablet is in airplane mode.


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## wave_is

Do you use Y cable? 
If i dont use Y cable - All work Fine.
But i need connect my usb flash drive to the tablet.

And
When i use y cable,
[background=rgb(245, 245, 245)]when you turn on the ignition the tablet not became power to usb ;([/background]
[background=rgb(245, 245, 245)]My Nexus didnt see charging. I need unplug, and plug usb OTG cable. ;([/background]


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## puffmais

i use a y-cable and a usb hub. everything works fine, with usb dac and usb stick..


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## nu!me!

Hi...sorry to high jack this but as I'm planing to buy nexus 7 for in car installation have some questions ;
the plan ;
- nexus 7
- usb dac
- external storage / doesn't meter is it HDD or microSD
- volume control on USB over Nexus 7
- would like to keep steering wheel controls, so I'm thinking to use some bluetooth controller and hard wire it to it (any suggestions ?)
(have read about *CPJex(CarPc Joycon EX)* but don't know will this work on nexus?)

would this work, and what do I nead to make it work ?
(I have read couple treads about this theme and I'am kinda lost in all those information's, as I see, so far no one is abile to made Nexus 7 to work with external usb dac, external storage and charging on sime time ? hope I'm wrong)


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## dcplaya

jmcguire525 said:


> I switched out the Micro II for a Behringer UCA202 and have been getting better results when reconnecting the DAC. I've tested a good bit and as long as you pause audio before or right after unplugging the power source it will return once you reconnect power and press play. If anyone is good with tasker could you suggest a way to set up a profile telling the N7 to stop audio, no matter what app it is coming from, when the device is not being charged and to restart audio when charging is restored.


That could be why my DAC is not playing audio again after a disconnect. When I get home today I will try this fix and if it works post a Tasker profile.

Also, unrelated to the quote above, I have my JoyCon EXR working on my N7 except so far the mute button doesn't mute the N7. Anyone run into this problem?

Also, has anyone spec'ed out a good power supply for the car? I was thinking this one
http://www.mini-box.com/DCDC-USB?sc=8&category=981
But I dont know how the N7 would act with a on/off pulse for automotive and I dont want the UPS option really. I sometimes leave my car sit for weeks at a time due to work and travel and I would be afraid I would kill my battery.


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## Kookie_Monster

dcplaya said:


> Also, has anyone spec'ed out a good power supply for the car? I was thinking this one
> http://www.mini-box.com/DCDC-USB?sc=8&category=981
> But I dont know how the N7 would act with a on/off pulse for automotive and I dont want the UPS option really. I sometimes leave my car sit for weeks at a time due to work and travel and I would be afraid I would kill my battery.


Here's what I'm planning on doing. Connect an "add-a-fuse" (I didn't invent that, fyi. lol) to the fuse that runs the current for the lighter sockets (or radio unit), connect a lighter socket hub to it, usb charger and stock usb cable. More connections than desired, I know.
The hub has an on/off switch to every plug, which will allow me to turn it off whenever I don't want the tablet to boot (short drives, for instance).

As for the Joycon... are you removing the stock radio? If not how do you control both things?

Sent from my Transformer TF101 using Tapatalk 2


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## dcplaya

Kookie_Monster said:


> Here's what I'm planning on doing. Connect an "add-a-fuse" (I didn't invent that, fyi. lol) to the fuse that runs the current for the lighter sockets (or radio unit), connect a lighter socket hub to it, usb charger and stock usb cable. More connections than desired, I know.
> The hub has an on/off switch to every plug, which will allow me to turn it off whenever I don't want the tablet to boot (short drives, for instance).
> 
> As for the Joycon... are you removing the stock radio? If not how do you control both things?
> 
> Sent from my Transformer TF101 using Tapatalk 2


I will be removing my stock radio completely and using a PAC wiring harness to keep my Sync and steering wheel controls working. I will use the mute line to auto-switch the audio source between my tablet and Sync (For calls or bluetooth audio) and a 4.1 channel amp in the back to power everything. In between the amp and the tablet I will have a equalizer that can accept 2 inputs and modify it so it will switch electrically instead of manually between the 2 channels (Sync and tablet)


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## jmcguire525

sorry for not updating this thread lately, there have been some great developments that I am going to include in an update to the original post tomorrow. IMO these new mods/services/kernel features are a must have and the reason why I have waited to update the thread.


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## throwbot

Soooo, any problem with just taking out the old head, hooking an amp to the speakers that has a 3.5 mm audio port and then just plugging up the new pogo dock?

My head unit is trashed, I figured as long as I had an amp to the speakers I could plug whatever into the aux input for sound.

My big concern is the kernel, any reason I would need it if I was going a direct route like this. BTW, have an extra cigarette lighter that I was gonna run my power off of, and probably just plug a car charger into the dock.

Sent from my Galaxy Nexus using Tapatalk 2


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## dcplaya

throwbot said:


> Soooo, any problem with just taking out the old head, hooking an amp to the speakers that has a 3.5 mm audio port and then just plugging up the new pogo dock?
> 
> My head unit is trashed, I figured as long as I had an amp to the speakers I could plug whatever into the aux input for sound.
> 
> My big concern is the kernel, any reason I would need it if I was going a direct route like this. BTW, have an extra cigarette lighter that I was gonna run my power off of, and probably just plug a car charger into the dock.
> 
> Sent from my Galaxy Nexus using Tapatalk 2


The kernel we are using is mainly for USB audio out (For USB DACs) so if you use the headphone jack on the N7 you wouldnt really need the new kernel.


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## miketunes

moved my post to USB ROM thread


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## Statts

jmcguire525 said:


> sorry for not updating this thread lately, there have been some great developments that I am going to include in an update to the original post tomorrow. IMO these new mods/services/kernel features are a must have and the reason why I have waited to update the thread.


Hi mate. Any update on this? I'me just working my way through the threads on this topic now for the first time and can't tell if the OP has been updated or not.


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## davidadavila

to solve the issue of the screen turning off i figured that when the tabket recieves are looses power tve tablet wakes up so i just conected my tablet to a constant 12v source with a switch so if i want to charge the tablet when im gone i leave it on and the daydream feature keeps tablet awake, and when tabket is off i just hit the switch. problem solved...


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## davidadavila

btw i connected a cigg lighter socket at my 12v source so i can use any type of charger an like it d also because the12v chargers also has a fuse... to all u worried about the dac loosing power and the sound going away yes it does!!!! but the beauty of the 12v swith as that you have to turn the switch off and on again and it start working instead of closing the app or rebooting.... im on usb romm......connecting to acc would of been more elegant but the inability to charge over night stopped me... the one thing i have not figured is how to make google library understand gestures for play pause and next..... i have not found a write up and it gets tricky sometimes looking at the screen, i would not suggest buying a external drive that has moving parts buy like and usb thumbdrive because they dont requiere much power andy u can run a hub without electricity, my Seagate everytine it lost power when turned off would have a hard time being recognized againas a slave.


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## muthaBuccer

Great thread! I know this has been a stale thread for a bit but I am just getting started with my Nexus 7 2012 for the car. When I follow the link to the kernel you are referencing in the original post there doesn't appear to be a file there. If anyone can provide the correct kernel I would greatly appreciate the help.


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