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Discussion Starter · #1 ·
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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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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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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Discussion Starter · #4 ·
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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Discussion Starter · #5 ·
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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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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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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Discussion Starter · #8 ·
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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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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Discussion Starter · #10 ·
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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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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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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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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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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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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Discussion Starter · #16 ·
[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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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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Discussion Starter · #18 ·
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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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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Discussion Starter · #20 ·
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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