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How I displayed the Stock Screen on a Nexus 7

Old 02-23-2014, 10:31 PM
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chrismitch
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How I displayed the Stock Screen on a Nexus 7

After gathering inspiration from all of you on this website, I decided to embark on a CarPC project of my own. I really wanted to have an Android tablet as the centerpiece of my display, however I also knew that I could not live without the information that the stock display provided. I needed to be able to view the climate control information and to view any diagnostic information if I ever needed it.

After reading various posts, I came across modme’s description of how he was able to hack into the stock display and display his CarPC on the stock screen. As we now know from his work and the work of others, the stock display uses a “RGBS” signal. This is an older display signal used for Arcade games many years ago. It is a 15 Khz signal that is split up into “Red,” “Green,” “Blue,” “Combined Sync,” and “Ground.” You’ll see this signal called “CGA” in other places.

Modme was able to display his CarPC on the stock screen using the ScanDo 800, which converts a computer VGA signal into the RGBS signal which the stock screen uses. So I thought, if I were able to achieve the reverse of this, maybe I could display the stock image on an android tablet.

I was able to convert the stock signal using 2 pieces of equipment. The first one is called the “WEIYA CV-04.” It is advertised as a small printed circuit board for hobbyists who want to play old arcade games on a standard tv using composite video (that’s the yellow cable in the “Yellow, Red, White”). It goes for around $30 and you can find it on ebay and on many other websites. I’ll mention the second piece of equipment later on.

How I displayed the Stock Screen on a Nexus 7-cv-04_overview_features.jpg

In order to convert the signal, I spliced into the R, G, B, Combined Sync, and Signal Ground wires that go into the display. I also spliced into the Signal VCC and Main Ground wires to power the CV-04. Even though the CV-04 says it requires 12V and the wires going into the display unit are only 9V, I can confirm that this still works despite being slightly underpowered. I got the information on which wires to splice from the FSM (Factory Service Manual).

G37 Display Wires.pdf

It is also worth mentioning that the video display wiring harness still needs to be hooked into the stock LCD circuit board in order for it to work. This is because the stock LCD circuit board sends signals back to the AV Control unit telling it that is receiving signal. You don’t have to have the LCD screen itself hooked up, just the circuit board that is immediately behind it.

Now that the stock display has been converted into a more standard signal such as composite video, the second problem is how to display this signal on an Android Tablet. After thinking about this problem for quite a long time, I realized, “What if I can trick the tablet into thinking that the video signal was coming from a webcam?”

There are many “Video Grabber Cards” out there that convert a composite signal into USB. The problem is that most of these are designed for Windows computers and require the installation of drivers. Android tablets for the most part do not have the drivers for these cards. They do have one built in driver, which is a newer universal driver for webcams of the “UVC” type. UVC is a type of USB signal that stands for “USB Video Class.” Many newer webcams are using this because it doesn’t require drivers to be installed on the host machine. You can read about it on wikipedia: http://en.wikipedia.org/wiki/USB_video_device_class
After a good deal of searching, I came across a product called the “FEBON 100 UVC Grabber Card.” You can find it here: FEBON: FEBON100 Drvier free (No driver install) CVBS (a/v) input grabber user manual

How I displayed the Stock Screen on a Nexus 7-img_7155-001-.jpg

It doesn’t list a price on the website. In order to buy it you have to email the guy. The cost is $77 plus $10 for shipping. He will give you a link to his paypal account. Although the whole ordeal of sending money to this random guy in Japan seems somewhat shady, let me confirm that this guy is 100% reliable and he makes a great product.

Now that the composite video signal has been converted to a USB signal that doesn’t require drivers, the last step is to hook it up to a USB OTG cable (allows the tablet to act in host mode) which then connects into your tablet. Then download a program that is designed to display webcams. I used this program called Dashcam https://play.google.com/store/apps/d...eption.dashcam

How I displayed the Stock Screen on a Nexus 7-photo-on-2-3-14-at-8.38.jpg

Using this setup you can now display the stock LCD signal on an android tablet. I used the Nexus 7. The total cost of this conversion is about $120. It’s worth mentioning that the quality of the image displayed is not quite as good as it is on the stock LCD. This is because in the conversion process the signal is downgraded to composite video. However, for anyone who wants to do a Nexus 7 installation and still retain the ability to see the stock image, I can confirm that this method works.
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Old 02-23-2014, 10:48 PM
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I guess it's also worth mentioning that I have a 2008 G37 Coupe, with Bose, without Navigation.
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Old 02-24-2014, 12:01 AM
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This is good info. I take it, you've seen my nexus 7 install? I may try this or just remount my screen somewhere like the sunglass tray area. Although, I haven't found a need for the info screen...at all. Even the radio is obsolete since I use iheart radio for all my stations. As far as personal settings and maintenance intervals.. my plug is still there to restore those settings if my battery ever dies and resets it. Keep up the good work.
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Old 02-24-2014, 12:04 AM
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Did you get a host OTG that also has a charging wire? That's something I havent gotten to yet, I want to do a 4 port usb hub to run power, external HD, and a BT mouse.
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Old 02-24-2014, 12:54 AM
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Sold! I so badly want to put my nexus 7 in my 2010 non bose non navi coupe. I like what Paratrooper did but i still want the factory stock screen as well. You just gave me some hope Chris. Can we see it in action?

Last edited by Jamez3rd; 02-24-2014 at 12:55 AM. Reason: add in
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Old 02-24-2014, 02:01 AM
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Actually Paratrooper, I have to give you a big shout out because most of the actual installation of the Nexus 7 came from your original work. For my setup, I am using an OTG Y cable like the one you are talking about. I then have it hooked up to a 7 port hub. I used this one because it supplies up to 12 amps and thus can rapid charge my tablet, iPhone, and a few other devices, all with external power which I tapped off of the cigarette lighter power

Newegg.com - ORICO UCHA BK 1.2 Rapid Charging 5V12A 60 Watts 7 Port USB Charger HUB

To the hub I have my nexus 7, iPhone charger, the FEBON UVC 100, a USB OBD-ii, a RTL-SDR dongle for radio, and a 2.4ghz wireless keyboard.

As for software, I rooted my Nexus 7 and installed the "USB ROM" which is built upon CyanogenMod and Timur's USB Host kernel. Its great for a car install and allows for multiple usb devices connected at once. The link to the ROM is here:

http://mehrvarz.github.io/nexus-7-usbrom/

This is based upon Android 4.2.2, and it only works for the 2012 Nexus 7 and not for the 2013 Nexus 7.
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Old 02-24-2014, 02:01 AM
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Originally Posted by Jamez3rd View Post
Sold! I so badly want to put my nexus 7 in my 2010 non bose non navi coupe. I like what Paratrooper did but i still want the factory stock screen as well. You just gave me some hope Chris. Can we see it in action?
Sure, as soon as I get some time I'll post a video. Thanks for the support!
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Old 02-24-2014, 01:44 PM
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Here's a short video of the setup in action. At the bottom of the screen you will see the CV-04 RGBS to composite converter circuit board, and the FEBON UVC capture card (has a blue light on it)

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Old 02-24-2014, 01:59 PM
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Hey Paratrooper, how did you finally end up mounting the Nexus 7 to the dash. Did you end up sticking with the rubber bands or did you move onto something else. I actually like the rubber band idea and I may just stick with that.
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Old 02-24-2014, 03:48 PM
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Im still rocking the bands, nothing has shifted nor loosened up. Gonna stick with it until further notice.

I considered rooting my nexus but I tried once using a tutorial online from xda developers, and i got lost and had to restore my device. Its confusing. Maybe someday, I will have to hit you up for a walk through.
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Old 02-24-2014, 04:03 PM
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Originally Posted by Paratrooper View Post
Im still rocking the bands, nothing has shifted nor loosened up. Gonna stick with it until further notice.

I considered rooting my nexus but I tried once using a tutorial online from xda developers, and i got lost and had to restore my device. Its confusing. Maybe someday, I will have to hit you up for a walk through.
We are like night and day Paratrooper. I'm all over rooting, jailbraking and computers but what you did i'm lost. It's good that you guys provide guides for us noobs. Thanks for the vid Chris. I'm about to embark on this journey as i really wanted to have both. I can tether with my phone for internet, radio, etc.

Last edited by Jamez3rd; 02-24-2014 at 04:06 PM. Reason: correction
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Old 02-24-2014, 04:28 PM
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Originally Posted by Jamez3rd View Post
We are like night and day Paratrooper. I'm all over rooting, jailbraking and computers but what you did i'm lost. It's good that you guys provide guides for us noobs. Thanks for the vid Chris. I'm about to embark on this journey as i really wanted to have both. I can tether with my phone for internet, radio, etc.

I hope i wasn't too confusing, you mean the apps im using for screen brightness and the entire setup...or the install?
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Old 02-24-2014, 06:11 PM
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Originally Posted by Paratrooper View Post
I hope i wasn't too confusing, you mean the apps im using for screen brightness and the entire setup...or the install?
No you were very informative. I've never did any car audio mods myself but with enough guides and patience, it can be done. Just like rooting the Nexus 7. XDA is the right place to learn how to do it. I used the Nexus Root Toolkit. It looks like i'll have to downgrade from 4.4.2 to 4.2.2 for the USB rom/kernel tho like what Chris is using.
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Old 02-24-2014, 10:18 PM
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Holy crap this thread is a GOLDMINE. Thanks so much for sharing all the work you did chrismitch. This combined with Paratrooper's post should be a great replacement for my current non-nav setup.

Originally Posted by Paratrooper View Post
Im still rocking the bands, nothing has shifted nor loosened up. Gonna stick with it until further notice.

I considered rooting my nexus but I tried once using a tutorial online from xda developers, and i got lost and had to restore my device. Its confusing. Maybe someday, I will have to hit you up for a walk through.
If you ever decide you want to try rooting again, I can help with that.
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Old 02-25-2014, 12:07 AM
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It was also my first time rooting an android device as well. I used this webpage as a guide:

How to Root Nexus 7! | Nexus7Root.com - Nexus 7 Rooting, ROMs, Tips, and More!

He has a pretty good youtube video. He tells you to download his zip file which is totally legit. The only thing is his "SuperSU" and "recovery-clockwork" files are outdated. You can download the latest versions here:

SuperSU Download

https://www.clockworkmod.com/rommanager

Just download the new files and insert them where he tells you too.

Once that's done, you can install the "USB-ROM." Don't forget that by installing a custom ROM it doesn't come with the default google applications so you will have to install them. Its actually not as hard as it sounds. Just go to this website, download the "gapps manager" program and it will take care of the rest:

[APP][2.3+]Gapps Manager - Easily Download Gapps - xda-developers
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