Car install discussion thread

Hello all, I had a Nexus 7 tablet professionally installed into my 08 Lexus IS250 by Bing and Joey over at Simplicity in Sound, you can find their build log at DIYMA website (link coming after I post 10 times).

I just wanted to share some details for other people who are attempting a build/setup like this themselves, I have gotten plenty of useful information from this forum and would like to contribute by posting up my findings and research to make it easier for the next person. If you are interested in doing this for your own vehicle, I hope this will help. Thanks!

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List of Tablet Features:

- Tablet turns on when car is turned on (IGN/ACC), turns off when car is turned off. Minimal battery drain when car is off (<1% per day)

- CyanogenMod 11 and custom kernel installed: full customization of tablet settings (CPU/GPU tweaks, battery life optimization, screen auto brightness curve, etc.)

- Tablet physical buttons not needed: tablet can be rebooted or put to sleep (screen off) using on-screen software buttons; tablet can be turned back on (double tap on screen to wake) without pressing the physical power button

- Steering wheel controls (volume down, volume up, previous track, next track, mode) are mapped to android volume up/down, previous/next track, and back/home buttons, no need for physical tablet volume buttons

- Incoming calls and text messages are shown on tablet screen. Can reply to texts, answer calls from tablet screen directly, still requires bluetooth headset or car kit/headunit

- Rearview camera feed available on tablet screen (RCA or USB webcam) through Dashcam app (has to be started manually)

- USB audio output to a DAC (digital-analog converter) of your choice for high quality sound output (note: not all DACs compatible)

- Voice commands through Google for navigation, etc.

*Wifi connection to phone tethering required for maps/navigation and other apps

One thing I wanted to mention specifically: the Joycon series of modules has been used in many car PC installations as a way to control Windows PC functions with the OEM steering wheel buttons. What it does is turn the resistive (or in some cars, digital) signal from the OEM steering wheel buttons into a USB keyboard signal that can be recognized by Windows PCs, but also fortunately for us, Android devices. The functionality isn’t perfect, setup has to be done on a PC first before connecting it to the tablet, but in this manner we were able to eliminate the need to access the physical power and volume buttons located on the edge of the tablet, making for a super clean install (the power button functionality is replaced by an on-screen software button/widget). The driver can then control volume, track seek, and even the back/home keys from just the 5 steering wheel buttons. Please refer to the google doc linked at the beginning of this post for wiring and setup details.

One other comment on how the tablet outputs audio: I specifically wanted the tablet output from a USB audio DAC for a cleaner signal. We chose a DAC that does not require a separate power switch or a power supply, so that it turns on automatically when the car is turned on. This also allows us to not require a separate cable connected to the 3.5mm audio output on the tablet, again, a cleaner install. Bluetooth connectivity to the Mosconi 6to8 addon board is also an option, but costs more.

Finally, some comments on the software setup (details and links to all software/apps are provided in google doc):

CyanogenMod 11 (M7 snapshot build from June 2014, on 4.4.2 base in order to be compatible with Glitch kernel, see below) was chosen for its USB audio output capability, and all the extra customization it brings to the Nexus 7. Other ROMs may also provide this functionality, up to user preference.

The kernel by Glitch (r142) was chosen for AC charging, double tap 2 wake, and CAF compatibility (with CM11). For some reason, I cannot get OTG charging on startup to work with other kernels such as ElementalX.


Tasker is a MUST for automating functions such as tablet shutdown, Wi-Fi tethering, Tablet Talk connectivity, and anything else you desire.

Tablet Talk allows me to answer calls, view and answer texts, all from the tablet screen. No need to glance down at my phone to see who is calling or who just texted me.

The Dashcam app in conjuction with the FEBON UVC grabber card allows for display of a RCA video feed, but it has to be started manually. Automation is theoretically possible, as the Joycon exr can sense voltages on one of its input channels and you could tap into the power for the reverse lights, then convert that into a USB keypress combination, then use an app (such as keyboard helper pro) to automatically launch the dashcam app when that keypress is detected… but it takes me literally 1 second to tap the app on my tablet screen to launch it before I shift into Reverse.

Feel free to contact me via PM or post if you are attempting a build like this and would like more questions answered. If you are in the SF Bay Area and would like to get this done professionally, contact Bing and Joey at Simplicity in Sound.

Hardware Used (PM for links):

DCDC-USB voltage converter (used to maintain steady, constant 12V power to dashcam, portable USB battery pack, and to 5V buck converter)

AmazonBasics 4 port USB 2.0 hub (just a regular USB hub for all the various peripherals - USB DAC, UVC grabber card/webcam, and Joycon)

Febon100 UVC grabber card (converts a set of RCA video/audio signals into USB, to connect to an existing rear-view camera; otherwise a USB webcam can be installed instead)

ODAC USB digital-analog converter with RCA outputs (no on-off switch, no separate power requirement other than USB source, turns on automatically when car is turned on)

OTG USB y-cable (micro USB to connect to phone/tablet, male USB Type A to connect to power source, female USB Type A to connect to USB accessories (hub, DAC, camera)

5-wire USB extension cable (must have 5 wires for OTG functionality, unless you short two of the pins, just like an OTG cable)

Joycon exr

Nexus 7 (2013) 2nd gen, wifi version (flo), 16GB


Software used:

CyanogenMod 11 (CM11) Nightly ROM

Glitch kernel for flo/deb, CM/CAF version, r142

TWRP recovery

gapps for CM11

Tasker app

Secure Settings plugin for Tasker, Pro version

Dashcam app

Tablet Talk app

Tablet Talk Tasker plugin

To allow tablet to boot when car is turned on (tablet receives power/charging)
- When tablet is powered on and connected to computer in debugging mode (make sure adb is working first by checking with “adb devices” command):
- Type:
“adb reboot bootloader”
“fastboot oem off-mode-charge 0”

Set Tasker profile to shutdown tablet when car is turned off (State: power source = any, Invert)

Set Tasker profile using Tablet Talk plugin to turn on Tablet Talk when connected to Tethered wifi from phone

Phone: enable tethering hotspot when connected to headunit BT, turn on tablet talk app using plugin

Evo3dUser said:

How did you alter the bootloader? Thanks

Sent from my 0PJA2 using Tapatalk

---------- Post added at 01:35 AM ---------- Previous post was at 01:34 AM ----------


How did you alter the bootloader? Thanks

Sent from my 0PJA2 using Tapatalk

Click to expand...

Click to collapse

adb reboot bootloader
fastboot oem off-mode-charge 0

This tells the tablet to power on when a power source is connected, instead of staying off and charging.

masri1987 said:

anyone know of how i can cause the tablet to shut down with my car and how to power on with my car?

Click to expand...

Click to collapse

T1murs kernel

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darkmage1991 said:

I wanted to go ahead and let people know, that if the main reason you want this kernel is to save battery than you do not need this. i am running official cm11 07/06/2014 with elementalx kernel 2.13 with a few build.prop tweaks and tasker profiles i was able to get 1-2% drop after 18hours. after waking it up and checking battery stats it showed i only lost 1% battery but from keeping the screen on going into setting to turn on screenshoting it did drop to that 2%. so yea it technically only dropped 1% over 18hours.

http://i798.photobucket.com/albums/yy266/darkmage1991/Screenshot_2014-07-08-13-46-19_zps5636d2e8.png
http://i798.photobucket.com/albums/yy266/darkmage1991/Screenshot_2014-07-08-13-39-16_zps3d03fe66.png
http://i798.photobucket.com/albums/yy266/darkmage1991/Screenshot_2014-07-08-13-39-51_zps4a7d0131.png
http://i798.photobucket.com/albums/yy266/darkmage1991/Screenshot_2014-07-08-13-39-32_zpsd3a4244b.png

now i have my nexus 7 fiberglassed in my dash and have had it there for over a year with the nexus 7 1st gen and upgraded to the 2nd gen a few months back. these build.prop edits and tasker profiles make the battery much much better without having to purchase a kernel that should never be a pay for product in the first place. but this method has otg+charge working just fine and battery lasting ages.

if this is something people would be interested in let me know and i can either upload a CWM backup or try remembering all the changes i did to my build prob. this should be know i do not have anything other than my music player/tomtom nav/battery monitoring/tasker/ installed nothing else has been put on. but alot of unnecessary stuff was removed using root explorer in the system/apps directory including Bluetooth printing etc.

Click to expand...

Click to collapse

ok for those that pm'd me: these are the changes i did to build.prop:

add these lines-
pm.sleep_mode=1
ro.ril.disable.power.collapse=1

in tasker i did this
when tablet loses power - airplane mode on/kill music player/kill tomtom gps/brightnes 5
when tablet has power - airplane off/run app music player/run tomtom app/brightness 255

in development option in settings i set tablet to keep the screen on when charging
in lockscreen settings i set screen security to "none" and turn all screenlock widgets off (had to turn these off as cyanogenmods weather was taking some battery)
and in performance i set max cpu speed at 1ghz (did this so while screen is on and listening to music there's no chance of cpu overheating)

in adb i ran this command fastboot oem-off-mode charge 0 to force the tablet to power off if under power, just to be sure that if the tablet does freeze of something that it will power itself on.

other than those tweaks i used cm11 latest nightly and elementalx latest kernel, these settings allowed me to get very very little battery drop overnight.

with these settings i was able to get 18hours and only 1-2% battery drop and otg+charge works just fine with my dac plugged in. i will do a longer battery test here in the next few days to see what the battery drop is over like 2-3 days. sure beats giving 40$ to some greedy **** thats trying to sell a modified free licensed product

Just a heads up for ppl that wanna measure the charge current goint to the in dash

There are a couple apps but i use current widget on playstore

This helped me find the best cable combination and not 1% drop all day with timurs kernel and everything running ...

Hope it helps

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