Like the Odyssey project, a clean mobile tablet installation has been on my list for almost 10 years now. I started taking steps towards actually developing the project when I bought my 2003 Mercedes E55 AMG in 2016, which, like the BMW had an outdated audio system helplessly tied to the car's proprietary data busses. Unfortunately, I wasn't happy with the E55, so when I sold it at the end of 2016 and picked up my e39, my plans transitioned to the BMW.

My goals for this project are as follows:

  • Remove the e39's stock headunit,  and dsp / amplifier combination but leave all stock wiring unmodified so that going back to stock is a trivial operation.

  • Create a new headunit centered around the dated but feature packed 2013 Nexus 7 tablet.

  • Assume the responsibilities of the vacant stock dsp / amplifier with discrete aftermarket amplifiers and dsp that can process an active 8 channel setup.

  • Integrate the tablet into the environment with supporting electronics including, video capture (backup camera), ADC (analog to digital convertor), IBUS communication, and intelligent 5V power supplies.

  • Design a 3D printed bezel to house the tablet and auxiliary electronics in the e39 dash while retaining a polished and factory feel.

  • Manipulate the hardware and software of the tablet to create full featured and easy to use interface for the occupants that behaves like a factory system both from a usability and a power management standpoint.

  • Retain steering wheel controls

  • Add backup camera that cycles automatically when in reverse.

  • Link head-unit and DSP with digital S/PDIF to transfer lossless 2ch LPCM.

  • Assume control of the stock speakers via the aftermarket dsp and amplifier(s).

Wiring Diagram:

Only meant to paint the broad strokes of the installation so understand that it is not completely comprehensive. For example the chassis grounds and the AV grounds aren't shown for the sake of simplicity. I've also organized this with divisions between the electronics based on physical location in the car. Green = Cabin. Gray = Trunk

Software, Installation, and Configuration

Timur's Nexus 7 ROM

The biggest deciding factor for choosing the Nexus 7 tablet for the installation is the availability of Timur's modified rom for the N7 specifically tailored for automotive installations. I could fill this whole page with the features that this rom provides, so rather than do that I'll just link to them here. Installation instructions as well as the download link for the rom can be found here.

Although the rom is not being developed anymore, Timur finished strong and the 4.0 final is thoroughly debugged and very stable. To date, I have yet to see anything that can touch what the N7 tablet + Timur's ROM offers.

Front End

Years ago a person going by rxritalin on mp3car.com created a customizable psd background file formatted for the Nexus 7. He created the background and released several demonstrations of how it could be edited. One of the demonstrations is what I used as a basis for the frontend of this project. What makes the wallpaper special is that it is drawn to look like a user interface with slick icons, text, and ascetically pleasing textures.  When edited, you end up with a lifeless image file, but with some extra software, you can create invisible buttons over the drawn buttons in the wallpaper, and suddenly it becomes a real launching front end. The software combo I used was Nova Launcher and Desktop Visualizer, both of which are available in the Play Store. Mp3car.com has long since closed their forums but rxritalin's dropbox is still available here

I also used GMD GestureControl Lite to create gesture based commands.

The Bezel

I've always known that for a tablet install in a car to truly satisfy my OCD, it was going to require expert fabrication to build a purpose built bezel to emulate a factory fit and finish with the tablet being the focal point. Anyone who follows projects involving the grafting of a tablet into a dashboard knows that most of the time the end result is a compromise. I'm hoping to change that.

 

Enter the age of 3D printing

Years ago when key 3d printer patents started expiring and reprap printers really started taking off, I was paying attention, but I couldn't think of anything I could use one for seeing as most affordable options used pretty fragile polymers like PLA... That changed ~2 years ago when I started to realize that support for tougher materials like ABS and PETG may provide the means to fabricate the bezel in my head. I decided it was my best bet for success and took the plunge, buying a relatively inexpensive Folgertech 2020 i3 Prusa clone

After building and calibrating the printer, I did a lot of reading. Through a lot of trial and error, and other small projects I finally felt like I had the tools to start designing the bezel, so I got busy in OpenSCAD.

Very early in my design I realized I wanted a backplate that would serve the purpose of securing the tablet by sandwiching it between the bezel and the backplate while also providing a back surface to mount the raw pcb electronics (stripped of their enclosures to save space) like the power convertors, usb hub, Joycon EXC, UVC Video Capture, and the DAC. The end result will probably look something like this:

I knew from the start that the bezel would be too large to print on my 200x200x140mm printer, so the plan was to print it in ABS pre-cut (by design) so that it would fit together like a puzzle. From there the pieces could be fused together with acetone to form 1 piece. While this worked, it was a frustrating process and I started to long for a larger format printer that I could print the bezel out in one go.

Enter the TronXY X5S-400. A 400x400x400mm Core-XY 3D printer that's officially stalling this project while I build and calibrate it. Once it's built and capable of printing well. I'll be back to finish this up

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