After much time and little progress, I am getting back into this project. So here's the long short-version:
The plan is to install a touchscreen LCD in my dash in place of the stereo and climate controls. This LCD will be the interface to a Raspberry Pi that will be the primary brain of this project. Connected to the RasPi via various methods will be controllers for performing various tasks (volume control, lighting control, climate control, audio source control). If you follow this project, please be aware that I may not update it very often. ...sorry.
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I am currently working on a very detailed document describing every aspect of this project. It can be found at this link: Description on Google Docs. It is a work-in-progress and should reflect the most recent design. I will keep that link as up to date as possible, but this project page will not be updated as often as the G-Docs file. This project page will also not have the level of detail that the G-docs file contains.
I've changed my mind on the overall design for this project several times. Currently, the plan is to mount my Android tablet into the dash of my car and use it as my source for music and the primary interface for the other systems I'm installing / modifying in the car (lights, AC/heat controls, etc). The tablet will be connected to a USB DAC which will feed into a line level pre-amp, then on to the power amps. The tablet will also be the screen for my backup camera.
I'll be working on this project in stages but can only start installing pieces once all the main parts are done. This includes mounting the tablet in the dash, completing the software to run on the RasPi, completing the auxiliary battery and power supply, installing the audio hardware (including building the electrical interface for the steering wheel controls), and building the mechanical and electrical interfaces for the heat/AC controls. In the process of building all of these parts I have to take into consideration and plan the other things I plan on incorporating into this build, including the turn signal system rebuild, auxiliary lighting, and dash camera / DVR.
When I purchased my new phone (Galaxy Note 3, if you're curious), AT&T gave me a tablet for free (as long as I signed up for a two-year contract for the tablet). At that moment I had the great idea of installing this tablet in my 2012 Scion tC so I accepted their terms. Since then, I've been working on this project but haven't made much headway as far as installation goes. I've mostly been trying to work out the logistics of the project and have been tossing around several ideas for how to go about implementing my idea. At this point, I've been at it for about a year. The overall project design has gone through several iterations and I have finally arrived a a version that meets all of my requirements. Instead of mounting the tablet in the dash as the direct interface, I'm going to replace my stereo with a headunit that has HDMI / MHL capability. Using that feature, I'll route video from my old Galaxy S3 to the headunit and use the headunit itself as the primary interface. Because I'll be able to use the headunit screen as the interface to the phone, I'll be able to access all the features of the phone. I'll use the SIM card from the tablet to enable data-only access to the cellular network, and I'll still use the tablet to control accessories and view data about the vehicle.
Initial design ideas
When I first started working on this project, I had no idea how I was going to make it work. And so I started off with simply trying to decided where in the car I wanted to install the tablet. My first instinct was to install it where the stereo is but I didn't want to lose the option of playing a CD or listening to broadcast radio. And so I started to consider other places in the dash to install it. The location had to meet these requirements: easily reachable, plainly visible, not block line of sight, not block heat/AC vents. The best place that I could figure to install the tablet was where the heat and AC controls are. This would have meant integrating control of the heat and AC into the tablet somehow.
After inspecting the inner workings of the heat and AC controls, I decided that it would be a little more difficult to implement than I wanted to deal with. Therefore, I reconsidered the option of install the tablet in the current location of the stereo. About this time I realized that I had only ever used the bluetooth capabilities of the stereo and not the CD player or the AM/FM/XM tuner. This brings to the point I am at now: working on replacing the stereo with a tablet.
My current version of the design is to use the Android tablet as the interface for the stock stereo (it has all the features I'm looking for in an audio hub). Audio will be routed to component amplifiers. The only part of the stock stereo that I plan on using is the main circuit board along with the tuner circuit and one daughter board. The CD player will be removed since I have no need for it and the rest of the stereo operates just fine without it. Also, the front panel will be completely removed and a µController will spoof the presence of it along with the signals needed to control the unit.
The tablet will also be the interface for several controllers (grill/tag controller, ECU/vehicle state interface, vehicle starting controller). The Raspberry Pi will be the data aggregation hub/server.
After much fiddling with the stock stereo, I finally concluded that it would be very time consuming to emulate the necessary functions of the stereo and that replacing the stereo all-together with another stereo would be the more practical idea. So I have arrived at this newest version of this project: replace stock stereo with JVC KW-V50BT, interface with Galaxy S3 through the stereo's HDMI / MHL connetion, use the phone's web browser to interface with the RasPi / webserver and the RasPi interfaces with all the periphery devices. This provides me with touchscreen access to all the functions I want / need and doesn't involve an unnecessary amount of reverse engineering. I will have to hack the connections for the USB, auxiliary, and microphone inputs for the new stereo, but that's not that big of a deal.
More details to come. See G-docs file linked at top for more info. Also check out the build log below. I'll be updating the log as I work out implementation details.
I have again revised my plan, and I am going back to the original idea of using the tablet as the primary interface for the system. The JVC head unit will remain in place for audio control, and it will also serve as a monitor for the video cameras (backup camera, dash cam). The tablet, having a reasonably powerful web browser, will serve as the means of rendering the interface. The interface is loaded from the RasPi as a webpage.
New Latest Configuration Update (current)
Perhaps if I can just dedicate myself to one plan for this project, I can actually make some headway on it....
So here's the newest plan: install Android tablet into dash in place of stereo and heat/A/C controls; use tablet as interface for heat and A/C, as an audio source for the amplifiers, and as a display for a backup camera; make awesome.