Downloading Builds of OpenHU
Important: Only you are responsible for how you drive, and for how use this app. This app may contain bugs and glitches. It is offered without warranty. Focus on driving at all times, and don't allow any infotainment device to distract you.
First, you must enable unsigned sources, which is typically inside the Security tab of the Android Settings app. You may have already done this if you installed certain third-party apps like the Amazon Appstore.
If you are running Lollipop, KitKat, or Jelly Bean, you will need to activate USB Debugging. This should not be necessary on Marshmallow.
Once done, simple sideload the APK to your device and install it, as you would any other APK file obtained from the internet.
For best results, launch OpenHU once, then reboot the device. This loads the proper USB ID associations with the ADB system.
Requirements & Important Notes
OpenHU requires an Android device running Android 4.1 "Jelly Bean" or later. Android 4.4 "KitKat" or higher is strongly recommended. We are only focused on developing for Android 5.1 "Lollipop" and Android 6.0 "Marshmallow", so we encourage you to at least use Android 5.0 tablets with OpenHU.
In terms of hardware, your device must support USB On The Go (OTG) mode, and your build of the Android operating system must support it as well.
Your device also needs to be able to decode H.264, which is an Android compatibility requirement - but some low-end uncertified devices lack.
Currently x86 device support requires Intel's ARM translator "Houdini" - which all production Intel-based Android devices have. Still, this is a high priority to resolve, as it will improve power consumption and performance on x86, and there are no major roadblocks to making the app cross-architecture. While Mike Reid had crafted a fix for this, he passed away before uploading these changes to GitHub.
Finally, the phone or device you wish to connect - must be running the Android Auto app, obtained from Google Play. Unlike the OpenHU app, which is not a Google-endorsed app, the Android Auto client app must be obtained from Google Play - and the phone in question must have Google Play Services installed. In the very, very long term, the OpenHU project may pivot to developing a client-side app, but this is not a priority right now.
Currently Android N (Developer Preview) devices cannot run OpenHU. Android N adds additional security layers to ADB networking that will require reworking the app, routing USB networking calls through JNI instead of NDK. This is something we hope to incentivize the developer community to help us do. It may also change as Android N is in an active state of development - so we aren't going to treat this as a priority, until Android N ships.
It's important to note that this does not apply to Android N phones that you wish to run Android Auto from, and connect to a tablet running OpenHU. From our testing, a phone running Android Auto and the Android N Developer Preview, has no issue communicating to a tablet running OpenHU and an earlier version of Android.
We also expect most Android tablet users to be slow to upgrade to Android N. From our experience, most people installing OpenHU are using an older tablet - and even most Android Auto car manufacturers are not even running Android 6.0 today. We've even encountered some first-party cars that are using Google's Android Auto head unit app, atop Android 2.3, Gingerbread (which we do not support).
About Submitting / Getting OpenHU from Google Play
Google repeatedly removed Mike Reid's submissions of his predecessor app to the Google Play Store, routinely giving extremely vague reasons for removal. This despite Mike Reid's considerable efforts to engage the Google Play support team and issuing multiple fixes, aimed at their vague concerns - including removing all references to Android Auto from the app itself.
As such, we have no immediate plans to submit the app to the Google Play Store, and we discourage you to attempt doing so either.
It is a project goal to resolve any lingering concerns about the app with the Google Play team, but we ask that you aid this process by not flooding Google Play with your own APK builds of OpenHU. It may, in fact, endanger your developer credentials with Google Play to attempt submitting this app to the Google Play Store (though we are not aware of any Play Store rule that it inherently violates).