Automotive Computing (R)Evolution - The Android Head Unit Build - Hardware Overview
by, 06-11-2013 at 10:33 AM (18012 Views)
The Hardkernel ODROID-X2
The heart of the Android head unit was obviously the item most considered for a new project build. Because I demand a lot of power from my system, as well as a lot of connectivity options, I simply could not choose the easier way to get Android up and running. The ODROID-X2 is a powerhouse of a development board, boasting specs that meet or exceed my prior Windows based installation. The processor that powers the ODROID-X2 is the Exynos 4 Prime ARM Cortex-A9. With four cores, a default 1.7ghz of power that can be easily overclocked if need be, the ODROID-X2 is the ideal launching platform for a powerful Android car PC. The board houses 2GB of DDR 2 RAM, and boast a very capable 3D graphics processor which can handle more than one would need in the car, unless of course you plan on hosting 4 player Mario Kart 64 tournaments in traffic.
The Android standard benchmark utilities, Antutu and Quadrant, both prove the ODROID-X2 as a absolute powerhouse of a board. This coupled with its miniature profile at 90x94mm makes it the best choice for an Android head unit.
Another key factor in selecting the ODROID-X2 for my car PC needs was the ability to purchase compatible hardware accessories at once source. Hardkernel.com sells the board along with compatible Wifi, Bluetooth, UART, and Android-installed storage solutions. For my build, I selected the 64GB eMMC memory module with the thought I could also add a 64GB SD card for additional storage, but you cannot use both at once. The board has a jumper that allows you to select which option you choose.
The ODROID-X2 has a total of 6 host-enabled USB ports that can provide the max 500mA per port provided your supplied power meets the requirement. Considering that both wifi and Bluetooth need to be handled with dongles and your touchscreen needs an additional port, its safe to assume that at least one powered hub is a good option. Sound output is handled by a single 3.5mm port and input is handled by a second 3.5mm port. Additional components can be connected via the 50pin expansion slot. This allows interfacing with items like LVDS displays, GPIOs and more low-level device interfaces. If ribbon wires aren't your suite, the micro-HDMI port can be your primary display means. Take note though, that the ODROID-X2's HDMI port is hardware locked to display at either 720p or 1080p. That means that for devices like the Lilliput 669, you must use a HDMI-to-VGA adapter to achieve native resolution without overscan.
Because the ODROID-X2 requires a regulated source of 5 volt 2 amp power, it cannot be powered properly via the unregulated 12v found in most car systems. Because of this, I acquired a Mini-Box DC/DC Power converter. In fact, I acquired two, one for the ODROID, and one for the display, as they both run on entirely differently input voltages. There may be an all-in-one solution that fits your bill, but I like that the two will be isolated. The ODROID-X2 is out of the box capable of auto start on power up, and doesn't need to be shutdown or put to sleep with ignition, so you wont have to deal with any timing issues.
The rest of the Android head unit installation will allow me to use all of the car PC add-on equipment used from the Windows PC. OBD-II receiver, GPS receiver, USB hard drives, and cameras can all be plugged in and work without much muss or fuss. The eGalax touchscreen module found on the new Lilliput 669 charged with the task does however require some kernel modifying to work properly. More on this in the next blog.
While finding a spot for the ODROID in my compact vehicle wont nearly be the hassle of my Windows system, finding a suitable case to protect it from at least some of the bumps and bruises of the road became somewhat a chore. Custom cases aside, there are a few eBay retailers which provide a solution. My choice of casing can be shown below. While it doesn't provide much side protection, my new Android head unit looks good in it's two-piece .