The adoption of ISO 13400 diagnostics over IP, which provides rapid re-programming speeds over a standard Ethernet physical interface, has made Ethernet common in today's cars.
There remain challenges, however, for its adoption as the ubiquitous in-vehicle networking bus of choice for automotive makers. Advanced driver assistance systems (ADAS), including camera systems, are one application where the industry is looking maximize Ethernet's benefits.
Why should someone consider Ethernet-based connectivity over analog or LVDS methods? Especially as the camera and central unit processing cost can be greater (Figure 1). There are number key factors beyond this one metric that ultimately provide lower costs and greater performance.
One such factor is that the ability to employ low-cost unshielded cable significantly reduces cable costs. In addition, power-over-Ethernet (PoE) is possible with standard-based 100BASE-TX Ethernet, so no additional power cable is needed.
But the true value of Ethernet is greater than simply reducing the bill of materials.
The ultimate goal for Ethernet is to deliver a single ubiquitous in-vehicle network with seamless cross-domain communications — with a common data stream and physical media (cable) being utilized across vehicle domains, including chassis, powertrain, body, infotainment, and ADAS.
This vastly reduces cost and complexity because there is no need for bridging, as a single network now allows the sharing of information both within a domain as well as across multiple domains. In short, Ethernet is a networking technology; this is its greatest value and how it reduces costs in any market, be it automotive, consumer, enterprise or industrial.
ADAS camera design exemplifies the major challenges for in-vehicle connectivity because it is one of the most demanding applications in the vehicle:
- Image quality is directly impacted by thermal noise generated by the camera. Critical factors for achieving required performance include improved thermal power dissipation, unaided by necessary space constraints, and lower power.
- Lower noise is a must because electrical noise will also degrade sensor image quality. A further challenge when trying to use the desired low-cost, unshielded cable, is meeting automotive EMC emissions requirements.
- Automotive market quality and reliability demands must be adhered to. The vehicle is a harsh environment, with differing considerations for passenger, commercial and industrial vehicles.
- There is more need than ever to deploy sensors throughout the vehicle, making such applications increasingly space constrained. This need is driven by the mission for zero fatalities, which is created strong demand for ADAS applications, like collision avoidance, traffic light, sign and pedestrian recognition.
The solution: Ethernet-based ADAS
Micrel, together with automotive sensor specialist Silicon Micro Sensors (SMS), has designed a “production ready” solution for the most stringent automotive and industrial applications, featuring a high dynamic range (HDR) mega-pixel (720p) camera, field of view 55° up to 190°, MJPEG video compression, Ethernet AVB with PoE support, low-cost unshielded twisted-pair cabling, and IP68 / IP6k9 class, water-tight, anti-scratch and fog The camera is suitable for passenger, commercial and industrial vehicles, applications include; surround and rear view, side and rear mirror replacement, traffic sign, blind spot, pedestrian detection and lane departure assist.
This solution clearly demonstrates the ability of standard Ethernet to meet the needs of the ADAS camera. It is one of a number of ADAS designs featuring Quiet-WIRE™ Ethernet and Auto-PoE technologies. (Figure 1 )
Aptina AR0132AT or OmniVision OV10635 image sensors options are available. A Freescale MPC5604 processor provides MJPEG compression from the incoming YUV digital image data, and interfaces over media-independent interface (MII) to the Micrel KSZ8061 Quiet-WIRE™ 100BASE-TX Ethernet PHY. A Micrel MEMS oscillator DS1001 provides system timing while Power management is delivered using an optimised form of PoE for automotive: Auto-PoE.
To read more of this external content go to: “Solving automotive challenges.”