Networking Increases Functionality in the Car
By Roger Taylor, SMSC
The pervasiveness of modern technology is evident in today’s cars. The proliferation of low-cost navigation systems, along with the advent of digital audio broadcast, satellite radio, cellular communication, wireless networks and numerous other functions have led to ever increasing complexity in today’s cars. North American manufacturers have taken an approach that favors integrating multiple systems in one box, but that box has reached its limit as automakers are adopting these technologies into all levels of cars and trim packages.
Roger Taylor, SMSC's Automotive Infotainment Systems Group
By Roger Taylor, SMSC's Automotive Infotainment Systems Group
The pervasiveness of modern technology is evident in today’s cars. The proliferation of low-cost navigation systems, along with the advent of digital audio broadcast, satellite radio, cellular communication, wireless networks, DVD entertainment systems and the increased need for driver-friendly technologies has led to ever increasing complexity in today’s cars. High-end European car makers such as Mercedes and BMW have addressed the challenge by providing advanced multimedia networking capabilities. North American manufacturers have taken an approach that favors integrating multiple systems in one box, but that box has reached its limit as automakers are adopting these technologies into all levels of cars and trim packages.
To accommodate multimedia systems in a car, North American designers are now faced with the challenge of integrating additional functionality into the head-unit. This expansion of head-unit functionality causes designers’ integration efforts to become more complicated and more expensive. In order to meet this challenge, some functionality needs to be moved out of the head unit and placed elsewhere in the car.
Historically, car entertainment was simple. All functionality was integrated in one box and four speakers were driven by integrated amplifiers. To accommodate the expanded functionality functions such as amplifiers and CD changers are separated. Designers have typically interconnected the audio between components by analog cables. To limit interference with the audio signals, shielded cables and shielded connectors are required. If another source of entertainment was needed, a designer would have to add another set of shielded cables, shielded connectors and signal drivers and receivers. All of these interconnections must be tolerant of automotive fault conditions, such as short-to-power, and they must meet automotive EMI requirements for emissions and susceptibility.
But as the number of cables increased, so did the designers’ challenges. Analog signals are susceptible to noise, which degrades the fidelity of the audio signal. Many of these systems also convert the digital audio signal in the head-unit to analog for transmission to the amplifier where the signal is then converted back to digital for processing. These additional conversions added to the cost of the automobile’s design and degraded its performance. In addition the signal level required for one component might not be appropriate for another component and signal fidelity might be lost through stages of amplification and attenuation.
For control and monitoring in these systems, designers typically extend the Controller Area Network (CAN) bus to the additional multimedia components. CAN has been a networking solution for basic electronics functions such as engine control, but it was not developed to manage all of the multimedia components that are in today’s cars. Thus additional circuitry and cabling is required to include CAN in each multimedia component.
A new solution that supports interconnection of multimedia systems is INIC eLITE, a technology developed by SMSC. INIC eLITE eliminates extra wiring and the additional cost of transmitters, receivers, ADCs and DACs, while maintaining signal quality by keeping the signal in the digital domain. This simple, low-cost, entry-level automotive networking solution is excellent for transporting multiple channels of digital audio and video content between various components within a system.
INIC eLITE provides a networking system for digital audio and control information over a single digital link. This saves cost and improves performance compared to legacy analog plus CAN implementations. Since a digital signal is largely impervious to noise, signal fidelity is maintained while circuit complexity is reduced. Maintaining the signal in the digital format also helps the designer manage the signal level when interfacing between components that have differing signal level requirements.
Previously all-digital connectivity solutions weren’t implemented by designers because these systems couldn’t easily handle multiple channels of streaming data, such as digital audio. Just as importantly there are no other digital communication solutions that can meet automotive EMI and quality requirements. With INIC eLITE, streaming data links consisting of several channels are easily transferred between system components. Unlike other available networking technologies, the transfer is synchronous thus eliminating the added cost and complexity of data flow control, clock regeneration, and sample rate conversion.
In addition, this networking solution dedicates a portion of the bandwidth to a bi-directional control-message channel through which any node on the network can communicate with any other node. It is now a simple matter to manage a function or determine the status of a separate component, and no additional cabling is required.
Communication through INIC eLITE can take place over unshielded twisted-pair wire, and provides enough bandwidth to carry up to 59 16-bit audio channels. INIC’s ePHY technology provides this high bandwidth while keeping EMI in check. The network’s bandwidth is very flexible and can be segmented or channelized in a variety of ways, carrying different types of data supporting various applications, such as links between a head-unit and external amplifier or CD changer.
INIC eLITE also makes it easier for a designer to add additional nodes. Requiring only one INIC device per node, INIC eLITE can simply extend the network to include three or more nodes. In multiple node implementations, the cost advantages of this system are substantial. INIC eLITE also enables designers to easily adjust or add more functionality to a car’s infotainment system by supporting additional nodes on the network. In systems where more advanced networking and dynamic system management is required, it is easy to upgrade to Media Oriented Systems Transport (MOST) technology. This ability to upgrade to more advanced systems makes INIC eLITE a sound investment.
All the advanced features once found only in high-end cars are now cost effective enough to support the expanded functionality now being offered in the more popular mass-produced cars made by North American manufacturers. Through systems like INIC eLITE, the costs traditionally associated with having multimedia functionality in a car are substantially reduced. Designers can now network many different multimedia applications onto one integrated platform—efficiently and cost effectively.
Roger Taylor is a field application engineer for SMSC's Automotive Infotainment Systems Group. Check out the company's web site at www.smsc.com.
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