At the recent MOST Forum in Esslingen near Stuttgart (Germany), experts discussed the presence and future of the MOST data bus used in automotive environments. Against the background of the AVB/Ethernet camp seemingly having gained ground recently, the MOST proponents mulled the specifications of the next MOST bus generation MOST bus. Key parameters for the 5Gbps optical data bus already take shape.
In a joint presentation of Daimler and the FZI research centre, Guenter Dannhaeuser from Daimler and compared AVB and the current MOST generation, MOST 150. While the comparison covered many aspects, it boiled down to the deterministic nature of the MOST system versus the packet-based and thus not entirely deterministic behaviour of Ethernet-based AVB. Due to its deterministic nature, the MOST system offers better quality-of-service, concluded Dannhaeuser. "Today, there is no better alternative to MOST150", he said. The expert however conceded that flexible topology options are needed to remain competitive.
This is something the next MOST generation will achieve. Besides legacy channels for today's MOST 150, MOST nG will offer enhancements to the current ring architecture in that will be possible to add elements characterized by a bus or star topology. The strong market position of AVB will it also make necessary to ensure maximum interoperability.
At the event the MOST group also introduced a number of enhancements to the existing MOST universe, including a HDCP scheme for the secure transmission of HDMO video data over MOST. This allows a MOST network to move, for example, HDMI content with the required degree of content protection. In this context, the MOST Cooperation has optimized the network for high-quality video streaming.
Currently, MOST150 enables direct isochronous transport of, among others, MPEG video streams without bit-stuffing or transcoding. Now, the MOST standard supports approved content protection schemes for both Digital Transmission Content Protection (DTCP) and HDCP, thus enabling the digital transmission of DVD audio and video, HD-DVD, Blu-ray and HDMI content.
DTCP is used for the networked distribution of protected content and has been approved for MOST for many years. However, HDCP is used for a more direct point-to-point connection between the output of a data source and a renderer. HDMI requires HDCP protection. Data cannot be extracted from an HDCP system and moved with a different protection scheme. With this new specification, the integration of HDMI applications into vehicles is no longer an issue. As with MOST25 and MOST50, application developers can take advantage of secure pipes for transferring sensitive content.
In addition, the MOST group introduced a feature it called Remote Control as an enhancement to the MOST specs. It allows the reduction of the number of Microcontrollers and amount of memory in small and mid-size systems by obsoleting them in peripheral nodes such as displays, cameras, Amplifiers and the like. Instead of having a Microcontroller in each node, the other nodes can be controlled remotely by a central Microcontroller – for example, the one in the head unit. Leaving out the other Microcontrollers and memory can drive system cost down significantly.
Performing all control centrally in the head unit also simplifies the development process considerably, as only one piece of software needs to be developed. Amplifiers and displays run without a local Microcontroller and without local software.
Typical examples for peripheral devices are cameras and rear seat entertainment devices including auxiliary I/Os, displays, etc. At the MOST Forum, the feature was shown in a demo that connects a head unit with several displays and an amplifier over MOST50 with unshielded twisted pair (UTP) copper wire as well as over MOST150 with coaxial cable. The whole system only gets by with just one microcontroller.
This article originally appeared on EE Times Europe.