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A look at serial buses in vehicles

04 Mar 2014  | Blaine Bateman

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In my previous articles, I talked about integration of more wireless connectivity to vehicles, and the evolution of RF connectors used in vehicles. This time, let's look at data connectivity within the vehicle other than RF.

TE Connectivity has developed a 4-wire connectivity system that can support two twisted pairs of conductors and gigabit-per-second data speeds. Figure 1 shows examples of the HSD connector.

Figure 1: TE Connectivity High Speed Data (HSD) connector. On the left are images of straight and right-angle cable versions. On the right is a USB to HSD adapter. The interface and cable can be used for USB as well as Ethernet, Gigabit Video (GVIF), and Low Voltage Differential Signalling (LVDS).

The TE HSD Catalog lists straight and right-angled cable versions, as well as board mounted in various orientations. (Note: This particular catalogue has a very nice introduction to signal integrity for high speed data; it is worth looking at just for that.) TE indicates these connectors are compatible with the USCAR specifications I mentioned in the previous article. In addition, similar to the RF Fakra connectors I discussed before, the HSD connectors are available keyed and colour-coded. Figure 2 shows the scheme TE uses for these connectors.

Figure 2: Keying and colour coding for TE HSD connectors is similar in concept to the Fakra RF connectors used in automotive RF.

A different path
Molex has taken another path supporting high-speed data for automotive by repackaging a consumer grade, 5-pin shielded connector into what they call HSAutoLink. This data bus is also called USCAR USB, and meets automotive requirements for USB 2.0.

Figure 3: Molex HSAutoLink connectors. Source: Molex According to a datasheet and application note, Molex has certified the HSAutoLink parts to 5000 mating cycles and other USCAR-30 requirements. In addition to USB, Molex provides connectivity in this family for LVDS, IEEE 1394 for automotive, FlexRay (ISO 10681-1:2010), Ethernet, and MOST. FlexRay, now ISO 10681, was developed by a consortium of automotive companies to provide a higher-speed bus than the traditional CAN bus used in automotive.

MOST connectivity
In an article by Masahiko Otake of Mitsubishi in Laser Focus World last year, he gave the history of the MOST Cooperation (not Corporation). Formed in 1998 by Partners Audi, BMW, Daimler, Harman, and Microchip Technology, MOST was a response to Mercedes Benz's successful use of POF (plastic optical fibre) in cars in their D2B network. The Cooperation wanted to standardise a high-speed data architecture as well as take advantage of an EMI-impervious and lightweight solution.

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