Is there an open source version of the MOST protocol?

From the above link:

  • MOST (Media Oriented Systems Transport) is a high-speed multimedia network technology optimized by the automotive industry. It can be used for applications inside or outside the car.

    The serial MOST bus uses a ring topology and synchronous data communication to transport audio, video, voice and data signals via plastic optical fiber (POF) (MOST25, MOST50, MOST150) or electrical conductor (MOST50) physical layers.

    MOST technology is used in almost every car brand worldwide, including Audi, BMW, Hyundai, Jaguar, Land Rover, Mercedes-Benz, Porsche, Toyota, Volkswagen and Volvo.

  • \$\begingroup\$ What do you want to do? \$\endgroup\$
    – starblue
    Commented Dec 4, 2011 at 18:43
  • \$\begingroup\$ Control lights and stuff in the car with as little cabling as possible. \$\endgroup\$ Commented Dec 4, 2011 at 23:00
  • 2
    \$\begingroup\$ The lights are probably controlled via CAN and/or LIN, not MOST, which is for audio/video stuff. Or do you have evidence to the contrary? \$\endgroup\$
    – starblue
    Commented Dec 5, 2011 at 10:09
  • \$\begingroup\$ Oh, didn't know, no I don't. \$\endgroup\$ Commented Dec 5, 2011 at 10:48

2 Answers 2


If by Protocol you mean available functional open source software, then maybe not. It's said to be coming from several and may or may not have arrived.

If by protocol you mean protocol the "MOST cooperation site may be of value - but I'd expect that you were well aware of this already.

Here is their specifications and procedures page including PDFs of last years version 3VOE2 and older 2006 Rev V2.5.

MOST Specification, Rev 2.5, 10/2006 is 242 pages long and 3V0e2 is 262 pages. You have to register to access them but access is free.
They'd probably allow the terminally enthused to build something from scratch BUT are probably not what you are after,

Organisational procedures downloads here and here

Background for interest from here

MOST Protocol Gaining Ground
By David E. Zoia
Ward's AutoWorld, Nov 1, 2006 12:00 PM

  • The Media Oriented Systems Transport networking protocol, which has worked its way into mostly high-end European cars over the last five years, is gaining traction in Asia and eventually could see wider use in North America, a key supplier says.

    Designed to allow onboard infotainment systems to talk to each other, while reducing wiring needed to connect devices such as DVD players and radios, the MOST operating standard is in place on 38 vehicle platforms (soon to be 40), say officials from Hauppauge, NY-based SMSC.

    MOST was developed by a consortium of companies, beginning in 1998 with OASIS (since purchased by SMSC), DaimlerChrysler AG, BMW AG, Audi AG and Harman/Becker Automotive Systems GmbH. It since has expanded to include 16 auto makers and more than 70 suppliers.

    Its first application was in the BMW 7-Series in 2001, but the migration into mid-range vehicles is growing, and the list of vehicles now employing the protocol includes some low-end models such as DC's Smart and Mitsubishi Motors Corp.'s Colt. Other vehicles with MOST networks include Mercedes A-, C-, E- and S-Class cars and the Porsche Boxster and 911.

    In using MOST in one platform, DC reduced the number of cables from six to four, cut cable length by 25% to 29.5 ft. (9 m) and eliminated two of every three conductors per cable, SMSC says.

    Likewise, cable costs were slashed more than half. Initially, the MOST standard was designed to work with plastic optical fiber, in part to eliminate electromagnetic interference (EMI) issues, but also because of its lighter weight and ease of recycling.

    But using plastic optical fiber requires wiring harnesses to be assembled differently, and that may have caused some auto makers to shy away from the technology.

    However, earlier this year, under the direction of Toyota Motor Corp., the MOST consortium developed a way to substitute inexpensive and easy-to-handle unshielded copper wire in place of optical fiber, allowing OEMs to employ MOST while maintaining existing production methodologies.


I doubt if there is an open source protocol that provides substantially similar functionality as MOST, mainly because there's little need for it. The companies who make MOST equipment don't need an open source protocol, because they have MOST. Hobbyists, who might want to use open source resources, are not constrained by interoperability with other components in the vehicle, so they are free to invent their own protocol if they want some of the features of MOST.

The MOST Cooperation does provide an online book that at first glance seems to reveal most of the details of the protocol.

A simpler alternative to MOST, if you just want a point to point link for audio data, is S/PDIF and TOSLINK. Neither of these is open source, but there does seem to be substantial information online to enable designing interoperable components. If you look into MOST, you'll find it's basically S/PDIF multiplexed onto a packet ring network, with a bit of additional control information and low speed side channels added.

Olin, answering your other question, mentioned the CAN bus, which might be more accessible to you if this is a hobby project, but also might not be as well adapted to multimedia data as MOST.


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