Streamlining interconnections for high-performance, compact designs

August 28, 2015

Jurgen Urban-August 28, 2015

Engineers must address numerous concurrent trends as they strive to craft innovative designs for mobile and mobile-influenced devices. Miniaturization of silicon chips, gigabit-per-second data speeds, the Internet of Things and new interest in modular architectures, for example, are opening up compelling opportunities to improve functionalities and create new design efficiencies.

One challenge associated with these trends is the need to simplify the electronic interfaces that interconnect device chipsets and peripheral components. I’d like to use this article to discuss MIPI UniPro (Unified Protocol), a versatile transport layer that can address these important needs. MIPI UniPro simplifies interconnections for smartphones, tablets, laptops, cameras and multimedia devices, as well as the various types of smart watches, health monitors and other innovative products that are entering the market as part of the Internet of Things.

MIPI UniPro: Its purpose and applications in the market
MIPI UniPro, offered by MIPI Alliance, specifies a transport layer protocol stack for switched packet transfer. Implemented on top of the MIPI M-PHY physical layer, it forms the MIPI UniPort-M interface.

As its name indicates, MIPI UniPro is a unified protocol. It is not dedicated to specific applications, as protocols often are. It was designed from the outset as a general-purpose, lightweight protocol with excellent protocol efficiency that is dedicated to mobile devices. It does not suffer from the heavy overhead imposed by other well-known legacy protocols that have been developed for the PC industry, where power consumption is not always a concern. It can be used as a standalone interface for inter-processor communications (IPC) or as a building block for multimedia interfaces. It can be used with other MIPI or non-MIPI application layer protocols.

MIPI UniPro’s and MIPI M-PHY’s versatility are illustrated by the types of organizations that have adopted the specifications. The JEDEC organization uses UniPort-M to provide the basis for its Universal Flash Storage (UFS) specification. Google is using UniPort-M to connect the modules that will make up its Project Ara smartphone platform. The MIPI Camera Serial Interface (MIPI CSI-3) uses the UniPort-M interface to connect cameras with the application processor.

The specification’s history
MIPI UniPro has been available since 2007. The current release, v1.6, has been available since September 2013.

The role for MIPI UniPro in the industry began in 2004, when MIPI Alliance formed the MIPI UniPro Working Group to develop an interoperable interface that could meet a wide range of needs. The group’s objectives were to support a variety of component types and data traffic in a single protocol stack; reduce and standardize the number of physical links between devices and thus pave the way for design modularity to shorten the design and manufacturing cycle of new phones; simplify system integration of key components; and ensure backward compatibility of all versions to future-proof the specification.

Highlights of key technical features with use case scenarios
Following are summaries of some of the technical features that enable MIPI UniPort-M to meet so many diverse interface needs.

Versatile physical link: MIPI UniPort-M makes it possible to use multiple logical channels on one physical link. A so-called CPort serves as a bi-directional application entry and exit point for each of the up to 2047 logical channels. Application messages on each logical channel are fragmented, dispatched with a UniPro frame header and footer, and travel time-multiplexed through the physical M-PHY channel, as illustrated in Figure 1.

Figure 1. Example of a UniPro Frame Multiplex.

Therefore a single physical channel can be used to support the logic needed to interface multiple applications, such as display, audio, control, storage, and others. Alternatively, a single application can share a bi-directional CPort channel for multiple purposes: For example, a display device can use a CPort channel to connect to the display and use the reverse channel for touch screen data (see Figure 2).

Figure 2. Using MIPI UniPort-M as a common transport channel into a media module.

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