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Interface issues loom for full-featured phones

Posted: 19 Feb 2003 ?? ?Print Version ?Bookmark and Share

Keywords:telephone? digital cameras? mp3 player? handheld game device? contactless access card?

With more new phones poised to morph into digital cameras, MP3 players, handheld game devices, and even contactless access cards, the 3GSM World Congress, will grapple with how best to connect all of those non-phone peripherals with an application co-processor in handsets.

The interface discussion will unfold against a backdrop of chip rollouts from Texas Instruments Inc., STMicroelectronics, and Philips Semiconductors.

Philips today will launch the Nexperia Cellular System Solution, based on an ARM processor and an open DSP core originally developed in-house as the R.E.A.L. DSP but now offered by Adelante Technologies. Philips said it has pulled together all of the intellectual property related to multimedia and security, developed internally and externally, onto the Nexperia platform.

By using the same platform for co-processors and baseband processors, specific IP demanded by a handset vendor can be quickly ported to a requested processor, said Thierry Laurent, general manager of the mobile communications business unit.

TI, meanwhile, has just rolled out two Omap processors while ST has unveiled its Nomadik multimedia processors.

Elsewhere, TransChip, a developer of single-chip cameras, will use the GSM World Congress to announce that its camera has found a home in the Intel/Microsoft SmartPhone reference design, to be unveiled in Cannes tomorrow. The TransChip imager is integrated with Intel's Xscale PCA26x processor.

While the voice model is still the cellphone industry's gold standard, the multimedia trend shows that "this market today is transitioning from a telecom market to a consumer market," said Loic Lietar, GM for STMicroelectronics' Cellular Terminal Division. Chipmakers are pitching an unprecedented number of new application coprocessors at handset vendors as critical to the new breed of phones, and mobile chipset suppliers are confident that high-volume camera phones will find a market in Europe this year.

With or without network connections, picture taking, in fact, is considered one of the lowest-risk features among a plethora of non-phone phone functions. "Personal content creation is what gets people excited," said Richard Kerslake, director of TI's Wireless Computing Group, who termed digital photography "an easy-to-grasp new capability."

But selecting the most appropriate digital camera module, including a digital imaging processor, for a handset might not be as straightforward as chip vendors want handset system designers to believe. Partitioning between a pre- and post-imaging processor and a multimedia coprocessor is far from clear. Partitioning between an imaging module - a combination of a CMOS image sensor and an imaging-processing chip - and an application co-processor or baseband chip in a handset poses similar difficulties.

"Partitioning boundaries tend to shift around between a multimedia engine in a handset and a camera module," observed Mike Walters, mobile-imaging program manager at Agilent Technologies. In order to guarantee imaging quality, Agilent "hopes to maintain the control and the ownership of its image-processing pipeline," he added.

Even the same semiconductor company may offer several diverging solutions. Philips, for example, has three solutions, two of which are based on the new Nexperia platform. One is a standalone co-processor that could potentially provide everything from JPEG, MPEG-4, MP3, A/V streaming and GPS. Handling all these multimedia functions in software on an ARM core may not be the most efficient solution, but it works for high-end smart phones and "can get handset vendors faster to market without ever having to touch a baseband processor," said Laurent.

The second solution, also Nexperia-based, is a baseband processor already integrated with specific applications such as JPEG compression. This will be a cost-effective GPRS solution at the point when significant volume exists for camera phones, Laurent said. The third possibility is a separate imaging processor designed for Philips' own CMOS imaging sensor. OEMs could plug this chip into handsets without integrating a new application coprocessor or a new baseband processor embedded with multimedia features.

Calling the integration of camera modules in mobile phones the single largest technological challenge facing today's handset manufacturers, TransChip touted its TCS5700 chip's ability to output YUV directly, with no preprocessing from the cellphone's baseband DSP. The device is a complete VGA camera including image sensor, programmable image processor and real-time JPEG codec. The camera interface also supports scaling and formatting of the YUV or RGB output to various resolutions.

The uncertainty clouding the camera interface may be one of the factors that's motivating companies like TI and ST to work together on an Open Mobile Application Processor Interface (OMAPI). "When 20 camera modules are coming to the market with 20 different interfaces, handset vendors are bound to miss their cost targets or end up having a camera phone with bad imaging performance," TI's Kerslake said. OMAPI also will address interfaces for peripheral components, such as LCDs, and for serial ports such as UART and USB, according to ST.

On to the API

ST's Lietar called OMAPI "the last piece of the puzzle" for creating an application programming interface on a phone level. TI and ST are aligning the architecture of their multimedia co-processors by creating a hardware abstraction layer via OMAPI. "We are pulling this off without standardizing hardware," stressed Lietar.

But not everyone is climbing aboard the OMAPI bandwagon. Some companies are promoting their own APIs, such as Qualcomm's Brew. And Philips' Laurent said that Philips won't necessarily join ST and TI in the OMAPI effort. Philips is going for an even higher level of standardization, said Laurent, including "agreeing on a piece of software, or standard" that lets handset users switch seamlessly among GPRS, Bluetooth and 802.11, choosing the cheapest and clearest pipe. Philips hopes to create a forum for such an initiative this year, Laurent said.

- Junko Yoshida

EE Times

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