Expanding the PDA’s Potential

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Just as CD-ROM drives have gone from being expensive add-ons to required components of desktop computers, expansion memory card slots are now a ubiquitous feature on almost all Palm Powered™ handhelds, including models from Palm, Sony, Handspring and HandEra. Yet this feature remains one of the most confusing and widely misunderstood aspects of mobile computing today. The reasons for this confusion are numerous, and after considering the history of expansion memory cards on Palm Powered™ devices, we should not be surprised that PDA-buying consumers are largely unaware of the benefits of the tiny slot on the back or side of their new handheld device.

In this article we’ll clear up some of the confusion by:

  • Reviewing the history of memory Storage and expansion memory on the Palm OS® platform
  • Explaining the reasons why expansion memory is an attractive feature
  • Enumerating the various devices and standards offered by PDA manufacturers
  • Examining closely the Palm OS Virtual File System (VFS), which is the foundation of most of the expansion memory support that is available today

A Brief History of Memory Storage on Palm-Powered Handhelds

You may have heard the adage, "Data expands to fit available memory." It’s true. While we can’t imagine using a PC equipped with a mere 10 megabyte hard drive, that was once considered more memory than anyone could ever dream of using. In fact, the lowliest PC available today has a thousand times more storage than those early computers, and in the brave new world of MP3 digital music, digital photos and full motion video, the trend for the growth of memory capacity seems likely to continue. Given more memory, we inevitably find more ways to make use of that capacity, and our voracious appetite for data is never satisfied.

Predictably, memory capacity on handheld computers has been following a similar growth path. Early devices ran on 512KB of memory or less, but soon models with 1MB, 2MB, 4MB and 8MB appeared. Currently, many of the newer Palm Powered™ models contain 16MB of storage memory. Is the day far off when we will go to the store and buy a PDA that comes with a gigabyte of storage? If history tells us anything, the answer is obvious.

So with PDAs following in the footsteps of the personal computer, offering an ever-increasing standard amount of built-in data storage, why the need for expansion memory cards? First, upgradeability. Without an expansion slot your PDA would not be upgradeable, meaning that if your memory storage needs grew to be more than the available space on your PDA, you would need to go out and purchase a new device with more memory. Second, aside from adding what amounts to a "second hard drive" to your PDA, expansion cards offer other interesting uses, such as the ability to share information (such as photos) with other types of electronic devices, including cameras, music and video players, and printers. Third, expansion cards are perfect for storing large files that you use less frequently than your main applications, for example, a large dictionary, travel maps, or a medical database.

Given these interesting applications, we shouldn’t be surprised that handheld manufacturers have sought to bring to market new devices that offer expansion memory to their customers. Handspring was the earliest with its Visor line, offering a proprietary expansion slot called "Springboard" as a standard component for all of its devices. Beyond expansion memory cards, the Springboard slot has become famous for supporting miniature cameras, barcode scanners, and modems. trG (now Handera) offered an expandable model called the trGPro, which was unique in that the device embraced two industry standards, Compact Flash (CF) and Secure Digital (SD). Sony soon followed with its first Palm OS-based PDA, the Clie (pronounced CLEE-ay), which came standard with a slot that supported its Memory Stick technology, making its PDA compatible with Sony’s other consumer electronics products that (naturally) supported Memory Stick.

By 2001, Palm was in fact the only major device manufacturer that did not offer a built-in expansion memory card slot on its devices. But Palm soon rectified this situation with the introduction of the m500 and m505 (followed by the m125), which came standard with a single slot for handling SD and MMC cards. Now, most (if not all) of Palm’s line of products will embrace expansion card support, as will most of the devices offered by Palm’s OS licensees. At the same time, card manufacturers are offering cards with capacities ranging from 2 MB all the way up to 512 MB, and soon, we will see a card that holds more than 1 GB of data. Further, the price per megabyte of storage is also dropping, making these cards more affordable than ever.

So much for standards

storage cards Perhaps one of the most confusing aspects of expansion memory storage on PDAs is the dizzying array of formats supported. As opposed to the original floppy disk on the personal computer, which quickly became a de facto standard that all PC makers rallied around, handheld manufacturers cannot agree on a single standard format for their collective customers. Compact Flash, SD/MMC, Springboard and Memory Stick all represent different technologies and form factors, and they are incompatible with each other, which means that you cannot insert a card from one format into a slot designed for another.

Why is this?

Although vendors should, for the customers’ sake, decide on a single standard, for many reasons the standardization of memory in PDAs is not likely to happen. For one, each of the device manufacturers has a vested interest in differentiating its devices from those offered by a competitor. An example of this product differentiation is Handspring’s Springboard. Although one could argue on technical merits why existing standards were unsuitable for Handspring’s requirements, Handspring clearly sought to establish a unique brand for its Visor line. The Springboard is a hallmark that ties together the Handspring device lineup, and it is an important product differentiator in the marketplace.

Another reason for the diversity of formats can be traced to the history behind removable media. Before PDA Manufacturers expanded the functionality of their devices, one of the primary uses of expansion cards was with digital cameras. And in the digital camera world, the same situation exists, with CF, SD, MMC and Memory Stick all being used in different models. Because Sony already has an investment in Memory Stick technology across its entire product line, one would expect that it values compatibility across all Sony consumer electronics devices over compatibility with other manufacturers’ PDAs.

Finally, the device manufacturer must keep its target audience in mind. For some types of applications, certain media formats were already prevalent. Handera’s CF and SD slots are in part a response to the established presence these formats already enjoy in some segments of the enterprise market.

The following is a table that outlines the various device manufacturers and their supported expansion memory formats:

Vendor Model(s) Formats
Palm m500 series, m125, m130, i705 SD/MMC
Handspring Visor Springboard
Sony Clie Memory Stick
Handera 330 CF, SD/MMC
Vendor Pros Cons
Palm Embraced open standards; scalable capacities Poor introduction; lack of bundled software to highlight solution; late to market
Handspring Numerous 3rd party modules available Proprietary standard not supported by other device manufacturers; limited capacities; bulky; does not support Palm OS VFS interface
Sony Large capacities; compatibility with other Sony products; bundled software for MP3, photo/video Not supported by other device manufacturers
Handera Embraced open standards; scalable capacities Relatively few customers; lack of bundled software to highlight expansion card benefits

Palm’s Initial Rollout: A Closer Look

Palm was the last of the major device manufacturers to offer a handheld with an expansion card slot. However, the huge popularity of Palm’s devices, as well as its position as the "standard-bearer" for the Palm OS and its licensees, the implementation of this technology has a large impact on customers and the industry overall.

Unfortunately, the initial rollout of Palm’s expansion slot-enabled devices did not communicate the value of the memory slot as well as it could have. This lack of communication was in part responsible for the current mystery and confusion surrounding how expansion slots work on PDAs. The first units, the m500 and m505, did indeed ship with a single SD/MMC slot. However, the device packaging told customers almost nothing about the slot, offering no explanation of what it could be used for or how to use it even if they were able to figure out a use on their own. The device did not come with a blank card, and it was unclear where to obtain one. Although expansion-aware applications were available on a companion CD, many customers never installed the software from the CD, and none of the built-in Palm software applications (Address Book or MemoPad, for example) had been modified to make use of expansion media. Palm’s choice of how to give the user access to the expansion slot was also obscure, requiring the user to choose a category named "Card" in order to see any applications stored on the card.

Third party software developers were also slow to enhance their applications to support Palm’s expansion technology, leaving puzzled customers to figure it out for themselves. A slew of enhanced expansion-aware launchers, shells and file managers did appear on the scene in an attempt to bring order to the chaos, but the damage was done. A relatively small but enthusiastic community of adventurous early adopters took the plunge and made the effort to put the pieces together and spread the word on how to make use of the new slot.

After a slow start, we are finally starting to see a critical mass of expansion memory aware third party applications, but the industry still has a ways to go before one can say that expansion card support is universal in the sense that floppy drive support is universal on desktop PC’s. The operation is relatively obscure for individuals to migrate files and applications from their PC to their PDA’s memory card. The problem grows exponentially for IT managers responsible for the rollout of PDAs to hundreds or thousands of mobile employees. Improved tools appear to help manage these problems, but at present it requires some research to find 3rd party solutions that bridge the gap.

Palm OS 4.0 and VFS, the Virtual File System

Coinciding with the availability of Palm’s m-series devices was the introduction of a new version of the Palm operating system, version 4.0. Among other aspects, one of the more significant enhancements was the arrival of expansion card support built-in to the operating system with documentation for third-party developers on how to make use of the new cards. For non-programmers, the only visible signs of improvement were the addition of a new "Card" category in the standard application launcher, as well as a new menu command for copying a file to or from a card. Palm referred to the new built-in OS support as the Virtual File System, or VFS for short.

One of the biggest areas of confusion for customers and developers alike that are new to VFS is the assumption that an expansion card is treated like a "second hard drive" on the PDA. In the desktop world, you can add more hard drive storage to your PC in about half an hour with a screwdriver, and after you are done, you can work almost seamlessly with your new drive. You can run applications from the second drive just as easily as you would from the original, and you can even store your application data on a different drive than the application itself. Typically, the addition of memory is a relatively painless operation.

With VFS, Palm significantly changed the way that applications load and store their data, creating a situation where applications need to work with files one way if the files were on the original PDA’s memory ("RAM"), and work with files another way if the files were on a VFS-mounted expansion card. This distinction greatly slowed down the rollout of new VFS-aware versions of Palm applications. Further, Palm’s VFS implementation did not allow the ability to run applications directly from card storage. Palm’s launcher did allow you to store an application (such as a game or word processor) on the card, but when you tapped on the application icon, Palm OS would work behind the scenes to temporarily copy the application to RAM first, then run it. Depending on the size of the application, a noticeable but not unreasonable delay would occur while the application was being copied over. And Palm’s built-in "Core Four" (Address Book, Datebook, ToDo, and MemoPad) remained blissfully unaware of the existence of VFS and in fact could not be moved to card storage or store their data on a card.

A problem with this scenario is that even if you store a large application on a VFS-mounted card, that application will not be able to recognize and use its own databases if you choose to store them on the card as well. For example, if you take a VFS-unaware dictionary application and put it as well as the dictionary database on an expansion card, when the dictionary application is run, it will naturally be copied first to RAM, but then will be unable to find its dictionary database. To help solve this problem, Palm introduced the concept of "bundled components," in which a developer could tag the various databases and other components of their application, so that Palm OS would be obligated to move all of the application components from the card to RAM upon launching. Still, not every application vendor took this step, and as a result the end-user must determine on a case-by-case basis whether or not his or her applications can be run from an expansion card.

These issues stem from a design decision Palm made when it contemplated how to support expansion cards. One can sympathize somewhat with Palm’s dilemma: the core operating system’s file system is very minimal, and it would not scale well to support removable media that are expected to grow to very large sizes. Also, one gets the impression that Palm imagined most of the utility of expansion media being in terms of reference materials, e-books, and other read-only data. In my experience, this premise is counter to customers’ expectations, which usually assume they are expanding their 8MB device to become a 72MB device with the addition of a 64MB card.

Expectations notwithstanding, overall VFS is a good addition to the Palm OS, and even though it requires some commitment on the part of the developer community in order to fully utilize it, the system is built to handle a variety of uses, and appears to scale well to large sizes of expansion cards. To Palm’s credit, the company has also been very successful in migrating its OS licensees to the 4.0 version, so applications that are VFS-aware in general will run on any modern PDA (a notable exception to this trend is Handspring – Visors still run OS 3.5, and thus are not VFS-aware, although 3rd party vendors are working to resolve this with add-on utilities).

The Road Ahead

I’m pleased to report that the end result of these developments is that the industry will explore an increasingly rich variety of applications for expansion cards, and PDAs in general. My current device is a Sony Clie 760C, equipped with a 128MB Memory Stick. I have about an hour’s worth of music in the form of MP3 files on it that I listen to when I go for a jog. I’ve moved approximately 10 large 3rd party applications to the card, freeing up four or five megabytes on my Clie’s built-in RAM, and these applications launch just fine from the card, and I can store beautiful color pictures of friends and family on the card, making my PDA a virtual wallet. These capabilities were unheard of just a year ago, but now they are all possible, and my PDA is more indispensable than ever.

Beyond my own personal usage, some of the more exciting possibilities lie in the adoption of expansion media as an efficient distribution mechanism for company documents, reports, product data sheets and applications. This application of hardware brings significant convenience to the mobile workforce, making it very cost-effective to distribute large volumes of timely data in a lightweight format without requiring wireless connectivity or expensive laptops. Complete patient medical histories, large reference materials, product catalogs, real estate home listings, telephone books, maps and other navigation aids-all of these applications provide but a small peek at the possibilities.

In the coming months and years we can look forward to higher and higher Storage capacities–to 1GB and beyond–at sequentially lower prices. Creative people in the handheld industry will dream up new applications and tools, and in time, just as with our old friend the PC, we will have difficulty recalling how we ever got by with a PDA that came without one of those curious little expansion slots.

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