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By Chris De Herrera 
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The Myriad of Peripherals that are supported on
Pocket PCs, Notebooks and PDAs

By Chris De Herrera, Copyright 2003
 Version 1.00  Revised 10/27/2003

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When I think of Mobility and using my Pocket PC or Notebook PC, I also think of how I can use these devices to communicate and store information.  I want to be able to easily share information with other PCs via the internet or an internal network as well as transfer large amounts of information using memory card.  This article describes the different form factors that storage and peripherals take with the average Notebook PC or Pocket PC.  Also, I will focus on describing the different capabilities of these peripherals and how they may affect your mobile use on a day-to-day basis.

Whats Out There for me to use?

Right now there are 5 major standards for storage and peripherals that you can use with your Notebook PC or PDA.  The first form factor that most people think of with mobility and Notebook PCs is the PC Card.  The 4 other form factors are really focused on specific uses that are specialized.  CompactFlash, commonly abbreviated CF, is commonly used in digital photography as well as Pocket PCs.  SmartMedia cards were designed to offer storage for digital cameras.  Secure Digital cards, commonly abbreviated SD cards are a smaller design, which is supported, in smaller digital cameras and Pocket PCs as well as Palm handhelds.  The last common form factor is really vendor specific.  It is called the Memory Stick and it is commonly found in Sony products.  With this myriad of form factors there are multiple reasons that OEMs and users may choose to use one design over another.   Now lets take a closer look at each form factor.

PC Card The King of the Notebook PC

PC Cards originally started out as PCMCIA cards.  They provide the ability to store information on the cards in ATA FAT (like a regular hard disk) format so you can use them on your PC as well as your Pocket PC without reformatting the data.  The major manufacturers of storage include Sandisk, Lexar, Pretec and Kingston.  The PC Cards are the same size as a credit card but they are thicker.  They come in 3 different thicknesses called type I, type II and type III.  Type I cards are 3.3 millimeters thick, type II cards are 5 millimeters thick and type III cards are 10 millimeters thick.  Beyond the physical size of the card is the design of the electrical interface.  PC Cards support 2 different designs the original 16 bit design and a new 32 bit design called CardBus.  Cardbus enabled devices support both 16 bit cards and 32 bit cards.  Most Notebook PCs now support CardBus while only Pocket PCs support the original PC Card standard.  Also, most Notebook PCs and some Pocket PCs support type II cards.   PC Cards support 2 different voltages 3.3 volts for low power and 5 volts.  Also, the specifications for PC Cards allow designers to use up to 1 amp to power their designs.  Clearly this is outside of the design characteristics of most Pocket PCs and even some Notebook PCs.    Also, some manufacturers have designed multifunction PC Cards, which integrate Ethernet and Modems in the same card.  I am not aware of any PDA that can take advantage of the multifunction PC Cards functionality since none of the vendors offer their own special drivers to support their cards.  There are PC Card flash memory cards as large as 1 GB.  Also, there are type II hard disks from Toshiba as large as 5 GB!

CompactFlash PC Card Features but Smaller

CompactFlash cards use the same electrical connection as the original PC Card does but they are much smaller.  If you placed 2 CompactFlash cards end to end, they would still be smaller than existing PC Cards!  CompactFlash cards come in 2 thicknesses called type I and type II just like the PC Cards do.  Type I is 3.3 millimeters thick and type II is 5 millimeters thick.  The CompactFlash cards are designed to work at either 3.3 volts or 5 volts depending on the slot they are inserted into.  Also, you can use a CompactFlash card with a PC Card adapter in a standard PC Card slot.  This allows you to read and write storage information on the cards as well as use peripherals with your Notebook PC.  There is a standard called CF + which expands the CompactFlash slot functionality to allow for the use of peripherals.  There are CompactFlash ATA flash memory cards as large as 1 GB as well as real hard disks from IBM as large as 1 GB as well.

SmartMedia Cards

SmartMedia cards are a little larger than the CompactFlash cards and they are about 2 millimeters thick.  They are used for storing information for devices like digital cameras and MP3 players.  This form factor has not significantly changed since its introduction.  It is limited to supporting 128MB for storage.

Secure Digital and MultiMedia Cards

Secure Digital Cards are the smallest of all the storage devices available today.  They are just a little larger than a postage stamp!  They are about 1.5 millimeters thick and use a serial interface to read and write.  They also use 3.3 volts for lower power.  The current design allows for multiple speeds for reading and writing depending on the device you plug them into.  The speed varies from 2.5 megabits to 10 megabits with low power devices only supporting 2.5 megabits.  Also the Secure Digital cards can support storage and peripherals. The Secure Digital card has 2 unique features.  It includes a memory protection switch which makes the card read only.  Also, the Secure Digital card supports encryption of all data stored on the card as an option, however the hardware manufacturer of the device you are using it with has to support this as well for your data to be encrypted. A close cousin of the Secure Digital cards is the Multimedia Card, which does not support multiple read and write speeds.  The Multimedia Card is fading in favor of the Secure Digital card in the marketplace.  There is a standard called SDIO, which expands the capabilities of the Secure Digital slot to include the support for peripherals.   There are Secure Digital cards as large as 512 MB while the largest MMC card is 128 MB.

Memory Stick

In between the size of the PC Card and the Secure Digital cards lies a format called the Memory Stick.  It is commonly available in Sony 8mm digital video cameras as wlel as their Vaio line of notebook PCs.  Originally designed by Sony for storage, the Memory Stick is now used for some peripherals as well.

Transferring Data

With the PC Card, CompactFlash card, Secure Digital Card and Memory Stick you can purchase a USB adapter to read and write storage cards for these form factors.  Most USB adapters are designed to allow you to use only one type of card at a time.  However some vendors like 3M offer adapters that support multiple formats with adapters.  Other vendors like the TravelStar from Power Quotient International offers the ability to use multiple different formats at the same time such as the 4 in 1, 5 in 1 and 6 in 1.  Also, Sandisk offers the Cruzer that is a very small Secure Digital Card to USB adapter that easily fits in the palm of your hand.  These adapters are really designed to travel with you.  They are very small and can easily fit into an accessory bag.


There are a variety of adapters so users can use Secure Digital, MultiMedia Cards, Memory Stick and SmartMedia cards in PC Card slots and CompactFlash slots.  Sony offers a PC Card adapter, which allows notebook PCs, and Pocket PCs to read and write to the Memory Stick.  Sandisk offers a 4 in 1 adapter that allows you to read and write all formats with the same card!  Pretec offers a CompactFlash card adapter for SmartMedia and a 4 in 1 CompactFlash adapter to read all smaller memory card formats as well.   Further if you are using a CompactFlash card you can purchase a Type I or Type II CompactFlash to PC Card adapter.  This adapter will allow you to use your CompactFlash memory card or peripheral in a PC Card slot.  If you have a CompactFlash card, I recommend purchasing a Type II adapter since it supports both Type I and Type II cards.  With all of these adapters you can use 2 PC Cards in notebook PCs that have stacked PC Card slots since they do not extend beyond the width of the PC Card adapter.

Peripherals  - Different Ways to Communicate

Peripherals in these different form factors are really designed to allow Notebook PCs, Pocket PCs or other PDAs to communicate.  Probably the most common peripheral is either the PC Card Modem or Ethernet card since most earlier generation of notebook PCs did not have these built in.  The PC Card format has the widest range of supported peripherals including Wi-Fi 802.11b , Bluetooth, GPRS/GSM, CDPD, Ethernet, Serial and Modem.  The PC Card slots also support CompactFlash peripherals with an inexpensive adapter so you can use the same peripheral with your Notebook PC.  The CompactFlash cards include Wi-Fi 802.11b, Bluetooth, CDPD, GPS, Ethernet, Serial and Modem.  The small size of the CompactFlash form factor usually leads to a design with some portions of the peripheral external in either a box or a dongle.   So make sure you look at the design of your peripheral before deciding which one will best fit your needs.  Some vendors like Socket Communications have recognized the issues with the design of a dongle by creating their ruggedized connectors.  These ruggedized connectors are designed to not break as easily as the original dongles that were offered with PC Cards, however they are not removable.  Luckily Socket has a good warranty for their peripherals so you can contact them if you have a problem with a ruggedized CompactFlash card.  Right now we are at the beginning of a new set of peripherals that are designed to use the Secure Digital cards and Memory Stick for I/O.  Examples of early devices include the Toshiba Secure Digital Bluetooth adapter.

Here is a table of different vendors and the types of peripherals that they offer:




Socket Communications






PC Card, CompactFlash, SecureDigital Card, MultiMedia Card, Memory Stick

PC Card, CompactFlash, SecureDigital Card, MultiMedia Card, Memory Stick

CompactFlash Ethernet, Modem, Barcode Reader, Bluetooth, WiFi

CompactFlash Ethernet, Modem, Bluetooth, Camera

CompactFlash  Hard Disk

PC Card Hard Disk


Original designer of the CompactFlash card and Multimedia Card


Offers the widest range of CompactFlash solutions available.


Original designer of the CompactFlash hard disk

Provides the largest PC Card Hard Disk solutions available today

Peripherals Other Specialized Devices

Some of the other peripherals that are available in the PC Card and CompactFlash card form factor are specialized for specific purposes.  For example vendors like Symbol Technologies and Socket Communications offer 1D and 2D barcode scanners for inventory applications.  Also, mainstream vendors like HP offer peripherals like CompactFlash camera cards for Pocket PCs as well.  There are a myriad of specialty devices that are available to meet special needs like smart card readers, and credit card readers.  Also, there are adapters to allow CompactFlash slots to use PC Card peripherals that are low voltage and have driver.

Securing your Data

Most of these form factors for storage do not support encryption in their hardware design.  The one exception is the Secure Digital (SD) card.  The SD card does support built in encryption however there is one major caveat to using it.  The devices you use the SD card in need to support encryption as well.  Right now the Pocket PC 2002 does not support the hardware based encryption of the SD card.  For all other storage devices, I suggest using software based encryption for the specific platform you are using it with. You should be aware that you will need to have desktop software that supports encryption if you want to interoperate with your desktop.

Choosing Form factors and Their Future

Over time I expect some changes will occur with the form factors we have been discussing.  Right now the use of MultiMedia Cards is declining and I believe this is due to the Secure Digital card, which offers more flexibility and is about the same size.  I expect more users to purchase CompactFlash cards since they are smaller than PC Cards and they offer the same features.  Also, through the use of an adapter, users can purchase CompactFlash cards today for use in their notebook PCs and they are ready to use them in future PDAs with no additional costs for peripherals.  As for the Memory Stick, I do not see this form factor increasing in market share.  Sonys original desire to create a competitive design has not garnered the support in the marketplace that is required for vendor adoption in a wide variety of devices. 

Overall the choice of which form factor you need is largely dictated by the design of the devices you are using.  Make sure that your device supports the appropriate functionality for its slots so you can take advantage of storage and peripherals to meet your needs.


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