mall handheld computers are becoming both more powerful and less expensive. Consider this: the cheapest handheld models, currently priced at $150 to $600, are similar in computing power to a 1988 vintage Mac. (Of course that Mac didn't run for weeks on a couple of AAA batteries.) By combining much of the computing power of a desktop system with the portability of a graphing calculator, handhelds could become the first truly personal computer used by students both in and out of school.

Currently most systems are designed as personal and business organizers. The existing suite of applications needs to be adapted and new ones created in order to optimize these systems for student use. The best designs will also include low-power wireless networking to support ubiquitous communication and practical solutions for working with devices such as probes and cameras.

Currently I'm reviewing the communications and expansion capabilities of the PalmOS and Windows CE Pocket PC platforms, but within the next year I also expect a number of interesting handheld systems to appear based on GNU/Linux.

The PalmOS family of handheld computers as well as the more expensive Pocket PC systems running Microsoft CE v3.0 include several methods for communicating with external devices, other computers and over a network. No common standard has been adopted, so each device uses a slightly different method for this kind of communication. The implications for schools include capability, flexibility and price. Let's look at the choices.

All systems include a basic RS-232 serial port, and all but the most ancient Palms include wireless IR communications. Some of the handhelds can use USB to connect and synchronize data with a desktop computer; however, none of the systems allows connection of USB devices to the handheld. A few systems are capable of using a wireless Ethernet to communicate over a local area network. When selecting a system for use in a school, it is also important to remember that only the PalmOS family will work with MacOS computers.

The simplest wireless networking is based on IR communications. All the CE Pocket PCs include this. Starting with the Palm III, it was included on Palm systems. This allows applications or data to be easily beamed directly from one handheld to another handheld of the same type.

IR communication uses a narrow focused beam of modulated infrared light to transfer data. It is line-of-sight, which means it won't go around corners or through walls and the range extends to approximately one meter. IR communications is based on the IrDA networking protocols. These protocols allow both peer-to-peer communications as well as supporting TCP/IP encapsulated traffic. This means that with the correct hardware and software, such as the Clarinet EthIR LAN, a Palm or Pocket PC can use an IR network connection to send and receive email and browse the Web.

The Palm VII series introduced CDPD wireless WAN capability. This supports wide-area wireless LAN communication in most metropolitan areas of the U.S., using a small portion of the analog cellular phone system allocated to digital packet data. Nominal bandwidth is 19,200 bps but practical speed is about 4800 bps. This is one sixth the rate of a 28,800 bps modem. While this may seem quite slow, it compares well to the capability of an alphanumeric two-way pager. In addition, services like AvantGo will cut out the extraneous content of web sites and make them available without all the graphics. Unfortunately for school use, the monthly service cost is fifty dollars for unlimited usage.

A similar wireless WAN capability is available for the Compaq iPaq Pocket PC by using a Sierra Wireless AirCard 300. This is a PC card CDPD modem and can be combined with a service from Aether Systems to provide portable email and Web access.

Palm has licensed the PalmOS and underlying hardware designs to a number of other manufacturers who have extended the platform in interesting ways. Handspring makes the PalmOS Visor system with the Springboard expansion interface slot. This is an expansion slot on the back of the system into which many different modules can be attached. The interface is electrically quite similar to that of a PC card slot on a laptop and as such is a much more powerful interface than a serial port. Springboard modules not only include hardware expansion but also have the programs for accessing the hardware built into the module. Handspring has extended the PalmOS so that when a Springboard module is inserted, the software associated with it is automatically run. Additionally, the Handspring includes a high-speed USB slave interface for communication. This replaces the serial port on the Palm and allows much faster communication with newer computers that have standard USB ports.

Xircom has announced that a series of networking products called SpringPorts will be available this fall for the Visor. These include two different wireless RF LAN technologies. One is the new high-speed 11 Mbps version of wireless Ethernet called 802.11b (802.11 is the older 2 Mbps standard). The second is based on the new emerging Bluetooth short range, very low power wireless RF networking technology. The 802.11 wireless Ethernet is well established and is a mature technology. It has a 2 Mbps nominal bandwidth and usually a 50-meter range from a wireless hub. These systems are designed to use much less power than wireless Ethernet and also communicate over shorter ranges. Bluetooth devices are just starting to appear on the market.

Symbol has also licensed PalmOS, the Visor system from Handspring, and Windows CE from Microsoft. Around these hardware and software platforms they have created rugged systems with integrated bar code scanners and 802.11 2-Mbps wireless Ethernet communication. In order to support the increased power consumption of these accessories, the Symbol comes with a high-capacity rechargeable lithium-ion battery.

All members of the Palm family of handheld computers come with an RS-232 serial port. This is the default port that connects to the Palm cradle and is used for downloading applications and synching data with a larger computer. The serial port can also be used to communicate with external serial interface devices such as GPS systems and probeware.

True RS-232 communica-tion specifies that data is transmitted using a +/- 9-12 volt signal. To minimize power consumption the Palm devices transmit using only a 0-5 volt range. Without handshaking the Palm devices support communication speeds of 2400 bps. However, if the RTS and CTS hand-shaking signals are used, 115,200 bps is possible.

If you plan on building or adapting devices to connect to the Palm serial port it is best to buy the HotSync cable for the model of Palm you have. This is a cable that connects to the Palm and terminates in a standard female DB-9 connector for a PC serial port. This should be adaptable to any device with a serial interface. Palm also supplies a Mac adaptor for this cable that terminates in a mini-DIN-8 adaptor.

A more powerful handheld system than the Palm family is one based on the latest version 3.0 release of Windows CE from Microsoft. Typically these systems have four times the memory and much faster processors than the Palm family. The latest Pocket PC models range in price from $500-600.

CE systems come in many different form factors, of which three are useful in schools. The Pocket PC is basically a pumped-up Palm. It is a handheld with a small vertically oriented screen without a keyboard. Additionally, there is a handheld clamshell form. This includes a horizontally orientated screen as well as a very small keyboard. Lastly, there is a CE family, similar to a small laptop, that includes a full-sized keyboard and a 640x480 pixel screen.

The Casio E-115, the Compaq iPaq H-3600 and the HP Jornada 548 are Pocket PC systems. All three systems come with serial ports and IrDA networking built in.

The Casio supports a compact flash expansion slot, as well as IR and serial port networking, and a 16-bit color screen. Compact Flash (CF) is an expansion interface analogous to a PC card interface but smaller. It can be used to expand the memory of a system. IBM even has a tiny 300 MB hard drive, which can be attached. Casio expects to have CF wireless Ethernet cards available some time later this year.

The HP Jornada is similar to the Casio and comes with a CF expansion port. However, they have not announced wireless Ethernet capability yet.

The Compaq iPaq comes with neither a CF nor a PC expansion slot. But you can purchase an expansion "jacket" that slips over the body to add either expansion port. Compaq makes the WL100 and 802.11b 11 Mbps wireless Ethernet PC card that works with the PC card jacket.

Ubiquitous low-power wireless networking will make all these systems much more interesting for use by students; however, the educational market is not large enough to drive the technological advance by itself. Wireless Ethernet systems are practical but moderately expensive and power hungry. Wireless systems based on Bluetooth technology appearing this year should be cheaper, smaller, and use less power. The business and home market should be large enough within the next two years to enable successful adaptation for education uses.

Stephen Bannasch is director of technology for The Concord Consortium.
stephen@concord.org

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