Next time you're on a transoceanic flight, be sure to pay close attention when the flight attendants come around selling duty free merchandise. That handheld point-of-sale terminal which is used to enter your order and print your receipt may well contain Embedded Linux. Here's why: a Padova, Italy based manufacturer recently introduced a new Linux-based rugged handheld computer which is designed to meet… the needs of a wide range of commercial mobile computing applications. Earlier models of this device are already in use on several major airlines for duty-free sales, and the new Linux-based version won't be far behind.

Although the DAT500, from 4P Mobile Data Processing, includes all the expected functions of a consumer palm-top computer (graphical user interface, touchscreen, handwriting recognition), the device is highly rugged and reliable, and has successfully passed testing for compliance with commercial aviation safety standards. In addition to its PDA-like features, the unit also comes with a built-in bar code scanner, credit card reader, smartcard interface, and printer — making it perfect for mobile point-of-sale and inventory management applications. Best of all, it runs Embedded Linux!

Summary of features. . .

The DAT500's extensive list of features includes . . .

• 240 x 320 pixel (1/4 VGA) backlit LCD display
  
• Touch screen supports data pen input and handwriting recognition
  
• 19-key numeric/functional backlit keypad
  
• Built-in printer for fan fold or roll paper with internal paper housing
  
• Laser bar code scanner
  
• Magnetic card reader (for today's credit cards)
  
• Double smart card reader/writer (for next generation credit cards)
  
• Two Type II PCMCIA slots, protected by a lockable cover
  
• One RS232 serial interface, usable up to 115K bps
  
• One IrDA interface
  
• Quickly replaceable and rechargeable NiCd or NiMH battery pack

Typical applications

The target markets for the device are all those in the area of mobile computing where a rugged and fully self-contained handheld unit are required — mainly related to mobile sales, transportation logistics, and field service. Here are some of the ways the DAT500 is already being used . . .

• In-flight duty free sales — on several major commercial airlines, the DAT500 is used to scan product bar codes, read credit cards for payments, and print customer receipts. The DAT500 is certified to safely operate onboard aircraft, in accordance with RTCA DO-160C/EUROCAE ED-14C, Section 21.

• Door-to-door frozen food sales — several European retail food distributors use the DAT500 as a mobile inventory management and point-of-sale system for door-to-door frozen food sales. Delivery personnel use device to scan product bar codes, accept credit card payments, and print customer receipts. Purchased products are immediately delivered from the stock inside a refrigerated van. In this application, the device contains a full sales and inventory management application program, which is linked to a corporate database.

• Parcel tracking — the DAT500 is ideal for use as an aid in tracking security bags and boxes carrying money, checks, and other valuables that are individually bar coded and transported in armored vehicles. Pickups and deliveries are traced by scanning each bag's bar code, and printing a double copy receipt which must be signed by both driver and recipient.

Of course, there are many other possibilities. Some expected applications include utility meter reading, field service, parking violations, and fare collection on trains and buses.

What's inside the box?

The current version of the DAT500 is based on a three-level CPU architecture . . .

• Main CPU — at the top level, an AMD Elan SC300 CPU (equivalent to a 386 CPU) running at 33 MHz, controls the system. Memory resources consist of 4 MB static RAM and 512 KB Flash. I/O ports controlled by the SC300 are one RS232, one IrDA, and two PCMCIA slots. The SC300's parallel port is not externally available.

• Auxiliary CPU — an auxiliary CPU, communicating with the Elan SC300 via its built-in parallel port, manages all other peripherals. These include printer, laser bar code scanner, magnetic card reader, double smart card reader, and the battery charging circuitry.

• Peripheral CPUs — at the lowest level, the printer and laser bar code scanner are managed by their own dedicated microcontrollers.

All of the Embedded software required to manage these functions resides in Flash memory and is field upgradeable without requiring the device to be opened.

The DAT500 is currently offered with a choice of DOS or Linux OS. The device boots from internal Flash memory and divides its SRAM memory into a pair of 2 MB blocks: 2 MB as operating memory, and 2 MB as a RAM disk. The Flash disk cannot be written to by customer applications. Additional disk devices are installed by means of PCMCIA ATA Flash cards. An internal rechargeable Lithium battery backs up the SRAM and the real-time clock when the main battery is not present or is discharged, allowing the RAM disk data and clock to be maintained for up to two months of non-operation.

A next generation of the DAT500, based on a 206 MHz Intel StrongARM SA1110 system-on-chip RISC processor with 64 MB DRAM, is in development and is expected to become available during the first quarter of 2001. Other ongoing developments are in the areas of built-in wireless communication (GSM-GPRS, CDPD, CDMA) and multimedia capabilities.

The Linux implementation

The Linux version of the DAT500 makes use of an 8 MB Flash ATA PCMCIA card, on which the Linux files are stored. Currently, the Linux version first boots DOS, and then the Linux kernel is launched from the Flash card. The final version of the system will eliminate the two-step boot process, booting Linux directly.

4P developed the Linux support for the DAT500 by themselves, starting from Caldera Open Linux 2.3 and currently using Linux kernel version 2.2.10. Display management is based on OpenGUI. Microwindows was also tested, but its performance was found to be too slow on the 386-level processor. No other Linux software components are currently offered, but a web browser will be added to the system at the time wireless connectivity is added.

The main Embedded Linux challenge, according to Silvano Mansutti, managing director of 4P Mobile Data Processing, was to come up with the appropriate graphics screen management software. The project began by studying Microwindows. However, the performance of Microwindows was inadequate on the system's 33 MHz Elan SC300 386-class processor. Given the project's tight schedule constraints, the development team decided to switch to OpenGUI, which appeared to provide much better performance.

Another challenge, in attempting to embed Linux, was the system's extremely limited memory resources (4MB RAM, 512KB Flash). However, that was easily overcome through the use of an ATA Flash PCMCIA card from which Linux is loaded.

Why embed Linux?

“We selected Linux as the operating system,” says Mansutti, “because, as a hardware manufacturer, we wanted to offer our customers a product capable of supporting the best available application software solutions. Linux is growing very quickly, is stable, and is open source. As a result, more and more solution providers are migrating to Linux, and we wanted to be ready to support them.”

“What we like very much about Linux is that it really offers an excellent performance/hardware-resource ratio, which in the hand-held products industry is currently still the weakest point of Windows CE,” observes Mansutti. “Last, but not least: Linux is free.”

“Our plan is to make the sources to our Linux port available as soon as we reach the final stages of development,” adds Mansutti. “Our prediction/expectation is that Linux will become the only real alternative to Windows CE in industrial grade handheld computers.”

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