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GETTING STARTED WITH EMBEDDED PCs

by Bob Perrin

Start ý Selecting an Embedded PC ý Hello World ý Controlling Resources ý Thank You, Intel ý Sources and PDF

SELECTING AN EMBEDDED PC

When I began my quest to find my first embedded PC, I was concerned with price, service, and simplicity. I didn't want to pay a mint for a circuit board, but at the same time, I wanted to get good technical support. Furthermore, I wanted an embedded PC that was fairly simple. I didn't want one that was just a desktop PC shrunk in size.

Ampro, Adastra, WinSystems, and Ziatech all have offerings in the embedded PC market, but I finally settled on the Flashlite V25+ board from JK Microsystems. The development system was $159 and included everything I needed to get up and running. Certainly the cost was right, but what about customer support?

When you call JK Microsystems, you get to talk to an engineer. And when I say engineer, I don't mean some sales engineer, or a customer-support technician, I mean a seasoned design engineer. Often the person answering your questions is the designer of the board youýre asking about. That was my primary reason for selecting the JK embedded PC. I knew I could get tech support without long phone delays or hassles.

The Flashlite is a single-board PC with only six ICs on the PCB. These are the NEC V25+ MPU, an SRAM, a FLASH, a PAL and two RSý232-level converters. Although simple, the board provides a fairly extensive I/O set.

There are two RSý232-level serial ports on the V25+ Flashlite. There are 0.100" headers that pinout 32 digital I/O points and much of the processor's bus. Eight of the digital I/O points have variable input thresholds that are set in software. This arrangement provides a method to implement a crude ADC.

UP AND GOING

The Flashlite does not have an onboard regulator, it requires a single 5-V supply and draws about 200 mA. I used my trusty benchtop supply to provide power.

The board has a PC-compatible BIOS in the flash memory. The rest of the flash memory is used as a disk. The flash-memory disk is split between A: and B:. The A: disk is the boot disk, is read only, and contains DOS. The B: disk is 128 KB and is where user applications are stored.

On booting, the V25 will start in the BIOS, then move on to DOS, then run autoexec.bat off the A: disk. The last line of the autoexec.bat file will attempt to run a file named STARTUP on the B: disk. STARTUP may be an .exe, .com, or .bat file.

The Flashlite uses a serial port (serial port 0) as the console. Just plug in any serial terminal or a PC running a terminal program, such as HyperTerminal. As the Flashlite comes up and DOS begins to run, the console gets a startup message and then a B:\> prompt is displayed.

If you have the Flashlite's console port attached to a terminal, you can use the terminal to do all the normal things you can do with a desktop running DOS. Commands such as DIR, RENAME, and COPY, all work just like you would expect. There's a utility provided on the flash memory-based read-only A: disk, called UP.COM. This program is used to transfer files from the desktop PC on the Flashlite's console port to the B: disk on the Flashlite. This is the sole method used to transfer applications and data from the desktop development system to the target (Flashlite). UP.COM uses an X-MODEM protocol to transfer the files.

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