Issue 132 July 2001
Liquid Crystal Delight

Start • Working Glass Hero •Quarter Horse •Software To Boot •Widge Warrior •Highway Star •Beta Site •Take It Easy •Sources & PDF

WIDGE WARRIOR
The concept of using a standard web page editor to build an embedded user interface is intriguing, but Amulet goes even further.
As handy as it sounds, there are many things an embedded system needs to do that aren’t really in the domain of HTML or conventional web page development tools.

Photo 2—As this photo shows, a complete Amulet-based solution calls for the addition of just about a half dozen memory and I/O chips.

Although the RS-232 port provides the hardware connection between the display and application, there also needs to be a software scheme for communication. For example, pressing the touchscreen should update a variable or invoke action by the host controller. Likewise, an application should be able to overlay the static uHTML pages in flash memory with dynamic application data.

No doubt there are a lot of embedded apps that could take advantage of canned functions (e.g., a bar graph or line plot), which HTML knows nothing about. Java? Well, you’re close.
In the desktop world, Java applets are indeed the means by which web page functionality is extended in an open-ended manner beyond the confines of HTML.

No, the Amulet chip does not include a full-blown JVM. Instead, Amulet supplies a library of what it calls widgets to handle a variety of user-interface tasks.

At this point, astute readers are anticipating the gotchas for widgets, namely that they break the clever use-a-web-page-editor (which knows nothing about widgets) strategy. Fortunately, Amulet supplies Java applet versions of the widgets, preserving the ability to develop on the desktop with standard Java-capable web page editors and browsers.

Photo 3—The example interface runs in a web browser (a) and live on the LCD (b). Notice the minor difference in appearance, and the fact that the browser version doesn’t use real data (rpm).