Tear Down: Scientific calculator boils design down to two ICs
Just two key components
On one hand, I was disappointed to see what was actually inside the calculator. That's because it's not a very interesting design. It's just two key components--an 8502 microcontroller and a flash memory chip. Both of those parts are covered by a blob of epoxy, as you can see in Figure 2. The processor is under the bigger blob.
The 8502 is designed by Sunplus Technology, a Taiwanese company. It's based on the 6502, an 8-bit processor that first appeared on the Commodore 64, which was popular around the same time that I purchased my 15c. The flash memory is a generic part, and no specific vendor is used. It's generally based on whatever is available at the right price at the right time.
The 8502 that's used here also contains the system's power management and all the typical chip-set functions. This includes an LCD diver, a keyboard controller, and so on.
Kim explained that my old 15c was built with a 4-bit processor and had very limited memory. However, it had (and still has) the ability to perform matrix manipulation, a feature that was way before it's time, at least in a handheld calculator. And it was programmable.
Software is the key
With the design down to just the two main ICs, it quickly became clear that the real challenge of this product is in the software. Kim says, "The hardware has become pretty much routine. Most of it is off-the-shelf stuff. We spend the majority of our time on things like: what should the user interface look like; how will the programming occur; what kind of keys should we put on there; and the basic look and feel of the calculator when it's in the user's hand. How does it balance; is it too big or too small, too heavy or too light. So it's the industrial design and the software that are the most challenging parts of the design."
Unfortunately, it's the industrial design that I take issue with--the calculator is simply too big. It's not a true pocket-size calculator. While the HP folks wouldn't admit it, I got the sense that the next generation will be more to my liking, namely smaller. I also expect to see a larger display, more like a full matrix model. But then a tradeoff would have to be made somewhere, both in terms of the cost and the size of the calculator.
The firmware also resides on the 8502 microcontroller. That leaves almost the entire flash memory available for user programming. The 32-kbyte flash leaves about 30 kbytes available to the end user, enough for about 20,000 lines of code.
The initial specifications for the 35s came from a team within HP. Once that spec was agreed upon, the design was outsourced to a team in Taiwan. But even after it was sent overseas, the HP internal design team continued to work on other aspects of the 35s, in parallel with the external team in Taiwan. The internal HP team actually resided in four separate locales: Boise, Cupertino, San Diego, and Vancouver.
The eventual high-volume manufacturing is being done in China. All meetings for the design occurred by phone, as there were no "show-stopper" design issues to be overcome.
"We were working on the mechanical aspects while they were doing the software and electrical design," says Kim. "The original industrial design was done jointly by the two teams. It was never a 'throw-it-over-the-wall' design."
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