EE Times Under the Hood - June 23, 2008 - (Page U52)

UTH0623COMP_pg42_55.qxd 6/11/08 4:32 PM Page 52 under the hood: w w w. e e t i m e s . c o m C OMPUT ERS & GAM I NG • w w w. t e c h o n l i n e . c o m together by 25 screws. “The keyboard is the most important part of a calculator. It must work year after year,” Kim said. “Those 25 screws hold it down rock solid. The keyboard will never get loose, and this thing will last forever. It costs us more, but it demonstrates the attention to detail we’ve put in.” If the 25 screws weren’t enough, the engineers decided to add a slew of plastic hold-downs on top of the circuit board. As a result, I had to literally break off each of those hold-downs to get the board out. HP says the calculator performs a 1 million-key press-test on the keyboard, meaning the keyboard will survive at least a million keystrokes—far more than a user will ever subject it to. HP put the 35s through 11 different abuse tests and 20 common tests. These generally have to do with temperature thermal shocks, drops and so on. Many of the tests highlight common occurrences that a handheld calculator would be subjected to in everyday use, but others are in the category of unlikely assaults. For example, the testers did environmental tests, using the calculator at 55°C for four hours, then storing it at 65°C, with 95 percent relative humidity, for 120 hours. There are similar tests for low temperatures. The team isn’t satisfied unless 100 percent of the tested units pass. Unlike one of the predecessor models (the 41), there’s no way for the owner to tap into the 35s’ firmware. The programming occurs only at the user level, although HP is tinkering with the idea of giving customers limited access to the firmware. “The 35s is pretty much hackerproof, but the old 41 had a lot of hacking going on because it was more of an open platform,” Kim said. “There was something called synthetic programming, and there was a crowd that evolved around it. I was actually a member of that crowd—the diehard HP users.” Despite the testing and overengineering, the key to building a popular and powerful scientific calculator comes down to basics—making it easy to use, programmable, with all the functions a user would want, all accessible via the keyboard using a simple menu structure. ■ that the real challenge of this product was in the software. “The hardware has become pretty much routine,” Kim said. “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 35s is simply too big. It’s not a true pocketsize 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 fullmatrix model. But then a trade-off would have to be made somewhere, in terms of both the cost and the size. The firmware also resides on the 8502 microcontroller. That leaves almost the entire flash memory available for user programming. The 32kbyte 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 IN BRIEF The Hewlett-Packard 35s is a handheld scientific calculator. It’s the latest in a long line of such devices, which are extremely popular with the engineering community. I was looking forward to this particular teardown because I used an earlier member of this family (probably the great, great, great grandfather) when I was in engineering school.The functionality has changed much over the years, and the form factor has actually grown somewhat. One of the most notable characteristics was the price:The 35s costs about $60, while I paid about $125 for my 15c 20+ years ago. Taiwan. The internal HP team actually resided in four separate locales: Boise, Idaho; Cupertino and San Diego, Calif.; and Vancouver, Wash. The eventual high-volume manufacturing is being done in China. All meetings for the design occurred by phone, since there were no show-stopper design issues to overcome. “We were working on the mechanical aspects while they were doing the software and electrical design,” said Kim. “The original industrial design was done jointly by the two teams. It was never a ‘throw it over the wall’ design.” An interesting aspect of the 35s is that it takes “overengineering” to a new level. For example, it’s held Component focus The Hewlett-Packard 35s is comprised mostly of two key components—an 8502 microcontroller and a flash memory chip. Both parts are covered by a blob of epoxy.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 about 20 years ago.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.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. After the program code is stored in the flash memory, there is about 30 kbytes available to the end user, enough for about 20,000 lines of code. 52 Electronic Engineering Times, TechOnline | June 23, 2008 http://www.techonline.com http://www.eetimes.com

Table of Contents Feed for the Digital Edition of Under the Hood - June 23, 2008

Under the Hood - June 23, 2008 Extreme Design: SuitSat Pushes Desigers' Limits Evolution of the Smart Phone Mature Devices get Rolly Rocking GPS: Garmin Nuvi 750 vs. HP iPaq 310 Inside the Sony OLED TV Multizone Dgital Audio Flip Ultra Camcorder - An Ode to Clean Design Robot Guitar Tunes Itself E-book is a Sight for Sore Eyes Scientific Calculator Boils Down to Two ICs $100 BOM Eludes First OLPC Laptop 45 nm: What Intel Didn't Tell You Next Step in NAND Flash Evolution Surveillance on a Shoestring Hot 3G Phone Owes Debt to Analog SecurID Fob: Single-Chip Safety Net

Under the Hood - June 23, 2008

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