A Hardware Hacker’s Perspective

By Gary Friedman

PPC #6522

CHHU #2866

I won my first HP calculator at an electronic design competition at UCLA (University of California, Los Angeles) in 1980. It was an HP-41, an incredibly powerful computer that was far ahead of the rest of the world. (As a reference point, my high school was still teaching how to use slide rules in the first weeks of its chemistry class!) Being an engineering major and not owning a personal computer, this little wonder was like a godsend -- I could do any required calculations in less than half the time it took those losers who owned T.I. calculators, and, because of its humble calculator-like exterior, provided me with a significant competitive advantage while completing my engineering courses. It may be unhealthy to be in love with a calculator, but during my college days that is probably how it appeared: I carried it everywhere; usually on my belt loop, and used it for everything. Using the time module, it became my customized alarm clock (with an 11-minute snooze cycle) which would wake me up on different times depending on the day of the week. I had programs that kept a phone book, calculated sunset times (for my photography), an HP 16C emulator, and even solved the Rubik’s Cube. Using synthetic instructions, I created a Hangman game program which I played with the elementary school students I was tutoring at the time. My most-used utility was a quick polynomial root finder. And I never, never had to worry about anyone asking to borrow my calculator, for if they did, exactly 13 seconds would elapse before I heard the inevitable phrase, “Where’s the equals?”

And I’ll never forget my first PPC meeting. A very soft-spoken individual came up to me and handed me a piece of paper with two numbers on it. “That is the smallest number pair which, when divided, will result in your phone number!” Later I learned that this person was Clifford Stern, a famous and regular contributor to the journal. That evening I also met Richard Nelson (“Fearless Leader”) and Joseph K. Horn, a priest for whom exploring algorithms was sheer entertainment. I realized then that I had joined a club which attracted some very intelligent and unique people.

Unlike the vast majority of PPC members, I was also adept at hardware as well as software, and relished in the opportunity to merge the two. The first thing I did after talking with folks who knew was to take the calculator apart and double the clock speed by simply bypassing one capacitor. This proved to be a valuable lesson in engineering tolerances when, during a final exam on a very, very hot summer's day, the calculator crashed. (Did I mention it was a closed-book, closed-note exam and I secretly had all the formulas I was supposed to memorize in extended memory?) The next day I installed a switch that could slow the machine back down again as required. 

With the advent of the Hewlett Packard Interface Loop (HP-IL) and the 16-bit port IL Converter ("82166A" for those of you who love HP's nomenclature), real world I/O was possible, and I ended up writing more than a dozen “hardware project” articles for the PPC Journal.  In one article, I hooked up my 41 to my 35mm camera so I could take nighttime "time exposure" images, bracketing in 1/2 stop increments, while I stayed warm inside. In another, I completely automated my photographic darkroom using my 41 - from negative analyzer to enlarger timer to developer/bath timer. (This allowed me to concentrate on creative darkroom pursuits instead of being consumed by the 'dog work'.) For my final project before earning a degree in Electrical Engineering, I turned my 41 into an interactive telephone answering machine, complete with speech synthesis and Touch Tone (r) decoding.

When the 71 was introduced, I immediately took it apart and brought some unused CPU lines to the outside. Burying myself in the 71 IDS manuals and teaching myself how to program in Saturn assembly language, I distinctly remember the moment when I successfully produced an 18 kHz square wave using a simple loop in assembly language: I was sitting in the passenger seat of a car, en route to the PPC club meeting! (Fortunately, I also had a battery-powered Tektronix oscilloscope with me to measure the frequency of the square wave produced!) Later on I used this CPU-control-of-I/O-lines technique to hook the 71 up to a Polaroid Ultrasonic Transducer so I could measure distances by bouncing sound off of them and timing the echo’s return. I also used the 71 in the heart of an intelligent telephone autodialer (it would recognize a busy signal and automatically redial), and to control multimedia shows, including a "dissolve unit" controlling the light intensity of 2 slide projectors using pulse-width modulation of the AC signal. Many PPC Journal articles followed, explaining the circuitry and the software to control all these cutting-edge hardware projects. Fame and fortune followed. (Well, fame anyway.) All of this was eventually rolled into a book, "Control the World with HP-IL", published in 1987.

For me this was a very exciting time, because in a world which was dominated by large, immobile, clunky, takes-five-minutes-to-boot-up (things don’t change, do they?) DOS-based IBM PC's, I was playing with Hewlett Packard's little wonders which were powerful, portable, completely self-contained development systems. They were so far ahead of their time in terms of form factor, power consumption, user interface, number crunching abilities, and programmability (the HP-71 could be programmed in 3 different language environments, all of which could call each other!). And while the rest of the world was impressed with 1 parallel and 1 serial port that came with their bulky PCs, HP's innovative HP-IL interface could allow my pocket device to access up to 960 connected peripherals simultaneously!

What enthralled me most about working with the HP handheld computers is that this was my first inkling that technology could actually set you free. The vast majority of what I built could be carried with me and used anywhere. (The 41-based camera controller, for example, continues to have a place in my camera bag, ready to do work for me while I am far from civilization.) I could set it up as a data logger and have it wake up, take a measurement, and shut off again all on its own. Because all the IL peripherals ran on batteries, the controller could power up all peripheral devices, print something out, save some data to tape, and shut everything off again until the next measurement cycle. All the units had their own keyboard and display, so software development and testing could be done interactively, without a bulky and constraining development system. And since it was an open-ended interface, there was virtually no limit to the amount of I/O that could be performed with this handheld device - just add another peripheral or 16-bit parallel port to the loop! Compared to the non-portable, power-hungry, limited I/O Personal Computer, HP's calculators were light years ahead of the accepted world standard.

Much has changed since those exciting days. Hewlett Packard has changed course in their calculator strategy many times; first dropping I/O in favor of sophisticated symbolic manipulation, then dropping symbolic manipulation in favor of 4-bangers with an equals key. Calculator operations moved from Covallis to Singapore to Australia to Middle Earth. Spreadsheets and more powerful symbolic math processors running on PCs took over as the professionals’ tool of choice. The era in which a person could get excited about a serious, number-crunching calculator is rapidly drawing to a close. (Today when someone mentions a handheld computer, for example, they now automatically think of a Palm Pilot!)

That is why the book which you are reading now has been compiled -- to document, in an easily-digestible way, the worldwide phenomena of the handheld calculator clubs and the culture, activities, and values which grew from it. Like the slide rule and the Jedi Light Saber before it, the HP calculator is a long-forgotten tool for which its user needed to dedicate and train themselves to use effectively – it became an extension of the user, because the user was such an integral part of the system. To this day, HP handhelds remain unrivaled in terms of portability, versatility, expandability, and power consumption. And although the calculators which once brought us all together are now a piece of forgotten history, the original mantra they carried continues to this day: Technology can set us free. Imagination can make us soar.


(The above text was a chapter in the RCL 20 book, celebrating and reflecting on 20 years of the Hewlett Packard Handheld Calculator Users's group called PPC.)


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