Programmable Ruler Keeps 1970’s Computing Alive

A ruler seems like a pretty simple device; just a nice straight piece of material with some marks on it. There are some improvements out there to the basic design, like making it out of something flexible or printing a few useful crib notes and formulas on it so you have a handy reference. But for the most part, we can all agree that ruler technology has pretty much plateaued.

Well, not if [Brad] has anything to say about it. His latest creation, the Digirule2, is essentially an 8-bit computer like those of the 1970’s that just so happens to be a functional ruler as well. Forget lugging out the Altair 8800 next time you’re in the mood for some old school software development, now you can get the same experience with a piece of hardware that lives in your pencil cup.

Even if you’ve never commanded one of the blinkenlight behemoths that inspired the Digirule2, this is an excellent way to get some hands-on experience with early computer technology. Available for about the cost of a large pizza on Tindie, it represents one of the easiest and most cost-effective ways to tell your friends that as a matter of fact you have programmed a computer in binary.

The Digirule2 is powered by a Microchip PIC18F43K20, and is programmed by punching binary in one byte at a time with a bank of eight tactile switches. To make things a little easier, programs can be saved to the internal EEPROM and loaded back up just as easily thanks to the handy buttons next to the power switch. Now all you’ve got to do is figure out what all those blinking LEDs mean, and you’ll be in business.

The original Digirule was a logic gate simulator that we first covered back in 2015. We’re always happy to see projects grow and evolve over time, and think this new retro-computer themed variant is going to be quite popular with those who still love toggle switches and blinking lights.

23 thoughts on “Programmable Ruler Keeps 1970’s Computing Alive

  1. Add bluetooth or wifi and add some measurement capabilities then maybe something useful to dump figures into a spreadsheet/database. Not even hex display and hex keyboard. Well in thirty years or so can glue a PI to a tape ruler. That should sell.

      1. Like the average modern tablet? Oh hell no. Thats at least three gen away from this project . lmao. Better digitizers use RF pens. More of RF meter than magnetometer. Mince. Was thinking Vernier caliper and some encoding like a cheap digital caliper at horrofreight but with maybe EiA232 over IR or something equally archaic to transmit data to VisiCalc spreadaheet. Ha.. I was reaching too far futuristic with WiFI or BT.

  2. I’d like to see a light sensor like a LDR or opto sensor so you can use a web interface to write programs and have some Javascript flash a square on the screen to upload code to the digirule.

    I bought a digirule (1) and was going to re-code it but I ended up giving it away. I am not that keen on the PIC.

    1. I mean no disrespect, but as an amateur geek when it comes to the rule, as well as rulers, I wanted to point out that there IS an exception to that, lol. (one of my prized possessions is a Stanley No 88 Four-fold Rule) According to the Oxford English Dictionary and Merriam Webster, among others, the second definition of the noun “ruler” is:

      “A straight strip or cylinder of plastic, wood, metal, or other rigid material, typically marked at regular intervals and used to draw straight lines or measure distances.”

      The middle English origin of the word is from the old French noun of “reule” which as a verb is “reuler”, essentially the act of using a measuring stick.

      So, yes, a measuring device can be called a rule, (4th definition of the word rule), but within the last ~50 years this type of device is more commonly referred to as a ruler.

  3. While inserting a computer into a ruler is all very cool, I feel you’ve given the advancements of rulers a bum rap. E.g. Slide rulers, folding rulers, collapsible rulers, rulers than can measure angles or logarithms, or even protractors!

  4. I want to see someone make a digital slide rule out of absolute position digital calipers. Then make several of them for props in a movie of Hal Clement’s “Mission of Gravity”.

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