An Open-source Scientific RPN Calculator

June 5, 2021 by Jenny List 69 Comments

Why reach for a bland, commercially available calculator when you be using a model that employs RPN (Reverse Polish Notation) in its calculations and be a custom build all at the same time? The kids may have colour TFTs and graphing functions, but your keyboard has no equals sign, and that means something.

Unfortunately for RPN enthusiasts, the RPN calculator is a little on the rare side. Since classic models from the 1970s and ’80s are rather pricey, [Anton Poluektov]’s just build his own called the OpenCalc. This glorious specimen is an open hardware RPN calculator with more than a nod to the venerable Hewlett Packard HP42 in its design.

At its heart is an STM32L476 low-power ARM processor and a Sharp Memory LCD, all on a PCB clad in a 3D-printed case you’d have been proud to own in the 1980s. It runs from a CR2032 which is more than can be said for some modern styles of calculator, and it gives the user everything you could wish for in a scientific calculator. The key legends are a set of printable stickers, which when printed on self-adhesive laser film prove durable enough to last. All the resources can be found in a GitHub repository, so if RPN is your thing there’s nothing to stop you building one for yourself.

If RPN interests you, it’s a subject we’ve looked at in greater detail in the past.

Scientific Calculator Whipped Up In Python

June 2, 2020 by Lewin Day 31 Comments

Scientific calculators were invaluable to most of us through high school and college, freeing us from the yoke of using tables to calculate logarithms and trigonometric functions. Once out in the real world, it’s no longer necessary to use an education board approved device to do your maths – you can do it all on your PC instead. For those keen to do so, [AstusRush]’s latest Python work may be just the ticket!

Far exceeding the capabilities of the usual calculator apps, there’s plenty of useful features under the hood. Particularly exciting is the LaTeX display, which shows equations in textbook-quality human-readable format. There’s also a graphing suite, and capability to handle matricies and vectors. LAN chat is implemented too, useful for working in teams.

It’s a useful tool that may suit better than a full-fat MATLAB install, particularly at the low, low price of free. This is one calculator that CASIO will have to keep their nose out of!

A Calculator In 2020?

March 7, 2020 by Elliot Williams 91 Comments

This week, Al Williams wrote up an article on what might be the last scientific calculator. Back in the day, the fanciest of scientific calculators had not just sin, cos, and tan, but were also programmable so that you could code in frequently used formulae. And the calculator that he reviews is certainly powerful: with a screen, processor, and memory almost rivalling a mid-scale smartphone.

Wait a minute! “Almost”? I have a smartphone in my pocket right now. Why would I want something less powerful, when all that the calculator brings to the table is a bit of software? And that app can even be purchased for $20!

I’ll confess. I want a proper desktop calculator from time to time. But why? Sure, I can run calculations on the very computer that I’m using to type right now. And in terms of programming languages, the resources are far superior on my laptop. Unit conversions? Units, or the Interwebs. Heck, I can even type calculations directly into the Unix world’s default editor.

But there’s something nice about the single-purpose device. Maybe it’s the feel of the keys. Maybe it’s because it doesn’t require a context-switch on the computer. Maybe it’s irrational calculator nostalgia. Or maybe it’s an elegant tool from a more civilized age: the user experience is better because the tool is just simpler.

I like stand-alone devices that do their one thing right, and I almost always pick them over their more complex, if also more capable, counterparts when I only need that function. The fixed wrench over the adjustable wrench. The standalone audio recorder over my computer’s software. The simple bench power supply over the programmable. And, when I’m actually setting out to take good photos, a real camera instead of my cell phone’s. Purpose-built tools tend to work much better for their purpose than devices that try to do everything.

The days of the standalone calculator are nearly gone, though, so what am I going to do? I’m certainly not going to shell out megabucks for an overly-fancy calculator, nor am I going to be lured by nostalgia into picking up an antique at the ridiculous prices they fetch online. That leaves one option, and it’s both the Hackaday and the Jedi way. I’m going to have to build it myself. Where am I going to get a nice-feeling numeric keypad?

[Ken Shirriff] Completely Reverse Engineers The 1974 Sinclair Scientific Calculator

August 30, 2013 by Mike Szczys 44 Comments

Wow. Seriously… Wow! The work [Ken Shirriff] put into reverse engineering the Sinclair Scientific is just amazing. He covers so much; the market forces that led [Clive Sinclair] to design the device with an under-powered chip, how the code actually fits in a minuscule amount of space, and an in-depth look at the silicon itself. Stop what you’re doing and read it right now!

This calculator shoe-horned itself into the market when the HP-35 was king at a sticker price of $395 (around $1800 in today’s money). The goal was to undercut them, a target that was reached with a $120 launch price. They managed this by using a Texas Instruments chip that had only three storage registers, paired with a ROM totaling 320 words. The calculator worked, but it was slow and inaccurate. Want to see how inaccurate? Included in the write-up is a browser-based simulator built from the reverse engineering work. Give it a try and let us know what you think.

Now [Ken] didn’t do all this work on his own. Scroll down to the bottom of his post to see the long list of contributors that helped bring this fantastic piece together. Thanks everyone!

[Thanks Ed]

Programmable Scientific Calculator Watch

January 19, 2009 by Nick Caiello 17 Comments

When the band support on [David]’s Casio CFX-400 Scientific Calculator Watch finally broke after 10 years of use, he found it almost impossible to find another watch with the same functionality. Like any good engineer, [David] decided to design a watch to meet his needs. The result of his endeavors was the µWatch, a programmable watch based on a PIC24 with both RPN and Algebraic calculation modes. The watch runs open source software and is expandable thanks to a serial port, an ICSP programming port, and a spot for an infrared LED on the board. On his site, [David] shows how he made the first µWatch and offers kits for anyone who wants to build their own. We’ve been told that the next batch of kits will be made available in 1-2 weeks and are expected to sell out fast.

[Thanks Tomesz]