Hackaday Prize Entry: DIY ARM Scientific Calculator

What does a hacker do when he or she wants something but can’t afford it? They hack one together, of course. Or, in the case of [Ramón Calvo], they thoughtfully plan and prototype. [Ramón Calvo] wanted a scientific calculator, but couldn’t afford one, so he designed and built one himself.

[Ramón] started off with Arduino but upgraded initially to Freescale’s Freedom KL25Z development board upgraded to an ARM Cortex-M0+ programmed using mbed. The display is an Electronic Assembly DOGL-128 128×64 pixel LCD. [Ramón] did a couple of iterations on the PCB, going from a large DIY one in order for the Arduino version to work, to the current, smaller version for the ARM chip with hand soldered SMD components. After that, [Ramón] looked into the algorithms needed to parse mathematical input. He settled on the shunting-yard algorithm, which converts the input into Reverse Polish Notation (RPN), which is easier for the software to work with.

[Ramón] has a ton of features working, including your standard add, subtract, multiply and divide operations, square root, nth root and exponentiation, trigonometry, log and log10, and factorial(!) There are a few things still on the to-do list, such as low power and a graphing mode, and there are a couple of bugs still in the system, but the overall system is up and running. [Ramón] has put up the schematic and KiCAD files up on his Hackaday.io project page along with the bill of materials.

We’ve had a few Hackaday prize entries in the form of calculators, such as this one with Nixie tubes and this one that emulates 70’s HP calculators.

Crippled Calculator Features Unlocked with Automated Help

[Aguilera Dario] likes his Casio fx-82ES calculator. However, it was missing a few functions, including complex numbers. A Casio fx-991ES has more functions but, of course, costs more. A quick Google revealed that if you press the right buttons, though, you can transform an fx-82ES into an fx-991ES.

Because it is apparently a buffer overflow exploit, the hack involves a lot of keys and once you cycle the power you have to do it again. [Aguilera] realized this would be a good candidate for automation and added a microcontroller to push his buttons. You can see a video of a breadboard version below. He also has a PCB version in the works that should be better integrated.

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Fail Of The Week: Talking Chinese Calculator Synth Orchestra

There are times when you set out to do one thing, and though you do not achieve your aim you succeed in making something else that’s just a bit special. [TheKhakinator] sent us something he described as a fail, but even though we’re posting it as one of our Fail Of The Week series we think the result still has something of the win about it. It may not be the amazing hack he hoped it would become, but that really does not matter in this case.

On his travels in China his attention was caught by an everyday electronic gadget, an electronic calculator  that speaks the numbers and operations in Chinese as you use it. He bought a few of them, hoping that when he got them back to his bench he’d find an EEPROM containing the samples, which he could replace with his own for a cheap but low bitrate sampler.

Sadly this neat hack was not to be, for when he tore the surprisingly well-built calculators down he found only an epoxy blob concealing a single chip. All was not lost though, for while investigating the device’s features he discovered that as well as speaking Chinese numbers and operands it also had a selection of alarm tunes built-in, plus a mode in which it operated as a rudimentary electronic organ. He leaves us with a couple of videos we’ve posted below the break, first his teardown, and then a virtual orchestra of calculators playing dance music as he forgets the fail and concentrates on the win.

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Fun Audio Waveform Generator Is More Than The Sum Of Its Parts

[Joekutz] wanted to re-build an audio-rate function generator project that he found over on Instructables. By itself, the project is very simple: it’s an 8-bit resistor-ladder DAC, a nice enclosure, and the rest is firmware.

[Joekutz] decided this wasn’t enough. He needed an LCD display, a speaker, and one-hertz precision. The LCD display alone is an insane hack. He reverse-engineers a calculator simply to use the display. But instead of mapping each key on the calculator and typing each number in directly, he only taps the four 1, +, =, and clear keys. He can then enter arbitrary numbers by typing in the right number of ones and adding them up. 345 = 111 + 111 + 111 + 11 + 1. In his video, embedded below, he describes this as a “rather stupid” idea. We think it’s hilarious.

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45-Year Old Nixie Calculator Turned UDP Server

In this beautiful and well-documented reverse engineering feat of strength, [Eric Cohen] reverse-engineered a 1971 Singer calculator to gain control of the fabulous Nixie tubes inside. Where a lesser hacker would have simply pulled the tubes out and put them in a more modern housing, [Eric] kept it all intact.

Not even content to gut the box and toss some modern brains inside, he snooped out the calculator’s internal wiring, interfaced a Raspberry Pi to it, and overrode the calculator’s (860 Hz) bus system. With the Pi on the inside, controlling the Nixie tubes, he did what any of us would do: set up a UDP server and write an Android app for his phone to push ASCII data over to the former calculator. When it’s not running in its default clock mode, naturally.

nixie-internals

All of this is extraordinarily well documented both on his website, in a slide presentation (PDF), and in video (embedded below). Our hats are tipped to the amazing attention to detail and fantastic documentation.

Now where is that Singer EC1117 calculator from 1971 that we’ve been saving for just such an occasion?

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Hackaday Prize Entry: A Programmable Calculator With Nixie Tubes

For [Robert]’s entry into The Hackaday Prize, he’s starting off with some basic questions. What’s better than a Nixie tube? More Nixies. What’s better than a calculator? An RPN calculator. What do you get when you combine the two? A calculator that is absurdly large, even by 1970s desk calculator standards, uses a lot of power, and takes up too much space. Sounds good to us.

Nixies, at least when there are a lot of them, are tricky devices. They only draw about 50mA of current, but they only light up when above 150V. That’s only about seven watts, and it’s easy enough for the Arduino-heads out there to build a circuit to drive a few Nixies for a clock. Driving dozens of Nixies is a bit harder. For [Robert]’s RPN calculator, he’s estimating a little under 50W of power being dumped into this calculator.

With the considerable power considerations taken care of, [Robert] turned his attention to the display board. This is going to be a very impressive build, with 80 IN-12B tubes organized in four stack levels of twenty tubes each. The tubes will be controlled with the Maxim MAX6922 VFD driver. This chip has a serial interface, which means it’s relatively easy to have any microcontroller blink these tubes. And of course, it does double-duty as a clock.

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Who Needs the MSP430 When You Have TI’s Other Microcontroller, The TI-84?

We’re sure there are more expensive LED controllers out there, but the TI-84 has got to be up there. Unless you have one on hand, then it’s free. And then you’ll doubtless need an SPI library for the famously moddable graphing calculator.

[Ivoah] is using his library, written in assembly for the Z80 processor inside the TI, to control a small strip of DotStar LEDs from Adafruit. The top board in the photograph is an ESP8266 board that just happened to be on the breadboard. The lower Arduino is being used as a 5V power supply, relegated to such duties in the face of such a superior computing device.

Many of us entertained ourselves through boring classes by exploring the features of TI BASIC, but this is certainly a step above. You can see his code here on his GitHub.

After his proof-of-concept, [Ivoah] also made a video of it working and began to program a graphical interface for controlling the LEDs. Video after the break.

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