DIY Scientific Calculator Powered By Pi Zero

It’s the eternal question hackers face: do you built it, or do you buy it? The low cost and high availability of electronic gadgets means we increasingly take the latter option. Especially since it often ends up that building your own version will cost more than just buying a commercial product; and that’s before you factor in the time you’ll spend working on it.

But such concerns clearly don’t phase [Andrea Cavalli]. Sure he could just buy a scientific calculator, but it wouldn’t really be his scientific calculator. Instead, he’s taking the scenic route and building his own scientific calculator from scratch. The case is 3D printed, the PCB is custom, and even the software is his own creation.

His PCB hooks right up to the GPIO pins of the internal Raspberry Pi Zero, making interfacing with the dome switch keyboard very easy. The board also holds the power management hardware for the device, including the physical power switch, USB connection for charging, and TPS79942DDCR linear regulator.

The case, including the buttons, is entirely 3D printed. At this point the buttons don’t actually have any labels on them, which presumably makes the calculator more than a little challenging to use, but no doubt [Andrea] is working on that for a later revision of the hardware. A particularly nice detail is the hatch to access the Pi’s micro SD card, making it easy to update the software or completely switch operating systems without having to take the calculator apart.

After the kernel messages scroll by, the Pi boots right into the Java calculator environment. This gives the user a fairly standard scientific calculator experience, complete with nice touches like variable highlighting. The Mario mini-game probably isn’t strictly required, but if you’re writing the code for your own calculator you can do whatever you want.

Here at Hackaday we’ve seen a calculator that got a Raspberry Pi upgrade, a classic scientific calculator emulated with an Arduino, and of course we’ve raved about the NumWorks open source graphing calculator. Even with such stiff competition, we think this project is well on its way to being one of the most impressive calculators we’ve ever come across.

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Classroom Gadget Turned Arduino Compatible

Cheap second-hand hardware is usually a fertile ground for hacking, and by looks of this project, the digital classroom aids that were all the rage a few years back are no exception. [is0-mick] writes in to tell us how he managed to hack one of these devices, a Smart Reponse XE, into an Arduboy compatible game system. As it turns out, this particular gadget is powered by an ATmega128RFA, which is essentially an Arduino-compatible AVR microcontroller with a 2.4GHz RF transceiver tacked on. This makes it an extremely interesting platform for hacking, especially since they are going for as little as $3 USD on eBay.

There’s no USB-Serial converter built into the Smart Response XE, so you’ll need to provide your own external programmer to flash the device. But luckily there’s a labeled ISP connector right on the board which makes it pretty straightforward to get everything wired up.

Of course, getting the hardware working was slightly more complicated than just flashing an Arduino Sketch onto the thing. [is0-mick] has provided his bootloader and modified libraries to get the device’s QWERTY keyboard and ST7586S controlled 384×160 LCD working.

Playing games is fun, but when his friend [en4rab] sent him the Smart Response XE to fiddle with, the goal was actually to turn them into cheap 2.4 GHz analyzers similar to what was done with the IM-ME. It seems they’re well on their way, and [is0-mick] invites anyone who might be interested in filling in some of the blanks on the RF side to get involved.

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Sonar in Your Hand

Sonar measures distance by emitting a sound and clocking how long it takes the sound to travel. This works in any medium capable of transmitting sound such as water, air, or in the case of FingerPing, flesh and bone. FingerPing is a project at Georgia Tech headed by [Cheng Zhang] which measures hand position by sending soundwaves through the thumb and measuring the time on four different receivers. These readings tell which bones the sound travels through and allow the device to figure out where the thumb is touching. Hand positions like this include American Sign Language one through ten.

From the perspective of discreetly one through ten on a mobile device, this opens up a lot of possibilities for computer input while remaining pretty unobtrusive. We see prototypes which are more capable of reading gestures but also draw attention if you wear them on a bus. It is a classic trade-off between convenience and function but this type of reading is unique and could combine with other bio signals for finer results.

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Pocket-size Pi Zero Desktop features e-paper Display

[Ramin Assadollahi] uses his Raspberry Pi Zero W as a self-contained mobile desktop, connecting to it over VNC from another computer when he wants to hack away at some code or work on a new project. But he often found himself wishing there was some convenient way of displaying pertinent into right on the device, such as what IP address the Pi Zero had pulled. Then he found the 2.13 inch e-Paper HAT for the Pi Zero from Waveshare, and it all clicked into place.

The final device, which he refers to as the StickPi, combines a Pi Zero W, the Waveshare e-Paper display, and a strip of protoboard featuring a few tactile buttons, all inside of a 3D printed case. To really get the most out of the internal volume of his case, [Ramin] soldered the header pins to the Pi Zero in the middle, allowing him to create a space-saving “sandwich” out of all the components.

With the e-Paper display, [Ramin] now has a way to show information on the device itself without having to connect to it over the network. But thanks to the tactile switches on the back connected to the Pi’s GPIO, he also has six programmable buttons that could do anything he wants.

In the most basic implementation, each button could execute a command or script on the Pi. But [Ramin] has something a little more advanced in mind. In the video after the break, he explains that his next step is going to be working on an actual user interface for the Pi’s e-Paper screen, making use of the roughly gamepad style layout of the rear buttons. A “paged” interface with scrolling options would allow the user to perform all sorts of functions quickly and easily, and we’re looking forward to seeing what he comes up with.

This isn’t the first time we’ve seen somebody try to turn the Pi Zero into a more mobile-friendly platform, and the construction method here actually reminds us of a much smaller version of the Zero Phone.

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Open Source Calculator Teaches us about Quality Documentation

Graphing calculators are one of those funny markets that never seem to change. Standardized testing has created a primordial stew of regulatory capture in which ancient technology thrives at modern retail prices while changing little. The NumWorks calculator certainly isn’t the first competitor to challenge the Texas Instruments dynasty with a more modern interface (and a design from this decade), but behind it’s subtle color pops and elegant lines lies the real gem; a fantastically well documented piece of open source hardware. The last time we wrote about the NumWorks, it was to demonstrate a pretty wild hack that embedded an entire Pi Zero but it’s worth drawing attention to the calculator itself.

Hackaday readers traveling to the NumWorks website might spy the section at the bottom of the page titled “Developers” with tantalizing links like “Hardware,” “Software,” and “GitHub.” These lead to a wealth of knowledge about how the product is put together and sources to build the enclosure and firmware yourself (the PCB schematic and layout sources seem to be missing, though there is this handy gerber viewer). However merely posting sources is a low bar NumWorks far exceeds.

How is the firmware put together? Here’s a handy architecture guide! Why did they choose C++ and what tradeoffs were made to fit everything in a resource constrained embedded system? Here’s a design guide! How exactly does the math engine take in text, comprehend the expression contained therein, and evaluate it? There’s a document for it! There’s even a multi-platform SDK setup guide.

Firmware documentation is old hat; we’ve come to expect (or at least hope!) for it. For us the most interesting documentation is actually for the mechanical and electrical systems. The EE guides start with part selection (with datasheet links) then move on to walkthroughs of major areas of the schematic. At this point is should be no surprise that the board has pads for a completely standard 10 pin ARM debug connector and documented test points for UART, SPI, and an SD card.

The mechanical pages read like a quick primer on design for injection molding and tricks to reduce assembly errors (called “poka-yoke“). Ever wondered what that funny frame plastic models come in is called? The NumWorks calculator’s buttons are made in one, and it’s called a “sprue”. There are pages describing each piece of the housing one at a time.

Treat yourself to a reading of NumWorks’ excellent documentation. And if you need a new calculator, maybe consider the open source option.

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Circuit-Sword Delivers Retro Justice

You can’t search for “retro gaming” without hitting a plethora of single board computers attached to all manner of controls, batteries, etc. Often these projects have an emphasis on functionality above all else but [Kite]’s Circuit-Sword is different. The Circuit-Sword is the heart of a RaspberryPi-based retro gaming machine with an enviable level of fit and finish.

Fundamentally the Circuit-Sword is a single board computer built around a Raspberry Pi Compute Module 3. We don’t see many projects which use a Compute Module instead of the full Pi, but here it is a perfect choice allowing [Kite] to useful peripherals without carrying the baggage of those that don’t make sense for a portable handheld (we’re looking at you, Ethernet). The Circuit-Sword adds USB-C to quickly charge an onboard LiPo (rates up to 1.5A available) and the appropriate headers to connect a specific LCD. The Compute Module omits wireless connectivity so [Kite] added an SDIO WiFi/Bluetooth module. And if you look closely, you may notice an external ATMega mediating a familiar looking set of button and switches.

Optional Drill Holes

We think those buttons and switches are the most interesting thing going on here, because the whole board is designed to fit into an original GameBoy enclosure. It turns out replacement enclosures are available from China in surprising variety (try searching for “gameboy housing”) as are a variety of parts to facilitate the installation of different screen options and more. One layer deeper in the wiki there are instructions for case mods you may want to perform to make everything work optimally. The number of possible options the user can mod-in are wide. Extra X/Y buttons? Shoulder buttons on the back? Play Station Portable-style slide joysticks? All detailed. For even more examples, try searching the SudoMod forums. For example, here’s a very visual build log by user [DarrylUK].

The case mod instructions are worth a glance even if you have no intent to build a device. There are some clever techniques to facilitate careful alignment of buttons and accurate hole drilling. Predicting their buyers might want a variety of options, [Kite] added reference drill holes in the PCB for the builder to re-drill for mounting buttons or joysticks. To facilitate adding status LEDs externally there is a tiny PCB jig included. There are even instructions for adding a faux game cartridge for the complete look.

If you want to buy one (we certainly do!) [Kite] does group buys periodically. Check out the wiki for links to the right interest form.

Thanks [Speednut Dave] for the tip!

The Era of Orville Props Has Officially Begun

Over a decade after the last Star Trek show warped off of television, we finally have a new series in the form of Star Trek: Discovery. But much to the chagrin of many old school Trek fans, Discovery has gone all in on the gritty and hyper-serialized storytelling that’s taken over TV since Starfleet last patrolled the airwaves. But for those who are looking for somewhat more lighthearted space adventures, Seth MacFarlane (of Family Guy fame) has created a show which is essentially a love-letter to Star Trek: The Next Generation called The Orville. Some have gone as far as to claim that The Orville is the true continuation of the Trek legacy, though such discussion sounds awfully close to a Holy War to us so we’ll steer clear.

Unfortunately for The Orville fans, the series doesn’t have nearly the commercial draw of Trek. Accordingly, the market for things like replica uniforms and props from the show is still in its infancy, meaning fans of the show have to go the DIY route. [JohnSmallBerries] is one such fan, and his 3D printed “Comscanner” from The Orville is a shot across the bow to the well established Trek prop-making scene.

Without so much as an official toy version of the device, [John] was forced to do his initial 3D rendering based completely on screenshots from the show. Even the scale of the device had to be guessed, as it’s usually only seen being held in a crew member’s hand. In the end he reasoned it’s probably supposed to be about the size of a large smartphone.

Not content with just a static prop, [John] managed to integrate not only the spring-assisted retractable display of the scanner from the show, but also some LED backlit panels complete with a screen-accurate user interface. Judging by the internal shots of the scanner, it looks like there’s still plenty of room inside to add some more advanced electronics. The next evolution of this prop will surely be to add in a microcontroller and potentially even a real screen to add some more elaborate effects and (relatively) practical functions.

We’ve seen plenty of impressive builds of Star Trek gadgets, arguably bringing the devices much closer to reality than the original show runners ever did. It will be interesting to see if The Orville inspires a new generation of engineers to bring their favorite fictional pieces of kit into the real world.