Earlier this month, we posted coverage of an ingenious calculator hack that took a Casio calculator and put an ESP8266 module and an OLED display in the space occupied by its solar cell. Controlled by a pair of unobtrusive Hall effect devices, the calculator could have been used as an ingenious cheating device but was to us the epitome of a well-executed hack. We may have liked it but it seems the folks at Casio didn’t, because they’ve issued a DMCA takedown notice for the project’s GitHub repository.
We’re not lawyers, but if you’d care to visit our original coverage and watch the video in full, you’ll see that the ESP does not in any way tap into the calculator’s functions. The epoxy blob over the Casio processor is intact and no wires connect to the calculator mainboard, so it is difficult to imagine how any Casio code could have found its way into a repository full of ESP8266 code for the Arduino IDE. A quick search for “Hack-Casio-Calculator” on GitHub, at the time of publishing, turned up the relevant code despite Casio’s takedown, and we can’t see what they’re on about. Maybe you can?
Over the years there have been many attempts to use the DMCA on projects in our community. Some have been legitimate, others have been attempts to suppress exposure of woeful security, and still more have been laughably absurd. This one seems to us to edge into the final category, because it is difficult to see how the project described could contain any Casio code at all. It would be entirely legitimate to issue a DMCA takedown had the epoxy blob been removed and Casio’s code been retrieved from the calculator chip (and we’d certainly cover that story!), but as far as we can see taking a scalpel to a calculator’s case and stuffing a module behind the solar panel window does not come close.
It’s evident that Casio do not like the idea of one of their calculators being turned into a cheating device, and we understand why that might be the case. But to take the DMCA route has served only to bring more publicity to the affair, and those of us with long memories know that this can only lead to one conclusion.
Not content to rule the world of digital watches, Casio also dominated the home musical keyboard market in decades past. If you wanted an instrument to make noises that sounded approximately nothing like what they were supposed to be, you couldn’t go past a Casio. [Marwan] had just such a keyboard, and wanted to use it with their PC, but the low-end instrumented lacked MIDI. Of course, such functionality is but a simple hack away.
The hack involved opening up the instrument and wiring the original keyboard matrix to the digital inputs of an Arduino Uno. The keys are read as a simple multiplexed array, and with a little work, [Marwan] had the scheme figured out. With the Arduino now capable of detecting keypresses, [Marwan] whipped up some code to turn this into relevant MIDI data. Then, it was simply a case of reprogramming the Arduino Uno’s ATMega 16U2 USB interface chip to act as a USB-MIDI device, and the hack was complete.
Now, featuring a USB-MIDI interface, it’s easy to use the keyboard to play virtual instruments on any modern PC DAW. As it’s a popular standard, it should work with most tablets and smartphones too, if you’re that way inclined. Of course, if you’re more into modular synthesizers, you might want to think about working with CV instead!
Obviously, we would never endorse cheating on an exam, but sometimes a device is just too tempting to be left untouched. For [Neutrino], it was an old Casio calculator that happened to have a perfectly sized solar panel to fit a 128×32 OLED as replacement. But since the display won’t do much on its own, he decided to connect it to an ESP8266 and mount it all inside the calculator’s housing, turning it into a spy-worthy, internet-connected cheating device, including a stealthy user interface controlled by magnets instead of physical buttons. (Video, embedded below.)
To achieve the latter, [Neutrino] added two Hall effect sensors and a reed switch inside each end of the calculator. Placing a magnet — possibly hidden in a pen cap — near the reed switch will turn the display on, and placing another magnet near the Hall-effect sensors will navigate through the display’s interface, supporting two inputs with long, short, and multi-tap gestures each. To obtain information through WiFi, the ESP8266 connects to Firebase as backend, allowing to set up predefined content to fetch, as well as a possibility to communicate with your partner(s) in crime through a simple chat program.
As the main idea was to keep visible modifications to a minimum, one shortcoming is that charging the additional battery that powers the whole system would require an additional, external charging circuit. But [Neutrino] had a solution for that as well, and simply exposed two wires to the back, which could easily be mistaken for random solder splatters. And well, of course, requiring WiFi might also be tricky in some situations, so maybe you might want to consider a mobile network upgrade for yourself.
Despite his best efforts to repair the LCD on his Casio FX-702P, it soon became clear to [Andrew Menadue] that it was a dead-end. Rather than toss this relatively valuable device in the trash, he wondered if would be possible to replace the LCD with a more modern display. Knowing that reverse engineering the LCD panel itself would be quite a challenge, he decided instead to focus his efforts on decoding the communications between the calculator’s processor and display controller.
With his logic analyzer connected to the Casio’s four bit bus [Andrew] was able to capture a sequence of bytes during startup that looked promising, although it didn’t quite make sense at first. He had to reverse the order of each nibble, pair them back up into bytes, and then consult the FX-702P’s character map as the device doesn’t use ASCII. This allowed him to decode the message “READY”, and proved the concept was viable.
Of course a calculator with a logic analyzer permanently attached to it isn’t exactly ideal, so he started work on something a bit more compact. Armed with plenty of display controller data dumps, [Andrew] wrote some code for a STM32 “Blue Pill” ARM Cortex M3 microcontroller that would sniff and decode the data in near real-time. In the video after the break you can see there’s a slight delay between when he pushes a button and when the corresponding character comes up on the LCD below, but it’s certainly usable.
Unfortunately, the hardware he’s created for this hack is just slightly too large to fit inside the calculator proper. The new LCD is also nowhere near the size and shape that would be required to replace the original one. But none of that really matters. While [Andrew] says he could certainly make the electronics smaller, the goal was never to restore the calculator to like-new condition. Sometimes it’s more about the journey than the destination.
The Casio F-91W is probably the most popular wristwatch ever made. It’s been in production forever, it’s been worn by presidents, and according to US Army intelligence it is “the sign of al-Qaeda”. There’s a lot of history in this classic watch. That said, there is exactly one problem with this watch: it’s barely water resistant. [David] thought he had a solution to this problem, and it looks like he may have succeeded. This classic watch is now waterproof, down to 700 meters of depth. If you’re ever 700 meters underwater, you have bigger problems than a watch that isn’t waterproof.
The basic idea of this hack is to replace the air inside the watch with a liquid. This serves two purposes: first, the front glass won’t fog up. Second, liquids are generally incompressible, or at least only slightly compressible. By replacing the air in the watch with mineral oil, the watch is significantly more water resistant.
Filling a watch with mineral oil is done simply by disassembling the watch, submerging it in a dish of mineral oil, and carefully reassembling the watch. Does it work? Don’t know about this watch, but this was done to another classic Casio watch and tested to 1200 psi. That’s a kilometer underwater, and the watch still worked afterward. We’ll take that as a success, although again if you’re ever a kilometer underwater, you have bigger problems than a broken watch.
Before Wolfram Alpha, before the Internet, before even PCs, calculations more complex than what could be accomplished with a “four banger” required some kind of programmable calculator. There were many to choose from, if you had the means, and as time passed they became more and more sophisticated. Some even added offline storage so your painstakingly written and tediously entered programs didn’t evaporate when the calculator was turned off.
One such programmable calculator, a Casio PRO fx-1 with magnetic card storage, came across [amen]’s bench recently. Sadly, it didn’t come with any cards, so [amen] reverse engineered the card reader and brought the machine back to its 1970s glory. The oddball mag cards for it are no longer available, so [amen] had to make do with. He found some blank cards of approximately the right size for cheap, but somehow had to replicate the band of vertical stripes adjacent to the magnetic strip on the card. Reasoning that they provide an optical synchronization signal, he decided to use a CNC router to cut a series of fine-pitched slots in the plastic card. It took a little effort to get working, including tapping the optical sensor and reading the signal on an oscilloscope, but as the video below shows, the hacked cards work fine with the vintage calculator.
We’ve got to admit to being a bit of a Casio G-Shock watch geek. The big, chunky watches were every day carry items that survived everything we dished out, right up until the smartphone made wearing one seem redundant. But others continue to use and abuse G-Shocks, and some brave souls even hack them.
Replacing the standard quartz crystal with a temperature-compensated MEMS oscillator is one hack that [Alex] tried, and it appears to have worked out well. His project write-up doesn’t specify which MEMS oscillator was used, but we suspect it’s the SiT1552 TCXO. With its extremely small size, stability over a wide range of temperatures, and ultra-low power requirements, the chip is a natural choice to upgrade the stock 32.768-kHz quartz crystal of the watch. Trouble is, the tiny 1.5 mm x 0.8 mm chip-scale package (CSP) device presented some handling problems. After overcooking a few chips in the reflow oven, [Alex] was able to get one mounted to a tiny breakout board, which went into the space formerly occupied by the watch’s quartz crystal. He stole power for the TCXO from a decoupling capacitor, sealed the watch back up, and it’s back in service with better stability and longer battery life to boot. The video below shows the TCXO undergoing tests alongside the original quartz crystal and a comparatively huge DS3231 RTC module, just for fun.
[Alex]’s MEMS transplant seems a long way to go and a lot of fussy work for marginal gains, but who are we to judge? And it does make the watch susceptible to punking with a little helium, which might make things interesting.