The Casio Smartwatch You Never Had

In a way, you have to feel a bit sorry for the engineers at Casio. They can produce the most advanced digital watches ever to grace the wrist, but their work will forever be associated with one of their more lowly creations. The Casio F91 is the archetypal digital watch — it’s affordable, it’s been in production since the Ark, it does the job so well that it’s become a design classic, and it remains a very tough act to follow.

If it has a flaw though, it’s that the functions of a watch from 1989 are very basic. Wouldn’t it be nice if a Casio F91 could be a modern smartwatch! Well thanks to [Pegor] it can, with a complete re-engineering of the classic watch’s internals. Now the simple classic timepiece is fully up-to-date!

All the Casio internals are removed, and a new movement holder supports a fresh PCB with an OLED display mounted via a flexible sub-PCB. The brains comes courtesy of a Texas Instruments CC2640 BLE microcontroller. This gives it a 15-day battery life, which is nothing like what the original watch would have but compares favorably to smartwatches. He admits that the software needs some work, but with hardware this well-executed we hope that others can contribute some improvements.

This is probably the most impressive F91 hack we’ve seen, but it’s by no means the first revamped Casio we’ve shown you.

Old Casio Calculator Learns New Tricks

[George Stagg] recently found himself stung by the burden of free time while in lockdown. Needing a project to keep him occupied, he decided to upgrade his 90s Casio CFX-9850G calculator to run custom machine code.

All [George] really wanted was for his vintage calculator to understand Reverse Polish Notation (RPN). The calculator in question can already run its own version of BASIC, however the bespoke Hitachi CPU struggles performance-wise with complex programs, and wouldn’t be a realistic way of using RPN on the calculator. An RPN interpreter written in assembly language would be much faster.

The first step in cracking this calculator wide open was a ROM dump, followed by writing a disassembler. Incredibly, the MAME framework already featured a ‘partial implementation’ of the calculator’s CPU, which was a much needed shot in the arm when it came time to write a full-featured emulator.

With the entire calculator emulated in software, the plan from here involved replacing one of the BASIC commands in ROM with new code that would jump to an address in RAM. With 32KB of RAM there ended up being plenty of room for experimentation, and uploading a program into RAM was simplified by using Casio’s original backup software to dump the RAM onto a PC. Here, the contents of RAM could be easily modified with custom code, then uploaded back into the calculator.

With RAM to burn, new routines were created to write custom characters to the screen, and a new font was created to squeeze more characters onto the display than normal. [George] ended up porting a Forth interpreter, which defaults to RPN style, to finally achieve his humble objective. He also managed to get a version of Conway’s Game Of Life running, check out the video after the break.

We can’t get enough of our calculator hacks here, so make sure to check out the CPU transplant on this vintage Soviet calculator.

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Remoticon 2021 // Joey Castillo Teaches Old LCDs New Tricks

Segmented liquid crystal displays are considered quite an old and archaic display technology these days. They’re perhaps most familiar to us from their use in calculators and watches, where they still find regular application. [Joey Castillo] decided that he could get more out of these displays with a little tinkering, and rocked up to Remoticon 2021 to share his findings.

[Joey’s] talk is a great way to learn the skills needed to reverse engineer a typical segment LCD.
[Joey] got his start hacking on these displays via his Sensor Watch project –  a board swap for the venerable Casio F-91W wristwatch, with the project now available on CrowdSupply. It kits out the 33-year-old watch design with a modern, low-power ARM Cortex M0+ microcontroller running at 32 MHz that completely revolutionizes what the watch can do. Most importantly, however, it repurposes the watches original segmented monochrome LCD.

Segment LCDs are usually small monochrome devices made out of glass, that have the benefit of using very little power in their operation. They come with a fixed layout, which cannot be changed – so they’re often designed specifically for a given purpose. A calculator will have segments laid out to display numbers, often in the usual 7-segment fashion, while a watch may add dedicated segments for displaying things like “AM,” “PM,” or “ALARM.” Continue reading “Remoticon 2021 // Joey Castillo Teaches Old LCDs New Tricks”

A vintage pocket calculator with extra exposed circuitry added

I2C Breathes New Life Into Casio Pocket Calculator

When is a pocket calculator more than just a calculator? [Andrew Menadue] has been pushing the limits of his 1970s Casio FX-502P by adding all sorts of modern functionality via the calculator’s expansion port.

Several older Casio calculators included an expansion port for connecting cassette tape storage and printing functionality. Data on the FX-502P could be saved on cassette tape using the well-known Kansas City standard, however this signal was produced by Casio’s FA-1 calculator cradle, not the FX-502P itself. To interact with the calculator itself would require an understanding of whatever protocol Casio designed for this particular model.

It turns out that the protocol is a little quirky compared to its contemporaries, with variable length data packets and inverted data logic, (zero volts is ‘1’ and three volts is ‘0’). Once the protocol was untangled, it was ‘simply’ a matter of connecting the calculator to the GPIO interface on the STM32, and using some software wizardry to start shooting data packets back and forth.

This hack can be used to send and receive data from an SD card (via a RAM buffer), however it’s the other expansion capabilities that really make us wonder. [Andrew] has demonstrated how easy it is to add a real-time clock or thermal printer. Using the I2C capabilities of the STM32, it’s likely that all sorts of gadgets and sensors could be coupled with this vintage calculator, and many others like it.

You can find even more details about this hack over here, including some follow up videos to the original hack. No stranger to vintage calculators, we last featured [Andrew] after he retrofitted a modern LCD display to an old Casio. It’s charming to see how these calculators are far from obsolete.

Continue reading “I2C Breathes New Life Into Casio Pocket Calculator”

The Internet – On A Casio Calculator!

Over the years we’ve become used to seeing some impressive hacks of high-end calculator software and hardware, most often associated with the Z80-based models from Texas Instruments. But of course, TI are far from the only player in this arena. It’s nice for a change to see a Casio receiving some attention. The Casio fx series of graphical calculators can now communicate with the world, thanks to the work of [Manawyrm] in porting a TCP/IP stack to them.

As can be seen in the video below, lurking in the calculator’s menu system is an IRC client, there is also a terminal application and a webserver which you can even visit online (Please be aware that it’s only a calculator though, so an onslaught of Hackaday readers clicking the link may bring it down). The Casio doesn’t have a network interface of its own, so instead, it speaks SLIP over the serial port. In this endeavor, it uses a UART driver sourced from [TobleMiner].

It’s always good to see a neglected platform get some love, and also to note that this is an unusual outing for an SH4 CPU outside its most familiar home in the Sega Dreamcast. It’s a surprise then to read that the SH4 in a calculator of all products, is a custom version that lacks an FPU. This deficiency doesn’t mean it can’t be overclocked though, as this very old Hackaday article describes.

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Just How Water Resistant Is The Casio F91W?

Water resistance is an important feature of a modern watch. It makes wearing the watch far more practical in this modern world of sudden rainstorms and urban water balloon ambushes. The Casio F91W, one of the company’s most popular watches, is claimed to be water resistant to “30 meters”, which in ISO parlance, means it is suitable for splashes and rain resistance only. [Rostislav Persion] wanted to get a better idea of what this really meant, so set about investigating for himself.

The first step was to simply immerse the watch under 5.5″ of cold tap water while pressing the buttons and observing for any signs of water ingress. Already, the watch proved it is far more than just rain resistant, so [Rotislav] decided to disassemble the watch and learn how it achieved this.

Disassembly revealed that the watch’s case was entirely sealed, except for three buttons. The buttons, however, are specially designed in order to seal with the plastic case of the watch. Each button consists of a stainless steel pin, machined to be larger on the outside-facing side than the inside. The buttons also have a rubber O-ring seal to allow them to move in the case without allowing water to leak inside. [Rotislav] then compares the simple design to buttons used on watches with higher water resistance ratings, which boast multiple O-ring seals and more complex designs.

Given [Rotislav’s] results, we’d be far more confident getting our affordable Casio watches a little wet. Obviously, we wouldn’t expect to make a warranty claim if damage occurred from use outside the specs, but it’s clear the watch is far more capable than standards might suggest. If that’s not enough though, you can always set about modifying the watch to improve its water resistance even further.

A Tidy Octave Mod For The Casio SK-1

1985 saw the release of the Casio SK-1, a compact sampling keyboard that brought the technology to a lower price point than ever before. However, one drawback of this was that it comes stock with only a 2.5 octave keyboard. [Jonas Karlsson] wanted a little more range out of the instrument, so set about hacking in his own octave mod.

The build consists of fiddling with the SK-1’s microprocessor clock to change the pitch of the notes generated by the instrument. The original clock is generated by a simple LC circuit, which in this mod is fed to an inverter, and then a pair of flip-flops to divide the clock by four. The original clock and the divided version are then both sent to a mux chip. With the flick of the switch, either the original or downshifted clock can be sent to the microprocessor.

With the slower clock feeding the microprocessor, all the notes are downshifted an octave. The resulting sound, which you can listen to on Soundcloud, is similar to what you get when chopping down sample rates. It bears noting, however, that as this mod changes the master clock, other features such as rhythms are also effected.

It’s a great mod which gives the instrument a gloomier, grittier sound on demand. The Casio SK-1 has long been prized for its hackability; we’ve seen them completely worked over in previous mods. If you’ve got your own twisted audio experiments cooking up in the workshop, be sure to drop us a line.