casio

34 Articles

A vintage pocket calculator with extra exposed circuitry added

I2C Breathes New Life Into Casio Pocket Calculator

February 21, 2022 by 6 Comments

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.

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The Internet – On A Casio Calculator!

July 18, 2021 by 12 Comments

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?

June 18, 2021 by 25 Comments

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

June 17, 2021 by 5 Comments

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.

Modding A Casio W800-H With A Countdown Timer

April 30, 2021 by 28 Comments

Stock, the Casio W800-H wristwatch ships with dual time modes, multiple alarms, and a stopwatch – useful features for some. However, more is possible if you just know where to look. [Ian] decided to dive under the hood and enable a countdown timer feature hidden from the factory.

The hack involves popping open the case of the watch and exposing the back of the main PCB. There, a series of jumpers control various features. [Ian]’s theory is that this allows Casio to save on manufacturing costs by sharing one basic PCB between a variety of watches and enabling features via the jumper selection. With a little solder wick, a jumper pad can be disconnected, enabling the hidden countdown feature. Other features, such as the multiple alarms, can be disabled in the same way with other jumpers, suggesting lower-feature models use this same board too.

It’s a useful trick that means [Ian] now always has a countdown timer on his wrist when he needs it. Excuses for over-boiling the eggs will now be much harder to come by, but we’re sure he can deal. Of course, watch hacks don’t have to be electronic – as this custom transparent case for an Apple Watch demonstrates. Video after the break.

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Casio F-91W, Going Dark

January 22, 2021 by 19 Comments

The Casio F-91W is easily one of the most iconic and popular watches worldwide. But what’s cool about having the same exact thing as millions of other people? Not much, unless of course you modify it to make it your own. That’s exactly what [Gautchh] did to their beloved watch. Between permanent dark mode, stereo blue LED backlights, and a new strap, this timepiece really stands out from the crowd.

Once [Gautchh] got the watch open, the first order of business was to re-polarize the LCD with a different film so the digits are light and the background is dark. This watch ships with a single green backlight LED that’s fairly faint, so [Gautchh] upgraded it to bright blue and added a second 1206 LED in parallel on the other side of the readout. Finally, they replaced the rubber strap with something less likely to chafe.

We think dark mode looks great, though [Gautchh] says it requires a little bit of training to hold your wrist just right to make it readable. They make these mods look easy, but they likely aren’t for the faint of heart. If you want to give it a shot, there are good step-by-step instructions and several pictures to help out.

We’ve seen a lot of Casio F-91W projects over the years, including a method for waterproofing the internals. If you have a lot of love for this watch, why not make a giant version?

Casio Computer Rebuild Puts New Wine In An Old Bottle

September 18, 2020 by 8 Comments

With a glut of vintage consumer electronics available from eBay it should be easy to relive your glory days, right? Unfortunately the march of time means that finding gear is easy but finding gear that works is not. So was the case when [Amen] acquired not one, but two used calculator/computer units hoping to end up with one working device. Instead, he went down the rabbit hole of redesigning his own electronics to drive the Casio QT-1 seen here.

Especially interesting is the prototyping process for the replacement board. [Amen] used a “BluePill” STM32 microcontroller board at its heart, and used point-to-point soldering for the rest of the circuitry on a rectangle of protoyping board. That circuit is non-trivial, needing a 23 V source to drive the original VFD from the computer, a battery-backed real-time-clock (MCP7940), and a GPIO expander to scan the keys on the keypad.

It worked great, but couldn’t be cut down to fit in the case. The solution was a PCB designed to fit the footprint of the original. The modern guts still need more firmware work and a couple of tweaks like nudging that 23 V rail a bit higher to 26 V for better brightness, but the work already warrants a maniacal cry of “It’s Alive!”.

This isn’t [Amen’s] first rodeo. Back in March we looked in on another vintage Casio refurb that sniffed out the display protocol.