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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A Gaggle Of Boards Makes For An I2C Playground

It’s not much of a stretch to assume that the majority of Hackaday readers are at least familiar with I2C. In fact, there’s an excellent chance that anyone who’s ever done more with an Arduino than blink the onboard LED has at one time or another used the serial communication protocol to talk to a sensor, display, or other external gadget. Of course, just because most of us have used it in a few projects doesn’t mean we truly understand it.

If you’re looking to brush up on your I2C knowledge, you could do worse than to follow the guide [András Tevesz] recently wrote up. With a title like Hardware Hacking 101: E01 I2C Sniffing, How to Listen to Your Arduino’s I2C Bus, you know you’re in for a good time. While the document is arguably geared more towards security researchers than electronic hobbyists, the concepts presented can be useful even if you’re just trying to debug your own projects. Continue reading “A Gaggle Of Boards Makes For An I2C Playground”

Accessible Arduino Mouse Helps

We enjoy access to cheap stuff because of the mass market for things like mice, keyboards, and cell phones. But if you need a device that doesn’t have mass appeal, you will have to pay a lot more if you can find it at all. However, with modern techniques like 3D printing and Arduino-like microcontrollers being cheap and simple to use, you now have the option to build that special one-of-a-kind device. Case in point: [Davy’s] mouse for people who have brain or nervous system disorders. This particular device is helping a 6-year-old who can’t manipulate a normal mouse.

The device uses an Arduino Pro and an MPU-6050 accelerometer and gyroscope. The original design uses machined aluminum, but 3D printing should work, too. There’s something wrong with the link to the design files in the post, but it is easy to find the correct link.

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Hacking A Fuel Sensor Into A Portable Tank, Literally

Regular readers of Hackaday will know that the projects we feature are generally of the high-tech variety. Microcontrollers, 3D printed parts, embedded Linux, lots of wires, that sort of thing. But that’s not to say we don’t appreciate the somewhat more visceral builds out there; after all, hacking is about creative problem solving and thinking outside the box, and none of that is limited to how complex the fix actually is.

Take for example this quick hack that [R. Preston McAfee] recently sent our way. Looking for a way to check how much fuel was left in his outboard motor’s small portable gas tank without crawling back to look at it, he decided to rig it up with a sending unit. While they’re technically designed for larger tanks which are permanently installed into a boat’s hull, he reasoned there was nothing about the float sensor that would keep it from working in his case so long as it could be safely mounted.

To that end, [Preston] started by cutting a 38 mm (1.5″) hole in the thickest part of the tank, and sanded the area around the opening to smooth things out. He then measured the depth of the tank at that point, and ordered an appropriately sized float sensor. He drilled out the holes for the five mounting bolts, and inserted them through the larger whole so their heads would be inside the tank. By holding the exposed threads with a pair of vice grips he was able to crank the nuts down on each bolt to form a tight seal to the gasket, though it should be noted that the resulting damage to the threads will likely make it difficult to remove the nuts in the future.

Admittedly this is a pretty simple fix, but it’s well thought-out and we appreciate the effort [Preston] put in to documenting the whole process. We’ve certainly covered more elaborate ways of seeing what’s left in the tank, but just because a solution is flashier doesn’t mean it’s necessarily any better.

Pong In Hardware… Virtually

We are big fans of the Falstad circuit simulator. Sure, it isn’t perfect, but there’s nothing else like it when you want to whip up a simple circuit. But we were blown away when we saw a more or less complete hardware implementation of Pong in Falstad. No kidding. Starting with the original schematics, there are multiple pages that show each sub-circuit and even a playable subset that you can play the game in your browser.

But wait… you probably noticed there’s no CRT display in the simulator’s component menu. That’s true, there isn’t. However, you can write JavaScript to interact with a running simulation, so the display is a simple bit of JavaScript that samples signals at predetermined points and does the appropriate drawings. There’s even audio output for the sound effects, although that is built into the simulator.

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Whales Help Scientists Investigate The Mystery Of Menopause

Menopause is the time of life when menstrual periods come to a halt, and a woman is no longer able to bear children. The most obvious cause of menopause is when the ovaries run out of eggs, though it can also be caused by a variety of other medical processes. While menopause is in many ways well-understood, the biological reason for menopause, or the way in which it evolved in humanity remains a mystery. The process was once thought to be virtually non-existent in the animal kingdom, raising further questions.

Surprisingly recently, however, scientists began to learn that humans are not alone in this trait. Indeed, a small handful of sea-going mammals also go through this unique and puzzling process.

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Magnetic Hockey Game Uses A 555

We love a good project here at Hackaday, particularly one that makes us want to pick it up and have a go at whatever it does for ourselves. And when we see such a project and find that it contains the One Chip To Rule Them All (otherwise known as the NE555 timer), our collective cup runneth over with joy. So [Andrew Fentem]’s magnetic hockey project certainly pushes all our buttons, as it’s a game superficially similar to an air hockey table in which a magnetic puck is accelerated by a handheld electronic bat.

The bats look extremely high-tech but are in fact surprisingly simple. Each one contains a Hall effect sensor which triggers the 555 which we’d expect is wired as a monostable, this in turn fires a MOSFET which energises an electromagnet for a set period of time. The puck is a magnet, and thus when it is detected by the Hall sensor it is shot away at high speed by the electromagnet. the result is a fast-paced game which has an extra edge over conventional air hockey, and which being honest, we’d love to have a go at. You can see it in the video below the break.

Of course, if your budget doesn’t stretch to not one but two chips in this era of semiconductor shortages, you can always try a conventional table.

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