Z80 Computer Is Both Arduino And Shield

March 7, 2020 by Erin Pinheiro 7 Comments

There have been plenty of Z80 computer builds here on Hackaday, but what sets them apart is what you do with them. [Andrew] writes in with his Z80 single-board computer made from scratch, using the Arduino standard headers for its I/O. In turn, since he needed an easy way to program the flash memory which holds the software to run on the Z80, he used an Arduino Mega as a debugger, making the SBC an Arduino shield itself.

Using such a common header pinout for the Z80 computer allows it to be used with a variety of readily-available Arduino shields. This compatibility is achieved with an analog-digital converter and a 3.3 V regulator, mimicking the pins found in an Arduino Uno. The code, available on GitHub, includes an extensive explanation and walkthrough over the process in which the Mega takes over the bus from the Z80 to function as a fully-featured debugger. Programs can be loaded through embedding an assembly listing into the Mega’s sketch, or, once the debugger is up you can also upload a compiled hex file through the serial connection.

This isn’t the first time [Andrew] has been featured here, and his past projects are just as interesting. If you need to translate a Soviet-era calculator’s buttons into English, hack a metallurgical microscope or even investigate what’s that Clacking Clanking Scraping Sound, he’s the one you should call.

Giant Clock Made In The Nick Of Time

March 2, 2020 by Kristina Panos 12 Comments

When [tnjyoung] was asked to build a huge lighted clock for a high school theater’s production of Cinderella with only two weeks before opening night, he probably wished for a fairy godmother of his own to show up and do it for him. But he and his team pulled it off, and it looks amazing. That medallion in the middle? It was laid out painstakingly by hand, using electrical tape.

This thing is 12 feet wide and weighs more than 500 pounds. Even so, it isn’t a permanent set piece, so it has to move up and down throughout the show on airplane cables. Now for the minutiae: there’s an Arduino Uno with built-in Wi-Fi that receives UDP commands from a phone to raise and lower the clock at the appropriate times. The ‘duino is also controlling two stepper motors, one for the hour hand and one for the minute hand.

Time is almost a minor character in the story of Cinderella, since she has to get back by midnight. Because of this, [tnjyoung] programmed a dozen or so time cues that move the steppers at various speeds to achieve different effects, like time flying by as she dances the night away with the Prince. Hour you still just sitting there? Sweep past the break to watch the build process fly by in a matter of minutes.

Got all the time in the world? Make a clock out of clocks. Clocks all the way down.

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Casual Tetris Comes In At $9

February 28, 2020 by Al Williams 3 Comments

[Michael Pick] calls himself the casual engineer, though we don’t know whether he is referring to his work clothes or his laid back attitude. However, he does like to show quick and easy projects. His latest? A little portable Tetris game for $9 worth of parts. There is an Arduino Pro Mini and a tiny display along with a few switches and things on a prototyping PC board. [Michael] claims it is a one day build, and we imagine it wouldn’t even be that much.

Our only complaint is that there isn’t a clear bill of material or the code. However, we think you could figure out the parts pretty easy and there are bound to be plenty of games including Tetris that you could adapt to the hardware.

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A Tetris To Be Proud Of, With Only A Nano

February 28, 2020 by Jenny List 12 Comments

Tetris may have first arrived in the West on machines such as the PC and Amiga, but its genesis at the hands of [Alexey Pajitnov] was on an Electronika 60, a Soviet clone of an early-1970s DEC PDP-11. Thus those tumbling blocks are hardly demanding in terms of processor power, and a game can be implemented on the humblest of hardware. Relatively modern silicon such as the Atmega328 in [c0pperdragon]’s Arduino Nano Tetris console should then have no problems, but to make that assumption is to miss the quality of the achievement.

In a typical home or desktop computer of the 1980s the processor would have been assisted by plenty of dedicated hardware, but since the Arduino has none of that the feat of creating the game with a 288p video signal having four gray scales and with four-channel music is an extremely impressive one. Beside the Nano there are only a few passive components, there are no CRT controllers or sound chips to be seen.

The entire device is packaged within a clone of a NES controller, with the passives on a piece of stripboard beside the Nano. There is a rudimentary resistor DAC to produce the grey scales, and the audio is not the direct PWM you might expect but a very simple DAC created by charging and discharging a capacitor at the video line frequency. The results can be seen and heard in the video below the break, and though we’re sure we’ve heard something like that tune before, it looks to be a very playable little game.

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Writing Arduino Libraries, An Expert View

February 27, 2020 by Al Williams 32 Comments

The Arduino IDE has a bit of a split personality. On the one hand, it is a simple environment where you can just pick and choose a few libraries, write a few lines of code, and make lots of interesting things. On the other hand, it is also an ecosystem in which many different boards and libraries can be supported. Writing a great library that everyone can easily use takes a little forethought. There is an official style guide, but a recent post by [Nate] from Sparkfun points out lessons learned from writing more libraries than most people.

Of course, as you might expect, some of this is a matter of opinion, and [Nate] admits that. For example, they always use the serial port at 115,200 baud, but they do note that 9,600 baud is also popular. They also suggest making code as readable as possible, which is usually good advice. In the old days, writing terse code might lead to higher efficiency, but with modern compilers, you ought to get a tight final result even when doing things in a pretty verbose fashion.

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MIL-SPEC Keyboard Now Salutes USB

February 27, 2020 by Kristina Panos 6 Comments

When [easyjo] picked up this late ’80s Marconi mil-spec keyboard for cheap, he knew it wouldn’t be easy to convert it to USB — just that it would be worth it. Spoiler alert: those LEDs aren’t a mod, they’re native. They get their interesting shape from the key traces, which are in the four corners.

Despite having way-cool buttons such as WPNS HOLD, and the fact that Control is on the home row where it belongs, this keyboard does not look fun to type on at all for any length of time. Of course, the point of this keyboard is not comfort, but a reliable input device that keeps out dust, sweat, liquids, and the enemy.

This is probably why the controller is embedded into the underside of the key switch PCB instead of living on its own board. [easyjo] tried to analyze the signals from the existing 26-pin connector, but it didn’t work out.

So once he was able to decode the matrix, he removed the controller chip and wired the rows and columns directly to an Arduino Leonardo. Fortunately, the LEDs were just a matter of powering their columns from the front side of the board.

The availability of certain kinds of military surplus can make for really interesting modernization projects, like adding POTS to a field telephone.

Via r/duino

Gravity-Defying Water Droplet Fountain Gets An Upgrade

February 25, 2020 by Rich Hawkes 2 Comments

When we last saw [isaac879]’s levitating RGB time fountain, it was made of wood which meant that it would absorb water and didn’t really show off the effect very well. His new version solves this problem with an acrylic case, new PCB and an updated circuit.

Like the original, this project drops water past strobing RGB LEDs creating an illusion of levitating, undulating colored water droplets. The pump at the top creates the droplets, but the timing has a tendency to drift over time. He thus implemented a PID controller to manage the pump’s drip rate, which was done by having the droplets pass by an infrared diode connected to an ATTiny85. The ’85 used the diode and PWM to control the pump motor speed and communicated to the Arduino over I2C.

The video shown below shows the whole process of designing and building the new time fountain. Everything from circuit and PCB design to 3D printing to assembly is shown along with narration describing what’s going on in case you want to build one yourself. If you do, all the files and components required are listed in the info section of the video.

There’s more that [isaac879] wants to do to improve the time fountain, but V2 looks great. It’s sleeker and smaller than the original and solves some of the design issues of the first. For more inspiration, check out some of the other levitating water fountain projects that have been posted over the years.

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