A Keypad Joypad For Your Retro Gaming

April 1, 2016 by Jenny List 15 Comments

[TK] is a retro computer enthusiast who’s had some difficulty locating a joystick for his trusty Amiga 500. New ‘sticks are expensive, and battered survivors from the 80s go for more than they should.

Happily these old controllers were simple devices, having only five control lines for the four directions and a fire button which were active low. [TK] therefore cast around the available components and decided to craft his own controller from a numerical keypad.

Numerical keypads may be ubiquitous, but they’re not the perfect choice for a joypad. Instead of individual switches, they are wired as a matrix. [TK]’s controller works within that constraint without butchering the keypad PCB, though his layout has the left and right buttons below the up and down buttons. Looking at the schematic we wonder whether the 4-5-6 and 7-8-9 rows could be transposed , though joypad layout is probably a matter of personal choice.

Making the controller was a simple case of wiring the pad to a 9-pin D socket in the correct order, and plugging it into the Commodore. He reports that it’s comfortable to use and better than some of the lower-quality joysticks that were on the market back in the day. Veterans of Amiga gaming will understand that sentiment, there were some truly shocking offerings to be had at the time.

Quite a few home-made game controllers have made it onto these pages over the years. There is this one using tactile switches and a ballpoint pen, and a stick made from the idler wheel from a surplus VCR, but the ultimate crown of junkbox joysticks should go to this joystick made from clothes pins. If we take one thing away from all this home-made controller ingenuity, it is that what really matters is not the hardware but the gameplay.

Spark Gap And Coherer Meet Beagle Bone

March 29, 2016 by Dan Maloney 8 Comments

Getting back to basics is a great way to teach yourself about a technology. We see it all the time with computers built from NAND gates or even discrete transistors. It’s the same for radio – stripping it back to the 19th century can really let you own the technology. But if an old-school wireless setup still needs a 21st-century twist to light your fire, try this spark gap transmitter and coherer receiver with a Beagle Bone Morse decoder.

At its heart, a spark gap transmitter is just a broadband RF noise generator, and as such is pretty illegal to operate these days. [Ashish Derhgawen]’s version, which lacks an LC tuning circuit, would be especially obnoxious if it had an antenna. But even without one, the 100% electromechanical transmitter is good for a couple of feet – more than enough for experimentation without incurring the wrath of local hams.

The receiver is based on a coherer, a device that conducts electricity only when a passing radio wave disturbs it. [Ashish]’s coherer is a slug of iron filings between two bolts in a plastic tube. To reset the coherer, [Ashish] added a decoherer built from an electromagnetic doorbell ringer to tap the tube and jostle the filings back into the nonconductive state. He also added an optoisolator to condition the receiver’s output for an IO pin on the Beagle, and a Python script to decode the incoming Morse. You can see it in action in the video below.

If this build looks familiar, it’s because we’ve covered [Ashish]’s efforts before. But this project keeps evolving, and it’s nice to see where he’s taken it and what he’s learned – like that MOSFETs don’t like inductive kickback much.

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BlinkenBone Meets The PiDP8

March 23, 2016 by Brian Benchoff 10 Comments

Years ago when the old mainframes made their way out of labs and into the waiting arms of storage closets and surplus stores, a lot got lost. The interesting bits – core memory boards and the like – were cool enough to be saved. Some iconic parts – blinkenlight panels – were stashed away by techs with a respect for our computing history.

For the last few years, [Jörg] has been making these blinkenlight panels work again with his BlinkenBone project. His work turns a BeagleBone into a control box for old console computers, simulating the old CPUs and circuits, allowing them to work like they did thirty years ago, just without the hundreds of pounds of steel and kilowatts of power. Now, [Jörg] has turned to a much smaller and newer blinkenlight panel, the PiDP-8.

The PiDP-8 is a modern, miniaturized reproduction of the classic PDP 8/I, crafted by [Oscar Vermeulen]. We’ve seen [Oscar]’s PiDP a few times over the last year, including a talk [Oscar] gave at last year’s Hackaday Supercon. Having a simulated interface to a replica computer may seem ridiculous, but it’s a great test case for the interface should any older and rarer blnkenlight panels come out of the woodwork.

What Lies Beneath: The First Transatlantic Communications Cables

March 18, 2016 by Dan Maloney 81 Comments

For some reason, communications and power infrastructure fascinates me, especially the long-haul lines that move power and data over huge distances. There’s something about the scale of these projects that really gets to me, whether it’s a high-tension line marching across the countryside or a cell tower on some remote mountain peak. I recently wrote about infrastructure with a field guide that outlines some of the equipment you can spot on utility poles. But the poles and wires all have to end at the shore. Naturally we have to wonder about the history of the utilities you can’t see – the ones that run under the sea.

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Testing DRAM, One Byte At A Time

March 18, 2016 by Brian Benchoff 26 Comments

A few weekends ago, [Chris] was in the mood for some retrogaming. That meant digging out the old Apple IIgs equipped with a monstrous RAM card with a whole three megabytes of RAM. This particular Apple IIgs had intermittent issues for a long time, and [Chris] was beginning to suspect the RAM was the culprit. Testing this required testing a few dozen individual RAM chips, so why not build something with an Arduino to make [Chris]’ life easier?

The chips found in [Chris]’ Apple are standard 1 M x 1 DRAM chips, the standard for late-80s computers. To test these chips on an Arduino, he picked up a beautiful ZIF socket, wired up the chip to an Arduino shield, and began the joyous process of figuring out how to interface DRAM to an Arduino.

Unlike static memories, DRAM needs to be refreshed periodically to recharge the capacitors. While this refresh cycle was the bane of designers and engineers throughout time, [Chris] actually doesn’t need to care about refreshing the DRAM. He’s just writing 1024 rows to the memory and reading it straight out – no need to refresh the memory. The trick comes from the multiplexed address bus. For his project, [Chris] needs to write 10 bits of the address, latch it, then write the other half of the address bits.

The DRAM tester was a success, and [Chris] put all the code and schematics up on GitHub. Solving the mystery of the broken Apple IIgs wasn’t as simple, as [Chris] thinks the problem might be in one of the support chips on the gigantic RAM card or the IIgs motherboard. Still, it’s a neat, quick build to test out a few DRAM chips.

The Origin Of QWERTY

March 15, 2016 by Brian Benchoff 72 Comments

There are very few things that are surrounded with as much hearsay and rumor as the origins of the QWERTY layout of typewriters and keyboards. The reason behind the QWERTY layout isn’t as simple as ‘so the bars for each letter don’t collide with each other.’ That’s nonsense – it would make far more sense to improve the mechanism before changing the arrangement of the keyboard around.

That’s not the only fallacious argument for the creation of QWERTY. It’s also been called a marketing ploy; Stephen Jay Gould popularized the idea of the QWERTY keyboard being as it is so a salesman could peck out TYPE WRITER on the top row [1]. This also makes little sense. Why would the top row and not the home row be so privileged as to contain all the letters the make up the name of the machine. For that matter, wouldn’t a sales pitch be more impressive if TYPE WRITER were typed with one hand?

This doesn’t mean there’s not a method behind the madness of QWERTY – it’s just not as simple as jammed typewriter mechanisms or appeasing the wishes of salesmen in the 1870s. QWERTY didn’t come out of thin air, though, but folk tale history of this keyboard layout is sadly deficient.

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How Low Can You Go? The World Of QRP Operation

March 8, 2016 by Dan Maloney 51 Comments

Newly minted hams like me generally find themselves asking, “What now?” after getting their tickets. Amateur radio has a lot of different sub-disciplines, ranging from volunteering for public service gigs to contesting, the closest thing the hobby has to a full-contact sport. But as I explore my options in the world of ham radio, I keep coming back to the one discipline that seems like the purest technical expression of the art and science of radio communication – low-power operation, or what’s known to hams as QRP. With QRP you can literally talk with someone across the planet on less power than it takes to run a night-light using a radio you built in an Altoids tin. Now that’s a challenge I can sink my teeth into.

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