Four Chips To Retro Perfection

July 10, 2019 by Brian Benchoff 24 Comments

Over the years, we’ve seen many people build a computer from the ground up. It’s always great, but this one takes the cake. I’m not just saying that because there’s a cute little ‘Z80 Inside’ logo on the silk screen, either. It’s a four IC Z80 computer, a tiny board, and [Just4Fun]’s entry into this year’s Hackaday Prize.

This single board computer is only four chips, the most important being the CMOS Z80 CPU. This is the same CPU as was found in the TRS-80 and the ZX Spectrum, both classics from the early days of computing. In addition to the PCU, there’s a Toshiba SRAM with 128 whole kilobytes of random access memories. A 74HC00 is thrown into the mix for glue logic, and everything else happens through a specially-programmed ATMega32A. This last chip provides a universal I/O subsystem, the EEPROM, and the 4/8MHz clock for the CPU.

Those four chips are really all you need for a fully functional computer, but you can do so much more with this little board. There’s a uCom board, or basically a ‘transparent’ USB-to-serial emulator that will allow you to upload a hex file to the board. Of course this means you can also connect it to a terminal, and with FuzixOS, there’s Unix for the Z80. It’s a wonderment of retrocomputing, and one of the best ways to build an old computer today.

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Space Age Bitcoin Mining On An Apollo AGC

July 9, 2019 by Dan Maloney 6 Comments

Imagine you’ve got an Apollo Guidance Computer, the machine that took men to the Moon 50 years ago. You’ve spent ages restoring it, and now it’s the only working AGC on the planet. It’s not as though you’re going to fly to the Moon with it, so what do you do with it? Easy – turn it into a perfectly awful Bitcoin mining rig.

The AGC that [Ken Shirriff] and others have been restoring barely resembles a modern computer. The AGC could only do about 40,000 operations per second, but raw speed was far less important than overall reliability and the abundant IO needed to run a crewed spacecraft. It was a spectacular success on the Apollo missions, but [Ken] wanted to know if turning it into a Bitcoin mining rig was possible.

[Ken] gives a great overview of how Bitcoin mining works, with one of the best explanations of the hashing algorithm we’ve seen. Getting that to run on the AGC was no mean feat, especially with limits imposed by the memory addressing scheme and the lack of machine instructions for manipulating words. He eventually got it working, though, clocking in at a screaming 10.3 seconds per Bitcoin hash. [Ken] estimates that the first coin will be successfully mined in a mere 400 zettaseconds, which is about a billion times older than the universe. With about 13 quadrillion years to the first ka-ching, you have plenty of time to watch a block mined in the video below; alas, it was an old block, so no coins were awarded to compensate the team for their efforts.

This isn’t the first time [Ken] has implemented a useless Bitcoin mine. The Xerox Alto mine was actually fast compared to the AGC, but it sure beats the IBM mainframe and punchcards.

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BGA Hand Soldering Uses Tombstone Resistor Technique, Demands Surgical Precision

July 8, 2019 by Jenny List 19 Comments

Most Hackaday readers will be a pretty dab hand with a soldering iron. We can assemble surface-mount boards, SOICs and TSSOPs are a doddle, 0402s we take in our stride, and we laugh in the face of 0201s. But a Twitter thread from [Greg Davill] will probably leave all but the most hardcore proponents of the art floundering, as he hand-wires a tiny FPGA in a BGA package to the back of a miniature dot-matrix LED display module.

Resistors soldered on-end, awaiting wires to connect to the BGA microcontroller

As far as we can see the module must once have had its own microcontroller which has been removed. We’d guess it was under an epoxy blob but can’t be sure, meanwhile its pads are left exposed. The Lattice LP1k49 fits neatly into the space, but a web of tiny wires are required to connect it to those pads. First, [Greg] populates the pads with a set of “tombstoned” tiny (we’re guessing 0R) resistors, then wires them to the pads with 30μm wire. He describes a moment of confusion as he attempts to tin a stray hair, which burns rather than accepting the solder.

The result is a working display with a new brain, which surprises even him. We’ve seen more than one BGA wiring over the years, but rarely anything at this scale.

It’s worth mentioning that [Greg] was behind the FLIR frame grabber that was a runner-up in last year’s Hackaday Prize. We admire the photos he’s able to get of all of his projects and aspire to reach this level with our own. Take this as inspiration and then check out the Hackaday contest for Beautiful Hardware images happening right now.

Thanks [Sophi] for the tip.

Low Res Video Card Is Still Amazing Since It’s Made Out Of Logic Chips

July 7, 2019 by Brian Benchoff 33 Comments

[Ben Eater] has been working on building computers on breadboards for a while now, alongside doing a few tutorials and guides as YouTube videos. A few enterprising hackers have already duplicated [Ben]’s efforts, but so far all of these builds are just a bunch of LEDs and switches. The next frontier is a video card, but one only capable of displaying thousands of pixels from circuitry built entirely on a breadboard.

This review begins with a review of VGA standards, eventually settling on an 800×600 resolution display with 60 MHz timing. The pixel clock of this video card is being clocked down from 40 MHz to 10 MHz, and the resulting display will have a resolution of 200×150. That’s good enough to display an image, but first [Ben] needs to get the horizontal timing right. This means a circuit to count pixels, and inject the front porch, sync pulse, and back porch at the end of each horizontal line.

To generate a single horizontal line, [Ben]’s circuit first has to count out 200 pixels, send a blanking interval, then set the sync low, and finally another blanking interval before rolling down to the next line. This is done with a series of 74LS161 binary counters set up to simply count from 0 to 264. To generate the front porch, sync, and back porch, a trio of 8-input NAND gates are set up to send a low signal at the relevant point in a horizontal scan line.

The entire build takes up four solderless breadboards and uses twenty logic chips, but this isn’t done yet: all this confabulation of chips and wires does is step through the pixel data for the horizontal and vertical lines. A VGA monitor detects it’s in the right mode, but there’s no actual data — that’ll be the focus of the next part of this build where [Ben] starts pushing pixels to a monitor.

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This Chiptune Player’s Got What Nintendon’t

July 6, 2019 by Brian Benchoff 7 Comments

When it comes to chiptunes, the original Nintendo Entertainment System and the Game Boy get all the accolades. The OPL synths have all the fun. But there’s another chip out there in dusty old machines that is at least as interesting with a repertoire at least as influential as the Mega Man 2 OST. It’s the YM2612, the chip in the Sega Mega Drive/Genesis.

[natalie] created a portable device capable of playing back the files targeting the sound chips in this venerable machine. It’s the MegaGRRL, and it’s the iPod for the original Genesis sound tracks.

Inside the MegaGRRL is an ESP32 in the form of an ESP-WROOM-32 module. There is, of course a YM2612 chip in there, along with a headphone amplifier and a battery charger. The display is a fairly standard and cheap affair that’s 240 x 320 pixels in full color, and there are seven buttons on this device, because of course you need an A, B, and C button.

Combined with a 3D printed enclosure, the GameGRRL does exactly what it says it will: it plays all the music from old Sega games. Now, when you’re in the inevitable argument with someone over the fact that Michael Jackson wrote the Sonic 3 soundtrack, the proof is right in your pocket. Of if you want to jam out on the Toe Jam And Earl soundtrack, that’s right there too. You can check out the video demos below.

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Sprucing Up A Bell & Howell Model 34 Oscilloscope

July 4, 2019 by Tom Nardi 20 Comments

We’ll admit it, in an era when you can get a four channel digital storage oscilloscope with protocol decoding for a few hundred bucks, it can be hard not to see the appeal of analog CRT scopes from decades past. Sure they’re heavy, harder to use, and less capable, but they just look so cool. Who could say no to having one of these classic pieces of gear on their bench?

[Cody Nybo] certainly couldn’t. Despite the fact that he already has a digital scope, he couldn’t pass up the chance to add a Bell & Howell Schools Model 34 from circa 1973 to his collection. It needed a bit of TLC before it could be brought back into service, but now it’s all fixed up and ready to put in some work. Not bad for a piece of gear with nearly a half-century on the clock.

The restoration of the Model 34 was aided by the fact that [Cody] got the original manual and schematics for the scope in the deal, which he was kind enough to scan and upload for the rest of the class to enjoy. Those of you who have worked on older electronics can already guess where the scope needed the most love: all the capacitors needed to be swapped out for fresh ones. He also found a few resistors that were out of spec, and the occasional bad solder joint here and there.

Even if you’re not looking to repair your own middle-aged oscilloscope, his pictures of the inside of Model 34 are fascinating. The scope was sold as a kit, so the construction is surprisingly simple and almost entirely point-to-point. Of course, there’s something of a trade-off at work: [Cody] says it won’t display much more than 2.5 MHz before things start getting wonky. But then again, that’s a more than reasonable frequency ceiling for audio work and most hobbyist projects.

Oscilloscopes have come a long way since the days when they had to draw out their readings on a piece of paper. While newer devices have all but buried the classic analog scope, a beauty like this would still have a place of honor in our lab.

This Arduino Is Feeding The Fishes

July 2, 2019 by Lewin Day 11 Comments

Fish are easy to keep as pets, requiring little more than regular feeding to keep them happy in the short-to-medium term. If you’re going on holiday, it can be nice to know that your pets are being taken care of, but finding someone to take on the chore can be hard. [Trevor_DIY] doesn’t need to worry about that, however – he’s built an automatic feeder to handle the job.

The build uses an Arduino Uno as the brains, with the only additional hardware required being a stepper motor and driver. The stepper motor drives a 3D printed wheel, with 14 slots – each one holding one meal for the fish. This allows the feeder to deliver two meals a day for a full week before requiring attention.

The feeder is configured to feed a breakfast meal, then a dinner meal 8 hours later, and then wait 16 hours before breakfast comes around again. Rather than use a real-time clock, this is simply handled with the Arduino’s built in delay function. While it isn’t super accurate, this should be close enough over a week to keep the fish alive. We’d be interested as to just how far it drifts over time.

Overall, it’s a quick and tidy way to keep the pets going without a lot of fuss. Pet feeders are a popular project, as they solve a common problem faced by owners the world over; this one can even handle wet cat food. Video after the break.

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