There was a time when Radio Shack offered an incredible variety of supplies for the electronics hobbyist. In the back of each store, past the displays of Realistic 8-track players, Minimus-7 speakers, Patrolman scanners, and just beyond the battery bin where you could cash in your “Battery of the Month Club” card for a fresh, free 9-volt battery, lay the holy of holies — the parts. Perfboard panels on hinges held pegs with cards of resistors for 49 cents, blister packs of 2N2222 transistors and electrolytic capacitors, and everything else you needed to get your project going. It was a treasure trove to a budding hardware hobbyist.
But over on the side, invariably near the parts, was a rack of books for sale, mostly under the Archer brand. 12-year old me only had Christmas and birthday money to spend, and what I could beg from my parents, so I tended to buy books — I figured I needed to learn before I started blowing money on parts. And like many of that vintage, one of the first books I picked up was the Engineer’s Notebook by Forrest M. Mims III.
Many years rolled by, and my trusty and shop-worn first edition of Mims’ book, with my marginal notes and more than one soldering iron burn scarring its pulp pages, has long since gone missing. I learned so much from that book, and as I used it to plan my Next Big Project I’d often wonder how the book came about. Those of you that have seen the book and any of its sequels, like the Mini-notebook Series, will no doubt remember the style of the book. Printed on subdued graph paper with simple line drawings and schematics, the accompanying text did not appear to be typeset, but rather hand lettered. Each page was a work of technical beauty that served as an inspiration as I filled my own graph-paper notebooks with page after page of circuits I would find neither the time nor money to build.
I always wondered about those books and how they came about. It was a pretty astute marketing decision by Radio Shack to publish them and feature them so prominently near the parts — sort of makes the string of poor business decisions that led to the greatly diminished “RadioShack” stores of today all the more puzzling. Luckily, Forrest Mims recently did an AMA on reddit, and he answered a lot of questions regarding how these books came about. The full AMA is worth a read, but here’s the short story of those classics of pulp non-fiction.
A few years ago, Roombas — everyone’s favorite robotic trash can — graced the pages of Hackaday with reverence. There was nothing this little robot couldn’t do, save for going up stairs. Roomba hacks have died off since then, and these little trash cans have been swallowed up by dumpsters. It’s all very sad, really.
[Mike] has had one of these Roombas around for a while, sitting in a closet, waiting for someone to make use of it. He recently dug it out, looked it over, and watched the LEDs light up after troubleshooting a problem with the batteries. Then the problem was how to control it.
He had wanted to connect it to a VIC-20, but the handy serial port on the Roomba only accepted baud rates between 19.2k and 57.6k. The VIC-20, with the ancient 6522 VIA, could only bitbang a serial port up to 2400bps. Then the idea hit him. In his closet of ancient technology, [Mike] had a Tandy 102, a slightly upgraded TRS-80 Model 100 that could easily drive a serial port at 19.2k.
When it comes to a mobile retro robotics platform, [Mike] couldn’t have found a better computer. The Tandy 102 has a display, a BASIC interpreter, enough RAM to run a Roomba, and is powered by a few AA batteries. He did need a little bit of level conversion for the serial port, but a MAX232 took care of that easily.
With everything put together, [Mike] had a robot and a computer that is at least as good as the old Heathkit HERO robot. You can check out a video of the Tandy bot below.
[Dirk] has some great documentation to go with his computer. He started with a classic MOS 6502 processor. He surrounded the processor with a number of support chips correct for the early 80’s period. RAM is easy-to -use static RAM, while ROM is handled by UV erasable EPROM. A pair of MOS 6522 Versatile Interface Adapter (VIA) chips connect the keyboard, LCD, and any other peripherals to the CPU. Sound is of course provided by the 6581 SID chip. All this made for a heck of a lot of wires when built up on a breadboard. The only thing missing from this build is a way to store software written on the machine. [Dirk] already is looking into ways to add an SD card interface to the machine.
The home building didn’t stop there though. [Dirk] designed and etched his own printed circuit board (PCB) for his computer. DIY PCBs with surface mount components are easy these days, but things are a heck of a lot harder with older through hole components. Every through hole pin and via had to be drilled, and soldered to the top and bottom layers of the board. Not to mention the fact that both layers had to line up perfectly to avoid missing holes! To say this was a lot of work would be an understatement.
[Dirk] designed a custom 3D printed case for his computer and printed it out on his Ultimaker. To make things fit, he created his design in halves, and glued the case once printing was complete.
If awesome hardware and a case weren’t enough, [Dirk] also spent time designing software for the machine. He wrote his own abbreviated BASIC interpreter along with several BASIC programs. You can find everything over on his GitHub repository.
We always love writing up well-documented, and just generally awesome projects like [Dirk’s]. If you know of any retro computers like this one, drop us a tip!
Retro is in the air today as [John] has tipped us off about a new game he has written for the Tandy Color Computer (CoCo), The game, inspired by the homebrew game DOWNFALL for the Atari Jaguar, features what looks like snappy game play, lots of bright colorful animation and has just entered the Alpha stages. The blog page above sheds some insight on what it takes to make a game for these old 8 bit wonders, cause no matter how easy it sounds, you do have to do some dancing to get even the simplest of things working correctly on such limited resources.
The game was part of this years Retrochallenge which is typically held in January, which we recommend checking out if you want your fill of random projects for old computers. From building an Apple I replica kit, to making a soccer game for a SGI system, getting a 5160 XT online or just noodling with a KIM, there is plenty of interesting projects to keep you occupied during the afternoon.
Join us after the break for a quick video of Fahrfall, the fun looking CoCo Game.
[John W. Linville] wrote a digital video player for the Tandy Color Computer (aka TRS-80). The decades-old hardware performs quite well considering the limited resource he had to work with. This is the second iteration of his player, and can be seen after the break playing a promo video for CoCoFEST 2011 where he’ll show it off in person.
In the most recent thread post (at the time of writing) [John] shares the methods used to get this running. FFMPEG is used on a modern computer to process the source video by separating the audio into an 8-bit 11040Hz file, and it generates several PPM files with the proper video frame rate. ImageMagick takes it from there to convert the PPM files to a bitmap format. It also processes each frame for differential changes, reducing the size to fall within the available bandwidth. They are then interleaved with the audio to produce the final format. Video is 128×192 with rectangular pixels. [John’s] already used it to watch such classics as War Games on the antiquated hardware.
[Becky Stern] shows how to take an old electronic knitting machine and interface it with a computer. After seeing the Brother KH-930E knitting machine in the video after the break it looks like the controls function quite like a CNC milling machine. Patterns can be programmed in and stored on a floppy disk. Since we don’t want to use those anymore (unless they’re hacked as an SD card carriage) it is nice to see that this is how the machine is connected to a computer. Using an altered FTDI cable and a floppy-drive emulator written in Python a blank design file can be saved on the knitting machine, manipulated in the computer to add your own pixel art, then loaded back onto the machine for production. At the very least, it’s interesting to watch the knitting happen, but fans of knitted apparel and geek paraphernalia must be salivating by now.