An 8085 Retrocomputer From The Heart

The world of 8-bit retrocomputing splits easily into tribes classified by their choice of processor. There are 6809 enthusiasts, 6502 diehards, and Z80 lovers, each sharing a bond to their particular platform that often threads back through time to whatever was the first microcomputer they worked with. Here it’s the Z80 as found in the Sinclair ZX81, but for you it might be the 6502 from an Apple ][. For [Craig Andrews] it’s the 8085, and after many years away from the processor he’s finally been able to return to it and recreate his first ever design using it. The SBC-85 is not wire-wrapped as the original was, instead he’s well on the way to creating an entire ecosystem based around an edge-connector backplane.

The CPU board is an entire computer in its own right as can be seen in the video below the break, and pairs the 8085 with 8k of RAM, a couple of 2732 4k EPROMs, and an 8155 interface chip. This last component is especially versatile, providing an address latch, timer, I/O ports, and even an extra 256 bytes of RAM. Finally there is some glue logic and a MAX232 level shifter for a serial port, with no UART needed since the 8085 has one built-in. The minimal computer capable with this board can thus be slimmed down significantly, something that competing processors of the mid 1970s often struggled with.

Craig’s web site is shaping up to be a fascinating resource for 8085 enthusiasts, and so far the system sports that backplane and a bus monitor card. We don’t see much of the 8085 here at Hackaday, perhaps because it wasn’t the driver for any of the popular 8-bit home computers. But it’s an architecture that many readers will find familiar due to its 8080 heritage, and could certainly be found in many control applications before the widespread adoption of dedicated microcontrollers. It would be interesting to see where Craig takes this next, with more cards, and perhaps making a rival to the RC2014 over in Z80 country.

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Magnets Make This Panda Move

A single board computer on a desk is fine for quick demos but for taking it into the wild (or even the rest of the house) you’re going to want a little more safety from debris, ESD, and drops. As SBCs get more useful this becomes an increasingly relevant problem to solve, plus a slick enclosure can be the difference between a nice benchtop hack and something that looks ready to sell as a product. [Chris] (as ProjectSBC) has been working on a series of adaptable cases called the MagClick Case System for the LattePanda Alpha SBC which are definitely worth a look.

The LattePanda Alpha isn’t a run-of-the-mill SBC; it’s essentially the mainboard from a low power ultrabook and contains up to an Intel Core M series processor, 8GB RAM, and 64GB of eMMC. Not to mention an onboard Atmega32u4, WiFi, Gigabit Ethernet, and more. It has more than enough horsepower to be used as an everyday desktop computer or even a light gaming system if you break PCIe out of one the m.2 card slots. But [Chris] realized that such adaptability was becoming a pain as he had to move it from case-to-case as his use needs changed. Thus the MagClick Case System was born.

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Reverse Engineering An Ancient SBC With An Apple ][

We spend a lot of time in our community discussing the many home computers from the 8-bit era, while almost completely ignoring their industrial equivalents. While today a designer of a machine is more likely than not to reach for a microcontroller, four decades ago they would have used a single-board computer which might have shared a lot of silicon with the one you used to play Pac Man.

[Epooch] recently came into possession of a CMS 9619A Advanced Single Board Microcomputer, a rather unique Programmable Logic Controller intended for industrial applications. It’s powered by a Motorola 6809 CPU and features the usual array of peripheral chips. To unlock its secrets he reached not for an array of tools from 2019 but for a venerable Apple ][e microcomputer.

In this type of 8-bit machine the various peripherals are enabled through address decoding logic that toggles their chip select line when a particular I/O address is called. Sometimes this task is performed by a set of 74 or similar logic chips, but in the case of the CMS 9619A it falls upon a Programmable Array Logic (PAL). These chips, which could be thought of as a simple precursor to today’s FPGAs, were ideal for creating custom decoding logic.

As you might expect though, a PAL is an opaque device, so to deduce the address map it was necessary to reverse engineer it using the Apple ][‘s printer card and a bit of BASIC code. It then remained to do some ROM disassembly work and wire up the serial ports, before some ROM patching with the Apple ][ as an EPROM programmer to finally access the machine’s debugger.

The 6809 is famous as the brains of Radio Shack’s CoCo and the Dragon computers, but this isn’t the first time we’ve seen it in an SBC.

Single Board Computer Plays Nice With NVIDIA GPU

It’s about convenience when it comes to single board computers. The trade-off of raw compute power for size means the bulk of them end up being ARM based, but there are a few exceptions like the x86 based Udoo Ultra. The embedded Intel 405 GPU on the Udoo Ultra is better than most in the category, but that won’t begin to play much of anything outside of a browser window. Not satisfied with “standard” [Matteo] put together his build combining an Udoo x86 Ultra with a NVIDIA 1060 GPU. It seems ridiculous to have an expansion card almost three times longer than the entire computer its attached to, but since when did being ridiculous stop anyone in the pursuit of a few more polygons?

M.2 adapter board trim comparison
M.2 to PCIe adapter board (Top) Trimmed adapter board (Bottom)

Since the Udoo Ultra doesn’t feature a PCIe slot [Matteo] slotted in a M.2 to PCIe adapter board. There are two PCIe lines accessible by the Udoo Ultra’s M.2 port although trimming the adapter board was required in order to fit. The PCIe female slot was cut open to allow the 1060 GPU to slide in. All of the throughput of the 1060 GPU wouldn’t be utilized given the Udoo Ultra’s limitations anyway.

Windows 10 was the OS chosen for the machine so that all those NVIDIA drivers could be installed, and there’s also the added benefit of being able to sneak in a little Trackmania Turbo too. So to accompany the build, [Matteo] created a graphics comparison video to show the remarkable improvement over the embedded graphics chip. You can see the Time Spy benchmark results in the video below.

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OMEN Alpha: A DIY 8085-Based Computer

[Martin Malý] has put together a sweet little 8085-based single board computer called OMEN. He needed a simple one for educational purposes, and judging by the schematic we think he’s succeeded.

Now in its fourth iteration, it has a 32K EEPROM, 32K of memory, one serial and three parallel ports. In the ROM he’s put Tiny BASIC and Dave Dunfield’s MON85 Serial Monitor with Roman Borik’s improvements. His early demos include the obligatory blinking LED, playing 8-bit music to a speaker, and also a 7-segment LED display with a hexadecimal keyboard. There is also a system connector which allows you to connect a keyboard, a display, and other peripherals. Of course, you can connect serially at up to 115200 baud, making it very easy to compile some assembly on a PC and use the monitor to paste the hex into the board’s memory and run it. Or you can just jump into the Tiny BASIC interpreter and have some nostalgic fun. He demos all this in the video below.

He’s given enough detail for you to make your own and he also has the boards available in kit form on Tindie for a very reasonable price. With some minimal soldering skills, you can be back in the ’80s in no time.

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Build Your Own Linux Single Board Computer

We are fortunate enough to have a huge choice of single-board computers before us, not just those with a bare-metal microcontroller, but also those capable of running fully-fledged general purpose operating systems such as GNU/Linux. The Raspberry Pi is probably the best known of this latter crop of boards, and it has spawned a host of competitors with similarly fruity names. With an entire cornucopia to choose from, it takes a bit more than evoking a berry to catch our attention. The form factors are becoming established and the usual SoCs are pretty well covered already, show us something we haven’t seen before!

[Marcel Thürmer] may have managed that feat, with his Blueberry Pi. On the face of it this is just Yet Another SBC With A Fruity Pi Name, but what caught our attention is that unlike all the others, this is one you can build yourself if you want. It’s entirely open-source, but it differs from other boards that release their files to the world in that it manages to keep construction within the realm of what is possible on the bench rather than the pick-and-place. He’s done this by choosing an Alwinner V3, an SoC originally produced for the action camera market that is available in a readily-solderable TQFP package. It’s a choice that has allowed him to pull off another constructor-friendly feat: the board is only two layers, so it won’t break the bank to have it made.

It’s fair to say that the Allwinner V3 (PDF) isn’t the most powerful of Linux-capable SoCs, but it has the advantage of built-in RAM to avoid more tricky soldering. With only 64Mb of memory, it’s never going to be a powerhouse, but it does pack onboard Ethernet, serial and parallel camera interfaces, and audio as well as the usual interfaces you’d expect. There is no video support on the Blueberry Pi, but the chip has LVDS for an LCD panel, so it’s not impossible to imagine something could be put together. Meanwhile, all you need to know about the board can be found on its GitHub repository. There is no handy OS image to download, u-boot instructions are provided to build your own. We suspect if you’re the kind of person who is building a Blueberry Pi though this may not present a problem to you.

We hope the Blueberry Pi receives more interest, develops a wider community, and becomes a board with a solid footing. We like its achievement of being both a powerful platform and one that is within reach of the home constructor, and we look forward to it being the subject of more attention.

VCF West: Adding A Front Panel To The 6502

When you think about vintage computers from the 1970s, the first thing that should spring to mind are front panels loaded up with switches, LEDs, and if you’re really lucky, a lock with a key. Across all families of CPUs from the ’70s, you’ll find front panel setups for Z80s and 8080s, but strangely not the 6502. That’s not to say blinkenlights and panel switches for 6502-based computers didn’t exist, but they were astonishingly rare.

If something hasn’t been done, that means someone has to do it. [Alexander Pierson] built The Cactus, a  6502-based computer that can be controlled entirely through toggle switches and LEDs.

If you’re wondering why something like this hasn’t been built before, you only have to look at the circuitry of the 6502 CPU. The first versions of this chip were built with an NMOS process, and these first chips included bugs, undefined behavior, and could not be run with a stopped clock signal. These problems were fixed with the next chip spin using a CMOS process (which introduced new bugs), but the CMOS version of the 6502 would retain the contents of its registers with a stopped clock signal.

The specs for the Cactus computer are what you would expect from a homebrew 6502 system. The chip is a WDC 65C02S running at 1MHz, there’s 32k of RAM and a 16k EPROM, dual 6551s give serial access at various baud rates, and there are 16 bits of parallel I/O from a 65C22 VIA. The ROM is loaded up with OSI Basic. The real trick here is the front panel, though. Sixteen toggle switches allow the front panel operator to toggle through the entire address space, and eight flip switches can set any bit in the computer. Other controls include Run, Halt, Step, Examine, and Deposit, as you would expect with any front panel computer.

It’s a fantastic piece of work which I missed seeing at VCF East so I’m really glad [Alexander] made the trip between coasts. Cactus is truly something that hasn’t been done before. Not because it’s impossible, but simply because the state of the art technology from when the 6502 was new didn’t allow it. Now we have the chips, and the only limitation is finding someone willing to put in the work.