A 6502 with a Custom Language

The 6502 has a long history with hackers. The Apple computer (the one with no keyboard or even case) had a 6502. So did the Kim-1. [Dolo’s] version is a bit more refined, though. He started it a few years ago in response to one of our contests, but he’s been making improvements to it ever since. In particular, the custom programming language, Dflat, has many improvements lately, including true functions and high-resolution drawing.

The hardware has a CPU running at over 2.5 MHz, 44K of RAM, 16K of PROM, and 16K of video RAM. There’s plenty of I/O, including a keyboard, sound, and joysticks. An SD card provides mass storage and it all goes in a hacked BBC Micro case. You can see an overview video, below.

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Home Made 8-Bit CPU Is A Wiry Blinky Build

It might look like a random pile of wires to some, but it is far from random: [Paulo Constantino] built this 8-bit CPU himself from scratch. He built his remarkable creation using wires and 74HC shift register chips, plus a selection of LEDs to show the various registers.

Running at a maximum of 5MHz, it has an 8-bit data and address bus, although the latter can be expanded to 16 bits. It’s not mining Bitcoin (yet), but it can do things like play the Mario theme. His latest addition is the addition of the ability to write data out to flash memory, and he is looking to add a keyboard to make programming easier.

At the moment, he has to program the CPU by setting DIP jumpers. It’s an impressive, if somewhat frightening build that [Paulo] says took him a couple of days to design and a week or so to build. We’ve seen a few breadboard CPU builds, (some of which were tidier) and builds with similar shift register chips, but this one scores big in the blinky light and mad genius stakes.

Thanks to [AnalogMind] for the tip!

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Making an Arduino Shield PCB with Fritzing

[Allan Schwartz] decided to document his experience using Fritzing to design, fabricate, and test a custom Arduino shield PCB, and his step-by-step documentation makes the workflow very clear. Anyone who is curious or has been looking for an opportunity to get started will find [Allan]’s process useful to follow. The PCB in question has two shift registers, eight LEDs, eight buttons, and fits onto an Arduino; it’s just complex enough to demonstrate useful design features and methods while remaining accessible.

[Allan] starts with a basic breadboard design, draws a schematic, prototypes the circuit, then designs the PCB and orders it online, followed by assembly and testing. [Allan] had previously taught himself to use Eagle and etched his own PCBs via the toner transfer method, but decided to use Fritzing instead this time around and found it helpful and easy to use.

About a year ago we saw Fritzing put through its paces for PCB design, and at the time found that it didn’t impress much from an engineering perspective. Regardless, as a hobbyist [Allan] found real value in using Fritzing for his project from beginning to end; he documented both the process and his observations in order to help others, and that’s wonderful.

No-Solder Breadboarding for SMD LEDs

Breadboarding is a great way to get started with electronics, and with the wide availability of those little wire jumpers, it’s never been easier – until you hit roadblocks due to poor connections and parasitic capacitance futzing with your signals. However, in today’s current climate, the latest and greatest modules are too often available only in SMD packages, and while breakout boards can help, it’s probably overcomplicating things a bit when it comes to SMD LEDs. It’s all good, though – [Simon Merrett] has a workaround, as part of his Yapolamp project.

[Simon] first took a flat strip of steel, and placed two neodymium magnets on top. The assembly was then wrapped in electrical tape for insulation, and two contacts were created with copper tape. The LEDs were then placed across the two contacts and wires were attached to join them to the breadboard. The 5630 LEDs [Simon] must contain some sort of ferrous material, because they were attracted to the magnets and sat neatly in place.

It’s a neat hack that would be particularly useful if you needed to quickly swap out LEDs, and saves them from damage by soldering. Meanwhile, check out this SMD LED matrix from 2009. 

TMS9900 Retro Build

[Robert Baruch] found a TMS9900 CPU from 1983 in a surplus store. If that name doesn’t ring a bell, the TMS9900 was an early 16-bit CPU from Texas Instruments. He found that, unlike modern CPUs, the chip took several voltages and a four-phase twelve-volt clock. He decided to fire it up and — of course — one thing led to another and he wound up with a system on a breadboard. You can see one of the videos he made about the machine below.

This CPU had some odd features, most notably that it stored its registers in off-chip memory and can switch contexts by changing where the registers reside. That was a novel idea when the memory and the CPU were similar in speed. In a modern computer, the memory is much slower than the CPU and this would be a major bottleneck for program execution. The only onboard registers were the program counter, the status register, and a pointer to the general-purpose registers in memory.

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Homemade Computer from 1970s Chips

Sometimes it starts with a 555 timer and an op-amp. Other times with a small microcontroller. But the timing’s not so great and needs a dedicated timing crystal circuit. And maybe some more memory, and maybe the ATtiny should be swapped out for some 74LS-series chips. And now of course it needs video output too. Before you know it, you’re staring at a 40-chip computer that hearkens back to a simpler, yet somehow more complex, time of computing. At least that’s where [Marcel] is with his breadboard computer based on 1970s-era chips.

For what it does, this homebrew computer is relatively simple and straightforward. It gets 8 bits of processing power from 34 TTL chips. Another 6 round out the other features needed for the computer to operate. It is capable of rendering 64 colors in software and has more than enough memory for a computer of this sort. So far the only recurring problem [Marcel] has had has been with breadboard fatigue, as some of the chips keep popping out of the sockets.

This is a great project for anyone interested in homebrew or 8-bit computing, partially because of some of the self-imposed limitations that [Marcel] imposed on himself, like “only chips from the 70s”. It’s an impressive build on its own and looks to get much better since future plans call for a dedicated PCB to solve the issue with the worn-out breadboards. If you’re already invested in a project like this, don’t forget that the rabbit hole can go a little deeper: you can build a computer out of discrete transistors as well.

8-Bit Breadboard Computer is up to 8 Hours

[Ben Eater] posted some videos of an 8-bit computer with no CPU chip that he built completely on a breadboard a few years ago. After being asked for schematics, he finally admitted that he didn’t have any. So, instead, he decided to rebuild it and keep a video log of each step in the process. You can see his kickoff video, below, but you can also find 30 more recent videos covering topics from the ALU design and troubleshooting to the decimal LED display. He even uses an Arduino to program a EEPROM that he uses to replace a lot of logic.

You probably want to wait until you have some free time as there are around eight hours of videos so far. The videos start off with a simple 555 timer and work up from there. Each piece gets a test separate from the whole, so with luck you won’t have an impossible job trying to troubleshoot the whole thing at the end.

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