Over the years we’ve seen a number of homebrew 6502 computers assembled with little more than a breadboard, a sack full of jumper wires, and an otherworldly patience that would make a Buddhist Monk jealous. Anyone who takes the time to assemble a fully functional computer on a half-dozen breadboards lined up on their workbench will always be a superstar in our book.
While we’re still too lazy to attempt one of these builds ourselves, we have to admit that the Vectron 64 by [Nick Bild] looks dangerously close to something you might be able to pull off within a reasonable amount of time. It’s still an incredible amount of work, but compared to some of the other projects we’ve seen, this one manages to keep the part count relatively low thanks to the use of a simple 16×2 LCD for output and user input provided by a PS/2 keyboard. You won’t be playing Prince of Persia on it, but at least you might be able to finish it in a weekend.
The computer is clocked at 1 MHz, and features 32KB RAM
along with 32KB EEPROM. That should be enough for anyone. [Nick] also points out he tried to use era-appropriate 7400 series ICs wherever possible, so no worries about historical revisionism here. If you’re looking for a design that somebody could have potentially knocked together back in the 1970s, this one would get you fairly close.
The astute reader might notice there’s no removable media in this build, and may be wondering how one loads programs. For that, [Nick] allowed himself a bit of modern convenience and came up with a scheme that allows an Arduino (or similar microcontroller) to connect up to the computer’s 28C256-15 EEPROM. With a Python script running on your “real” computer, you can write a new ROM image directly to the chip. He’s included the source code for a simple program which will write whatever you type on the keyboard out on the LCD, which should give you a good framework for writing additional software.
If you’re looking for a bigger challenge, don’t worry. We’ve covered 6502 breadboard computers that will make your eyes water. Incidentally, this isn’t the first time we’ve seen a similar LCD used for one of these computers, so looks like there’s no shame in sneaking in modern parts where it makes sense.
There are a range of integrated circuits that most of us would regard as definitive examples of their type, devices which became the go-to for a particular function and which have entered our collective consciousness as electronics enthusiasts. They have been in production since the early days of consumer integrated circuits, remaining in use because of a comprehensive understanding of their characteristics among engineers, and the job they do well.
You can probably name the ones I’m going to rattle off here, the µA741 op-amp designed by David Fullagar for Fairchild in 1968, the NE555 timer from Hans Camenzind for Signetics in 1971, and a personal favourite, Bob Widlar’s µA723 linear regulator for Fairchild in 1967. There may be a few others that readers will name in the comments, but there’s one that until today it’s likely that few of you would have considered. Texas Instruments’ 5400 and 7400 TTL quad 2-input NAND gate has been in continuous production since 1964 and is the progenitor of what is probably the most numerous breed of integrated circuits, yet it doesn’t trip off the tongue when listing famous chips, and none of us can name its designer. So today we’re turning the spotlight on this neglected piece of silicon, and trying to bring it the adulation it deserves. Continue reading “The 7400 Quad 2-Input NAND Gate, A Neglected Survivor From A Pre-Microprocessor World”
Have you ever wondered how you could look at a chip and map out its schematic? [Robert Baruch] wants to show you how he does it and he does in a new video (see below). The video assumes you know how to expose the die because he’s made a video about that before.
This video focuses on using his Beaglebone-driven microscope stage to get high-resolution micrographs stitched together from smaller shots. A 3D-printed sample holder keeps the part from moving around. Luckily, there’s software to stitch the images together. Once he has the die photo, he will etch away the metal to remove the passivation, the metal layer, and the silicon dioxide under the metal and takes another set of photos.
Continue reading “How to Reverse Engineer a Chip”
Logic probes are simple but handy tools that can be had for a couple of bucks. They may not be the sexiest pieces of test gear, nor the most versatile, but they have their place, and building your own logic probe is a great way to understand the tool’s strength and weaknesses.
[Jxnblk]’s take on the logic probe is based on a circuit by [Tony van Roon]. The design hearkens back to a simpler time and is based on components that would have been easy to pick up at any Radio Shack once upon a time. The logic section is centered on the venerable 7400 quad 2-input NAND gate in the classic 14-pin DIP format. The gates light separate LEDs for high and low logic levels, and a 555 timer chip in a one-shot configuration acts as a pulse stretcher to catch transients. The DIP packages lend themselves to quick and dirty “dead bug” construction, and the whole thing fits nicely into a discarded marking pen.
It’s a simple build and a nice form factor for a useful tool, but for an even slimmer package like an old syringe you’ll probably have to go with SMD components. And when you graduate from the simple logic probe, you might want to check out the capabilities of this smart probe.
As an electronics rookie, one of the first things they tell you when they teach you about logic gates is, “You can make everything from a combination of NAND gates”. There usually follows a demonstration of simple AND, OR, and XOR gates made from NAND gates, and maybe a flip-flop or two. Then you move on, when you want a logic function you use the relevant device that contains it, and the nugget of information about NAND gates recedes to become just another part of your electronics general knowledge.
Not [Alexander Shabarshin] though. He’s set himself the task of creating an entire CPU solely from NAND gates, and he’s using 74F00 chips to give a hoped-for 1MIPS performance. His design has an 8-bit data bus but a 4-bit ALU, and an impressive 2-stage pipeline and RISC instruction set which sets it apart from the computers most of us had when 74-series logic was a much more recent innovation. So far he has completed PCBs for a D-type flip-flop and a one-bit ALU, four of which will work in parallel in the final machine
Unsurprisingly, we have maintained a keen interest in TTL computers here at Hackaday for a very long time. You might say that we have featured so many for the subject to deserve a review article of its own. There is the ASAP-3, the Magic-1, the Duo Basic, the Apollo181, the unnamed CPU made by [Donn Stewart], the BMOW, and a clone of the Apollo Guidance Computer. But what sets [Alexander’s] project aside from all these fine machines is his bare-metal NAND-only design. The other 74-series CPU designers have had the full range of devices such as the 74181 ALU at their disposal. By studying the building blocks at this most fundamental level a deeper understanding can be gained of the inner workings of parts normally represented just as black boxes.
One of the briefs for writing a Hackaday article is that if the subject makes the writer stop and read rather than skim over it then it is likely to do so for the reader too. This project may not yet have delivered a working CPU, but its progress so far is interesting enough for an in-depth read. Definitely one to watch.
It’s not uncommon to bitbang a protocol with a microcontroller in a pinch. I2C is frequently crunched from scratch, same with simple serial protocols, occasionally complex systems like Ethernet, and a whole host of other communication standards. But VGA gets pretty tricky because of the timing requirements, so it’s less common to bitbang. [Sven] completely threw caution to the wind. He didn’t just bitbang VGA on an Arduino, but he went one step further and configured an array of 7400 logic chips to output a VGA signal.
[Sven]’s project is in two parts. In part one, he discusses choosing a resolution and setting up the timing signal. He proceeds to output a simple(-ish) VGA signal that can be displayed on a monitor using a single gate. At that point only a red image was displayed, but getting signal lock from the monitor is a great proof of concept and [Sven] moved on to more intricate display tricks.
With the next iteration of the project [Sven] talks about adding in more circuitry to handle things like frame counting, geometry, and color. The graphics that are displayed were planned out in a simulator first, then used to design the 7400 chip configuration for that particular graphic display. It made us chuckle that [Sven] reports his monitor managed to survive this latest project!
We don’t remember seeing non-programmable integrated circuits used for VGA generation before. But bitbanging the signal on an Arduino or from an SD card slot is a great test of your ability to calculate and implement precise timings with an embedded system. Give it a try!
Continue reading “Spit Out VGA with Non-Programmable Logic Chips”
This clock is the first thing that [Kevin] ever made, way back before the Arduinofication of making, and long before the open hardware community exploded, and before the advent of cheap, custom PCBs. It’s an elegant design, with six seven-segment displays, a time base derived from line frequency, controlled entirely by 74-series logic chips. There was only one problem with it: it kinda sucked. Every so often, noise would become a factor and the time would be displayed as 97:30. The project was thrown in the back of the closet, a few revisions were completed, and 13 years later, [Kevin] wanted to fix his first clock.
The redesign used the same 1Hz timebase to control the circuitry, but now the timebase is controlled by a DS3231 RTC with an ATtiny85. The bridge rectifier was thrown out in favor of a much simpler 7805 regulator, and a new board was designed and sent off to OSHPark. Oh, how times have changed.
With the new circuitry, [Kevin] decided to construct a new case. The beautiful Hammond-esque enclosure was replaced with the latest and greatest of DIY case material – laser cut acrylic. Before, [Kevin] would put a jumper on the 1Hz timebase derived from the line frequency to set the clock – a task that makes plugging a clock in exactly at midnight a much simpler solution. Now, the clock has buttons to set the hours and minutes. Much improved, but still an amazing look at how far DIY electronics have come in a little over a decade.