WS2812s On A 6502

December 23, 2021 by Elliot Williams 40 Comments

We can still remember when the WS2812 LED first came into our consciousness, way back in the mists of time. The timing diagrams in the datasheet-of-questionable-veracity made it sound quite tricky, with tight timing tolerances and essentially a high-speed two-bit PWM data protocol at 500 kHz. It was a challenge to bit-bang with an ATtiny85 back then, but there’s no way something as old and crusty as an Apple II would be up to snuff, right?

[Anders Nielsen] took up the challenge of getting the venerable 6502 processor to drive Neopixels and won! After all, if the chip is good enough for Bender and the Terminator T-800, it should be able to blink some colored LEDs, right? The secret sauce is shift registers!

Specifically, [Anders] abuses the 74LS165 parallel-in, serial-out shift register for his dirty work. Instead of bit-banging the WS2812’s “long high is a 1, short high is a 0” signal directly, the first few bits of the shift register are hard-wired to VCC and the last few to GND.

The bits in the middle determine if the pulse shifted out is long or short, and they’re set by the 6502, through a 6522 VIA chip, just like the Apple II would have. Clocking the data out of the shift register handles the timing-critical stuff. Very clever!

Video below the break.

Continue reading “WS2812s On A 6502” →

Retro Reproduction Captures The Style Of The Sol-20

December 7, 2021 by Dan Maloney 26 Comments

In the early years of the computer revolution, a machine like the Sol-20 really stood out. Where most hobbyist machines had front panels that bristled with toggle switches and LEDs, the Sol-20 was a sleek, all-in-one that looked like an electric typewriter in a walnut-trimmed box. Unfortunately, it was also quite expensive, so not that many were sold. This makes them hard enough to find 40 years later that building his own reproduction Sol-20 is about the only way for [Michael Gardi] to have one of his own.

In a lot of ways, the Sol-20 anticipated many of the design elements that would come into play later. Like the Apple and Commodore machines that were coming down the pike, the Sol-20 was intended to be plug and play. [Mike] celebrates that design with a full-size reproduction of the original, concentrating on its unique aesthetic aspects. The reproduction mimics the striking blue case, with its acrylic front panel and walnut sides. The keyboard is also an exact match for the original, in looks if not in function — the capacitive mechanism proved too difficult to replicate, so he opted for a kit using Cherry switches and custom keycaps. [Mike] also used his proven technique for 3D-printing the memorable Sol-20 logo for the front panel, in the correct font and color.

Under the hood, a Raspberry Pi runs an 8080 emulator, which supports a range of virtual devices, including a cassette tape drive and the video output. For fun, [Mike] also imagined what a CRT display for the Sol-20 would have looked like, and added that to his build. It’s a great-looking machine that never was, and we appreciate the attention to detail. We’ve seen that before — his 2/3-scale VT-100 terminal comes to mind, as does his reproduction of a 1960s computer trainer.

Building The DIY HP41C: A Field Report

December 3, 2021 by Al Williams 21 Comments

I have a confession to make. I write about a lot of projects for Hackaday, but there are very few I read about and then go actually build a copy of it. I don’t have a lot of time and I’m usually too busy building my own stuff. But once in a while, something strikes my fancy and I’ll either raid the junk box or buy the kit. The most recent case of that was the PX-41C, a replica of the classic HP-41C.

The HP-41C is a somewhat legendary reverse-polish notation calculator. I still have my original HP-41C from 1979 (a very low serial number). It is still a workhorse but at 43 years old or so, I don’t like to leave it hanging around or near anything that might damage it. It has enough wear from the daily use it received 40 years ago. Sure, I have great emulation on my phone and I use that too, but the PX-41C kit looked fun, and with all through-hole parts it would be a quick build. The black Friday sale on Tindie sealed the deal for me.

Start-Up

The kit arrived on the Saturday after Thanksgiving, I decided to tackle it while waiting for some 3D prints. The components were all nicely bagged and marked. Tearing into the bags was a bit frustrating, but not hard and it did keep everything separate. There was a bill of materials, but — I thought — no instructions. Turns out the last part of the bill of materials is a link to some instructions. They aren’t much and I didn’t realize they were until after completing the board, but it isn’t hard to figure out. All the parts are marked on the silkscreen and you can probably figure it out — with a few caveats.

Continue reading “Building The DIY HP41C: A Field Report” →

Build Your Own HP41C

November 24, 2021 by Al Williams 42 Comments

There was a time when engineers carried slide rules. Then there was a time when we all carried calculators. Sure, calculators are still around, but you are more likely to use your phone. If you really need serious number crunching, you’ll turn to a full computer. But there was that awkward time when calculators were very important and computers were very expensive that calculators tried to be what we needed from full-blown computers. The HP41C was probably the pinnacle of that trend. If you’ve ever had one, you know that is a marvel of the day’s technology with alphanumeric capabilities and four plug in ports for more memory or ROMs. It really was a little hand-held computer. Didn’t have one? Don’t worry, you can now build your own. In fact, the HP emulator will also act like an HP15C or 16C, if you prefer.

You can see the device in action in the video below. As you might expect, this version uses a through-hole ATMEGA328 and even at 8 MHz, the emulation is faster than the original calculator. The machine also has over double the memory the original calculator had along with a real-time clock built-in. The display is also backlit, something we all wanted in the original.

Continue reading “Build Your Own HP41C” →

A PDP 11 By Any Other Name: Heathkit H11 Teardown And Repair

November 22, 2021 by Al Williams 33 Comments

[Lee Adamson] is no stranger to classic computers. He recently picked up a Heathkit H11A which, as you might remember, is actually a PDP-11 from DEC. Well, technically, it is an LSI-11 but still. Like a proper LSI-11, the computer uses the DEC QBus. Unlike a lot of computers of its day, the H11 didn’t have a lot of switches and lights, but it did have an amazing software library for its day.

[Lee] takes us through a tour of all the different cards inside the thing. It is amazing when you think of today’s laptop motherboards that pack way more into a much smaller space. He also had to fix the power supply.

Continue reading “A PDP 11 By Any Other Name: Heathkit H11 Teardown And Repair” →

Vintage Computers With A Real Turbo

November 3, 2021 by Bryan Cockfield 42 Comments

In prior centuries, it was common practice to tie the operation of a program to a computer’s clock speed. As computers got faster and faster, the programs tied to that slower clock speed sometimes had trouble running. To patch the issue temporarily, some computers in the early 90s included a “TURBO” button which actually slowed the computer’s clock speed down in order to help older software run without breaking in often unpredictable ways. [Ted Fried] decided that he would turn this idea on its head, though, by essentially building a TURBO button into the hardware of old computers which would greatly increase the execution speed of these computers without causing software mayhem.

To accomplish this, he is running CPU emulators on Teensys (Teensies?), but they are configured to be a drop-in replacement for the physical CPU of several retro computers such as the Apple II, VIC-20, and Commodore 64 rather than an emulator for an entire system. It can be configured to run either in cycle-accurate mode, making it essentially identical to the computer’s original hardware, or it can be placed into an accelerated mode to take advantage of the Teensy 4.1’s 800 MHz processor, which is orders of magnitude faster than the original hardware. This allows (most of) the original hardware to still be used while running programs at wildly faster speeds without needing to worry about any programming hiccups due to the increased clock speed.

The video below demonstrates [Ted]’s creation running in an Apple II but he has several other cores for other retro computers. It’s certainly a unique way to squeeze more computing power out of these antique machines. Some Apple II computers had a 4 MHz clock which seems incredibly slow by modern standards, so the 800 MHz Teensy would have been considered wizardry by the standards of the time, but believe it or not, it’s actually necessary to go the other direction for some applications and slow this computer down to a 1 MHz crawl.

Continue reading “Vintage Computers With A Real Turbo” →

An Emulator For OBP, The Spaceflight Computer From The 1960s

November 1, 2021 by Donald Papp 9 Comments

[David Given] frequently dives into retrocomputing, and we don’t just mean he refurbishes old computers. We mean things like creating a simulator and assembler for the OBP spaceflight computer, which was used in the OAO-3 Copernicus space telescope, pictured above. Far from being a niche and forgotten piece of technology, the On-Board Processor (OBP) was used in several spacecraft and succeeded by the Advanced On-board Processor (AOP), which in turn led to the NASA Standard Spaceflight Computer (NSSC-1), used in the Hubble Space Telescope. The OBP was also created entirely from NOR gates, which is pretty neat.

One thing [David] learned in the process is that while this vintage piece of design has its idiosyncrasies, in general, the architecture has many useful features and is pleasant to work with. It is a bit slow, however. It runs at a mere 250 kHz and many instructions take several cycles to complete.

Sample of the natural-language-looking programming syntax for the assembler. (Example from page 68 of the instruction set manual for the OBP.)

One curious thing about the original assembler was documentation showing it was intended to be programmed in a natural-language-looking syntax, of which an example is shown here. To process this, the assembler simply mapped key phrases to specific assembly instructions. As [David] points out, this is an idea that seems to come and go (and indeed the OBP’s successor AOP makes no mention whatsoever of it, so clearly it “went”.) Since a programmer must adhere to a very rigid syntax and structure anyway to make anything work, one might as well just skip dealing with it and write assembly instructions directly, which at least have the benefit of being utterly unambiguous.

We’re not sure who’s up to this level of detail, but embedded below is a video of [David] coding the assembler and OBP emulator, just in case anyone has both an insatiable vintage thirst and a spare eight-and-a-half hours. If you’d prefer just the files, check out the project’s GitHub repository.

Continue reading “An Emulator For OBP, The Spaceflight Computer From The 1960s” →