Rob Weinstein Builds An HP-35 From The Patent Up

April 7, 2022 by Chris Lott 40 Comments

Fifty years ago, Hewlett-Packard introduced the first handheld scientific calculator, the HP-35. It was quite the engineering feat, since equivalent machines of the day were bulky desktop affairs, if not rack-mounted. [Rob Weinstein] has long been a fan of HP calculators, and used an HP-41C for many years until it wore out. Since then he gradually developed a curiosity about these old calculators and what made them tick. The more he read, the more engrossed he became. [Rob] eventually decided to embark on a three year long reverse-engineer journey that culminated a recreation of the original design on a protoboard that operates exactly like the original from 1972 (although not quite pocket-sized). In this presentation he walks us through the history of the calculator design and his efforts in understanding and eventually replicating it using modern FPGAs.

The HP patent ( US Patent 4,001,569 ) contains an extremely detailed explanation of the calculator in nearly every aspect. There are many novel concepts in the design, and [Rob] delves into two of them in his presentation. Early LED devices were a drain on batteries, and HP engineers came up with a clever solution. In a complex orchestra of multiplexed switches, they steered current through inductors and LED segments, storing energy temporarily and eliminating the need for inefficient dropping resistors. But even more complicated is the serial processor architecture of the calculator. The first microprocessors were not available when HP started this design, so the entire processor was done at the gate level. Everything operates on 56-bit registers which are constantly circulating around in circular shift registers. [Rob] has really done his homework here, carefully studying each section of the design in great depth, drawing upon old documents and books when available, and making his own material when not. For example, in the course of figuring everything out, [Rob] prepared 338 pages of timing charts in addition to those in the patent. Continue reading “Remoticon 2021 // Rob Weinstein Builds An HP-35 From The Patent Up” →

Turn Timing Diagrams Into ASCII Art, For Friendlier Pasting

April 4, 2022 by Donald Papp 21 Comments

We all use text-based fields at one time or another, and being limited to ASCII only can end up being a limitation. That’s what led [Luke Wren] to create asciiwave, a fantastic tool that turns WaveDrom timing diagrams into ASCII art. Unlike images, ASCII timing diagrams are suitable for pasting into comment fields, change logs, or anywhere else that accepts text only. [Update: As the author kindly shared in the comments below, this tool’s original niche is pasting into HDL (e.g. Verilog) source code comments, where it has a special kind of usefulness.]

WaveDrom itself is a nifty JavaScript tool that we have covered before. It accepts timing diagrams expressed as JSON data, and renders nicely-readable digital timing diagrams as images directly inside one’s browser.

As cool and useful as that is, images can’t be pasted into text fields. That’s where asciiwave comes in. It reads the exact same format that WaveDrom uses, but generates an ASCII-art timing diagram instead. So if you’ve found WaveDrom useful, but wish you could generate ASCII versions, here’s your solution.

Al Williams Tells All In The Logic Simulation Hack Chat

March 4, 2022 by Tom Nardi 1 Comment

The list of requirements for hosting one of our weekly Hack Chats is pretty short: you’ve got to be knowledgeable, passionate, and above all else, willing to put those two quantities on display for a group of like-minded strangers. Beyond that, we’re not too picky. From industry insider to weekend hobbyist, high school dropout to double doctorate, if you’ve got something interesting to talk about, we’re ready to listen.

But in casting a such a wide net, we occasionally forget that we’ve got a considerable collection of potential hosts within our own worldwide roster of contributors. Among this cast of characters, few can boast the same incredible body of knowledge as Al Williams, who was able to pencil in some time this week to host the Logic Simulation Hack Chat.

Or at least, that was the idea. In reality the Chat covered a wide range of topics, and was peppered with fascinating anecdotes pulled from Al’s decades of experience in the field. Though to be fair, we expected no less. He was building hardware before many of us were born, and can take credit for designs that have been at the bottom of the ocean as well as launched into orbit. He’s been writing about it just as long too, with articles of his appearing in iconic print magazines such as Dr. Dobb’s Journal.

Al has seen and done so much that he still surprises us with the occasional nugget, and we’ve been working with him for years. It was only a week or two back that he started a story with “Back when I used to manage a gas pipeline…” in the middle of a conversation about utility metering.

Of course, that’s not to say some technical discussion didn’t sneak in there from time to time. Sure Al’s recollection of how they used to literally crawl over the schematics for the 68000 back at Motorola might stick out as a particular high point, but he also explains his personal preference for vendor-specific software tools over their more generic open source counterparts. He also draws comparisons between hardware description languages (HDLs) like Verilog and parametric CAD tools such as OpenSCAD in the way that they help model complex relationships in ways that can’t be easily done by more traditional means.

At one point the conversation lingers on the design and production of application-specific integrated circuits (ASICs), and how they compare to field-programmable gate arrays (FPGAs). Traditionally ASICs have been out of reach for the hobbyist, but with the recent collaboration between Google and SkyWater Technology to create an open source process design kit (PDK), they’re now within the capabilities of a dedicated individual. Matt Venn spoke on the topic during Remoticon 2021, and it’s good to see more folks in the community openly discussing the possibilities of custom silicon designed by hackers.

From there, things start really getting wild. From dreaming of virtual reality circuit simulators that let you fly amongst your creations like in Tron, to salivating over high-end technologies such as reflective memory, this Chat really runs the gamut. But then, that’s sort of why we hold them in the first place. Whether you actively participate or are just along for the ride, the Hack Chat gives everyone in the community a chance to gather around a virtual water cooler with fascinating characters that you won’t find anywhere else.

The Hack Chat is a weekly online chat session hosted by leading experts from all corners of the hardware hacking universe. It’s a great way for hackers connect in a fun and informal way, but if you can’t make it live, these overview posts as well as the transcripts posted to Hackaday.io make sure you don’t miss out.

Homebrew 16 Bit Computer Reinvents All The Wheels

December 3, 2021 by Ryan Flowers 23 Comments

Building your own computer has many possible paths. One can fabricate their own Z80 or MOS 6502 computers and then run a period correct OS. Or a person could start from scratch as [James Stanley] did. [James] has invented a completely unique computer and CPU he calls SCAMP. SCAMP runs a custom OS called SCAMP/os which you can check out in the video below the break.

[James] describes the CPU and computer as purposefully primitive. Built out of discrete 74xx series logic chips, it runs at a fast-enough-for-homebrew 1 MHz. Plus, it has a lot of blinking lights that can’t help but remind us of the original Imsai 8080. But instead of a panel of switches for programming, the SCAMP/os boots to a shell, which is presented through a serial terminal. Programs are written in a bespoke language with its own compiler. The OS is described as a having a Unix-like feel with CP/M-like functionality. That’s quite a combination!

What we love most about the build, other than its clean looks and blinkenlights, is the amount of work that [James] has put into documenting the build both on his blog and on Github, where the source code and design is available. There’s also an open invitation for contributors to help advance the project. We’re sure he’ll get there, one bit at a time.

While [James] is using a Compact Flash card for storage currently we can’t help but wonder if a Cassette Tape storage system might be a worthwhile future upgrade.

Continue reading “Homebrew 16 Bit Computer Reinvents All The Wheels” →

Using VHDL To Generate Discrete Logic PCB Designs

November 13, 2021 by Lewin Day 36 Comments

VHDL and Verilog are hardware description languages, used to describe and define logic circuits. They’re typically used to design ASICs and to program FPGAs, essentially using software to define hardware. However, [Tim] has done something altogether quite creative, creating tools to take VHDL and Verilog and spit out PCB designs for discrete logic.

Yes, you read that correctly. The basic idea is to take VHDL source code, and then make a PCB layout that implements the desired logic using resistor-transistor logic. From there, the PCB design files can be shipped off to a manufacturer for pick-and-place assembly at a fraction of the cost of producing a bespoke ASIC.

The drawbacks are obvious; tons of individual discrete parts are required, the size penalty is hilariously bad, and power usage is almost certainly orders of magnitude higher than doing the same logic on an ASIC or even FPGA. Oh, and everything’s much slower, too.

However, as an academic exercise or simply for fun, it’s an awesome bit of work. The idea that one can define a complicated logic circuit and have a PCB implementing the logic whipped up by automated tools is amazing, and we absolutely want to see more of this type of thing.

We’ve seen similar work done with VHDL synthesis into 74-series logic design. If you’ve been developing your own fancy digital-logic-fu, be sure to drop us a line!

[Thanks to Yann Guidon for the tip!]

RISC-V In… Typescript?

October 14, 2021 by Al Williams 8 Comments

We are accustomed to seeing RISC-V implementations in Verilog or VHDL, but [Low Level JavaScript] has one in TypeScript. Before you dismiss it as a mere emulator, know that the project relies on gateware-ts, a conversion between TypeScript and Verilog. From there, you can actually put the CPU on an FPGA. You can see the launch video below and there is one development video as well as, presumably, more to come.

We aren’t sure if many FPGA designers will be willing to switch to TypeScript. But if you are comfortable with it, it might open up FPGA development without having to learn as much of a new language.

Continue reading “RISC-V In… Typescript?” →

Slice Your Next FPGA Design

June 28, 2021 by Al Williams 12 Comments

A recent trend has been to convert high-level constructs into FPGA code like Verilog or VHDL. Silice goes the other way: it converts very hardware-specific concepts to Verilog and aims to be a more expressive and easier to use language.

Why Silice? The project’s web page enumerates its design goals:

A clean, simple syntax that clearly exposes the flow of operations and where clock cycles are spent.
Precise rules regarding flow control (loops, calls) and their clock cycle consumption.
Familiar hardware constructs such as always blocks, instantiation, expression tracking (wires).
An optional flow-control oriented design style (automatic FSM generation), that naturally integrates within a design: while, break, subroutines.
The possibility to easily describe pipelines.
Automatically takes care of creating flip-flops for variables, with automatic pruning (e.g. const or bindings).
Generic interfaces and grouped IOs for easy reuse and modular designs.
Generic circuits that can be instantiated and reused easily.
Explicit clock domains and reset signals.
Familiar syntax with both C and Verilog inspired elements.
Inter-operates with Verilog, allowing to import and reuse existing modules.
Powerful LUA-based pre-processor.