The Q2, A PDP8-Like Discrete Transistor Computer

February 6, 2022 by 39 Comments

[Joe Wingbermuehle] has an interest in computers-of-old, and some past experience of building computers on perfboard from discrete transistors, so this next project, Q2, is a complete implementation of a PDP8-like microcomputer on a single PCB. Like the DEC PDP-8, this is a 12-bit machine, but instead of the diode-transistor logic of the DEC, the substantially smaller Q2 uses a simple NMOS approach. Also, the DEC has core memory, but the Q2 resorts to a pair of SRAM ICs, simply because who wants to make repetitive memory structures with discrete 2N7002 transistors anyway?

SMT components for easy machine placement

Like the PDP-8, this machine uses a bit-serial ALU, which allows the circuit to be much smaller than the more usual ALU structure, at the expense of needing a clock cycle per bit per operation, i.e. a single ALU operation will take 12 clock cycles. For this machine, the instruction cycle time is either 8 or 32 clocks anyway, and at a maximum speed of 80 kHz it’s not exactly fast (and significantly slower than a PDP-8) but it is very small. Small, and perfectly formed.

The machine is constructed from 1094 transistors, with logic in an NMOS configuration, using 10 K pullup resistors. This is not a fast way to build a circuit, but it is very compact. By looking at the logic fanout, [Joe] spotted areas with large fanouts, and reduced the pull-up resistors from 10 K to 1 K. This was done in order to keep the propagation delay within bounds for the cycle time without excessive power usage. Supply current was kept to below 500 mA, allowing the board to be powered from a USB connector. Smart!

Memory is courtesy of two battery-backed 6264 SRAMs, with the four 12-bit general purpose registers built from discrete transistors. An LCD screen on board is a nice touch, augmenting the ‘front panel’ switches used for program entry and user input. A 40-pin header was added, for programming via a Raspberry Pi in case the front panel programming switches are proving a bit tedious and error prone.

Discrete transistor D-type flip flop with indicator. Latest circuit switched to 2N7002 NMOS.

In terms of the project write-up, there is plenty to see, with a Verilog model available, a custom programming language [Joe] calls Q2L, complete with a compiler and assembler (written in Rust!) even an online Q2 simulator! Lots of cool demos, like snake. Game of Life and even Pong, add some really lovely touches. Great stuff!

We’ve featured many similar projects over the years; here’s a nice one, a really small 4-bit one, and a really big one.

 

IBM PalmTop Running Modern (Modified) Linux

February 6, 2022 by 19 Comments

The handheld computing market might seem dominated by smartphones today, but before their mass adoption there were other offerings for those who needed some computing power on-the-go. If a 90s laptop was too bulky, there was always the IBM PalmTop which packed punch for its size-to-weight ratio, and for the era it was created in. [Mingcong Bai] still has one of these antiques and decided to see if it was still usable by loading a customized Linux distribution on it.

The PalmTop sported modest hardware even for its time with an Intel 486SL running at 33 MHz with 20 MiB of RAM. This one also makes use of a 1 GB CompactFlash card for storage and while [Mingcong Bai] notes that it is possible to run Windows 95 on it, it’s not a particularly great user experience. A Linux distribution customized for antique hardware, AOSC/Retro, helps solve some of these usability issues. With this it’s possible to boot into a command line and even do some limited text-based web browsing as long as the Ethernet adapter is included.

While the computer is running at its maximum capacity just to boot and perform basic system functions, it’s admirable that an antique computer such as this still works, especially given its small size and limited hardware functionality. If you’re curious about more PalmTop-style computers, take a look at the first one ever produced: the HP-200LX.

Continue reading “IBM PalmTop Running Modern (Modified) Linux” →

An OpenBikeSensor

OpenBikeSensor Measures Close Calls

February 5, 2022 by 54 Comments

Cycling is fun, healthy, and good for the environment. But unfortunately it’s not always the safest of activities, as inconsiderate drivers can be a significant hazard to cyclists. Several countries, including Germany, France, and Belgium have introduced legislation mandating a minimum passing distance of at least 1.5 meters between cars and bikes. Enforcing such a rule is tricky however, and without accurate data on average passing distances it’s hard to know how many drivers are following it.

Enter OpenBikeSensor, an open-source hardware and community science project designed to gather exactly this information. Currently in its prototype phase, it aims to make a simple bike-mounted sensor that measures the lateral distance to any passing vehicles. The resulting data is collected online to generate maps highlighting danger zones, which can ultimately be used by city planners to improve cycling infrastructure.

The hardware is based around a set of ultrasonic sensors that measure the lateral distance to any large object. A GPS module keeps track of the bike’s location, while an ESP32 reads out the data and stores it onto an SD card. The user interface consists of a handlebar-mounted display that shows the system’s status. There’s also a button that the user needs to press any time they are passed by a vehicle: this will trigger a measurement and log the location. Once back home, the user can connect the OpenBikeSensor to their WiFi network and download their trip data.

The initial results look promising, and any project that gets people cycling and tinkering with electronics at the same time is worth looking into. It’s not the first time we’ve seen bike-mounted sensors either: people have designed their own sensors to measure air pollution in South America, or simply their own bike’s speed or tire pressure. Continue reading “OpenBikeSensor Measures Close Calls” →

Camping For $25: Thrift Store Hacks To Keep Cozy

February 5, 2022 by 18 Comments

A hacker is somebody who’s always thinking creatively to solve problems, usually using what they have on hand. Sometimes that means using a 555 to build a CPU, and other times it means using a dead flashlight to start a fire. In the video below the break, [Kelly] shows us a series of hacks you can use while camping in the woods for a night to keep you warm, dry, and well fed!

[Kelly] started his camping trip not in the woods, but rather at a local thrift store. Instead of packing along hundreds of dollars in gear, his aim was to keep costs low. Very low. With some searching he was able to find a blanket, cooking utensils, rope, knife, tarp, and several other camp necessities for just $25.

A good campfire is a necessity of course, and [Kelly]’s full of great ways to start a fire even if all you have is a lighter with no butane or an old flashlight with dead batteries. The purpose of the video is to show how anyone can get their bush craft on even when all they have is a few dollars and a little know-how, which he generously shares. And after watching, we’re sure you’ll agree that he met his mark.

Will you raid the local second hand store before your next camping trip? After seeing this video, you just might! And while you’re there, make sure to grab the things you’ll need to make your own camping-friendly French press so you have some good coffee while you’re out camping in your… uh… Corolla?

Continue reading “Camping For $25: Thrift Store Hacks To Keep Cozy” →

Twist Promises Easier Quantum Programming

February 5, 2022 by 17 Comments

We keep trying to learn more about quantum computers. But the truth is, the way we program quantum computers — or their simulators — today will probably not have much in common with how we program them in the future. Think about it. Programming your PC is nothing like programming the ENIAC. So we expect we’ll see more and more abstractions over the “bare metal” quantum computer. The latest of these is Twist, from MIT.

According to the paper (and the video, below), Twist expresses entangled data and processes in a way that traditional programmers can understand. The key concept is known as “purity” of expressions which helps the compiler determine if data is actually entangled with another piece of data or if any potential entanglement is extraneous. A pure expression only depends on qubits it owns, while a mixed expression may use qubits owned by other expressions.

Continue reading “Twist Promises Easier Quantum Programming” →

Backpack COVID-19 lab

HDD Centrifuge Puts COVID-19 Testing Lab In A Backpack

February 5, 2022 by 11 Comments

Throughout this two-year global COVID-19 nightmare, one thing that has been sorely lacking is access to testing. “Flu-like symptoms” covers a lot of ground, and knowing if a sore throat is just a sore throat or something more is important enough that we’ve collectively plowed billions into testing. Unfortunately, the testing infrastructure remains unevenly distributed, which is a problem this backpack SARS-CoV-2 testing lab aims to address.

The portable lab, developed by [E. Emily Lin] and colleagues at the Queen Mary University of London, uses a technique called LAMP, for loop-mediated isothermal amplification. LAMP probably deserves an article of its own to explain the process, but suffice it to say that like PCR, LAMP amplifies nucleic acid sequences, but does so without the need for expensive thermal cycling equipment. The kit contains a microcentrifuge that’s fashioned from an e-waste hard drive, a 3D printed rotor, and an Arduino to drive the motor and control the speed. The centrifuge is designed to run on any 12 VDC source, meaning the lab can be powered by a car battery or solar panel if necessary. Readout relies on the trusty Mark I eyeball and a pH-indicating buffer that changes color depending on how much SARS-CoV-2 virus was in the sample.

Granted, the method used here still requires more skill to perform than a simple “spit on a stick” rapid antigen test, and it’s somewhat more subjective than the “gold standard” quantitative polymerase chain reaction (qPCR) assay. But the method is easily learned, and the kit’s portability, simple design, and low-cost construction could make it an important tool in attacking this pandemic, or the next one.

Thanks to [Christian Himmler] for the tip.

Gaming Twitter’s Trending Algorithm To Make A Point

February 5, 2022 by 13 Comments

If you have ever taken to Twitter to gauge the zeitgeist, you’ll have noticed that among the trending hashtags related to major events of the day there are sometimes outliers of minority interest associated with single-issue causes. When a cause with a distasteful pedigree was cited one as proof of widespread public support in a debate in the UK’s House of Lords there were concerns raised that a flaw in the ranking algorithm might be responsible, and it was left to [Mallory Moore] to prove the hypothesis by getting a #ThisIsAnExploit hashtag trending without a groundswell of popular support.

Some previous detective work had established that equal ranking might be awarded equally not simply for Tweeting a hashtag but also for retweeting it. The exploit takes advantage of this by means of a relatively small cadre of people all Tweeting the tag a number of times, then retweeting all other instances of it. The resulting rank gain is then in the order of the square of the number of accounts interacting with the tag, and thus hugely inflated over the number of real participants. To test this she created the #ThisIsAnExploit tag and asked her followers to do just that: Tweet it and retweet all others containing it. In a short time the exploit succeeded, beating a very high-profile tag associated with the travails of the British Prime Minister in the process, and with most of the effort due to only 50 accounts.

Our world is now significantly influenced by social media because for many it appears more trustworthy than the old-style mass media with a print origin. Work like this is important because a reminder that transferring the message from newspaper proprietors to tech barons does not confer credibility is sorely needed. Meanwhile now the weakness is in the wild we wonder how Hackaday readers might have fun with it. Does anyone want to see a #RaiseTheJollyWrencher hashtag top the pile?