CP/M 8266

Hands up if you’ve ever used a machine running CP/M. That’s likely these days to only produce an answer from owners of retrocomputers. What was once one of the premier microcomputer operating systems is now an esoteric OS, a piece of abandonware released as open source by the successor company of its developer.

In the 1970s you’d have seen CP/M on a high-end office wordprocessor, and in the 1980s some of the better-specified home computers could run it. And now? Aside from those retrocomputers, how about running CP/M on an ESP8266? From multi-thousand-dollar business system to two-dollar module in four decades, that’s technological progress.

[Matseng] has CP/M 2.2 running in a Z80 emulator on an ESP8266. It gives CP/M 64K of RAM, a generous collection of fifteen 250K floppy drives, and a serial port for communication. Unfortunately it doesn’t have space for the ESP’s party piece: wireless networking, but he’s working on that one too. If you don’t mind only 36K of RAM and one less floppy, that is. All the code can be found on a GitHub repository, so if you fancy a 1970s business desktop computer the size of a postage stamp, you can have a go too.

There’s something gloriously barmy about running a 1970s OS on a two-dollar microcontroller, but if you have to ask why then maybe you just don’t understand. You don’t have to have an ESP8266 though, if you want you can run a bare-metal CP/M on a Raspberry Pi.

Doing It With Fewer Bytes Than Bill Gates

The MITS Altair 8800 occupies a unique place in computing history as the first commercially succesful microcomputer for personal rather than business use. It is famous as the platform upon which the first Microsoft product ran, their first BASIC interpreter.

[Josh Bensadon] has an Altair 8800, and became intrigued by its bootloader. The simplest method of programming the machine is through binary using a set of switches on the front panel, and he remarks that there should be a warning in the manual: “fingers will get sore after repeated use of the small switches on the ALTAIR”.

In the Altair manual there are two listings, one 21 byte, and another in 20 bytes. Bill Gates is on record as saying that their first effort was 46 bytes long, but with more work he managed to create one in 17 bytes. Now [Josh] has beaten that, he’s created an Altair 8800 bootloader in only 14 bytes.

His write-up goes into great detail about how those bytes are shaved off, and provides us with a fascinating insight into the 8800’s architecture. Even if your 8-bit assembler is a little rusty, it’s a fascinating read.

We’ve featured Altair-inspired projects many times here at Hackaday, but rarely the real thing. This Altair PC case with the ability to emulate the original was rather a nice idea, as was this Altair front panel project. If you want the joy without the heartache though, there is an online emulator.

The Icon Of American Farming That You Now Have To Hack To Own

If you wanted to invoke American farming with colour, which colours would you pick? The chances are they would be the familiar green and yellow of a John Deere tractor. It’s a name that has been synonymous with US agriculture since the 1830s, when the blacksmith whose name appears on the tractors produced his first steel plough blade. The words “American icon” are thrown around for many things, but in the case of John Deere there are few modern brands with as much history to back up their claim to it.

A trip across the prairies then is to drive past Deere products in use from most of the last century. They will still supply parts for machines they made before WW2, and farmers will remain loyal to the brand throughout their lives.

Well… That used to be the case.  In recent years a new Deere has had all its parts locked down by DRM, such that all maintenance tasks on the tractors must be performed by Deere mechanics with the appropriate software. If your tractor breaks in the field you can fit a new part as you always have done, but if it’s a Deere it then won’t run until a Deere mechanic has had a look at it. As a result, Motherboard reports that American farmers are resorting to Ukrainian-sourced firmware updaters to hack their machines and allow them to continue working.  An icon of American farming finds itself tarnished in its heartland.

We’ve reported on the Deere DRM issue before, it seems that the newest development is a licence agreement from last October that prohibits all unauthorised repair work on the machines as well as insulating the manufacturer from legal action due to “crop loss, lost profits, loss of goodwill, loss of use of equipment … arising from the performance or non-performance of any aspect of the software”. This has sent the farmers running to illicit corners of the internet to spend their dollars on their own Deere electronic updating kits rather than on call-out fees for a Deere mechanic. Farmers have had centuries of being resourceful, this is simply the twenty-first century version of the hacks they might have performed decades ago with baler twine and old fertiliser sacks.

You might ask what the hack is here, as in reality they’re just buying a product online, and using it. But this is merely the latest act in a battle in one industry that could have ramifications for us all. Farmers are used to the model in which when they buy a machine they own it, and the Deere DRM is reshaping that relationship to one in which their ownership is on the manufacturer’s terms. How this plays out over the coming years, and how it affects Deere’s bottom line as farmers seek tractors they can still repair, will affect how other manufacturers of products non-farmers use consider DRM for their own business models.

Outside the window where this is being written is a Deere from the 1980s. It’s a reliable and very well-screwed-together tractor, though given the subject of this piece it may be our last green and yellow machine. Its dented badge makes a good metaphor for the way at least for us the brand has been devalued.

Thanks [Jack Laidlaw] for the tip.

Daunting Interactive LED Dancefloor Build is Huge Win

If you’ve ever thought about having a light-up dance floor at an event, the chances are you will have been shocked at the rental cost. Doing your best impression of a young John Travolta in Saturday Night Fever doesn’t come cheap, it seems. When faced with this problem before the Furnal Equinox 2017 convention, [Av] and friends decided instead to build their own LED-lit floor.

Their design and build is shown in the video we’ve placed below the break, and though each individual light unit is straightforward it is the scale of the project and its epic build that makes it a very impressive achievement. There are 64 panels of 4 light cells, giving a total of 256 cells and 7680 RGB LEDs arranged as 2560 pixels. Each panel has a shift register PCB interfacing LEDs to the Teensy that controls the floor, and there are also microswitches talking to an Arduino Mega which provides the floor with interactivity. It’s hard to imaging this build would be possible without the people numerous who pitched in at the Toronto Hacklab for the assembly process.

The resulting 17 foot square dancefloor is a work of art, with custom programmed graphics responding to dancers moves, and even a few games along the lines of Dance Dance Revolution built in. After watching the video below, how many of you will secretly want one?

Continue reading “Daunting Interactive LED Dancefloor Build is Huge Win”

An Android Phone Makes A Better Server Than You’d Think

There was a time a few years ago when the first Android phones made it to market, that they seemed full of promise as general purpose computers. Android is sort of Linux, right, or so the story went, so of course you must be able to run Linux on an Android phone and do all sorts of cool stuff with it.

As anyone who tried to root an Android phone from 2010 will tell you, it was a painful and unrewarding process. There was normally a convoluted rooting process followed by somehow squeezing your own Linux filesystem tree onto the device, then chroot-ing into it. You’d then have to set up a VNC server and VNC into it, and eventually you’d feel immensely proud of your very slow tiny-screen Linux desktop that you’d slaved over creating. It was one of those things that’s simple in theory, but extremely convoluted in practice.

But six years have passed since those days, phones have gotten much faster and so has the software for tasks such as rooting, so maybe it’s time to return to the topic of Linux on an Android device. [Pete Scargill] gave it a try when a friend gave him a Chinese quad-core Android phone with a broken screen. He proceeded to put a Debian installation on it, upon which he runs his collection of server processes.

Rooting the phone was straightforward process using the KingRoot app, a sideloaded version as it seems there’s a bogus copy on the Play Store. Then bringing a Linux system to it could be achieved with the LinuxDeploy app. The result is surprisingly useful, after some installation steps upon which he goes into detail.

You might ask what would be the point of this exercise, given that you can do the same thing much more easily with a single board computer such as a Raspberry Pi. But to buy a Pi, SD card, screen, and UPS, as he points out you’d have to spend a lot more than you would for a second-hand phone from eBay — or a free, slightly broken, one from friends or family.

If getting more from your Android phone is your thing, perhaps you’d like to know about installing Busybox on it. We’ve also advocated for using old Android phones for ARM dev.

Negative Resistance: It Shouldn’t Make Sense!

When you leaf through a basic electronics textbook, you’ll find chapters describing in detail the operation of the various components. Resistors, capacitors, inductors, and semiconductors. The latter chapter will talk about P and N type regions, introduce us to the diode, and then deal with the transistor: its basic operation, how to bias it, and the like.

A tunnel diode amplifier circuit. Chetvorno [CC0]
Particularly if your textbook is a little older, you may find a short section talking about the tunnel diode. There will be an odd-looking circuit that seems to make no sense at all, an amplifier formed from just a forward-biased diode and a couple of resistors. This logic-defying circuit you are told works due to the tunnel diode being of a class of devices having a negative resistance, though in the absence of readily available devices for experimentation it can be difficult to wrap your head around.

We’re all used to conventional resistors, devices that follow Ohm’s Law. When you apply a voltage to a resistor, a current flows through it, and when the voltage is increased, so does the current. Thus if you use a positive resistance device, say a normal resistor, in both the top and the bottom halves of a potential divider, varying the voltage fed into the top of the divider results in the resistor behaving as you’d expect, and the voltage across it increases.

In a negative resistance device the opposite is the case: increasing the voltage across it results in decreasing current flowing through it. When a large enough negative resistance device is used in the lower half of a resistive divider, it reduces the overall current flowing through the divider when the input voltage increases. With less current flowing across the top resistor, more voltage is present at the output. This makes the negative resistor divider into an amplifier.

The tunnel diodes we mentioned above are probably the best known devices that exhibit negative resistance, and there was a time in the early 1960s before transistors gained extra performance that they seemed to represent the future in electronics. But they aren’t the only devices with a negative resistance curve, indeed aside from other semiconductors such as Gunn diodes you can find negative resistance in some surprising places. Electrical arcs, for example, or fluorescent lighting tubes.

A typical negative resistance I-V curve. Chetvorno [CC0]
The negative resistance property of electric arcs in particular produced a fascinating device from the early twentieth century. The first radio transmitters used an electric arc to generate their RF, but were extremely inefficient and wideband, causing interference. A refinement treated the spark not as the source of the RF but as the negative resistance element alongside a tuned circuit in an oscillator, These devices could generate single frequencies at extremely high power, and thus became popular as high-powered transmitters alongside those using high-frequency alternators until the advent of higher powered tube-based transmitters around the First World War.

It’s unlikely that you will encounter a tunnel diode or other similar electronic component outside the realm of very specialist surplus parts suppliers. We’ve featured them only rarely, and then they are usually surplus devices from the 1960s. But understanding something of how they operate in a circuit should be part of the general knowledge of anyone with an interest in electronics, and is thus worth taking a moment to look at.

1N3716 tunnel diode header image: Caliston [Public domain].

Cigar Box Opens to Raspberry Pi Laptop

If you were to go back to the middle years of the twentieth century and talk to electronic constructors, you would find a significant number had a cigar box radio among their projects. Cigar boxes were fairly robust, readily available, and could easily accommodate the parts required to make a crystal set or a simple one-tube regenerative receiver. These days there isn’t much attraction to a simple AM radio though, so while they can still be fun to build, the cigar box radio only occupies a niche in vintage radio circles.

Cigar boxes, however, remain. [Mike] found a very nice antique cigar box, and made something unexpected, he put a Raspberry Pi in it and made something close to a laptop. Into the lid goes an LCD screen secured with wooden blocks, while in the body of the box goes the LCD controller, Pi 3, and battery charger and PSU modules. There are two sets of cells, one each for screen and Pi.

We like the idea and we like his write-up for its clear run-down of the modules required even though it’s mostly a plug-together build. We described it as “Something close to a laptop” because it has one glaring omission. He’s using an external keyboard rather than having incorporated one within the case. We think there looks as though there is plenty of room for one, so perhaps he’ll return to the project and upgrade it in that way. For reminding us that cigar boxes can make excellent laptop cases though, we’re thankful.

We’ve featured numbers of Raspberry Pi laptops over the years since the little computer’s launch. Just a small selection are this one using the official touch screen, a rather beautiful one in the style of a Psion palmtop, and one that is rather chunky but has a small footprint. Meanwhile in cigar boxes, we’ve brought you an excellent little 555 organ.