If you are a devotee of the Sinclair series of 8-bit home computers then a piece of news from the Centre For Computing History in Cambridge may be of interest to you, they’ve released a copy of the ROM from their ZX Spectrum prototype. This machine surfaced last year as part of a donation form the company originally contracted to write the Spectrum ROM and has been given pride of place int heir exhibition ever since. They’ve been doing some very careful work on it, and while The Register reports they can’t yet make the board boot, they have extracted the code for study. In the video below the break, we see it running on the Speccy emulator on an older Windows PC.
The ROM comes with an invitation to the ZX Spectrum community to analyze it against the stock version, in the hope of revealing ossified fragments of code such as that for the Microdrive storage peripheral which never made it into the stock Spectrum. But should you simply want to try your favorite games with the earliest possible version of the ROM, you can do that too.
It should be a feature of every device powered by a lithium-ion battery, that it has a protection chip on board that automatically disconnects it should it go out of its safe voltage range. A chip most often used for this purpose in single-cell applications is the Fortune Semiconductor DW01, and [Oliver] shares a tip for using this chip to power down the battery. The DW01 has a CS, or current sense pin, which if taken high momentarily will put the chip into an off state until the battery is disconnected.
Looking at the DW01 datasheet we can see that this would work, but we can’t help having a few questions. The CS pin is a safety sensor pin, providing over current, short circuit, and reverse polarity detection. It’s the kind of pin one might mess with only when one is absolutely certain it’s not likely to trigger a dangerous fault condition, so a bit of care should be required. However, we can see that leaving its resistor in place and supplying it a momentary logic level through another resistor should work. We’d be interested in the views of any readers with more experience in the world of lithium battery protection on this hack.
Regular followers of space news will know that when satellites or space probes reach the end of their life, they either are de-orbited in a fiery re-entry, or they stay lifeless in orbit, often in a safe graveyard orbit where they are unlikely to harm other craft. Sometimes these deactivated satellites spring back into life, and there is a dedicated band of enthusiasts who seek out these oddities. Dead satellite finder extraordinaire [Scott Tilley] has turned up a particularly unusual one, a craft that is quite likely to be the oldest still-working geostationary satellite.
LES-5 is an experimental satellite built by MIT’s Lincoln Labs, launched in 1967, and used to test military UHF communications in a geosynchronous orbit. It had an active life into the early 1970s after which it was placed in a graveyard orbital slot for redundant craft. It’s lain forgotten ever since, until this month when [Scott] found its beacon transmitting on 236.75 MHz. The Twitter thread is an extremely interesting glimpse into the satellite finder’s art, as first he’s not certain at all that it is LES-5 so he waits for its solar eclipse to identify its exact position.
Whether anything on the craft can find another use today is not certain, as he finds no evidence of its transponder. Still, that something is working again 53 years after its launch is a testament to the quality of its construction. Should its transponder be reactivated again it’s not impossible that people might find illicit uses for it, after all that’s not the first time this has happened.
A lot of projects we feature use video in some form or other, but that video is invariably digital, it exists as a stream of numbers in a computer memory or storage, and is often compressed. For some of us who grew up working with composite video there is a slight regret that we rarely get up-close and personal with an analogue stream, so [Kris Slyka]’s project putting video on a conventional audio cassette is a rare opportunity.
It’s fair to say this isn’t the highest quality video.
Readers with long memories may recall the Fisher-Price PixelVision toy from the late 1980s which recorded black-and-white video on a conventional cassette running at many times normal speed. This system does not take that tack, instead it decreases resolution and frame rate to a point at which it can be recorded at conventional cassette speeds. The result is not particularly high quality, but with luminance on one side of a stereo recording and chrominance on the other it does work.
The video below the break is a run through the system, with an explanation of how video signals work. Meanwhile the code for both encoder and decoder are available through the magic of GitHub. If you’re interested further, take a look at our examination of a video waveform.
We are hearing so much in the news about shortages of personal protective equipment, or PPE, for healthcare workers. Factories are being asked to perform the impossible when it comes to production be the need is so real, so immediate, and so widespread.
The problem with rapid consumption of PPE is that once it has been exposed to infection, it’s contaminated and can’t be used again. Physically it may be fine, but it retains the capability to infect other people. If there were some way it could be effectively cleaned and decontaminated for re-use, it would reduce the strain on the supply chain and result in a greater availability of PPE for all those who require it.
Whether your home Internet connection comes by ADSL, fibre, cable, or even satellite, at some point in the chain between your ISP and your computer will be a router in your home. For some of us it’s a model we’ve bought ourselves and loaded up with a custom distro, but for the majority it’s a box supplied by our ISP and subject to their settings and restrictions. [Paddlesteamer] has just such a router, a Huawei model supplied by the Turkcell ISP, and decided to do a little snooping into its setup.
In a tale of three parts, we see the device unravel, from uncovering a shell to reverse engineering its update process, to delving in its firmware and finally removing all its restrictions entirely. It’s a fascinating process in which we learn a lot, such as the way a man-in-the-middle attack is performed on the router’s connection tot he ISP, or that it contains an authorised SSH key seemingly giving Huawei a back door into it. You may never do this with your ISP’s router, but it pays to be aware of what can be put in your home by them without your realising it.
The Golden Age of router hacking may be behind us as the likes of the Raspberry Pi have replaced surplus routers as a source of cheap Linux boards, but as this shows us there’s still a need to dive inside a router from time to time. After all, locked-down routers are hardly a new phenomenon.
As we enter our second week of official COVID-19-related lockdown where this is being written, it’s evident that there are some resources we will have to conserve to help get us through all this. Instead of just using all of something because we can nip out to the store and buy more, we have to look at what we’ve got and treat it as though it will have to get us through the next three months. It’s not always certain that on our infrequent trips to the supermarket they’ll have stocks of what we want.
This is the very last of the toilet paper in my local supermarket, on the 8th of March.
A particular shortage has been of toilet paper. The news was full of footage showing people fighting for the last twelve-pack, and since early last month there has been none to be had for love nor money. To conserve stocks and save us from the desperate measures of having to cut the Daily Mail into squares and hang them on the wall, a technical solution is required. To this end I’ve created a computerised toilet roll dispenser which carefully controls the quantity of the precious sanitary product, in the hope of curbing its consumption to see us through the crisis.
In the midst of a full lockdown it’s difficult to secure immediate delivery of our usual maker essentials, so rather than send off for the controller boards I might have liked it has been necessary to make do with what I had. In the end I selected an older single board computer I had in a box under my bench. The Sinclair ZX81 has a single-core Z80 processor running at 3.25 MHz, dual-channel memory, a Ferranti GPU, and plenty of expansion possibilities from its black plastic case. I chose it because I could repurpose its thermal printer peripheral as a toilet paper printer, and because it has an easily wiped and hygienic membrane keyboard rather than a conventional one that could harbour germs.
Hardware wise I found I was fairly easily able to adapt a standard roll of Cushelle to the ZX printer, and was soon dispensing sheets with the following BASIC code.
10 REM TOILET PAPER PRINTER
20 FOR T=0 TO 44
30 LPRINT ""
40 NEXT T
50 LPRINT "---------- TEAR HERE -----------"
For now it’s working on the bench, but it will soon be mounted with a small portable TV as a monitor on the wall next to the toilet. Dispensing toilet paper will be as simple as typing RUN and hitting the ZX’s NEW LINE key, before watching as a sheet of toilet paper emerges magically from the printer. It’s the little hacks like this one that will be so useful in getting us through the crisis. After all, this Sinclair always has a square to spare.
