An NRF24L01 module soldered onto a 6502 single-board computer

Wireless Bootloader Saves You From Swapping ROM Chips

April 5, 2022 by 14 Comments

Flashing your code into an Arduino, an ESP32 or any other modern microcontroller platform is pretty straightforward: connect the device through USB, fire up the appropriate software platform, and press “program”. But those who followed embedded programming classes in the ’80s and ’90s will remember a more complicated procedure that consists of swapping EPROM chips between a programmer, a target board and a UV eraser. Veterans of that era might even remember how you could overwrite a previous program with NOPs and place new code behind it, to save yourself a trip to the “blank chips” bin.

If you’re a retrocomputer enthusiast and would like to have the easy programming of modern tools, but the authenticity of a self-contained ROM-loading computer, you might want to check out [Anders Nielsen]’s latest design of a wireless boot loader for a 6502 single board computer. The target platform for this project is a beautiful custom-made 6502-based retrocomputer that [Anders] documented in detail on his Hackaday.io page.

The basic idea here is to have a wireless receiver on the target system that receives data from a transmitter connected to a modern PC. When you click “program”, the object code is sent to the 6502 machine, stored in RAM and executed. The wireless link is implemented with a pair of nRF24L01 2.4 GHz modules that communicate through SPI. Since [Anders]’s Mac Mini doesn’t come with GPIO ports he hooked up the transmitter to a Raspberry Pi which he controlled through a network link.

On the 6502 side he wrote a bootloader in assembly language, which bit-bangs the SPI protocol to communicate with the wireless module. A simple user interface is included to allow the user to control the loading and running of programs. All code and hardware documentation is available on Github for use by anyone with a similar 6502 system.

Those nRF24L01s are versatile little things: we’ve seen them being used to transfer anything from MIDI data to TCP/IP links, as well as code for other microcontroller platforms.

Continue reading “Wireless Bootloader Saves You From Swapping ROM Chips” →

How Did Dolby Digital Sound Work On Film?

April 5, 2022 by 26 Comments

When we go to the cinema and see a film in 2022, it’s very unlikely that what we’re seeing will in fact be a film. Instead of large reels of transparent film fed through a projector, we’ll be watching the output of a high-quality digital projector. The advantages for the cinema industry in terms of easier distribution and consistent quality are obvious. There was a period in the 1990s though when theatres still had film projectors, but digital technology was starting to edge in for the sound. [Nava Whiteford] has found some 35mm trailer film from the 1990s, and analysed the Dolby Digital sound information from it.

The film is an interesting exercise in backward compatibility, with every part of it outside the picture used to encode information. There is the analogue sound track and two digital formats, but what we’re interested in are the Dolby Digital packets. These are encoded as patterns superficially similar to a QR code in the space between the sprocket holes.

Looking at the patent he found that they were using Reed-Solomon error correction, making it relatively easy to decode. The patent makes for fascinating reading, as it details how the data was read using early-1990s technology with each line being scanned by a linear CCD, before detailing the signal processing steps followed to retrieve the audio data. If you remember your first experience of Dolby cinema sound three decades ago, now you know how the system worked.

The film featured also had an analogue soundtrack, and if you’d like to know how they worked, we’ve got you covered!

ESP32: Is Two Better Than One?

April 4, 2022 by 9 Comments

We’ve looked at the WROOM-DA module before. It’s an ESP32 with two antennas, and [Andreas Spiess] says it is the ugliest ESP32 he’s ever seen. But beauty is only skin deep, after all. Did [Andreas] find beauty in the twin antennas? Watch the video below and see for yourself.

According to the block diagram, the twin antennas are not used simultaneously but offer diversity one at a time. There is also 8GB 8 MB of flash, double the amount on traditional WROOM modules. Mounting the device was a bit difficult since most ESP32 carrier boards will block some portion of the antenna array.

Continue reading “ESP32: Is Two Better Than One?” →

Detailed Big Screen Multimeter Review

April 4, 2022 by 5 Comments

It seems like large-screen cheap meters are really catching on. [TheHWcave] does a very detailed review of a KAIWEETS KM601, which is exactly the same as a few dozen other Chinese brands you can get from the usual sources. You can see the review in the video below.

If we learned nothing else from this video, we did learn that you can identify unmarked fuses with a scale. The fuses inside were not marked, so he wanted to know if they appeared to be the right values. We would have been tempted to just blow them under controlled conditions, but we get he didn’t want to destroy the stock fuses until after testing.

Continue reading “Detailed Big Screen Multimeter Review” →

Rubber Band “Slide Rule” Doesn’t Slide, But Rotates

April 4, 2022 by 11 Comments

Around here we mostly enjoy slide rules. We even have our own collections including some cylindrical and circular ones. But [Mathologer] discusses a recent Reddit post that explains a circular slide rule-like device using a wheel and a stretchable rubber band. While it probably would be difficult to build the actual device using a rubber band, it can do wonders for your understanding of logarithms which still show up in our lives when, for example, you are calculating decibels. [Dimitri] did simulate the rubber band for you in software.

The idea is that a perfect rubber band has numbers from 0 to 10 evenly marked on it. As you rotate a wheel attached at the 10 mark, the rubber band stretches more and more. So the 10 and the 9 have relatively little space between them, but the 1 and the 2 are much further apart. The wheel’s circumference is set so that the 1 will exactly overlay the 10. What this means is that each spot on the wheel can represent any number that differs only by a decimal point. So you could have 3 mean 0.03, 300, or — of course — 3. Of course, you don’t need to build the wheel with a rubber band — you could just mark the wheel like a regular circular slide rule.

Continue reading “Rubber Band “Slide Rule” Doesn’t Slide, But Rotates” →

Monitor Space Weather And The Atmosphere With Your Cellphone!

April 4, 2022 by 9 Comments

Above our heads, the atmosphere is a complex and unpredictable soup of gasses and charged particles subject to the influence of whatever the Sun throws at it. Attempting to understand it is not for the faint-hearted, so it has for centuries been the object of considerable research. A new project from the European Space Agency and ETH Zurich gives the general public the chance to participate in that research in a small way, by crowdsourcing atmospheric data gathering to a mobile phone app. How might a mobile phone observe the atmosphere? The answer lies in their global positioning receivers, which can track minute differences in the received signals caused by atmospheric conditions. By gathering as much of this data as possible, the ESA scientists will gain valuable insights into atmospheric conditions as they change across the globe.

The app requires an Android phone equipped with a dual frequency satnav receiver, and having been duly installed on the trusty Hackaday Motorola it in turn started picking up all the different constellations of satellites. The instructions are to leave it somewhere such as a windowsill with an unobstructed view of the sky and move it as little as possible, to which we’d add clicking the “Log in background” button and connectign a charger. There’s a promise that uploaders can win prizes, so aside from contributing to scientific discovery there might be an unexpected benefit. More details on the app can be found here, meanwhile many readers will know that this isn’t the only crowdsourced atmospheric data gathering effort.

Levitate The NE555 Way

April 4, 2022 by 16 Comments

Ultrasonic levitation — the practice of creating a standing wave between two ultrasonic sources and positioning lightweight objects such that they can float in the pressure minimums between them — has been a source of fascination to more than one experimenter. [Peter Lin] demonstrated this in the video below the break, by creating an ultrasonic levitation system using only the trusted chip of all true experimenters, the NE555. (Video, embedded below.)

The circuit is simplicity itself, just an astable of the type that has made a billion beepers and flashing LEDs. It drives two ultrasonic transducers in parallel, and with them pointing towards each other and a bit of gap adjustment work it can successfully levitate pieces of polystyrene. There was some work in adjusting the frequency to the transducer resonance, but that’s not a huge challenge given the right instrumentation. We can see that it would make a great demonstration of standing waves, and also a fantastic desk toy for not a lot.

We celebrate everyone’s favourite timer chip here at Hackaday, so much so that we recently ran a contest to find the best creations using it.

Continue reading “Levitate The NE555 Way” →