Fan-tastic Misuse Of Raspberry Pi GPIO

[River] is a big fan of home automation. After moving into a new house, he wanted to assimilate two wirelessly controlled fan lights into his home automation system. The problem was this: although the fans were wireless, their frequency and protocol were incompatible with the home automation system.

Step one was to determine the frequency the fan’s remote used. Although public FCC records will reveal the frequency of operation, [River] thought it would be faster to use an inexpensive USB RTL-SDR with the Spektrum program to sweep the range of likely frequencies, and quickly found the fans speak 304.2 MHz.

Next was to reverse-engineer the protocol. Universal Radio Hacker is a tool designed to make deciphering unknown wireless protocols relatively painless using an RTL-SDR. [River] digitized a button press with it and immediately recognized it as simple on-off keying (OOK). With that knowledge, he digitized the radio commands from all seven buttons and was quickly able to reverse-engineer the entire protocol.

[River] wanted to use a Raspberry Pi to bring the fans into his home automation system, but the Raspberry Pi doesn’t have a 304.2 MHz radio. What it does have is user-programmable GPIO and the rpitx package, which converts a GPIO pin into a basic radio transmitter. Of course, the Pi’s GPIO pin’s aren’t long enough to efficiently transmit at 304.2 MHz, so [River] added a proper antenna, as well as a low-pass filter to clean up the transmitted signal. The rpitx package supports OOK out of the box, so [River] was quickly able get the Pi controlling his fan in no time!

If you’d like to do some more low-cost home automation, check out this approach to using a Raspberry Pi to control some bargain-bin smart plugs.

Raspberry Pi Spigot Puts Digits Of Pi On Tap

What did you do for Pi Day? Play with your Raspberry Pi 400? Eat some pizza or other typically round objects and recite all nine digits you’ve got memorized? That’s about where we were at this year. But not [bornach], no. [bornach] went all out and built a spigot that spews digits of Pi well past the first nine decimal places.

This clever spigot sculpture implements the spigot algorithm for generating digits of Pi one-by-one in a stream on to a chain of 8×8 matrices, and does so using a Raspberry Pi (of course). The point of the spigot algorithm is to store as few numbers as possible at any given time by reusing variables. We love the way the digits materialize on the matrix, almost as if they are ink being activated by water. Be sure to check out the build and demo video after the break.

That 10k pot on the top really does control the spigot — since the Pi has no ADC, [bornach] is using the potentiometer to charge a capacitor and using the time it takes to reach the threshold to decide whether the faucet is open or closed. There are a couple of hacks at play here, including the Popsicle-stick LED matrix bracing and the HAT [bornach] fashioned so the daisy-chained 8×8 LED modules could interface with the Pi.

We love Raspberry Pis of all eras around here, especially the darling new Pico. Diminutive as it may be, the Pico can be sliced even smaller with a hacksaw if you don’t mind losing a few GPIO pins.

Continue reading “Raspberry Pi Spigot Puts Digits Of Pi On Tap”

Slimming The Raspberry Pi Pico With A Hacksaw

The Raspberry Pi Pico is the hot new star of the microcontroller scene, with its fancy IO hardware and serious name recognition. Based on the RP2040 “Raspberry Silicon” chip, it’s introducing fans of the single-board computer line to a lower level of embedded development. The Pico isn’t big, as its name suggests, but miniaturization is a never ending quest for improvement – so [That Dragon Guy] decided to see if the devboard could be smallified further at a minimum of cost.

While other smaller RP2040 boards are reaching the marketplace, they all cost a lot more than the $4 of the Pico. Thus, [That Dragon Guy] got creative. Having realised that the bottom section of the board was only full of passive traces and pads, he simply hacked it off with a scroll saw and sander. This gives a 30% reduction in footprint, at the cost of some mounting holes, GPIO pins and the debug interface.

In testing, the rest of the board continued to function perfectly well, so we’re calling this a win. It builds on amusing experiments [That Dragon Guy] had done before with the Raspberry Pi B+ which gave us a good chuckle. The Raspberry Pi has always been a minimalist darling, with the Pi Zero of 2015 being a bit of a gamechanger, and much beloved by this writer. Video after the break.

Continue reading “Slimming The Raspberry Pi Pico With A Hacksaw”

A Floppy Controller For The Raspberry Pi

The Raspberry Pi is the darling single board computer that is everything to everyone. It even has lit up the eyes of the older set with the Pi 400 mimicking the all-in-one keyboard computer design so popular in the 1980s. Another project that harkens back to that golden era is this Raspberry Pi floppy controller board from [Dr. Scott M. Baker].

[Scott] is no stranger to floppy controllers, having worked with the popular WD37C65 floppy controller IC before with the RC2014 homebrew Z80 computer. Thus, it was his part of choice when looking to implement a floppy interface on the Raspberry Pi. The job was straightforward, and done with just the IC itself. Despite the Pi running at 3.3 V and the controller at 5 V, [Scott] has found no problems thus far, implementing just a resistor pack to try and limit damage from the controller sending higher voltage signals back to the Pi. With that said, he plans to implement a proper level shifter down the road to ensure trouble-free operation long term.

The project is rounded out with a bunch of Python tools used to interface with the controller, available on Github. Performance is limited by the non-realtime nature of the Raspberry Pi’s user mode operation, which [Scott] notes could be fixed with a kernel module. With that said, if you’re looking for performance, floppies aren’t it anyway.

We do love the Pi put to use in retro tasks; it can even be a SCSI Swiss Army Knife if you need one. Video after the break.

Continue reading “A Floppy Controller For The Raspberry Pi”

Raspberry Pi Zero Beams Back Video From 100,000 Feet

The Project Horus team routinely launches high-altitude balloons in Australia. However, despite their desire for it, they haven’t beamed back live video. Until now. Horus 55 beamed video back to the ground from over 100,000 feet using a Raspberry Pi and some software-defined radio gear. Be sure and check out their video, below.

You might think this is easy, but there are many technical hurdles. First, the transmitter needs some power, but the thin atmosphere creates problems with cooling. In addition a really good receiving station is required, and the project wanted to stream that video to the Internet, which they were able to do.

The balloon carried a Raspberry Pi Zero W to capture and compress video. A LimeSDR Mini provided the DVB-S transmission on 70cm along with a power amplifier to get to about 800mW. Power dissipation in the payload was about 6 watts and required a special heat sink system to operate. The payload was powered by eight lithium AA primary cells, which perform well at low temperatures.

Continue reading “Raspberry Pi Zero Beams Back Video From 100,000 Feet”

A Raspberry Pi Tablet, With A DSI Screen

Since the Raspberry Pi arrived back in 2012, we’ve seen no end of interesting and creative designs for portable versions of the little computer. They often have problems in interfacing with their screens, either on the very cheap models using the expansion port or on more expensive ones using an HDMI screen with associated controller and cabling. The official Raspberry Pi touchscreen has made life easier with its DSI convector, but as [jrberendt] shows us with this neat little tablet, there are other DSI-based options. This one uses a 5″ DSI touchscreen available through Amazon as well as a Pi UPS board to make a tablet that is both diminutive and self-contained.

Having fooled around ourselves in the world of Pi tablets we like this one for its clean look and a bezel that is little bigger than the screen itself. As is the case with so many Pi tablets though it has to contend with the bulk of a full-sized Model B board on its behind, making it more of a chunky brick than a svelte tablet. The screen has potential though, and we can’t help wondering whether there’s any mileage in pairing it with a much thinner Pi Zero board and a LiPo board for a slimmer alternative.

Probably the nicest Pi tablet we’ve brought you was this one, which managed to remain impressively slim despite its HDMI screen.

A Raspberry Pi-Packing Cassette Powers This ZX Spectrum Emulator

Sometimes we are vaguely aware of the inexorable march of technological progress. Other times it thrums steadily under the surface while we go about our lives. And sometimes, just sometimes, it smacks us right in the face.

Few projects can demonstrate the advancement and miniaturization of computing technology like putting an entire functional computer inside a storage medium that once only held mere kilobytes of data. And that’s exactly what [JamHamster] has done by stuffing a Raspberry Pi Zero W inside a cassette tape to run his ZX Spectrum emulator. It’s an impressive and clean build, and it pairs so well with a downright gorgeous, retro inspired, CRT-lookalike LCD monitor, which is another creation of his.

A Raspberry Pi Zero with several areas lightly trimmed away inside an open cassette tape.

The Pi did have to undergo a bit of light surgery; though he managed to lose only four GPIO pins in the operation. He also put a ton of love into a literally-highly-polished aluminum heatsink, which is entirely hidden within the case but does keep the computer cool in its claustrophobic quarters. Of course, [JamHamster] isn’t new to these cassette builds. You may recognize his work from the TZXDuino, a virtual tape loader for the ZX Spectrum.

Honestly, sometimes we just have to sit back and be amazed at the kind of computer power that can be packed into such tiny packages. The Pi Zero isn’t the smallest or the most powerful of options, but it is far more capable than the computer it is emulating here. So whether they’re hiding inside outdated storage formats or powering a stock-looking sleeper PSP, we just can’t help but be impressed.