Raspberry Pi Pico Oscilloscope

June 26, 2021 by Danie Conradie 47 Comments

As you dive deeper into the world of electronics, a good oscilloscope quickly is an indispensable tool. However, for many use cases where you’re debugging low voltage, low speed circuits, that expensive oscilloscope is using only a fraction of its capabilities. As a minimalist alternative for these use cases [fhdm-dev] created Scoppy, a combination of firmware for the Raspberry Pi Pico and an Android app to create a functional oscilloscope.

As you would expect, the specifications are rather limited, capturing a maximum of 100 kpts at a speed of 500 kS/s shared between the two channels. Without some additional front end circuitry to protect the Pico, the input voltage is limited to 0-3.3 V. Neither the app nor the firmware is open source, and getting access to the second channel and removing ads requires a ~$3 in-app purchase. Even so, we can still think of plenty of practical uses for a ~$7 oscilloscope. If you do decide to add some front-end circuitry to change to voltage range, you can set them in the app, and switch between them by pulling certain GPIO pins high or low. The app has most of the basic oscilloscope features covered, continuous and single shot capture, adjustable trigger settings and a scalable waveform display.

Simple, cheap oscilloscopes like these have their place, but you start to understand why the “real” ones are so expensive when you see what goes into developing a high performance oscilloscope.

A Pi USB Webcam That Was Born To Boot Quick

June 24, 2021 by Sonya Vasquez 16 Comments

In the age of business Zoom rooms, having a crisp webcam is key for introducing fellow executives to your pet cat. Unfortunately, quality webcams are out of stock and building your own is out of the question. Or is it? [Dave Hunt] thought otherwise and cooked up the idea of using the Raspberry Pi’s USB on-the-go mode to stream video camera data over USB. [Huan Trong] then took it one step further, reimagining the project as a bootable system image. The result is showmewebcam, a Raspberry Pi image that transforms your Pi with an attached HQ camera module into a quality usb camera that boots in under 5 seconds.

Some of the project offerings on showmewebcam are truly stunning. Not only does the setup boot quickly, the current version requires a mere 64MB micro SD card for operations. What’s more, the project exposes camera settings like brightness, contrast, etc. via UVC, a standard USB protocol such that they can be controlled via typical software applications.

What’s truly exciting about this project is to see it take shape as different people tackle the same concept whilst referencing the prior milestone. [Dave Hunt] landed early to the scene with a blog post that established that the Pi could indeed be used as a USB webcam. [Huang Truong] built on that starting point, maturing it into an uploadable system image with notes to follow. Now, with showmewebcam on Github, it has seen contributions from over a dozen folks. Its performance specs are gradually improving. And it has a detailed wiki complete with suggested lenses and user-contributed cases to make your first webcam building experience a success.

And that’s not to say that others aren’t tackling this project from their own perspective either! For an alternate encapsulated solution, have a look at [Jeff Geerling’s] take on Pi-based USB webcams.

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Gorgeous Specimen Is The Final Word In Word Clocks

June 23, 2021 by Tom Nardi 14 Comments

At this point, it’s safe to say that word clocks aren’t quite as exciting as they once were. We’ve seen versions that boil the concept down to what amounts to a parts bin build, which for better or for worse, takes a lot of the magic out of it. You just get an array of LEDs, put some letters in front of it, write some code, and you’re done.

But then [Mark Sidell] sent in his build, and we remembered why we collectively fell in love with these clocks in the first place. It wasn’t the end result that captivated us, although the final clock is indeed gorgeous, but the story of its painstaking design and construction. The documentation created for this project is unquestionably some of the best we’ve seen in a very long time, and whether or not you have any desire to build a word clock of your own, you won’t regret sitting down and reading through it.

If you can somehow come away from reading through that build log and not be impressed, surely the clock’s feature set will put you over the edge. The ability to show time in just five minute increments makes this one of the most practical word clocks we’ve seen, and the quality of life features such as automatic brightness control based on ambient light level, and a smartphone-controlled web interface for configuring the clock are just a few of its standout features.

Incidentally the glow behind the clock, provided by a dedicated array of WS2812 RGB LEDs, isn’t just for ambiance. It indicates the position of the sun in the sky as calculated by the Python astral package, as well as mimicking the colors of the sunrise and sunset. There’s even a compass onboard to make sure the LEDs are properly aligned with their astronautical counterpart.

[Mark] actually made several of these clocks, most of which were given away as gifts. Some of the lucky recipients lived far enough away that the clock had to be shipped, so he designed a custom shipping case to hold everything securely during the trip. It also meant he had to come up with a way of remotely maintaining the code on these clocks without user intervention, so he created a firmware update and telemetry gathering backend with Amazon Web Services that they check into periodically. Honestly, the attention to detail put into every element of this project is just staggering.

If you’re interested in seeing what all the fuss is about with these word clocks, but aren’t quite at [Mark]’s level, don’t worry. As we said earlier, you can build a small version with little more than an LED array and a microcontroller. Just don’t blame us if it ends up turning into an obsession.

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The Compromises Of Raspberry Pi Hardware Documentation

June 23, 2021 by Maya Posch 86 Comments

[Rowan Patterson] informed us about a recent ticket he opened over at the Raspberry Pi Documentation GitHub repository. He asked about the the lack of updates to the Raspberry Pi 4’s USB-C power schematics for this board. You may recall that the USB-C power issue was covered by us back in July of 2019, yet the current official Raspberry Pi 4 schematics still show the flawed implementation, with the shorted CC pins, nearly two years later.

[Alasdair Allan], responsible for the Raspberry Pi documentation, mentioned that they’re in the process of moving their documentation from Markdown to AsciiDoc, and said that they wouldn’t have time for new changes until that was done. But then [James Hughes], Principal Software Engineer at Raspberry Pi, mentioned that the schematics may not be updated even after this change due to a of lack of manpower.

As [James] emphasized, their hardware will probably never be open, due to NDAs signed with Broadcom. The compromise solution has always been to publish limited peripheral schematics. Yet now even those limited schematics may not keep up with board revisions.

An easy fix for the Raspberry Pi 4’s schematics would be for someone in the community to reverse-engineer the exact changes made to the Raspberry Pi 4 board layout and mark these up in a revised schematic. This should be little more than the addition of a second 5.1 kΩ resistor, so that CC1 and CC2 each are connected to ground via their own resistor, instead of being shorted together.

Still, you might wish that Raspberry Pi would update the schematics for you, especially since they have updated versions internally. But the NDAs force them to duplicate their efforts, and at least right now that means that their public schematics do not reflect the reality of their hardware.

Raspberry Pi Floppy Driver Uncovers Fishy Secrets

June 21, 2021 by Chris Lott 13 Comments

A forum post by New Zealand electronics enthusiast [zl2wrw] about retreiving waypoints from a mysterious floppy disk caught our eye. The navigation system on his friend’s fishing boat had died and was replaced. But the old waypoints were stored on a 3-1/2 inch floppy disk that was unreadable on a normal PC. Not to be deterred, [zl2wrw] then looked for another solution — apparently a list of hot NZ fishing spots is worth quite the effort.

The tool he discovered, and the main point of this story, is the bbc-fdc by [Jasper Renow-Clarke] aka [picosonic]. [Jasper] made this project to read 5-1/4 inch Acorn DFS floppies from his BBC Micro. But bbc-fdc can be used to read a variety of floppy disk formats, such as DOS, C64, Apple II, and others It can also just capture raw magnetic flux transitions on the disk, blissfully unaware of any logical structure to the data. We recently wrote about another Raspberry Pi Floppy Drive Controller project by [Scott Baker]. What sets [picosonic]’s project apart is that he’s not using an FDC controller chip here. The only interface electronics is a couple of open-collector 7406 ICs. Data is read using the SPI peripheral. If you need to archive old floppy disks or do a forensic analysis of unknown disks like [zl2wrw], then one of these two projects will almost certainly do the trick.

Meanwhile back in New Zealand, [zl2wrw] discovered that the floppy format was standard (Modified Frequency Modulation, MFM) by examining the raw flux dump. However, the filesystem was a mystery — it didn’t quite match any of the usual suspects. So [zl2wrw] dug into the hex dump of the data and figured out enough of the structure to manually recover the waypoints. Subsequently, a user on the forum found a document describing the file system used by Furuno GPS units, which proved to be a close match albeit after the fact. Alas, [zl2wrw] hasn’t publish the coordinates of those good fishing spots.

Have you had any successes (or failures) when it comes to reading data from old disks? Or have you encountered peculiar disk formats and/or file systems, where having a tool like this could have been helpful? Let us know in the comments below.

Raspberry Pi Hat Adds SDR With High Speed Memory Access

June 20, 2021 by Al Williams 57 Comments

An SDR add-on for the Raspberry Pi isn’t a new idea, but the open source cariboulite project looks like a great entry into the field. Even if you aren’t interested in radio, you might find the project’s use of a special high-bandwidth memory interface to the Pi interesting.

The interface in question is the poorly-documented SMI or Secondary Memory Interface. [Caribou Labs] helpfully provides links to others that did the work to figure out the interface along with code and a white paper. The result? Depending on the Pi, the SDR can exchange data at up to 500 Mbps with the processor. The SDR actually uses less than that, at about 128 Mbps. Still, it would be hard to ship that much data across using conventional means.

On the radio side, the SDR covers 389.5 to 510 MHz and 779 to 1,020 MHz. There’s also a wide tuning channel from 30 MHz to 6 GHz, with some exclusions. The board can transmit at about 14 dBm, depending on frequency and the receive noise figure is under 4.5 dB for the lower bands and less than 8 dB above 3,500 MHz. Of course, some Pis already have a radio, but not with this kind of capability. We’ve also seen SMI used to drive many LEDs.

Scratch Built Tracked Robot Reporting For Duty

June 17, 2021 by Tom Nardi 18 Comments

Inspired by battle-hardened military robots, [Engineering Juice] wanted to build his own remote controlled rover that could deliver live video from the front lines. But rather than use an off-the-shelf tracked robot chassis, he decided to design and 3D print the whole thing from scratch. While the final product might not be bullet proof, it certainly doesn’t seem to have any trouble traveling through sand and other rough terrain.

Certainly the most impressive aspect of this project is the roller chain track and suspension system, which consists of more than 200 individual printed parts, fasteners, bearings, and linkages. Initially, [Engineering Juice] came up with a less complex suspension system for the robot, but unfortunately it had a tendency to bind up during testing. However the new and improved design, which uses four articulated wheels on each side, provides an impressive balance between speed and off-road capability.

Internally there’s a Raspberry Pi 4 paired with an L298 dual H-bridge controller board to drive the heavy duty gear motors. While the Pi is running off of a standard USB power bank, the drive motors are supplied by a custom 18650 battery pack utilizing a 3D printed frame to protect and secure the cells. A commercial night vision camera solution that connects to the Pi’s CSI header is mounted in the front, with live video being broadcast back to the operator over WiFi.

To actually control the bot, [Engineering Juice] has come up with a Node-RED GUI that’s well suited to a smartphone’s touch screen. Of course with all the power and flexibility of the Raspberry Pi, you could come up with whatever sort of control scheme you wanted. Or perhaps even go all in and make it autonomous. It looks like there’s still plenty of space inside the robot for additional hardware and sensors, so we’re interested to see where things go from here.

Got a rover project in mind that doesn’t need the all-terrain capability offered by tracks? A couple of used “hoverboards” can easily be commandeered to create a surprisingly powerful wheeled platform to use as a base.

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