How Not To Build An RP2040 Board

October 11, 2023 by 26 Comments

We love that these days you can buy ready-made microcontroller boards that are very capable. But sometimes you need to — or just want to — do it yourself. Unfortunately, you really should design everything twice: once to figure out where all the problems are, and the second time to do it better. If you want to create your own board for the RP2040 then you are in luck. [Jeremy] has made the first (and second) iteration or an RP2040 board and shares with us what he would not do again.

In all fairness, he also has a blog post talking about what he did, so you might want to start there. However, we think his most valuable advice was his final word: Don’t fail to get started on your design. The longest journey, after all, begins with the first step.

His other advice is good, too. For example, don’t plug your new board into a computer because an error in the power supply could take the whole computer out. He also warns you not to do like he did and forget to order the $10 solder stencil with the PCBs.

Some of it is just good advice in general. For example — buy more small components than you think you need. There’s nothing worse than needing three resistors, having three resistors, and then watching one of the three fly across the room or stick to your soldering iron and melt into a pool of slag. Buy ten and you’ll save money in the long run.

In the end, the board did work and what he learned might help you if you decide to tackle a similar project yourself. [Jeremy’s] board is fairly large, but if you have an appetite for something smaller, check out the RPDot or the RP2040 Stamp.

Meshtastic And Owntracks To Kick Your Google Habit

October 11, 2023 by 20 Comments

I have an admission to make. I have a Google addiction. Not the normal addiction — I have a problem with Google Maps, and the timeline feature. I know, I’m giving my location data to Google, who does who-knows-what-all with it. But it’s convenient to have an easy way to share location with my wife, and very useful to track my business related travel for each month. What we could really use is a self-hosted, open source system to track locations and display location history. And for bonus points, let’s include some extra features, like the ability to track vehicles, kids, and pets that aren’t carrying a dedicated Internet connection.

You can read the title — you know where we’re going with this. We’re setting up an Owntracks service, and then tying it to Meshtastic for off-Internet usability. The backbone that makes this work is MQTT, a network message bus that has really found its niche in the Home Assistant project among others. It’s a simple protocol, where clients send brief messages labeled by topic, and can also subscribe to specific topics. For this little endeavor we’ll use the Mosquito MQTT broker.

One of the nice things about MQTT is that the messages are all text strings, and often take the form of JSON. When trying to get two applications to talking using a shared MQTT server, there may need to be a bit of translation. One application may label a field latitude, and the other shortens it to lat. The glue code to put these together is often known as an MQTT translator, or sometimes an MQTT bridge. This is a program that listens to a given topic, ingests each message, and sends it back to the MQTT server in a different format and topic name.

The last piece is Owntracks, which has a recorder project, which pulls locations from the MQTT server, and stores it locally. Then there’s Owntracks Frontend, which is a much nicer user interface, with some nice features like viewing movement a day at a time. Continue reading “Meshtastic And Owntracks To Kick Your Google Habit” →

Tiny Linux On A No-MMU RISC-V Microcontroller

October 11, 2023 by 21 Comments

In the vast majority of cases, running a Linux-based operating system involves a pretty powerful processor with a lot of memory on hand, and perhaps most importantly, a memory management unit, or MMU. This is a piece of hardware which manages virtual memory, seamlessly giving each process its own memory sandbox in which it shouldn’t be able to rain on its neighbours’ parade. If there’s no MMU all is not lost though, and [Uros Popovic] gives us a complete guide to building the MMU-less μClinux on a RISC-V microcontroller.

The result is something of a Linux-from-scratch for this platform and kernel flavour, but it’s so much more than that aside from its step-by-step explanation. It’s probable that most of us have heard something of μClinux but have little direct knowledge of it, and he leads us through its workings as well as its limitations. As examples, standard ELF binaries aren’t suitable for these systems, and programmers need to use memory-safe techniques.

Whether or not any of you will run with this guide and build a tiny MMU-less Linux system, anything which expands our knowledge on the subject has to be a good thing. it’s not the first time we’ve seen a RISC-V microcontroller turned to this task, with a nifty trick to get round the limitations of a particular architecture.

Dumping Spacecraft In The Middle Of Nowhere

October 11, 2023 by 33 Comments

The BBC has an interesting article on Point Nemo, AKA the Oceanic Pole of Inaccessibility, AKA the spacecraft graveyard. This is the place in the ocean that is furthest from land, in the middle of the usually stormy South Pacific. It’s as far out there as you can get without leaving the planet: about 2,688 kilometers (1670 miles) from the nearest dry land. Even the ocean floor is 4 km (2.5 miles) down; the closest human life is the International Space Station (ISS) astronauts flying 415 km (260 miles) above it. It is not near any shipping lanes or transport routes. It is, to put it bluntly, the middle of goddam nowhere. So, it is a perfect place to dump derelict spacecraft.

Since 1971, over 160 spacecraft have met their end in these chilly waters, from the fiery public end of the Mir space station to the secret death of numerous secret spy satellites. The article in question focuses on the Soviet satellites, but plenty of other countries dump their end-of-life satellites there, including trash from the ISS. The Chinese Taingong-1 space station crashed nearby, although that was more by accident than design. The ISS is scheduled to join its trash in a few years: the current plan is that the massive space station will be de-orbited and crashed near Point Nemo in 2030.

Will there be anyone to see it? When the Mir space station was de-orbited, some entrepreneurial companies offered flights to the area to catch a glimpse, but the best view was from the island of Fiji. So, start planning your trip now…

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Tiny Tape Cartridge Remembered And A Teardown

October 10, 2023 by 9 Comments

If you want to add sound to something these days, you usually store it digitally. Microcontrollers are cheap and fast, and you can hold a lot of audio on a small flash card or in a ROM. But back “in the day,” storing audio was often done with tape. If you wanted something you could automate, you often turned to an endless loop tape. They had the advantage of not needing rewinding and had a way to sense spots on the tape (usually the start). The 8-track, for example, was an endless loop tape, and radio stations used “carts” (technically Fedelipak cartridges). But what if you wanted to build something tiny? Bandai had the answer, and [Tech Moan] shows the 1986-era tiny carts.

In the US, these appear to be mainly in the realm of novelty items. [Tech Moan] has an Elvis figurine that sings thanks to the tape and a diminutive jukebox. He suspects these must have been used in something else, perhaps in the Japanese market.

Continue reading “Tiny Tape Cartridge Remembered And A Teardown” →

A monitoring station as set up in the CEZ, featuring both the legacy (ARMS) and new wireless monitoring system.

How The 2022 CEZ Event Shows The Fragility Of Environmental Sensors In High-Risk Areas

October 10, 2023 by 3 Comments

In what reads somewhat like a convoluted detective story, the events unfolding at the Chornobyl Exclusion Zone (CEZ) in Ukraine during late February had the media channels lighting up with chatter about ‘elevated gamma radiation levels’, which showed up on the public CEZ radiation monitoring dashboard for a handful of gamma radiation sensors. This happened right before this reporting system went off-line, leaving outside observers guessing at what was going on. By the time occupying forces had been driven out of the CEZ, the gamma radiation levels were reported as being similar to before the invasion, yet the computer hardware which was part of the monitoring system had vanished along with the occupying forces. After considering many explanations, this left security researchers like [Ruben Santamarta] to consider that the high values had been spoofed.

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Antennas Can Be A Total Mystery

October 10, 2023 by 14 Comments

The real action in the world of ham radio is generally in the high frequency bands. Despite the name, these are relatively low-frequency bands by modern standards and the antenna sizes can get a little extreme. After all, not everyone can put up an 80-meter dipole, but ham radio operators have come up with a number of interesting ways of getting on the air anyway. The only problem is that a lot of these antennas don’t seem as though they should work half as well as they do, and [MIKROWAVE1] takes a look back on some of the more exotic radiators.

He does note that for a new ham radio operator it’s best to keep it simple, beginning work with a dipole, but there are still a number of options to keep the size down. A few examples are given using helically-wound vertical antennas or antennas with tuned sections of coaxial cable. From there the more esoteric antennas are explored, such as underground antennas, complex loops and other ways of making a long wire fit in a small space, and even simpler designs like throwing a weight with a piece of wire attached out the window of an apartment building.

While antenna theory is certainly a good start for building antennas, a lot of the design of antennas strays into artistry and even folklore as various hams will have successes with certain types and others won’t. It’s not a one-size-fits-all situation so the important thing is to keep experimenting and try anything that comes to mind as long as it helps get on the air. A good starting point is [Dan Maloney]’s $50 Ham Guide series, and one piece specifically dealing with HF antennas.

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