Linux Hacks

551 Articles

A Linux Business Card You Can Build

July 14, 2022 by 22 Comments

It is a sign of the times that one of [Dmitry’s] design criteria for his new Linux on a business card is to use parts you can actually find during the current component shortage. The resulting board uses a ATSAMD21 chip and emulates a MIPS machine in order to boot Linux.

We like that in addition to the build details, [Dmitry] outlines a lot of the reasons for his decisions. There’s also a a fair amount of detail about how the whole system actually works. For example, by using a 0.8 mm PCB, the board can accept a USB-C cable with no additional connector. There is also a great explanation of the MIPS MMU and don’t forget that MIPS begat RISC-V, so many of the MIPS core details will apply to RISC-V as well (but not the MMU).  You’ll also find some critiques of the ATSAMD21’s DMA system. It seems to save chip real estate, the DMA system stores configuration data in user memory which it has to load and unload every time you switch channels.

By the end of the post you get the feeling this may be [Dimitry]’s last ATSAMD21 project. But we have to admit, it seems to have come out great. This isn’t the first business card Linux build we’ve seen. This one sure reminded us of a MIDI controller card we once saw.

It’s Linux. On An ESP32

July 14, 2022 by 30 Comments

By today’s standards, the necessities for running a Linux-based operating system are surprisingly meagre in terms of RAM and processor power. Back in the day we ran earlier Linux versions on Intel 386 and 486 machines with tiny quantities of memory compared to the multi-gigabyte many-core powerhouses we do today.

So it stands to reason that many of the more powerful microcontrollers should also run Linux, but of course they are often unable because the lack a memory management unit. The original ESP32 is just such a candidate, plenty of power but unable to run Linux. Not so fast, because [Dror Gluska] has managed to boot a Linux kernel on Espressif’s dual-core chip. How on earth? By emulating a RISC-V processor on it and booting a RISC-V version of the kernel.

The emulator in question is [Fabrice Belard]’s TinyEMU, a piece of software that brings both RISC-V and x86 to limited-spec platforms, and the write-up describes the extensive optimization and tracing of ESP32 bottlenecks which was finally able to get a Linux kernel booting in 1 minute and 35 seconds. Of course it’s simply an exercise to prove it can be done and we won’t be seeing Linux-based ESP projects any time soon, but it’s still an impressive piece of work.

This isn’t the lowest-spec microcontroller we’ve seen run Linux, back in 2012 we saw it on emulated ARM running on an 8-bit AVR.

Tio Is A Serial Terminal For Us

July 13, 2022 by 31 Comments

With Linux and the serial port there is good news and there is bad news. The good news is that Linux has great support for serial hardware of all sorts and a host of tools for accessing the serial port. That’s important when you use a lot of serial-like devices like Arduinos with USB ports and the like. The bad news is that most of the terminal software is made to accommodate the days when a computer had real serial terminals and modems with people interacting with them. We bet that’s why [lundmar] developed tio, a serial device I/O tool for people like us.

Honestly, how many times have you needed Zmodem file transfers and recognition of the DCD signal to detect an incoming connection? Sure there are many other programs that will do the job, but tio brings a clean simplicity along with functionality that embedded developers need.

The software will support arbitrary devices, show statistics, and give you control of the RS232 lines. There’s support for delayed characters and lines, useful if you are dealing with a super simple device with no handshaking. There’s also hex support and many ways to log data and statistics. We especially like that it can automatically reconnect which is a great feature.

Of course, you want some terminal features and tio includes those. For example, you can elect to have local echo turned on or map characters so that, for example, a carriage return turns into a carriage return and a line feed. You can use command line options to set up most items including features like redirecting to a network socket. Other commands inside the program — by default, triggered by Control+T — let you do things like send a break, toggle handshaking lines, and more.

You might think the serial port is dead, but it really just transformed into a USB port.  Of course, like everything else these days, you can also get your terminal in the browser.

Easier Self Hosting With Umbrel

July 9, 2022 by 12 Comments

While it is undeniable that cloud-based services are handy, there are people who would rather do it themselves. For many of us, it is because we want what we want the way we want it. For others, it is a distrust of leaving your personal data on someone’s server you don’t control. Umbrel is a Linux distribution just for people who want to self-host popular applications like NextCloud or Home Assistant. [ItsFoss] has a good review that points out some of the plusses and minuses of the early version of Umbrel.

What’s really interesting, though, is the approach the distro takes to installing software. Like most modern distributions, Umbrel has a package manager. Unlike most, though, the packages are actually docker containers. So when you install an app, it is preconfigured and lives in its own bubble, unlikely to conflict with other things you might install.

We also like that it has a specific build for a Raspberry Pi, although it will work on other 64-bit hardware and you can even install it within docker on top of your normal operating system. Of course, the docker container concept is also a drawback — at least for now — because it can be difficult to adjust settings inside the container compared to a more conventional install.

It amazes us that hardware has become so capable that it is easier to just duplicate entire operating systems than it is to work out the required dependency interactions. Still, it works, and in most cases, it works well.

If you want to know more about Docker, we’ve covered it a few times in the past. You can even use it for very simple development cases if you like.

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Linux Fu: The Browser Emacs Fusion

July 6, 2022 by 20 Comments

It is no secret that I have a few things permanently burned into my neurons: the 1802 instruction set, the commands for WordStar, and the commands for emacs. There was a time when emacs was almost my operating system. With no X11, emacs gave you a way to have a shell in one window, check your mail, and keep your work open.

I still use emacs a lot (although I’ve been getting more and more pleased with vscode with an emacs keybinding extension). But I also spend a lot of time — like right now — writing in a Web browser. Especially if I’m writing about code, it gets hard to remember which set of keys you have to use and I’ve wanted to do something about it for a long time. The answer is a very cool program called Autokey. (You can download my files for it, but you probably want to read more first.) It probably doesn’t work if you have switched to Wayland, but it can do a lot for you ranging from saving you some typing to reprogramming your favorite program to have different keystrokes. However, it isn’t without its problems, and I’ll tell you what I know about it.

The Value Proposition

Autokey sits in your system tray and it watches what you type. In its most simple usage, you can set up different phrases to substitute what you type.

For example, I might reprogram HaD to show up as Hackaday to save myself some typing. I usually use some odd character at the start or end so I don’t accidentally trigger things. So maybe I’m tired of typing or mistyping http://www.hackaday.com. I could set up ~had to automatically type the correct URL for me.

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Need A Linux Kernel Module? Scratch That

July 4, 2022 by 15 Comments

If you have been for (or against) Rust in the Linux kernel, get ready for a Linux kernel module written in… Scratch. That’s right. Scratch, the MIT-developed language with blocks popular for teaching kids to code. We didn’t mean “from scratch.” We meant IN Scratch. The bootstrap code and Makefile is out there on GitHub.

Of course, it is a simple module and the reason it is possible is because of the scratchnative system that lets you compile Scratch into C code. If you want to look at the decidedly simple code, you can open it in your browser.

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Linux Fu: Docking Made Easy

June 21, 2022 by 20 Comments

Most computer operating systems suffer from some version of “DLL hell” — a decidedly Windows term, but the concept applies across the board. Consider doing embedded development which usually takes a few specialized tools. You write your embedded system code, ship it off, and forget about it for a few years. Then, the end-user wants a change. Too bad the compiler you used requires some library that has changed so it no longer works. Oh, and the device programmer needs an older version of the USB library. The Python build tools use Python 2 but your system has moved on. If the tools you need aren’t on the computer anymore, you may have trouble finding the install media and getting it to work. Worse still if you don’t even have the right kind of computer for it anymore.

One way to address this is to encapsulate all of your development projects in a virtual machine. Then you can save the virtual machine and it includes an operating system, all the right libraries, and basically is a snapshot of how the project was that you can reconstitute at any time and on nearly any computer.

In theory, that’s great, but it is a lot of work and a lot of storage. You need to install an operating system and all the tools. Sure, you can get an appliance image, but if you work on many projects, you will have a bunch of copies of the very same thing cluttering things up. You’ll also need to keep all those copies up-to-date if you need to update things which — granted — is sort of what you are probably trying to avoid, but sometimes you must.

Docker is a bit lighter weight than a virtual machine. You still run your system’s normal kernel, but essentially you can have a virtual environment running in an instant on top of that kernel. What’s more, Docker only stores the differences between things. So if you have ten copies of an operating system, you’ll only store it once plus small differences for each instance.

The downside is that it is a bit tough to configure. You need to map storage and set up networking, among other things. I recently ran into a project called Dock that tries to make the common cases easier so you can quickly just spin up a docker instance to do some work without any real configuration. I made a few minor changes to it and forked the project, but, for now, the origin has synced up with my fork so you can stick with the original link.

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