The Limits and Interpretation Pitfalls of Fitts’ Law

I’m getting old, and there are things that I don’t notice too well anymore. But I’m pretty sure UI elements have been getting bigger. Everywhere.

That makes a lot of sense on touch devices. Fingers are big and bulky, and the widgets that press them need to be big and bulky. But why are UI elements getting bigger everywhere, even on devices that aren’t touch-enabled, or for applications that are nowhere near being productively used on touch-enabled devices, like IDEs?

There is a reason that everyone is citing ad nauseam these days: Fitts’ law. It’s “popular” formulation states that bigger widgets are easier to hit, and the obvious interpretation is that we need to make them bigger. The reason why you can fit about as much code on your 24″ Full HD monitor as you could fit on the old Trinitron you had back you saw The Matrix at the cinema is SCIENCE!

I want to argue that:

  1. This is an incomplete and narrow interpretation of Fitts’ law, and
  2. That this is an unproductive use of Fitts’ law, because
    2a) It is routinely applied without any numerical analysis, and
    2b) It fails to account for other metrics, and consequently it rarely results in good design trade-offs

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Custom BLE Services with the nRF SDK

It’s very hard to write an introduction to an article about BLE without sounding a little ridiculous. What are you going to say, that it’s all around us today? It’s been all around us for five years. It’s the #1 choice for IoT applications today, owing in no small part to the fact that you can connect to any IoT device with a phone.

Today, I’m going to “talk” you through one of the most common, but also one of the most illustrative tasks that BLE development involves: writing a custom service (or a “vendor-specific service”, in BLE jargon). We’re going to do it from scratch, and we’ll discuss all the background on why we do things as we do — a lengthy discussion but, I hope, a useful one.

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Systemd in Embedded Systems: Don’t Listen to the Hatemob

systemd, the (init?) system that everyone loves to hate, needs no introduction. It’s pretty ubiquitous today — to the point where you can find it, for example, in Yocto.

When it comes to its use in embedded systems, the (vocal) community response is either that it’s too bloated, or that it’s probably a fringe case where systemd is actually useful because it can speed up booting. Since the notorious optimum-in-the-middle — rule 8 in my favourite set of rules ever — is pretty hard to figure out in the climate of systemd-related online discussions, I figured I’d offer my non-flamebait take on the topic.

Fresh out of the oven, from someone who really does work on embedded systems — some of them systemd-infenabled.

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The Modbus CRC Endianness Kerfuffle

Modbus is a quaint protocol. It’s one of my favourite protocols — it’s not very convenient to use, but it’s pretty convenient to implement and remarkably flexible for an otherwise pretty opinionated protocol. Its specs are very self-contained and easy to follow.

That being said, like all protocols that are a) from an entirely different era of computing and b) royalty-free, there are a lot of non-conforming devices out there. When you run into one, you quickly start to doubt the specs, your documentation, your code and eventually your sanity. My favourite stumbling block? The endianness of the CRC value.

It’s not so much that nobody gets it right — in fact, it’s the one thing that even non-conforming devices get right, because their developers end up swapping the bytes until they get the order right, otherwise the device can’t talk to anything. It’s just that a lot of people don’t understand why they got it right.

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Perf-V, Vivado and Linux

A few days ago I got a Perf-V board. In case you’re wondering what that is, the Perf-V is an FPGA development board, supposedly “designed for [the] RISC-V opensource community” by PerfXLab, a Beijing-based company that does some pretty interesting things in addition to this particular board.

PerfXLab does (rightfully) claim that you can use the board and the enclosed JTAG adapter with Vivado, but they aren’t very forthcoming on the details. Since a lot of RISC-V enthusiasts are software developers who have never touched Vivado, I figured I’d fill you in about the missing piece of the puzzle.

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The Compatibility Struggle Looming Over the Horizon

It’s been nearly 20 years since Rob Pike’s infamously won the “Best at saying what we’re all thinking” prize with his talk about how systems software research is irrelevant. And, while systems software research is doing slightly (though not glamorously) better than in 2000, it’s still mostly circling the drain.

That being said, it’s not a field that’s devoid of challenges. But I think the main challenge of the next 10-15 years is going to be even less glamorous than we like to think.

I think the main challenge of the next 15 years will be to keep existing software and, more importantly, existing programming models, up and running.

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Lessons From the apt Remote Code Execution Vulnerability

Well, it’s happened before, so it was bound to happen again: a remote code execution bug was found in APT. And it’s particularly interesting in the context of an age-old debate that has been dragging on in Debian-related circles about the use of HTTPS – a question that has been asked often enough that the answer has its own website now.

How bad was it? What is there to learn from this? And what does it tell us about the importance of HTTPS in package management security?

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Disk Space Isn’t Meaningless

It’s impossible to discuss Electron without the topic of space being brought up, and once that happens, you have to survive the talk about how storage is cheap today and space just doesn’t matter anymore.

Here is why I think all that is bogus — for bonus points, without any unironic use of the terms “engineering”, “real programmers” and “web developers”

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