Author Archives: smittytone

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Arm Assembly on the Pi Pico: Mnemonics #2

A number of the Cortex-M0+ Thumb ops I covered last time update the core’s Program Status Register (PSR) based on the outcome of the operation. The ops that do so have an S appended to their mnemonics and they only work with the core’s ‘low’ registers, R0-7.

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ARM Assembly on the Pi Pico: Mnemonics #1

Last time, I covered the basics of doing ARM assembly programming on the Raspberry Pi Pico’s RP2040 microcontroller. Now it’s time to get to grips with the dozens of instructions to which the RP2040’s Cortex-M0+ cores respond.

ARM assembly instructions for the Raspberry Pi Pico's RP2040 chip
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Get Started with ARM Assembly on the Pi Pico

When I got my first microcomputer, I already knew Basic programming. My machine had a different Basic dialect from the one I’d learned at school, and there was a stack of graphics and sound functionality to get to grips with too, but it wasn’t long before I felt I’d mastered the high-level stuff and that it was time to move on to machine code. That’s how I’ve come to feel about the Raspberry Pi Pico’s RP2040 chip. The time’s right to learn ARM assembly programming on the Pico.

The Raspberry Pi RP2040 chip
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Fun with FreeRTOS and the Pi Pico: timers

I made use of FreeRTOS’ timer functionality in the most recent post in this series, but I didn’t go into detail because the post was focused on other features. It’s time to address that deficiency. Today I’m talking about timers.

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Notarise macOS command line apps more quickly

It’s June once more, and time for Apple’s Worldwide Developers’ Conference (WWDC). This is a chance to learn about new functionality and, yes, discover initiatives announced at previous WWDCs that you completely missed the first time around. A case in point: Apple’s revamp of how apps are notarised at the command line, which was revealed at WWDC 21 but I only encountered this week.

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How to write Unix man pages for macOS command line apps

Over the last few years I’ve released a number of command line utilities for macOS. I’ve always included online help within them, triggered with the --help switch, but I recently wondered how I might provide Unix Manual pages too. It would allow users to call up help with the CLI command man as well as a command switch. Belts and braces, perhaps, but I’m a completist and, more to the point, didn’t know how it was done and wanted to learn.

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How to do DNS over HTTPS with macOS

My last post detailed how you set up DNS over HTTPS (DoH) for a client Raspberry Pi. I mentioned that I tried this out first on a Mac, and so I’ve been asked to show how running DoH on macOS works. Here goes.

DNS-over-HTTPS on a Mac via a local DNS proxy
DNS-over-HTTPS on a Mac via a local DNS proxy
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How to do DNS over HTTPS on a Raspberry Pi

Last year, at the recommendation of a work colleague, I grabbed one of my spare Raspberry Pi 4s and installed the DNS proxy and content blocker Pi-Hole. It’s now handling all the DNS queries on my home network. Recently, I upgraded my Pi-Hole server to make its DNS requests over HTTPS.

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PreviewCode 1.2.0 released to support user-requested programming data file types

PreviewCode, my macOS Finder source code and data file preview app, has had a major update to support a bunch of developer-oriented file types requested by users. The new version, 1.2.0, is available now from the macOS App Store.

PreviewCode’s main UI
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Fun with FreeRTOS and the Pi Pico: interrupts, semaphores and notifications

One of the reasons why an embedded application developer might choose to build their code on top of a real-time operating system like FreeRTOS is to emphasise the event-driven nature of the application. For “events” read data coming in on a serial link or from an I²C peripheral, or a signal to a GPIO from a sensor that a certain threshold has been exceeded. These events are typically announced by interrupting whatever job the host microcontroller is engaged upon, so interrupts are what I’ve chosen to examine next in my exploration of FreeRTOS on the Raspberry Pi RP2040 chip.

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