bootloader

63 Articles

Windows On ARM On Arm

April 10, 2025 by 12 Comments

While some companies like Apple have gone all-in on the ARM architecture, others are more hesitant to dive into the deep end. For example, Microsoft remains heavily invested in the x86 architecture and although it does have some ARM offerings, a lot of them feel a bit half-baked. So you might question why someone like [Gustave] has spent so much time getting Windows to run on unusual ARM platforms. But we don’t need much of a reason to do something off-the-wall like that around these parts, so take a look at his efforts to get Windows for ARM running on a smartwatch.

The smartwatch in question here is a Pixel Watch 3, which normally runs a closed-source Android implementation called Wear OS. The bootloader can be unlocked, so [Gustave] took that approach to implement a few clever workarounds to get Windows to boot including adding UEFI to the watch. During the process Google updated these devices to Android 15, though, which broke some of these workarounds. The solution at that point was to fake a kernel header and re-implement UEFI and then load Windows (technically Windows PE) onto the watch.

Although this project was released on April 1, and is by [Gustave]’s own admission fairly ridiculous and not something he actually recommends anyone do, he does claim that it’s real and provides everything needed for others to run Windows on their smartwatches if they want to. Perhaps one of our readers will be brave enough to reproduce the results and post about it in the comments. In the meantime, there are a few more open options for smartwatches available if you’re looking for something to tinker with instead.

Thanks to [Ruhan] for the tip!

Self-Hosting A Cluster On Old Phones

April 9, 2025 by 34 Comments

The phones most of us carry around in our pockets every day hold a surprising amount of computing power. It’s somewhat taken for granted now that we can get broadband in our hands in most places; so much so that when one of these devices has reached the end of its life it’s often just tossed in a junk drawer even though its capabilities would have been miraculous only 20 years ago. But those old phones can still be put to good use though, and [Denys] puts a few of them back to work running a computing cluster.

Perhaps the most significant flaw of smartphones, though, is that most of them are locked down so much by their manufacturers that it’s impossible to load new operating systems on them. For this project you’ll need to be lucky enough (or informed enough) to have a phone with an unlockable bootloader so that a smartphone-oriented Linux distribution called postmarketOS can be installed. With this nearly full-fledged Linux distribution to work from, the phones can be accessed by ssh and then used to run Kubernetes for the computing cluster. [Denys] has three phones in his cluster that run a few self-hosted services for him.

[Denys] also points out in his guide that having a phone that can run postmarketOS might save some money when compared to buying a Raspberry Pi to run the same service, and the phones themselves can often be more powerful as well. This is actually something that a few others have noted in the past as well. He’s gone into a considerable amount of detail on how to set this up, so if you have a few old smartphones gathering dust, or even those with broken screens or other physical problems where the underlying computing resources are still usable, it’s a great way to put these machines back to work.

Thanks to [mastro Gippo] for the tip!

A 64-bit X86 Bootloader From Scratch

July 14, 2024 by 20 Comments

For most people, you turn on your computer, and it starts the operating system. However, the reality is much more complex as [Thasso] discovered. Even modern x86 chips start in 16-bit real mode and there is a bit of fancy footwork required to shift to modern protected mode with full 64-bit support. Want to see how? [Thasso] shows us the ropes.

Nowadays, it is handy to develop such things because you don’t have to use real hardware. An emulator like QEMU will suffice. If you know assembly language, the process is surprisingly simple, although there is a lot of nuance and subtlety. The biggest task is setting up appropriate paging tables to control the memory mapping. In real mode, segments have access to fixed 64 K blocks of memory unless you use some tricks. But in protected mode, segments define blocks of memory that can be very small or cover the entire address space. These segments define areas of memory even though it is possible to set segments to cover all memory and — sort of — ignore them. You still have to define them for the switch to protected mode.

In the bad old days, you had more reason to worry about this if you were writing a DOS Extender or using some tricks to get access to more memory. But still good to know if you are rolling your own operating system. Why do the processors still boot into real mode? Good question.

RP2040 Boot Loader Is A Worm

March 17, 2024 by 8 Comments

[Hunter Adams] has written a secondary bootloader for the RP2040 that uses an IR link and can be extended to behave like a polite worm virus. This allows the easy updating of a large cluster of co-located RP2040-based controllers. This could be handy in applications like swarm robotics or virtual cattle fencing. The project he demonstrates in the two videos ( below the break ) uses a pair of IR transmitters/receivers. But he purposely wrote the boot loader to be independent of the serial link, which could be infrared, radio, audio, or just wires.

Not only did [Hunter] make a boot loader, but he documented the entire boot process of the RP2040 chip. Whether or not you need a secondary bootloader, this is an excellent resource for understanding how the RP2040 responds to power cycling and resets. The boot loader code is available at his GitHub repository.

You may recall that [Hunter] is the lecturer of Cornell University’s Designing with Microcontroller classes, whom we’ve mentioned before. We’ve also covered some of his students’ projects as well, like these air drums and this CoreXY pen plotter.

Continue reading “RP2040 Boot Loader Is A Worm” →

Blinkenlights To Bootloader: A Guide To STM32 Development

August 6, 2023 by 15 Comments

While things like the Arduino platform certainly opened up the gates of microcontroller programming to a much wider audience, it can also be limiting in some ways. The Arduino IDE, for example, abstracts away plenty of the underlying machinations of the hardware, and the vast amount of libraries can contribute to this effect as well. It’s not a problem if you just need a project to get up and running, in fact, that’s one of its greatest strengths. But for understanding the underlying hardware we’d recommend taking a look at something like this video series on the STM32 platform.

The series comes to us from [Francis Stokes] of Low Byte Productions who has produced eighteen videos for working with the STM32 Cortex-M4 microcontroller. The videos start by getting a developer environment up and blinking LEDs, and then move on to using peripherals for more complex tasks. The project then moves on to more advanced topics and divides into two parts, the development of an application and also a bootloader. The bootloader begins relatively simply, and then goes on to get more and more features built into it. It eventually can validate and update firmware, and includes cryptographic signing (although [Francis] notes that you probably shouldn’t use this feature for production).

One of the primary goals for [Francis], apart from the actual coding and development, was to liven up a subject matter that is often seen as dry, which we think was accomplished quite well. A number of future videos are planned as well. But, if you’re not convinced that the STM32 platform is the correct choice for you, we did publish a feature a while back outlining a few other choices that might provide some other options to consider.

Continue reading “Blinkenlights To Bootloader: A Guide To STM32 Development” →

Using An Old Smartphone In Place Of A Raspberry Pi

April 27, 2023 by 63 Comments

The Raspberry Pi was a fairly revolutionary computing device when it came on the scene around a decade ago. Enough processing power to run a full Linux desktop and plenty of GPIO meant almost certain success. In the past year, though, they’ve run into some issues with their chip supplier and it’s been difficult to find new Pis, which has led to some looking for alternatives to these handy devices. [David] was hoping to build a music streaming server and built it on an old smartphone instead of the ubiquitous single-board computer.

Most smartphones are single-board computers though, and at least the Android devices are fully capable of running Linux just like the Pi. The only problem tends to be getting around the carrier or manufacturer restrictions like a locked bootloader or lack of root access. For [David]’s first try getting this to work, he tried to install Navidrome on a Samsung phone but had difficulties with the lack of memory and had to build the software somewhere else and then load it on the phone. It did work, but the stock operating system kept killing the process for consuming too much memory.

Without root access, [David] decided to try LineageOS, a version of Android which, among other benefits, is typically much more configurable than the stock version of Android that is shipped with smartphones. This allowed him to disable or uninstall anything not needed for his music server to free up enough memory. After some issues with transcoding the actual music files he planned on streaming, his music server was successfully up and running on a phone that would have otherwise been relegated to the junk drawer. The specific steps he took to get this working can be found on his GitHub page as well.

[David] also mentioned looking at PostmarketOS for this job which is certainly a viable option for some, but the Linux distribution for phones is only supported on a few devices. Another viable alternative for a project like this if no Raspberry Pis are available might be any of a number of Pine64 devices that might also be sitting around gathering dust, like the versatile Linux-based Pinephone.

Getting The Most From Fading ThinkPads

April 21, 2023 by 40 Comments

The ThinkPad line of laptops has been widely prized not only by businesses but also by those who appreciate a high standard of hardware quality and repairability. But some think the cracks are starting to form in their reputation, as it seems that new ThinkPads are sacrificing quality for aesthetics and cost. As a result a huge modding scene has popped up around models that are a few years old like [Cal] found out when working on this X230.

At first he only made some cosmetic improvements to the laptop like replacing the worn palm rest, but quickly found himself in a rabbit hole with other upgrades like swapping out the keyboard and battery. The new keyboard is a 7-row X220 keyboard, which required modification of the connector and flashing the embedded controller with a hacked image to change the keyboard map without needing to make changes at the OS level. From there, he decided to replace the lackluster screen with a 1920×1080 matte IPS panel using an adapter board from Nitrocaster, and finished off his upgrades with a customized Coreboot BIOS for improved performance and security.

While Coreboot doesn’t remove all of the binary blobs that a bootloader like libreboot does, the latter is not compatible with more modern machines like this X230. Still, you’ll get many benefits from using Coreboot instead of the stock bootloader. For running Linux on a daily driver laptop, we appreciate all of these updates and expect that [Cal] will get plenty of years of use out of his machine. We’ve definitely seen an active modding scene for ThinkPads that were (at the time) seven years old and still going strong, so we’d expect nothing less for this one.