bare metal

16 Articles

A handheld computer made on a piece of prototyping board running a Tetris clone

Tetris Clone Uses 1000 Lines Of Code, And Nothing Else

September 25, 2023 by 18 Comments

If you’re programming on a modern computer, you typically make use of lots of work done by other people. There’s operating systems to abstract away the complexities of modern hardware, standard libraries to implement common tasks, and tons of third-party libraries that prevent you from having to reinvent the wheel all the time: you’re definitely not the first one trying to draw graphics onto a screen or store data in a file.

But if it’s the wheels you’re most interested in, then there’s nothing wrong with inventing new ones now and then. [Michal Zalewski], for instance, has made a beautiful Tetris clone in just 1000 lines of C, without using anyone else’s code.

The purpose of this exercise is to show that it’s possible to make a game with graphics comparable to modern, complex computing systems, without relying on operating systems or third-party libraries. The hardware consists of not much more than an ARM Cortex-M7 MCU, a 240×320 LCD screen and a few buttons soldered onto a piece of prototyping board, all powered by a set of AAA batteries.

The software is similarly spartan: just pure C code running directly on the CPU core. Graphic elements, some generated by AI and others hand-drawn, are stored in memory as plain bitmaps. They are manipulated by 150 lines of code that shuffles sprites around the display at a speed high enough to generate smooth motion. Game mechanics take up about 250 lines, while sound consists of simple square-wave chiptunes written in just 50 lines of code.

[Michal]’s code is very well documented, and his blog post gives even more details about all the problems he had to solve. One example is the length of keypresses: when do you interpret a keypress as a single “press”, and when does it become “press and hold”? Apparently, waiting 250 ms after the first press and 100 ms after subsequent ones does the trick. [Michal] is a bit of an expert on bare-bones game programming by now: he has previously pushed several 8-bit micros to their very limits. Third-party libraries can make your programming life a lot easier, but it’s good to reflect on the dangers of relying too much on other people’s code.

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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.

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Roll Your Own WiFi Driver For The Pico W

December 13, 2022 by 28 Comments

The Raspberry Pi Pico is a handy little microcontroller that has become a widespread addition to many hackers’ workbench. The Pico W has a CYW4342W module (just like the Pi Zero W) to add WiFi capabilities and [Jeremy Bentham] ported his bare-metal WiFi driver to the Pico W.

The CYW43438 is an SDIO interface, so most of the code ported over from his Zerowi project, but there were a few notable tweaks along the way. Given that the Pi Pico SDK has the complete source code to drive the CYW43439 with an open source TCP/IP stack (lwIP) and the datasheets from Infineon are pretty detailed, why create your own driver?

The short answer is…because why not. But a second answer is to tweak it just how you like it. With his own implementation, [Jeremy] can focus on maximizing throughput and making WiFi a little easier to debug. He deeply delves into the hardware, scope traces, and code samples. It’s a tremendous five-part read over lunch. Some highlights include writing some code for the PIO (Programmable I/O) to interface with the SPI interface, bank switching in the WiFi RAM, handling the 140 different events, connecting to a network, and sending pings.

The PicoWi code is available on GitHub. Perhaps it can be integrated with this PCMIA interface to offer outstanding performance to an older laptop.

Nucleo-F429ZI development board with STM32F429 microcontroller

Epic Guide To Bare-Metal STM32 Programming

December 5, 2022 by 31 Comments

[Sergey Lyubka] put together this epic guide for bare-metal microcontroller programming.  While the general concepts should be applicable to most any microcontroller, [Sergey]s examples specifically relate to the Nucleo-F429ZI development board featuring the ARM-based STM32F429 microcontroller.

In the realm of computer systems, bare-metal programming most often refers to programming the processor without an intervening operating system. This generally applies to programming BIOS, hardware drivers, communication drivers, elements of the operating system, and so forth. Even in the world of embedded programming, were things are generally quite low-level (close to the metal), we’ve grown accustomed to a good amount of hardware abstraction. For example, we often start projects already standing on the shoulders of various libraries, boot loaders, and integrated development tools.

When we forego these abstractions and program directly on the microprocessor or microcontroller, we’re working on the bare metal. [Sergey] aptly defines this as programming the microcontroller “using just a compiler and a datasheet, nothing else.” His guide starts at the very foundation by examining the processor’s memory map and registers including locations for memory mapped I/O pins and other peripherals.

The guide walks us through writing up a minimal firmware program from boot vector to blinking an LED connected to an I/O pin. The demonstration continues with setup and use of necessary tools such as the compiler, linker, and flasher. We move on to increasingly advanced topics like timers, interrupts, UART output, debuggers, and even configuring an embedded web server to expose a complete device dashboard.

While initially more time consuming, working close to the metal provides a good deal of additional insight into, and control over, hardware operations.  For even more on the subject, you may like our STM32 Bootcamp series on bare-metal STM32 programming.

Making SVD Files Searchable With Svd2db

November 21, 2022 by 10 Comments

Everyone who writes bare-metal code for microcontrollers probably know the joys of looking up the details of specific registers in the reference manual, including their absolute address. Although the search function of the PDF viewer can be helpful, it’d be rather nice if there was a way to search only the registers, and have the offset calculations performed automatically. This is basically what [Terry Porter]’s Svd2db tool enables. As the name suggests, this tool turns the SVD hardware description files that come with ARM-based MCUs into a database file.

This database file is an SQLite database, which allows it to be searched using the provided readdb tool, or any other SQLite tool. This would make the utility useful not just for quick look-ups during development, but presumably also for automated testing scenarios where having an easily searchable database of registers is of use. At this point Svd2db is guaranteed to work with STM32 SVDs, but may work with SVDs for other ARM-based SVD files as well.

 

Embedded Rust Hack Chat

May 10, 2021 by 18 Comments

Join us on Wednesday, May 12 at noon Pacific for the Embedded Rust Hack Chat with James Munns!

Programming languages, like fashion, are very much a matter of personal taste. Professional developers often don’t have much say in which language they’ll use for a given project, either for legacy or team reasons, but if they did have a choice, they’d probably choose the language that works best with the way they think. Some languages just “fit” different brains better than others, and when everything is in sync between language and developer, code just seems to flow effortlessly through the keyboard and onto the screen.

One language that consistently scores at the top of developers’ “most loved” lists is Rust. For a language that started as a personal project and has only existed for a little more than a decade, that’s really saying something. The emphasis Rust puts on safety and performance probably has a lot to do with that. And thanks to its safe concurrency, its memory safety, and its interoperability with C and other languages, Rust has made considerable in-roads with the embedded development community.

To learn more about Rust in embedded systems, James Munns will stop by the Hack Chat. James is an embedded systems engineer, with a history of working on software for a wide range of systems, including safety-critical avionics, and rapidly prototyped IoT systems. He’s a founding member of the Rust Embedded Working Group, as well as a founder of Ferrous Systems, a consultancy focused on systems development in Rust, with a specialty in embedded systems development. James also used to write for Hackaday, so he must be a pretty cool guy. So swing by the Hack Chat and find out where Rust might be able to help you out with your next embedded project.

join-hack-chatOur Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, May 12 at 12:00 PM Pacific time. If time zones have you tied up, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on Hackaday.io. You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about.
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Bare-Metal STM32: Blinky And The Secret Of Delay Functions

December 11, 2020 by 35 Comments

One of the very first examples for an MCU or SoC usually involves the famous ‘Blinky‘ example, where an LED is pulsed on and off with a fixed delay. This is actually a lot more complicated than the ‘Pushy‘ example which we looked at in the first installment of this series. The reason for this is that there’s actually quite a story behind a simple call to delay() or its equivalent.

The reason for this is that there are many ways to implement a delay function on a microcontroller (MCU), each of which comes with their own advantages and disadvantages. On an STM32 MCU, we get to choose between essentially an active delay (while loop), one implemented using the SysTick timer and using one of the peripheral timers. In the latter two cases we also have to use interrupts.

In this article we’ll take a look at all three approaches, along with their advantages and disadvantages.

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