Benjamin Cabé

Zephyr Weekly Update – New Hardware Model

Benjamin Cabé
Zephyr Weekly Update - March 8, 2024

Zephyr Weekly Update - March 8, 2024

Howdy! Before diving into this week’s news, I would like to extend an invitation to all of you reading this weekly update to consider submitting a talk for an upcoming Zephyr Tech Talk. As you have probably noticed if you watched previous episodes, these are very informal sessions, so you shouldn’t worry about having to prepare super polished slides (but cool demos are definitely a nice to have!).

If you are a maintainer of a Zephyr area you feel deserves more attention, or simply a Zephyr contributor or enthusiast eager to share insights about a topic you’re passionate about, please propose your idea here!

New Hardware Model

As announced in previous weeks, a new hardware model has been introduced for making it easier to support hardware configurations that were becoming difficult or impossible to describe with the legacy model.

This new model allows to better address multi-core (and sometimes multi-archictecture, too!) SoCs, as well as boards with multiple SoCs.

All the hundreds of boards supported in Zephyr have already been migrated, and what you need to do to migrate your own existing board definitions that you may be maintaining out-of-tree is descibred in the Board porting guide.

We will be having a Zephyr Tech Talk on the topic in just a few weeks, so stay tuned for that!

LED matrices as regular display controllers

I am sure some of you may have a love & hate relationship with Devicetree. It certainly takes some time to get used to the syntax and the sometimes opaque error messages in case of misconfiguration, but it is a super powerful and versatile tool.

This week, a new driver was introduced that I believe really illustrates quite well how one can really decouple their application code from the underlying hardware.

Zephyr already has a generic driver class for LED strips. You will find several drivers in the Zephyr tree (ex. for the popular WS2812 RGB LEDs) that implement the LED strip API and allow to set the colors of all the LEDs in the strip. As you can imagine, on the Devicetree side of things, the configuration of the driver includes things like how many LEDs are in the strip, or which pins/bus should be used to control the strip.

There is also a driver class for all things display controllers. Here, we’re talking about drivers exposing properties for configuring the resolution of the display, which pins to use to transmit pixel data, etc. In most cases, the application developer couldn’t care less about the specifics of the display controller, and they only use the display driver API to effectively put pixels on the screen. In fact, there’s even higher levels of abstraction, like the pre-integration with LVGL, which you’ve heard me talk about many times.

OK, so can you guess where I am going with this? Yep, a new driver now sits kind of in the middle of these two classes of drivers. It’s a display controller driver for LED matrices. Give it a phandle to an led-strip node, and you have your new display ready to rock & roll!

chosen {
    zephyr,display = &led_strip_matrix;
};

led_strip_matrix: led_strip_matrix {
    compatible = "led-strip-matrix";
    status = "okay";
    led-strips = <&led_strip>;
    chain-lengths = <256>;
    width = <16>;
    height = <16>;
    circulative;
    start-from-right;
};
https://blog.benjamin-cabe.com/wp-content/uploads/2024/03/PXL_20240306_232146509-2.mp4

(PR #68614)

Boards & SoCs

General drivers

Miscellaneous

A big thank you to the 12 individuals who had their first pull request accepted this week, 💙 🙌: @Dermiste, @jthm-ot, @zhaynxp, @jonathonpenix, @cradzik, @ajf58, @Deedone, @pfarwsi, @ChangNice, @glenn-andrews, @sibertdeclercq, and @gangli02.

As always, I very much welcome your thoughts and feedback in the comments below!

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Catch up on all previous issues of the Zephyr Weekly Update:

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