Dzu's Blog (Posts about embedded)

Basic AMP on the i.MX8M Mini with Rpmsg

Detlev Zundel — Sat, 16 Apr 2022 12:48:52 GMT

In a recent post, I described the basics to execute code on the Cortex M4 micro controller inside the i.MX8M Mini SoC. However there was no communication going on between Linux on the Cortex A cores and the application running on the M4. In this post, I will look at an example using the remoteproc and rpmsg (Remote Processor Messaging) frameworks for communication between the processors. The remoteproc subsystem implements basic house keeping for co-processors in Linux and the rpmsg framework implements the actual data channels.

Using the M4 MCU on the i.MX8M Mini

Detlev Zundel — Mon, 11 Apr 2022 17:01:30 GMT

Over the last few years, SoCs targeted at embedded GNU/Linux applications became heterogenous architectures. Instead of adding more identical copies of CPU cores (Cortex-A class), a small companion micro controller core (Cortex-M class) was added. Compared to the complex architecture of Cortex-A systems, including their multi-layer caches, those cores are usually deterministic and thus predestined for low-latency "real time" jobs. NXP's first such SoC is the i.MX6 Solo X device featuring an Cortex-M4 next to an Cortex-A9 core. The i.MX8 family moved the Cortex-A cores into the 64 bit world and there are different combinations of Cortex-M companion micro controllers, but all of them do feature them as they are pretty "cheap" in terms of die space and transistor count.

From what I can see, it is still uncommon to use those micro controllers in actual projects though. Today I want to take a short look on how to run simple programs on the Cortex-M4 of the i.MX8M Mini SoC, especially we will use the official i.MX8M Mini EVK.

Testing Preempt RT on the i.MX8MM SoC in 15 minutes

Detlev Zundel — Wed, 23 Feb 2022 20:34:30 GMT

Looking at the kernel sources for NXP's i.MX8M SoCs, I noticed branch names like "lf-5.10.72-rt-2.2.0" and I wondered if NXP finally was going to offer RT preempt support within their BSP. Some other vendors have started supporting the patch set already a while ago but for NXP this is new.

In this post we are going to run this real-time enabled kernel on the i.MX8M-Mini evaluation board from NXP to get a first hand impression of what is required on the kernel level. We will not use the Yocto build system as this is only a wrapper around the distribution agnostic kernel development.

Taming The Serial Console

Detlev Zundel — Sat, 20 Mar 2021 10:41:57 GMT

Starting My Rust Journey

Detlev Zundel — Sun, 24 Feb 2019 20:38:22 GMT

With a few things coming together, I have finally decided to look into yet another programming language. On the one hand learning a new language is usually a good way to broaden the fundamenetal understanding of programming, but this time I do have a specific goal in mind that I want to reach.

Only recently I have been looking at various 32 bit Cortex-M ARM micro-controllers with the vendor provided C programming environments. Knowing modern programming languages like Haskell, OCaml or Go got me so frustrated with these environments that I decided to find a modern language also fit for this embedded space and no, I don't think Python is the answer to every problem just as Java wasn't. Ultimately, I would like to see a functional programming language in this space, but I am open to other approaches fitting the embedded space.

Being an FSF Emacs user for decades, I am also averse to these proprietary programming environments that may have some nice features but ultimately only try to lock the developer into a vendor controlled ecosystem. Usually they are all Eclipse based anyway but are incompatible with one another. It gives me the shivers installing the n-th copy of Eclipse for yet another Cortex-M based micro-controller and I really wonder how we ended up in this very frustrating assembly of walled in environments.

So this is the start of a small series of posts that evaluate how easy it will be to setup a programming environment on GNU/Linux for Rust based on GNU Emacs. Ultimately I want to target micro-controllers without a full GNU/Linux system running on them, so the aim is to also get a cross-compilation setup working.