Welcome to ‘Alice in Wonderland‘! For a university research project using an ARM Cortex-M33 we are evaluating position-independent code as way to load applications or part of it with a bootloader. It sounds simple: just add -fPIC to the compiler settings and you are done.
Unfortunately, it is not that simple. That option opened up a ‘rabbit hole’ with lots of wonderful, powerful and strange things. Something you might not have been aware of what could be possible with the tools you have at hand today. Leading to the central question: how is position-independent code going to work with an embedded application on an ARM Cortex-M?
Let’s find out! Let’s start a journey through the wonderland…
Dangling pointers and memory corruption problems are nasty issues for any developer, and usually hard to find and locate in the code. Luckily Google has developed an open source tool to solve such issues: the Address Sanitizer (ASAN). The tool is available for x86 and other desktop style architectures, including Android and Linux. This article describes how ASAN can be used for an embedded target, e.g. ARM Cortex-M4 or similar.
Managed linker scripts are great on one side: the simplify the otherwise complex GNU linker script handling. On the other side it requires knowledge how to tweak them in case ‘non-standard’ behavior is needed.
For a research project we selected the NXP LPC55S16 but because it has due the silicon shortage it is not available probably for the next 52 weeks (yikes!) we can use the EVK Board.
The FatFS file system from Elm Chan is the de-facto file system for many embedded systems. As such it comes integrated with silicon vendor SDKs like the NXP MCUXpresso SDK. The problem is that the SDK only has examples for things on the board, and because that board does not have a SD card socket, no example for using FatFS with an SDK card is provided :-(. So I had to create one, and you can get it from GitHub.
As time flies by, my projects are evolving. My lab projects get used over multiple semesters, and the MCUXpresso projects by default use the SDK version used at that time.
This is great because I do want to have control over what SDK is used. But from time to time it makes sense to upgrade a project to a newer version. In this post I’ll show how an existing project can be upgraded to use a new SDK.
Sometime I’m pretty sure I wrote about a topic I can find or refer to, and I was pretty sure I did write about ‘attaching to a running target’ using MCUXpresso IDE in an article, but Google does not find it? The only rational outcome is that I can blame Google and I have to come up with a potential duplicate ;-).
Anyway: attaching to a running target is such an essential life saver it deserves a dedicated article.