SWO (Single Wire Output) in ARM cores is probably one of the most under-used features. Which is surprising, because SWO can be very useful. In a nut shell: SWO is a single wire output pin/signal channel which can provide lots of different data, like PC sampling for coverage information, interrupt tracing data or ‘uart-like’ text packets.
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.
The previous parts were about installation, project setup, building, debugging and setting up a kit. This one is about setting up IntelliSense for Cross Development in Visual Studio Code which allows for browsing symbols or code completion:
One major concern of embedded system development is performance. Microcontroller have more MHz than in the past, but embedded applications are all about timing and real-time aspects.
The challenge is: how to get data off the target in realtime? SWO can help with this….