Recovering bricked LPC55Sxx EVK Boards

While developing applications, it can happen that things go wrong. And in my case I ended up with two LPC55Sxx EVK boards on my desk, which seemed not to be usable any more. The issue: the boards were not accessible with the debug probe, because right after main they muxed the pins in a wrong way :-(.

bricked board with set of debut probes

The standard GDB debug connections (both on-board and off-board) were not able to regain access of the board, because the MCU was running into the fault condition pretty much right out of reset.

Luckily, after a lot of trial-and-error, I have found a way to recover them.

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LoRaWAN with NXP LPC55S16 and ARM Cortex-M33

LoRaWAN is getting more an more popular, both for terrestrial and increasingly with low-orbit satellite systems. The ‘Long Range’ in ‘LoRa’ makes it an ideal solution for low-power and low data rate applications. For a university research project we selected the Semtech SX1261/62 transceiver together with the NXP LPC55S16 mikrocontroller. Because the board used for that project is not available for the public (yet), I share here how you can run the LoRaWAN stack with the NXP LPC55S16-EVK.

LoRaWAN with Semtech SX126x and NXP LPC55S16
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Standalone SWO

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.

SWO output from application
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Position-Independent Code with GCC for ARM Cortex-M

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…

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Placing Code in Sections with managed GNU Linker Scripts

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.

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SWO with ARM Cortex-M33

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….

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Using FatFS and MinINI with the NXP LPC55S16 EVK

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.

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