Tag Archives: software project

How to make sure no floating point code is used

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Float and double data types area a bad choice for embedded applications. At least in most applications, and can or should be avoided, even with hardware FPU support present.

But how can I be sure that no floating point operations are used?

wrapping float and double runtime routines

This article describes how to configure the GNU toolchain, so that no float or double operations are used, with the example of ARM Cortex-M. What I do? ‘Poisoning’ (!!!) the source code, force the gcc compiler to use software floating point operations and then catch them with the GNU linker :-).

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‘Experience Energy’ at the Verkehrshaus: The ‘House of Energy’ Construction Kit

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The ‘Verkehrshaus der Schweiz‘, the ‘Swiss Museum of Transport’ is Switzerland’s most popular museum.

In April 2023, it opened up a new building and the ‘Experience Energy!’ exhibition. For the opening event we created a unique construction kit to explore energy: from harvesting to storing and up to distributing and using energy.

“House of Energy” at the Swiss Museum of Transport in Lucerne
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Moving Pixel Clock Project

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Clock projects are cool. LED projects are cool too. And if it moves, the better. So why not building a moving pixel LED mechatronics clock? A matrix with addressable RGB LEDs, each can change color and is moved by a tiny stepper motor, to let pixels stand out?

Moving Pixel Clock
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GNU Coverage (gcov) for an Embedded Target with VS Code

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An important part of every CI/CD pipeline is having a testing phase. In this article I show how to use GNU gcov (coverage) with an embedded target, using Visual Studio Code as front end:

GNU gcov with VS Code

With this, I can run the code on the embedded target which stores the coverage data on the host.

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Implementing File I/O Semihosting for the RP2040 and VS Code

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I’m working recently on a new lecture module using the Raspberry Pi Pico (RP2040) board, which highlights several aspects of modern software engineering, including DevOps and CI/CD. An important part of any CI/CD pipeline is testing. For a host application, one could pass arguments to the application, e.g. ‘myapp --test=module1‘, or let it read such information from a configuration file which describes the tests. Or write GNU gcov data to a file to collect coverage information.

Unfortunately, a normal embedded application has no argv[], and many system have no file system. A solution to this problem would be using semihosting with file I/O. Unfortunately for the Raspberry Pi Pico SDK 1.5.1 for the RP2040, there is no semihosting file I/O implemented :-(.

I have now implemented and added file I/O to the SDK, making it possible for the RP2040 to access and use files on the host, among other things. This greatly extends the capabilities of the device, and is very useful for testing, including gathering test coverage information.

RP2040 writing files on the host with semihosting
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CI/CD for Embedded with VS Code, Docker and GitHub Actions

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“Our highest priority is to satisfy the customer
through early and continuous delivery
of valuable software.”

Agile Manifesto, https://agilemanifesto.org/principles.html

It is interesting to see that modern tools and agile development workflows are getting more and more into the embedded world. CI/CD is a strategy where code changes to an application get automatically integrated, tested and released automatically into a production environment.

VS Code with CI/CD
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VS Code: Building the Project

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In a previous article I have imported an example project. Now I want to compile and build it.

Traditionally, the build action inside VS Code is somewhat hidden. There is a keyboard shortcut, but recent additions to VS Code making the build action more accessible.

Multiple ways to start a build in Visual Studio Code
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LittleFS File System with MCU Internal FLASH Memory

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In many of my embedded projects I need persistent data or storage for settings. If using an SD card, then FatFS is usually my choice for the file system. But if using an external FLASH memory device, then my preferred choice is usually LittleFS: it is a little fail-safe filesystem, designed for micro-controllers, which I’m using with external flash memory devices.

In the case where there is enough MCU flash, or if there is no external FLASH device available in a design, it can use the MCU internal FLASH as storage storage too. This is the topic of this article:

LittleFS File System Data
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Catchpoints: Unlimited Number of FLASH Breakpoints with GDB

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Embedded hardware comes with limitations, and one if it is the given number of hardware breakpoints. Depending on your MCU, 4 or only 2 hardware breakpoints are available, making debugging and stepping in read-only memory (FLASH) a challenge.

Debugging NXP LPC845 with unlimited FLASH Breakpoints using MCU-Link

Did you know that one can have ‘unlimited’ number of breakpoints in FLASH, with the help of GDB? This is very useful for extended debugging, or if you want to use breakpoints for testing?

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Creating a GNU Assembly-Only Project

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Sometimes it makes sense to write everything in assembly, even these days. For example if using a tiny microcontroller. Or just if one just don’t need all the productivity of the C/C++ tools. And it is a good educational experience: getting hands-on on the lower levels.

Debugging an Assembly-Only Project
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