Category Archives: gcc

Low-Power Optimization Techniques for ARM Cortex-M Microcontrollers

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Europe is currently facing an ‘Energy Crisis,’ and ‘Sustainability’ is a popular topic among companies. However, embedded engineers go beyond talking—they take action and make tangible changes in the world. With the increasing use of electronic devices, minimizing their energy and power consumption is crucial. Optimizing systems for deep low power or deep low energy is a challenging task. Nonetheless, as I will demonstrate in this article, it is possible to reduce energy consumption by a factor of 100 or more. This article provides a brief overview of the foundational concepts and then applies them step-by-step to an ARM Cortex microcontroller.

Measuring on-board LPC804 with MCU-Link Pro
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Building Eclipse Projects with custom external Shell Scripts

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Eclipse includes many ways to build a project. One of it is the built-in builder which makes it super easy. And for more complex building needs I can use an external make (see Tutorial: Makefile Projects with Eclipse) or cmake or combination of multiple ways (see Building a Triumvirate: From Eclipse CDT to CMake, CMD and Visual Studio Code).

There is yet another use case how to easily tweak the build process in Eclipse: using a script file in the project to be used as the ‘compiler’:

External Build Script

That way I can do all kind of custom steps (analysis, re-formatting, static checkers, …) for each file compiled.

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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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Binary, do you use Hard-Float or Soft-Float?

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Many cost-sensitive ARM Cortex-M devices like the M0+ do not have a hardware floating point unit, and some like the M4 only has an optional single-precision floating point unit (FPU). As outlined in “Be aware: Floating Point Operations on ARM Cortex-M4F“, using floating point operations without a hardware unit can be costly.

Looking at the disassembly for sure will tell you if the hardware is handling the float or double operation or not:

Disassembly showing runtime routines

But who wants check the all the disassembly? With the GNU tools there is an easier way: readelf.

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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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Power Measurement with INA260 Sensor

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For a research project and demonstrator at HSLU university I have to measure voltage a DC voltage and current. For this I’m planning to use the Texas Instrument Texas Instruments INA260, so I had to quickly develop a software driver for it.

TI INA260 Power Sensor Breakout Board
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Processor Expert Components: 24-Dec-2023 Release

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The new year 2024 is coming, so time to close the current year with a new release: I’m pleased to announce a new release of the Processor Expert components, available on SourceForge and GitHub.

Processor Expert Components in Eclipse (KDS)

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Building with CMake Presets

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I’m getting my head more and more around CMake and its features. After having so many issues with VS Code dealing with CMake Kits, I have found feature in CMake which really is a game changer for me: CMake Presets.

Working with CMake Presets in VS Code
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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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“No Kit Selected”: Fixing VS Code CMake Kit Assignment

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One important thing in using VS Code and CMake projects is that one needs to have a CMake kit assigned to the project. But after a restart of VS Code or if I re-load a project, VS Code has lost the previously assigned CMake kit:

VS Code has forgotten about the previously assigned CMake Kit?

This is very annoying, but luckily I have found a fix for this.

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