Category Archives: CPU’s

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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Versatile OSHW Mini MCU-Link Debug Probe: External, On-Board, or Embedded

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Who needs a debug probe, if you have printf()? If doing serious development, you most likely want a hardware debug probe. We at the HSLU IET use different hardware, boards and kits, and for many of the classroom equipment it is very useful to have the debug probe embedded on the target board: less cables, easier to use. For this we have developed a new Open Source Hardware (OSHW) debug probe in KiCad which can used in different ways: as external debug probe, integrated and soldered on top of the target board, or fully integrated and embedded into a custom design.

OSHW Mini MCU-Link Debug Probe
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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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Multi-Core Symmetric Multi-Processing (SMP) with FreeRTOS

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Maybe you are using a multi-core device in your projects, but have not tapped into multi-core usage yet? FreeRTOS V11.0 is out, and the big news is that it has finally Symmetric Multi-Processing (SMP) integrated into the mainline. This greatly simplifies FreeRTOS usage, as I finally can use the same RTOS for my SMP targets and boards, and I can easily switch between single-core and multi-core applications.

Dual-Core Boards running with FreeRTOS
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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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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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Modern On-Target Embedded System Testing with CMake and CTest

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One key element of a CI/CD pipeline is the automatic testing phase: whenever I check in new source code or manually trigger it, I can run a test suite to make sure that the changes do not break anything. For this, I have to run automated tests. For an an embedded target, it means that I have to run some tests on the board itself too.

CTest with VS Code
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MCU-Link with Cortex-Debug and LinkServer

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The MCU-Link is a small and inexpensive $10 CMSIS-DAP debug probe from NXP. It can work with OpenOCD, but has better target support using the NXP LinkServer which implements a gdb server. This makes it an ideal combination for scripting or automated testing.

MCU-Link as external debug probe
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