Preserving debugging breadcrumbs across reboots in Cortex-M

Debugging embedded systems during development even with the best tools can be hard. Certainly a good debug probe makes life easier, but what do you do after the product is shipped? What if the customer complains that something strange is happening sometimes or a bug makes the device reboot, but only once a week? You make the firmware gather diagnostic information for you. This is the first post in series.
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Reducing firmware size by removing libc

The C standard library (libc) is a component that gets little attention. It is just there. However for embedded systems it brings some challenges and overhead in terms of code size. As firmware size is often critical, it sometimes makes sense to use a trimmed version of the standard library or to remove it entirely. I will focus on reducing the code size that may be beneficial for a small application like a bootloader.
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Fixing Cortex-M startup code for link-time optimization

Link-time optimization is a powerful output size reducing feature. Even though (as of 2018) still regarded as somewhat experimental, LTO is worth trying, if the binary size is very important and the application can be reliably tested afterwards, as link-time optimized code is hard to debug. A bootloader can be an ideal example. LTO is very easy to enable, but there are some small quirks that have to be taken care of. I will use GCC 7.2.1 from GNU Arm Embedded as an example.
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Practical FFT on microcontrollers using CMSIS DSP

Fourier transform is a vast domain of knowledge with many practical applications within signal processing. Virtually all communications protocols use Fourier transform at one step or another (including LTE, GPS and WiFi). Another popular example are the “jumping bars” in music players showing levels of low and high tones in real time. In this post I show the basics of obtaining spectrum of an audio signal on an EFM32 Cortex-M3 microcontroller. No scary math!
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EFM32 Cortex-M firmware project from scratch – step by step

Most popular microcontrollers come with IDEs and tools provided by the manufacturer, like NXP, STM, TI or Silicon Labs. IDEs are commonly based on Eclipse and creating a project for almost any chip in those IDEs is usually just a click away, so why would you ever want to make such a project from scratch, gather all header files, libraries and scripts? Read to find out why and how 🙂
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