Category Archives: Tips & Tricks

Getting Started: ROM Bootloader on the NXP FRDM-KL03Z Board

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A bootloader on a microcontroller is a very useful thing. It allows me to update the firmware in the field if necessary. There are many ways to use and make a bootloader (see “Serial Bootloader for the Freedom Board with Processor Expert“). But such a bootloader needs some space in FLASH, plus it needs to be programmed first on a blank device, so a JTAG programmer is needed. That’s why vendors have started including a ROM bootloader into their devices: the microcontroller comes out of the factory with a bootloader in FLASH. So instead writing my bootloader, I can use the one in the ROM.

FRDM-KL03Z with ROM Bootloader

FRDM-KL03Z with ROM Bootloader

And as with everything, there are pros and cons of that approach.

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Compiler Explorer

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If you are like me – someone who always wants to know what the compiler generates for a piece of source code – then have a look at the Compiler Explorer: A web-based compiler code comparison tool:

Compiler Comparison

Compiler Comparison

Thanks to Matt Godbolt, I can select different compilers and compare their output for a given source code. Very useful to see the impact of a compiler optimization or to compare different GCC compiler versions.

Happy Comparing 🙂

Using FreeRTOS with newlib and newlib-nano

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For reliable applications, I avoid using functions of the standard libraries. They are banned for most safety related applications anyway. I do not use or avoid malloc(), printf() and all the other variants, for many reasons including the ones listed in “Why I don’t like printf()“. Instead, I’m using smaller variants (see “XFormat“). Or I’m using only the thread-safe FreeRTOS heap memory allocation which exist for many good reasons.

Things get problematic if malloc() still is pulled in, either because it is used by a middleware (e.g. TCP/IP stack) or if using C++. Dave Nadler posted a detailed article (http://www.nadler.com/embedded/newlibAndFreeRTOS.html) about how to use newlib and newlib-nano with FreeRTOS.

FreeRTOS Newlib Memory Allocation Scheme

FreeRTOS Newlib Memory Allocation Scheme

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Transforming Eclipse Linked Projects into Standalone Projects

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Some silicon vendors provide their Eclipse example and SDK projects using linked files and folders. For example a bootloader demo application is provided in the context of an SDK or library. That’s fine until the time I want to transform such an example into a real project or if I want to have it without the hundreds of files for all the other devices I don’t need or use. I cannot take the project and put it into a version control system as the linked files won’t be in my VCS. I cannot move the project to another place as the links are pointing to many places. What I need is a ‘standalone’ project: a project which has all the needed files in it and is self-containing.

Eclipse Project with Linked Files

Eclipse Project with Linked Files and virtual groups

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Experimental Smokerless Pulled Pork Sous-Vide Style

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Don’t get me wrong. I love a good slow-smoked and true BBQ pulled pork shoulder just as probably everyone else out there. And I love the babysitting (aka beer drinking 🙂 ) while the shoulder gets that incredible taste inside the smoker. But my workload for this weekend is insane high with all the university exam and grading work. My family loves that pulled pork too, and I knew upfront that I would not have the time to check and handle the smoking process for 12-18 hours (see “Easter Weekend Apple Juice Brined Pulled Pork Smoked on Beech Wood“). So I decided to prepare pulled pork the ‘easy’ way: Using a Sous Vide cooker and then use a normal oven to finish it. So it was an experiment, and the result is interesting:

Pulled Pork on Toast

Pulled Pork on Toast

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Zooming In and Out of Text with Eclipse

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I like to have as many lines of source code visible on my notebook or desktop monitor. And I think I have found a good balance between font size and readability.

On the other side: I’m getting older and my eyes are not getting any better. At the same time I noticed that students start using these ‘high-resolution-retina-displays’. They are great, but result in tiny default system fonts, so I have a hard time to read the source code on their machines.

Another challenge I noticed are the high-resolution projectors in class rooms or conferences. They are not well suited to show source code or text files because of the tiny fonts. Starting with Eclipse Neon there is an awesome feature which I can use to dynamically increase and decrease the font size which solves that problem:

Eclipse with Large Font Size

Eclipse with Large Font Size

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Adding GNU Coverage Tools to Eclipse

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The GNU tools include powerful utilities to collect coverage information. With coverage I know which lines of my code have been executed, which is a very useful test metric. The GNU coverage tools are commonly used for Linux applications. But to my surprise not much for embedded application development, mostly because it requires a few extra steps to have it available? Why not using free and powerful tools for improving software quality? This article explains how to install the GNU gcov tools into the Eclipse IDE.

gcov with Embedded Target

gcov with Embedded Target

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ARM SWO Performance Counters

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In “Cycle Counting on ARM Cortex-M with DWT” I have used the ARM DWT register to count the executed cycles. With the MCUXpresso IDE comes with a very useful feature: it can capture the ARM SWO (Single Wire Output) trace data. One special kind of trace data is the ‘cycle counter’ information which is sent through SWO.

SWO Counters

SWO Counters

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2017 Spring Semester Sumo Challenge

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The spring university semester is coming to an end, and the Infotronic course closed with a Sumo robot challenge. Great challenge, new technologies, innovative approaches and funny designs 🙂

Groot

Groot

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