COVID-19 is by far not over, and in Switzerland the infection rate is going up again (2nd wave?). During the spring 2020 semester university lock-down we moved pretty much everything to a ‘distance learning’ setup. With that experience and with the request to prepare for the fall semester, I have constructed a DIY conference and teaching device which should make things simpler and easier: a combination of video camera, speaker phone and a muting device:
This is a follow-up article of my earlier project presented in “FatFS, MinIni, Shell and FreeRTOS for the NXP K22FN512“. I wanted to extend it with a USB MSD (memory stick) device: The USB storage device gets automatically mounted, and depending on a configuration (.ini) file on the memory device I can perform various actions, for example automatically copy data from the SD card to the USB device. For example the system logs data, and to get the data I insert the memory stick, it copies the data on it and automatically unmounts it, and I can remove the memory stick.
As promised I’m going to share more details about the “60 Billion Lights” project. It is about a project to build a piece of electronics behind a 100×50 cm canvas to show animations or to display information like temperature, humidity, weather, time or just any arbitrary text.
An essential tool especially developing larger applications or distributed firmware is to use logging. This article presents an open source logging framework I’m using. It is small and easy to use and can log to a console, to a file on the host or even to a file on an embedded file system as FatFS.
I’m using the NXP Kinetis K22FN512 in many projects, either with the FRDM-K22F or on the tinyK22: with 120 MHz, 512 KByte FLASH and 128 KByte it has plenty of horsepower for many projects. The other positive thing is that it is supported by the NXP MCUXpresso IDE and SDK. I have now created an example which can be used as base for your own project, featuring FreeRTOS, FatFS, MinIni and a command line shell.
OpenPnP is a great open source framework for building a DIY SMT Pick&Place machine. But it does not stop there: It is possible to use OpenPnP with a commercial pick & place machine, for example the Charmhigh CHM-T36VA. This Chinese machine comes with its own controller software which works but is not that great. The good news is that it is possible to hack and retrofit the machine so it can run the much more powerful OpenPnP.
FreeRTOS has many cool features, and one is that it can report the CPU percentage spent in each task. The downside is that to get this kind of information some extra work is needed. In this article I show how to do this for the NXP i.MX1064.
Using the debugger to inspect the application data is a very convenient thing. But if the data grows and if the data set is large, it makes more sense to dump the data to the host and process it offline. GDB is the de-facto debugger engine and includes a powerful command line and scripting engine which can be used in Eclipse too.
Maker spaces and ‘FabLabs’ are popular and accessible in many areas. 3D printers are on the cheap, and powerful laser cutters are in the range of the fearless hobbyist. You can get dirty-cheap PCBs from China in less than a week (ok, probably not right now because of Corona virus) and it is easy to SMD solder parts these days with a DIY SMD PnP machine and OpenPnP. With the right equipment and skill set it is possible to build many cool projects. It is very rewarding and a great learning thing. Blog about it so other can learn too. And it even could get featured on Hackaday.
But: The risk is that someone might send you letter about a ‘Copyright Infringement’. Sadly, this is what happened to me for one of my recent projects. I don’t think that ‘take down’ letter was justified, but I learned a great deal what I should have done differently to avoid that situation. So in the end, it was a learning opportunity, which I believe is worth to share. In essence: what can a maker or educator do?
Hackaday: building a giant meta-clock made of smaller clocks (image: original image from Hackaday)
The gnuplot is a versatile and powerful tool to plot and visualize all kind of data. I wish there would be a plugin for it in Eclipse. But as this is not (yet?) the case, here is how I’m using it with gdb and Eclipse, using the MCUXpresso IDE as example.
One great feature of Eclipse is its built-in spell checking engine. So no more excuses are possible for typos in the source code ;-). Eclipse scans the source code in the background and offers to correct it:
When using an RTOS like FreeRTOS, sooner or later you have to ask the question: how much time is spent in each task? The Eclipse based MCUXpresso IDE has a nice view showing exactly this kind of information:
FreeRTOS Runtime Information
For FreeRTOS (or that Task List view) to show that very useful information, the developer has to provide a helping hand so the RTOS can collect this information. This article shows how this can be done on an ARM Cortex-M.
Stack overflows are probably the number 1 enemy of embedded applications: a call to a a printf() monster likely will use too much stack space, resulting in overwritten memory and crashing applications. But stack memory is limited and expensive on these devices, so you don’t want to spend too much space for it. But for sure not to little too. Or bad things will happen.
The Eclipse based MCUXpresso IDE has a ‘Heap and Stack Usage’ view which can be used to monitor the stack usage and shows that a stack overflow happened:
Heap and Stack Usage
But this is using the help of the debugger: how to catch stack overflows at runtime without the need of a debugger? There is an option in the GNU gcc compiler to help with this kind of situation, even if it was not originally intended for something different. Continue reading →
That machine has now been modified to dispense solder paste. I did not had time yet to describe the build, but as I have received recently many questions: here are some pre-information about the build:
The ‘Black Magic Probe’ (or in short: BMP) is a very small and open source JTAG/SWD debug probe with a build-in GDB Server. I saw that probe referenced in different places, so I thought I try it out with a few of my NXP LPC and Kinetis boards: