“There is no ‘S’ for Security in IoT” has indeed some truth. With all the connected devices around us, security of code should be a concern for every developer. “Preventing Reverse Engineering: Enabling Flash Security” shows how to prevent external read-out of critical code from device. What some microcontroller have built in is yet another feature: ‘Execute-Only-Sections‘ or ‘Execute-Only-Memory‘. What it means is that only instruction fetches are allowed in this area. No read access at all. Similar like ‘read-only’ ‘execute-only’ it means that code can be executed there, but no other access from that memory is allowed.
In this article I describe the challenges for a toolchain like the GNU gcc, and how to compile and link code for such an execute-only memory.
In the C programming language it is good practice to pass values by reference (using a pointer), especially for large set of data. For example the following function takes a message string and pointer to integer data which then is printed to the console:
’m pleased to announce that a new release of the McuOnEclipse components is available in SourceForge. This release includes several smaller bug fixes and initial component support for the NXP S32 Design Studio and SDK.
The ARM DWT (Data Watchpoint and Trace) is an optional feature of the ARM-Cortex-M, and many Cortex-M3, M4 and M7 devices have it implemented. With it comes a cycle counter which counts the cycles spent. In Cycle Counting on ARM Cortex-M with DWT I described an approach how the application on the target can access the cycle counter.
The MCUXpresso IDE shows that cycle counter in the Eclipse Registers view:
Is BLACK the color of the season? My students really seem to love these ‘dark’ Eclipse themes. Well, I tried ‘dark’ themes in the past, but I have not been vey excited about it. Somehow I preferred more the ‘black on white background’ thing. But: I have now managed to install the ‘Darkest Dark’ Eclipse theme into the NXP MCUXpresso 10.2 IDE for my daily work, and I feel it hurts my eyes less? Maybe I’m getting older? Or could it really be that ‘dark’ look and feel?
By default, the GNU compiler (gcc) optimizes each compilation unit (source file) separately. This is effective, but misses the opportunity to optimize across compilation units. Here is where the Link Time Optimization (LTO, option -flto) can help out: with a global view it can optimize one step further.
The other positive side effect is that the linker can flag possible issues like the one below which are not visible to the compiler alone:
type of '__SP_INIT' does not match original declaration [enabled by default]
Hardware Timers are essential to most embedded applications: I use them mostly for triggering actions at a given frequency, such as acquiring data from a sensor. With using an RTOS I can do a similar thing using a task: the task will run with a given frequency and I can periodic work in it. However, using a task might be too much overhead doing this. The good news is that there is a much more efficient way to do this in FreeRTOS with Software Timers. And this is what this tutorial is about: how to use Software Timers with FreeRTOS.
When using the FreeRTOS Task List in the Eclipse based MCUXpresso IDE, it shows the list of tasks with their stack size used. But with the default FreeRTOS settings it is not able to determine the correct stack size and shows a warning icon:
Using IP (Ethernet) based debug probes is a very handy thing: I don’t have to be directly connected to the debug probe (e.g. with the USB cable). This article explains how to use an IP-based Segger or P&E probe with the Eclipse based MCUXpresso IDE.
The map file produced by the GNU linker includes lots of information, however it is very cryptic to read. In “Listing Code and Data Size for each Source File with GNU and Eclipse” I showed how the GNU size utility can be used to report the code and data size for each object file. The Eclipse based MCUXpresso IDE comes with another nice view which shows detailed information about code and data allocation:
It’s April Fool’s Day, but be assured this is not a joke ;-): I’m pleased to announce that a new release of the McuOnEclipse components is available in SourceForge. This release includes several smaller bug fixes and components have been upgraded for FreeRTOS V10.0.1.
One of the great things with the FreeRTOS operating system is that it comes with free performance analysis: It shows me how much time is spent in each task. Best of all: it shows it in a graphical way inside Eclipse too:
The Teensy boards are great, but as they are they are not really useful for real development, as they lack proper SWD debugging. In “Modifying the Teensy 3.5 and 3.6 for ARM SWD Debugging” I have found a way to get SWD debugging working, at that time with Kinetis Design Studio and the Segger J-Link. This article is about how debug the Teensy with free MCUXpresso IDE and the $20 NXP LPC-Link2 debug probe:
“Amazon FreeRTOS – IoT operating system for microcontrollers”: The announcement of FreeRTOS V10.0.0 was one of the biggest news last week for me. Not only is there now a Version 10, the bigger news is that FreeRTOS is now part of Amazon. Wow! Now this explains why Richard Barry (the founder behind FreeRTOS) was kind of hiding away for about a year: he joined Amazon as a principal engineer about a year ago. I think we all have to wait and see what it means for FreeRTOS.