I’m using in several projects different variants of Raspberry Pi boards: they are great and providing a lot of processing power. However, they are not suitable for any hard realtime systems. For a different class of projects I’m currently evaluating the NXP i.MX7 processors: the cool thing with these is that they have up to two ARM Cortex-A7 running at 1 GHz, plus a Cortex-M4 running at 200 MHz. And here things get really interesting: I can run a realtime application and FreeRTOS on that M4, while running Linux on the A7🙂.
As a standard procedure, I add some console functionality to my embedded applications. That way I have a command line interface and can inspect and influence the target system. One interesting hardware feature of ARM Cortex-M is Single Wire Output (SWO): it allows to send out data (e.g. strings) over up to 32 different stimulus ports, over a single wire.
The Carlina Aucalis (we call it locally the “Silberdistel”) is native to alpine regions in central Europe. When all the other flowers disappear in fall time, the Silberdistel is worth a stop while hiking in higher alpine regions.
From time to time I face some problems which are really hard to find. Mostly these kind of bugs are very timing sensitive and depend on interrupt execution order. Maybe a dangling pointer is overwriting memory, code is running wild, or some functions are not reentrant as they should be. For these kind of bugs, good tools are worth their weight in gold. The Percepio FreeRTOS+Trace and the Segger SystemView have helped me many times to narrow down such kind problems in my applications. Another ultimate tools is hardware trace: Now I have a Segger J-Trace Pro for ARM Cortex-M in my arsenal of bug extinguishing weapons on my desk:
Dear bugs, look what I have on my desk. Your hiding time is over!🙂
Playing with RFID and NFC is definitely fun🙂, and they are everywhere! For a research project I’m exploring different RFID tags and solutions. I several types around for a long time, but never found the time to actually work on it, so last nightI thought I give it a try, and I have it working with GNU ARM and Eclipse, powered by the NXP FRDM-K64F board🙂
The past weeks have been extremely busy with the new semester started. As a result, no time for new posts on this blog for nearly three weeks😦.
Until my projects-in-progress about MQTT, Time-of-Flight sensors, LoRa (long range) wireless networking and a cool robotics project are ready, here is something to share with you all: a cool time-lapse video of my home and work area, created by Pirmin Henseler: 2 years, 30’000 pictures, 2 broken cameras, and the result is amazing:
This is the third part about ARM Cortex-M and how the interrupts are used. In Part 1 I discussed the Cortex-M interrupt system and in Part 2 I showed nested interrupt examples. This part is about FreeRTOS and how it uses the Cortex-M interrupt system.
In “ARM Cortex-M, Interrupts and FreeRTOS: Part 1” I started with the ARM Cortex-M interrupt system. Because the ARM implementation cann be very confusing, I confused myself and had to fix and extend the description in Part 1🙂. Thank for all the feedback and comments!
Originally I wanted to cover FreeRTOS in Part 2. Based on the questions and discussions in Part 1 I thought it might be a good idea to provide visual examples.
When I have hit ‘publish’ for this post, the McuOnEclipse blog exists for exactly 0x888888 seconds. Or almost. I admit there might be a latency of a few seconds. But hey, that’s still a good (hexadecimal) number!🙂.
I would like to reach out about what you would like to see on McuOnEclipse in a not too distant future:
What do you like the most?
About what should I write more?
Any other subject or topic you would like to see?
Add a comment if you have anything else on your mind.
The ARM Cortex-M microcontroller are insanely popular. And it features a flexible and powerful nested vectored interrupt controller (NVIC). But for many, including myself, the Cortex-M interrupt system can be counter-intuitive, complex, inconsistent and confusing, leading to many bugs and lots of frustration😦.
ARM Cortex-M7: NXP KV58
Understanding the NVIC and the ARM Cortex-M interrupt system is essential for every embedded application, but even for if using an realtime operating system: if you mess up with interrupts, very bad things will happen….