After the Getting Started material from the previous weeks, today we are ready to investigate TrustZone®. We all remember TrustZone® – it is that magic piece of embedded IP that miraculously solves all of our IOT security problems – right? It’s true that TrustZone® is an embedded component related to security, but not in the way that you think.
Before we get stuck into all the fancy technical details, let us at first stop and think about some of the challenges that we face with embedded systems, and what can be done about them. This week I simply address the topic: What is TrustZone® and Why do we need it??
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 →
Clocks. I’ve always found the clock setting of a microcontroller one of the hardest things to get right during my embedded career. If I re-use the clocks setup from the development board it is easy. But if the development board runs from a crystal and I want to use the free-running internal clock, or if I change to a different frequency crystal (and keep the same PLL output frequency) it always gets difficult. To be honest I’ve developed some projects early in my career and never been 100% certain at what frequency the core, flash and peripherals are running.
That’s not good.
The Config Tools within the MCUXpresso brand have greatly simplified setting up the pins, clocks, peripherals (and next week – Trusted Execution Environment 🙂 ) on NXP microcontrollers. So I’m going to quickly show you how to set up 3 different clock arrangements, and output the main clock to an output pin named CLK_OUT.
When Espressif released in 2014 their first WiFi ESP8266 transceiver, they took over at least the hobby market with their inexpensive wireless devices. Yet again, the successor ESP32 device is used in many projects. Rightfully there are many other industrial Wi-Fi solutions, but Espressif opened up the door for Wi-Fi in many low cost projects. Many projects use the ESP devices in an Arduino environment which basically means decent debugging except using printf() style which is … hmmm … better than nothing.
What is maybe not known to many ESP32 users: there *is* actually a way to use JTAG with the ESP32 devices :-). It requires some extra tools and setup, but with I have a decent Eclipse based way to debug the code. And this is what this article is about: how to use a SEGGER J-Link with Eclipse and OpenOCD for JTAG debugging the ESP32.
Well let’s face it, modern microcontrollers are complicated. The User Manual for the LPC55S69 has 1148 pages (Rev 1.3) and that does not include any of the electrical characteristics – see the Datasheet (129 pages) nor does it include the details around the core or instruction set (see ARM documentation) . So there is a lot of technical information to read, and don’t get me started on the pin multiplexing… Well actually, do get me started on the pin multiplexing because that is my focus this week.
This week I turned my attention to writing a very simple example project in MCUXpresso IDE to run on the ARM Cortex® M33 core inside the LPC55S69. As in previous weeks I am again using the LPC55S69-EVK from NXP. My plan is to use this board every week but I have learned recently a few details about a new ultra-low-cost board. It’s going to be AMAZING and I’ll share more details with you when I can.
This is the second of my 17-part video tutorial series investigating the ARM Cortex® M33 core with TrustZone® security extension. My preferred platform for this investigation is the LPC55S69 from NXP, and of course it is necessary to have a development board and IDE. So I’m using the LPC55S69-EVK with NXP’s MCUXpresso IDE and the MCUXpresso Software Development Kit (SDK).
This week the video is really low on theory, but high on practical, step-by-step information to get started with these tools. Maybe you are similar to me, and make the same mistake every time?? I get the self-assembly furniture home from the store, or open the box containing the new development board and just get started. At some point it doesn’t work properly and that’s the time I must read the supporting information.
Well, with this video I show you beginning-to-end in just over 10 minutes, and you won’t need to refer to any other material.