Tutorial: Catching Rogue Memory Accesses with ARM Watchpoint Comparators and Instruction Trace

In my “Tutorial: Catching Rogue Memory Accesses with Eclipse and GDB Watchpoints” I have used Eclipse/CDT and GDB watchpoints.  I used a conditional watchpoint, but this comes with a performance hit. In this article I show how to use the ARM Cortex trace hardware to catch specific writes to a memory location. Without severe performance degradation. But for this I need a little helper: the DEADBEEF catcher!

0xdeadbeef catcher

0xdeadbeef catcher

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First Steps with the NXP i.MX RT1020 EVK Board

Powerful ARM Cortex-M7 microcontroller are on the rise, bridging the gap between traditional microcontroller and Embedded Linux systems. I already published articles for the NXP i.MX RT1052 which is an ARM Cortex-M7 running at 600 MHz. Because the RT105x is available in BGA196 package only, I have as oredered the i.MX RT 1050 EVK which has a similar device on it, but in LQFP package:

i.MX RT1021

i.MX RT1021

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i.MX RT1050 EVK vs. EVKB

I noticed on Mouser.com that there is a new i.MX RT1050 board: the EVKB one. I have used the EVK (the one without the ‘B’) for several weeks (see “MCUXpresso IDE V10.1.0 with i.MX RT1052 Crossover Processor” and “Adding a Rocktech Capacitive Touch LCD to the NXP i.MX RT1052 EVK“). I needed anyway a second board, so I ordered that EVKB from Mouser, and after some delay and waiting it arrived on my desk. So far this boards seems to be a better one:

i.MX RT1050 EVKB Board

i.MX RT1050 EVKB Board

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MCUXpresso IDE 10.2.1

NXP has just released the 10.2.1 update of their flagship Eclipse based IDE. While the number increase from 10.2.0 to 10.2.1 indicates a minor release, there are a several things which make me move over to that new release.

MCUXpresso IDE 10.2.1 build 795

MCUXpresso IDE 10.2.1 build 795

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Adding a Rocktech Capacitive Touch LCD to the NXP i.MX RT1052 EVK

It is never too early to start thinking about Halloween projects :-).

rended Eyes with i.MX RT

rendered Eyes with i.MX RT

When I ordered originally the MIMXRT1050-EVK from Mouser, it was without the LCD display (see “MCUXpresso IDE V10.1.0 with i.MX RT1052 Crossover Processor“. I ordered the LCD for the board soon after writing that article, but I was too busy with the university lectures and exams to get a hand on it. Finally I have spent a few hours at night and I proudly can say: the display is working 🙂

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Updating the S32K144EVB to Switch between 5V and 3.3V Logic Levels

By default, the NXP S32K144EVB and microcontroller is using a 5V supply voltage and logic levels which is great for noisy environment or any 5V devices. Many of my displays and sensors use 3.3V logic levels, so I would have to use a level shifter from 5V to 3.3V. There is another way: to change the board for 3.3V logic levels so I can use directly things like a SSD1306 display.

S32K144EVB with OLED SSD1306 using 3.3V Logic Levels

S32K144EVB with OLED SSD1306 using 3.3V Logic Levels

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Using custom FreeRTOS with S32K SDK and OSIF for ARM

In “Tutorial: FreeRTOS 10.0.1 with NXP S32 Design Studio 2018.R1” I showed how to use a custom FreeRTOS with the S32 Design Studio (ARM). The OSIF (OS Interface) provides an operating system and services abstraction for the application which is used by other S32K SDK components:

OSIF in S32K for ARM Eclipse Project

OSIF in S32K for ARM Eclipse Project

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Execute-Only Code with GNU and gcc

“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.

Locked Code

Locked Code

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.

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Tutorial: FreeRTOS 10.0.1 with NXP S32 Design Studio 2018.R1

NXP not only sells general purpose microcontroller, but as well a portfolio of automotive devices which includes the S32K which is ARM Cortex based. For this device family, they offer the S32 Design Studio (or S32DS) with its own Eclipse distribution and SDK. The interesting part is that the S32DS includes Processor Expert (which is a bit different from the ‘mainstream’ Processor Expert). It comes with its own components for the S32K SDK which includes a component for FreeRTOS. But that component in S32DS 2018.R1 comes with an old V8.2.1 FreeRTOS component:

FreeRTOS 8.2.1 in S32DS 2018.R1

FreeRTOS 8.2.1 in S32DS 2018.R1

So what to do if I want to use the latest FreeRTOS (currently 10.0.1) with all the bells and whistles?

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Show FreeRTOS Threads in Eclipse Debug View with SEGGER J-Link and NXP S32 Design Studio

By default, the FreeRTOS threads do not show up with the SEGGER J-Link debug connection in the Eclipse based NXP S32 Design Studio IDE. But don’t worry: Here is how to get it working with SEGGER J-Link debug connection:

FreeRTOS Threads in Eclipse Debug View

FreeRTOS Threads in Eclipse Debug View

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Measuring ARM Cortex-M CPU Cycles Spent with the MCUXpresso Eclipse Registers View

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:

Cycle Counter in Register View

Cycle Counter in Register View

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GNU Link Time Optimization finds non-matching Declarations

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]
Warning by LTO

Warning by LTO

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Understanding FreeRTOS Task Stack Usage and Kernel Awareness Information

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:

Warning for Stack Usage

Warning for Stack Usage

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Overview of MCUXpresso IDE v10.2.0

Decisions, decisions! Such long weekends like Pentecost are a real challenge for a family with engineers:

  1. Should we join that record long traffic jam to Italy and be stuck for more than 4 hours and analyze it?
  2. Or: should we stay home, turn the BBQ smoker engine on fire, load it with baby back pork rib racks for a slow-and-low smoke treatment, while doing some on-the-side IDE and technology exploration?

Well, my family vote was kind of clear: they have chosen that second option. Not to mention that hidden technology piece in it, but that was part of the deal ;-).

And I’m sorry: this article is not about BBQ (for this see “Smoking BBQ Baby Back Ribs – Swiss Style“), it is about technology: I’m using the NXP MCUXpresso IDE and tools for many of my projects (see “Eclipse MCUXpresso IDE 10.1 with integrated MCUXpresso Configuration Tools“). Right before the this extended weekend, NXP has released the new v10.2.0 version, so here is where that technology exploration piece comes into play. Checking the release notes, this version number change includes so many cool stuff I decided to have a look and to check it out. Of course always having an electronic eye on the baby back ribs!

MCUXpresso IDE v10.2.0

MCUXpresso IDE v10.2.0

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Debugging ARM Cores with IP based Debug Probes and Eclipse

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.

LAN Based Debugging

LAN Based Debugging

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Recovering OpenSDA Boards with Windows 10

Windows 8 and 10 have added a ‘feature’ to scan and index devices attached to the host machine. This means that bootloaders or MSD (Mass Storage Device) programming implementations on evaluation boards developed in the Windows 7 age might not be prepared for that. Up to the point that it can impact the bootloader as outlined in “Bricking and Recovering OpenSDA Boards in Windows 8 and 10“. So far one of the easiest way to get out that situation was to use a Windows 7 machine. But if you only have a Windows 10 machine available, this article describes the needed steps to update the bootloader with Windows 10 host machines.

OpenSDA LED

OpenSDA LED

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Listing Code and Data Size with GNU nm in Eclipse

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:

Symbol Viewer in MCUXpresso IDE

Symbol Viewer in MCUXpresso IDE

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Tutorial: CRC32 Checksum with the KBOOT Bootloader

In “Flash-Resident USB-HID Bootloader with the NXP Kinetis K22 Microcontroller” I presented how I’m using the tinyK22 (or FRDM-K22F) with a flash resident USB HID bootloader. To make sure that the loaded application is not corrupted somehow, it is important to verify it with a Cyclic redundancy Checksum (CRC). The NXP KBOOT Bootloader can verify such a CRC, but how to generate one and how to use it is not really obvious (at least to me), so this article explains how to generate that CRC.

CRC Values for KBOOT

CRC Values for KBOOT

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Flash-Resident USB-HID Bootloader with the NXP Kinetis K22 Microcontroller

The tinyK22 board (see “tinyK22 Boards arrived“) gets rolled out at the Lucerne University of Applied Sciences and Arts, so I thought I write-up an article this weekend how to use that board with a Flash Resident Bootloader.

tinyK22 with USB HID Bootloader

tinyK22 with USB HID Bootloader

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