Disabling NMI (Non Maskable Interrupt) Pin

The NMI is a special interrupt on ARM Cortex-M architecture: as the name indicates, it cannot be ‘masked’ by the usual ‘disable interrupts’ flags (PRIMASK, BASEPRI), similar to the Reset signal.

cortex-m-vector-table

cortex-m-vector-table (Source: adapted from arm.com)

Dealing with the reset signal is kind of obvious, and most designs and boards have it routed to a reset button or similar. The NMI is less obvious if you don’t pay attention to it: most ARM-Cortex implementations and boards have the NMI signal routed to a pin and are ‘hiding’ it in the schematics behind a normal GPIO pin or port: if you don’t pay attention to the NMI functionality, the board might not work as intended.

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Behind the Canvas: Making of “60 Billion Lights”

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.

Make it

Writing text

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McuLog: Logging Framework for small Embedded Microcontroller Systems

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.

Log Output

Log Output

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Tutorial: Adding FreeRTOS to where there is no FreeRTOS

FreeRTOS is pretty much everywhere because it is so simple and universal, and it runs from the smallest to the biggest systems. But it still might be that for the microcontroller device you have selected there is no example or SDK support for it from your vendor of choice. In that case: no problem: I show how you could easily add FreeRTOS plus many more goodies to it.

Binky on NXP LPC845-BRK Board

Binky on NXP LPC845-BRK Board

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FatFS, MinIni, Shell and FreeRTOS for the NXP K22FN512

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.

FRDM-K22F with SD Card

FRDM-K22F with SD Card

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FreeRTOS Task Runtime Statistics for NXP i.MX RT1064

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.

FreeRTOS Runtime Information

FreeRTOS Runtime Information

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Dumping Variables and Arrays with GDB in Eclipse

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.

GDB Debugger Console in Eclipse

GDB Debugger Console in Eclipse

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Tutorial: Rename, Copy or Clone Eclipse Projects with MCUXpresso

Especially in a lab or classroom environment it is convenient to start with a template project, and then explore different ways to shape the project for different needs. As for any IDE of this world, this requires an understanding of the inner workings to get it right. So in this article I show how to copy, clone or rename properly an Eclipse ‘template’ project in the MCUXpresso IDE.

Template Project

Template Project

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Optimized and Easy-to-Use Eclipse Toolbars and Menus

I love Eclipse because as an IDE it can do pretty much everything. Up to the point that some call it an ‘Eierlegende Wollmilchsau‘: something which can do anything. But with all the tools, menus and features, it can be daunting for a someone new to Eclipse. But the good news is: Eclipse is very versatile and can be customized to make it easier and simpler to use too. In this article I show how I’m tweaking it the way I want it, with just the menus and buttons I need:

Eclipse Optimized Menus and Toolbars

Eclipse Optimized Menus and Toolbars

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Visualizing Data with Eclipse, gdb and gnuplot

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.

Gnuplot with Eclipse

Gnuplot with Eclipse

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Enable Default FreeRTOS Debugging for LinkServer Debug Connections

Most of my projects are using FreeRTOS, and I’m using different Debug Probes (SEGGER, P&E and LinkServer) to debug NXP devices.

The NXP LinkServer debug connection is able to show the RTOS threads in Eclipse/MCUXpresso IDE which is incredibly helpful:

FreeRTOS Thread Aware Debugging with LinkServer Connection

FreeRTOS Thread Aware Debugging with LinkServer Connection

However, by default this is turned off. In this article I show how to turn this on by default.

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MCUXpresso IDE V11.1.0

Right before Christmas 2019, NXP has released a new version of the MCUXpresso IDE, the version 11.1.0. This gave me time to explore it over the Christmas/New-Year break and evaluate it for the next university semester. There are several new features which will make my labs using it easier, so I plan to get the course material updated for it.

MCUXpresso IDE V11.1.0 Welcome Screen

MCUXpresso IDE V11.1.0 Welcome Screen

After the break you will find the highlights …

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Implementing FreeRTOS Performance Counters on ARM Cortex-M

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

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.

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DIY ‘Meta Clock’ with 24 Analog Clocks

Human since 1982 claims

“Human since 1982 have the copyright to works displaying digital time using a grid arrangement of analog clocks…”

I’m not a lawyer, but without obligations (imho) I have removed the content.

Thanks for understanding,

Erich

World Stepper Clock with NXP LPC845

I really love clocks. I think this is I am living here in Switzerland. Beside of that: clock projects are just fun :-). After I have completed a single clock using stepper motors (see “DIY Stepper Motor Clock with NXP LPC845-BRK“), I wanted to build a special one which is able to show up to four different time zones: Below an example with London (UK), New York (USA), Beijing (China) and Lucerne (Switzerland):

Stepper Clock

Stepper Clock

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Open Source FTDI FT2232 JTAG and UART Adapter Board

In JTAG Debugging the ESP32 with FT2232 and OpenOCD I have used a FTDI FT2232 breakout board to JTAG debug with OpenOCD. With an adapter board on top of the TDI FT2232 the wiring is much easier and simpler to use:

JTAG Debugging the ESP32 with FT2232

JTAG Debugging the ESP32 with FT2232

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Using SEGGER J-Link with QSPI FLASH on NXP i.MX Boards

In “Seeed Studio Arch Mix NXP i.MX RT1052 Board” and “Debug and Execute Code from FLASH on the Seeed Arch Mix NXP i.MX RT1052 Board” I have used the NXP LPC-Link2 to debug the Seeed Arch Mix board with the NXP i.MX RT1052, because the SEGGER J-Link does not work out-of-the box with the i.MX RT using QSPI Flash. This article shows how the J-Link connection can be changed from HyperFlash to work with QSPI Flash.

J-Link EDU Mini with Seeed i.MX RT1052

J-Link EDU Mini with Seeed i.MX RT1052

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JTAG Debugging the ESP32 with FT2232 and OpenOCD

In “Eclipse JTAG Debugging the ESP32 with a SEGGER J-Link”  I used a SEGGER J-Link to debug an ESP32 device with JTAG. I looked at using one of the FTDI FT2232HL development boards which are supported by OpenOCD. The FT2232HL is dual high-speed USB to UART/FIFO device, and similar FTDI devices are used on many boards as UART to USB converters. With OpenOCD these devices can be turned into inexpensive JTAG debug probes. This article shows how to use a $10 FTDI board as JTAG interface to program and debug the Espressif ESP32.

FTDI JTAG Connection

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Stack Canaries with GCC: Checking for Stack Overflow at Runtime

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

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

Eclipse JTAG Debugging the ESP32 with a SEGGER J-Link

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.

Roboter with ESP32 and JTAG Debug Port

Robot with ESP32 and JTAG Debug Port

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