Tag Archives: Debugging

LinkServer for Microcontrollers

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GDB is the de-facto debugging engine and debug connection for micro-controllers these days: it is versatile and with its client-server architecture very flexible and powerful, and pretty much every debug probe and vendor (PEMICRO, SEGGER, OpenOCD, pyOCD, …) offers it. But a GDB server or command line implementation was not available for the NXP LinkServer family of debug probes (LPC-Link, MCU-Link, MCU-Link Pro). This has changed now: LinkServer is available as command line tool and can be used as GDB Server:

LinkServer as GDB Server with Eclipse

With the new LinkServer package I do not only get a gdb server implementation: I have now a command line tool I can use for automation and all kind of different things: programming boards, erasing flash, and so on.

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Booting J-Link as CMSIS-DAP Debug Probe

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Mostly unnoticed (at least for myself), SEGGER has enabled some of the J-Link debug probes to support the CMSIS-DAP debug protocol.

SEGGER J-Link as CMSIS-DAP Debug Probe

This greatly enhances the use of J-Link debug probes for CMSIS-DAP based tools.

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Added Heap Memory Monitoring and Tracking to FreeRTOS V10.5

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We all should know it: dynamic memory usage can be dangerous. There can be memory fragmentation, use-after-free, out-of-memory and memory leaks. While I do prefer static memory allocation for embedded systems, using a dynamic memory allocation in some applications is not avoidable or just makes sense.

In one of my lecture modules we develop a ‘Boulder’ game, where the player has to collect underground diamonds and avoid moving monsters:

LPC845-BRK with OLED using dynamic memory allocation

I’ll show you have FreeRTOS memory usage can be tracked and monitored.

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Open Source picoLink: Raspberry Pi RP2040 CMSIS-DAP Debug Probe

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One essential part of embedded development is the ability to debug the target application. The good thing with the Raspberry Pi Pico RP2040 Eco-system is: One can use another RP2040 Pico board as a debug probe to debug other ARM Cortex-M devices.

But instead using a Raspberry Pi Pico board with some wires, why not building a dedicated board? The result is a small, versatile and open source debugging probe which virtually can debug any ARM Cortex-M device as a standard ARM CMSIS-DAP probe:

picoLink Debug Probe debugging a Raspberry Pi Pico Board
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RP2040 with PIO and DMA to address WS2812B LEDs

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I love the WS2812B (aka SK6812) addressable LEDs: they are inexpensive and available in different packages. I have used them in different projects, including the MetaClockClock one. I used the NXP Kinetis for these projects, but because they are not available any more, for a new project we had to choose a new microcontroller, with the Raspberry Pi Pico RP2040 as the winner.

Raspberry Pi Pico RP2040 driving WS2812B with PIO and DMA
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Using Semihosting the direct Way

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Most embedded developers have probably used ‘semihosting’. And yes, it is generally seen as a bad thing. Maybe you have used it, without realizing what it really is and what it does. It is simple to add a printf() to the code (again: you should not use printf), and with the right standard library, it magically it shows up in a console view:

printf a hello world

That looks great, but what is behind this, to make it happen? Actually, it is really amazing technology. And it can be used for better things than just printing text.

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Avoiding Stack Overflows: Application Monitoring the Stack Usage

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One of the biggest fears of embedded systems developers are stack overflows. FreeRTOS includes a cool feature to monitor and catch task stack overflows. But what about the MSP (Main Stack Pointer) on ARM, or the interrupt stack? What if not using an RTOS and running a bare-metal application?

Checking stack size used

There is a simple way monitoring stack usage at runtime, and for this I want to share the routines and what is now available inside the McuArm module.

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Debugging Embedded Targets with pyOCD and Eclipse

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If doing embedded development, then the debugging solution is probably the most important single tool in the development chain. Because very debugging probe has its pros and cons, I usually have at least three different debug probes on my desk, simply to get the job done in all aspects.

What is true for the hardware debugging probes, is true for the gdb client and server side. I’m using mostly the P&E, SEGGER and CMSIS-DAP plugins (e.g. NXP LinkServer) and OpenOCD from the Eclipse IDE side. But there are more choices, for example pyOCD.

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ARM SWO ITM Console Bidirectional Standard I/O Retargeting

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The ARM Cortex M architecture has many features which are underused, probably simply because engineers are not aware of it. SWO (Single Wire Output) is a single trace pin of the ARM Cortex-M CoreSight debug block. trace pin uses the ITM (Instruction Trace Macrocell) on ARM Cortex. It provides a serial output channel, at a high speed higher than the usual UART, because it is clocked at half or a quarter of the core clock frequency, depending on the core and implementation.

As such, it is an ideal high speed output channel to send text or data to the host. This is how it is usually used, but what is unknown to many: it can be used in a bidirectional way with the help of the debugger.

The topic of this article: how to redirect standard I/O like printf() or scanf() using the SWO ITM console: means both sending *and* receiving data over the SWO debug channel: that way I can use it as a kind of UART with a single pin only.

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Loading Multiple (Binary) Files with GDB

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A typical debugging session involves just one ELF/Dwarf binary or executable. But what if I need to program multiple binary files with gdb? Things like loading both the bootloader and the application binary? Or I have a an on-chip file system or data section I need to program?

In this article I show how I can use gdb to load and program extra data, like a binary (.bin) file, both using command line interface and using an IDE.

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