Using Semihosting the direct Way

Posted on March 9, 2023 by Erich Styger

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:

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

Posted on February 19, 2023 by Erich Styger

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?

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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Adding the Picolib C/C++ Standard Library to an existing GNU ARM Embedded Toolchain

Posted on February 9, 2023 by Erich Styger

It looks like my previous article “Which Embedded GCC Standard Library? newlib, newlib-nano, …” stirred up something: I saw and knew about the Picolib created and maintained by Keith Packard, but never had the time to try it out. With the university grading mostly over, I have put aside a few hours to try it out. And the result is very interesting:

Footprint of different embedded libraries

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Debugging Embedded Targets with pyOCD and Eclipse

Posted on February 5, 2023 by Erich Styger

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

Posted on January 29, 2023 by Erich Styger

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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NXP MCUXpresso IDE 11.7.0

Posted on January 25, 2023 by Erich Styger

It is the exam and grading time at the university, and the same time I’m preparing the lectures and labs for the new semester starting mid of February. I’m always heading for using the latest and greatest tools in my labs. A few days ago, NXP released the new version of the MCUXpresso IDE, version 11.7.0. Time to check it out…

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Loading Multiple (Binary) Files with GDB

Posted on November 1, 2022 by Erich Styger

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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Picoprobe: Using the Raspberry Pi Pico as Debug Probe

Posted on September 17, 2022 by Erich Styger

In Getting Started: Raspberry Pi Pico RP2040 with Eclipse and J-Link I used a SEGGER J-Link EDU for debugging: unfortunately, probably because of silicon shortage, these EDU probes are out of stock everywhere. Luckily, there is a solution: just use another Raspberry Pi Pico!

This turns a $5 Raspberry Pi Pico board in to a very usable and versatile debug probe.

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Tutorial: Creating Bare-bare Embedded Projects with CMake, with Eclipse included

Posted on September 4, 2022 by Erich Styger

MCU vendors offer SDKs and configuration tools: that’s a good thing, because that way I can get started quickly and get something up and running ideally in a few minutes. But this gets you into a dependency on tools, SDK and configuration tools too: changing later from one MCU to another can be difficult and time consuming. So why not get started with a ‘bare’ project, using general available tools, just with a basic initialization (clocking, startup code, CMSIS), even with the silicon vendor provided IDE and basic support files?

In this case, I show how you easily can do this with CMake, make and Eclipse, without the (direct) need of an SDK.