Tag Archives: semihosting

Using Semihosting and File I/O in DevContainers

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With Optimizing Embedded Development with VS Code and DevContainer I showed the benefits of using development containers. And with Remote Debugging with DevContainer and VS Code I explained ways use hardware debugging using that concept.

One topic is still open: how to use semihosting with file I/O using development container? The challenge here is that we need to work with two different file systems.

DevContainer Development with File I/O and Semihosting

In this article I show how semihosting file I/O can be used with DevContainer.

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How to Use GNU Coverage (gcov) in a Freestanding Environment for Embedded Systems

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The GNU Coverage (gcov) is a source code analysis tool, and is a standard utility in the GNU gcc suite. It works great in a hosted environment (e.g. Linux or Windows), where you have plenty of resources and a file system. But the gcov tools is relevant and usable for restricted embedded systems too. I have used it for years with the help of debug probes and file I/O semihosting. But semihosting does not come for free, depends on a library with support for constructors and destructors, plus relies on file I/O.

Fortunately, there is a way to use gcov without debugger, semihosting, file I/O and special system initialization: using a freestanding environment:

gcov in freestanding environment with embedded target

This article explains how to collect coverage information using a data stream for example over UART or USB-CDC. Key benefits are less code side, no need for a debugger or on-target file system, improved performance, better automation and flexible data collection.

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Implementing File I/O Semihosting for the RP2040 and VS Code

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I’m working recently on a new lecture module using the Raspberry Pi Pico (RP2040) board, which highlights several aspects of modern software engineering, including DevOps and CI/CD. An important part of any CI/CD pipeline is testing. For a host application, one could pass arguments to the application, e.g. ‘myapp --test=module1‘, or let it read such information from a configuration file which describes the tests. Or write GNU gcov data to a file to collect coverage information.

Unfortunately, a normal embedded application has no argv[], and many system have no file system. A solution to this problem would be using semihosting with file I/O. Unfortunately for the Raspberry Pi Pico SDK 1.5.1 for the RP2040, there is no semihosting file I/O implemented :-(.

I have now implemented and added file I/O to the SDK, making it possible for the RP2040 to access and use files on the host, among other things. This greatly extends the capabilities of the device, and is very useful for testing, including gathering test coverage information.

RP2040 writing files on the host with semihosting
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Semihosting with VS Code on RP2040

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With semihosting I can use standard I/O function like printf() and I can read and write data on the host through the debug connection. If used with care, this is a great feature especially for unit testing.

Raspberry Pi Pico-W (RP2040) board
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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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Silicon Shortage and Semihosting with NXP MCUXpresso SDK on FRDM-KE02Z

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The silicon shortage is still going on. While the NXP Kinetis KE devices might not be my first choice, they still seem to be available, in at least in lower quantities. This has been recognized by others, as I’m getting more and more questions and requests for the KE and KV family. This is why I un-dusted my old FRDM-KE02Z to be used with the latest MCUXpresso SDK and IDE.

FRDM-KE02Z Board

And in case you want to use that board or device with semihosting, I have you covered.

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Semihosting with Eclipse and the NXP Kinetis SDK V2.0

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The world is changing, and the say is “change is good” :-). In the software and API world, change very often means that a change results into something broken. So I had battled with semihosting working on the NXP Kinetis parts, only to find out that it does not work any more with using the latest version 2.0. The semihosting output e.g. with P&E debug connection remains empty:

No Semihosting output

No Semihosting output

So how to fix this?

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