In an earlier article I explained how to generate GNU coverage information, for an embedded application written in C.
In this article, I show the steps and configuration needed to use GNU gcov targeting an embedded application with C++.
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:
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.
Continue readingFloat and double data types area a bad choice for embedded applications. At least in most applications, and can or should be avoided, even with hardware FPU support present.
But how can I be sure that no floating point operations are used?
This article describes how to configure the GNU toolchain, so that no float or double operations are used, with the example of ARM Cortex-M. What I do? ‘Poisoning’ (!!!) the source code, force the gcc compiler to use software floating point operations and then catch them with the GNU linker :-).
Continue readingIf one is using a dedicated logger module like the McuLog, then you don’t have to worry or care about timestamp support. But if your application is using normal printf() calls for for logging purpose, you will face issues to adding timestamps to it. You might consider to change all prinft() calls. This might be a lot of work, or not possible in all cases if you cannot change the source code.
But there is a really cool feature of the GNU linker to solve that problem. It allows to ‘wrap’ around any symbol or function, including the ones in the standard library. That way I can add my mode to the printf() code as a wrapper, for example adding a timestamp for every call.
In the example below you can see this in action:
In this article I’ll show how you can wrap any function with custom code.
Continue readingOne little nasty assertion in the GNU standard library appeared a few days ago, kind out of nowhere, reporting “REENT malloc succeeded”:
Obviously it was caused by the call to srand() which sets the ‘seed’ for the standard library (pseudo) random number generator. The assertion happens as well later for calling the rand() function.
Continue readingTool chains like the GNU compiler collection (gcc) have a plethora of options. The probably most important ones are the ones which tell the compiler how to optimize the code. Running out of code space, or the application is not performing well? Then have a look at the compiler optimization levels!
However, which one to select can be a difficult choice. And the result might very well depend on the application and coding style too. So I’ll give you some hints and guidance with an autonomous robot application we use at the Lucerne University for research and education.
You might never heard about ROM Libraries, and you are probably not alone. Some might thing that this refers to the boot ROM modern MCUs have built in, which is kinda close. But the thing here is about to build your own (possibly constant) ROM library, program it to your device of choice, and then use it from the application running on the device.
So the concept is to have a (fixed, stable) part with code and data on your device, which can be used by a (possibly changing) application: Think about a stable LoRaWAN network stack in the ROM, with a changing application using it: Would that not be cool?
This not only adds flexibility, but as well allows smaller updates, as only a part of the program has to be changed or updated.
The question is: how to create and use such a ROM Library with the normal GNU build tools?
Continue readingSometimes it is needed or desired just to add or link a piece of data or BLOB (Binary Large OBject) to the application. For example I have created a .bin file of my code and constant data, and I need to add it to an application using the linker file. How to do this?
This tutorial shows how to use and collect coverage data using the GNU gcov tool. As board and hardaware I’m using the NXP i.MX RT1064 EVK:
While this tutorial uses this specific board, things are pretty generic and should be applicable for any other board or MCU.
Continue readingManaged linker scripts are great on one side: the simplify the otherwise complex GNU linker script handling. On the other side it requires knowledge how to tweak them in case ‘non-standard’ behavior is needed.
MCU on Eclipse 