Category: Hardware Tools

Tools I use

dw-link: A New Hardware Debugger for ATtinys and Small ATmegas

As mentioned in an earlier blog post this year, hardware debuggers are the premier class of embedded debugging tools. However, until today, there were only very few relatively expensive tools around supporting the debugWIRE interface that is used by the classic ATtinys and a few ATmega MCUs.

The good news is that now you can turn an Arduino Uno, Nano, or Pro Mini into a debugWIRE hardware debugger that communicates with avr-gdb, the AVR version of the GNU project debugger.

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Surprise, Surprise!

The featured image of this post is by Albert Guillaume – Gils Blas, 24 décembre 1895, Public Domain, Link

When you develop a tool for a protocol that is undocumented, it is not surprising that you will encounter situations you will not have be anticipated. And this was exactly what I experienced developing the hardware debugger dw-link, which connects debugWIRE MCUs to the GDB debugger. Although a substantial part of the debugWIRE protocol has been reverse engineered, I encountered still plenty of surprising situations: Split personality MCUs, stuck-at-one bits in program counters, secret I/O addresses, half-legal opcodes, and more.

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Debugging a Debugger With Itself

The featured image of this post is is a comic from

The above xkcd comic, which is titled Debugger, alludes to the concern that when you try to apply a particular method to itself, you might not get what you asked for. Turing’s Halting problem is a very famous example of this, i.e., you cannot algorithmically decide whether an algorithm terminates on an input. So, does that issue apply to debuggers as well? In particular, I asked myself whether it makes sense to debug the hardware debugger I am developing with itself.

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Burnt Fuses and Bricked MCUs

Featured image: Clker-Free-Vector-Images on Pixabay

One of the most confusing things, in particular for newcomers, are the AVR fuses. Worse, by setting the wrong fuse bits, you can “brick” your MCU, i.e., a normal ISP-programmer cannot talk to the MCU anymore. In this blog post, we will present tools that help you to set the fuse bits right. And if push comes to shove, that is the wrong fuses have been burnt, I tell you how to recover …

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Debugging(3): Debugging is Like Being the Detective in a Crime Movie Where You are Also the Murderer

Featured picture: OpenClipart-Vectors on Pixabay.

One has to add to the title (quoted from a tweet by Filipe Fortes) that the detective suffers from a memory loss. Otherwise, the case could be solved easily. Similarly, with debugging: If I only knew what nasty things I have hidden in the source code, I could just remove them – but I simply do not know. In this blog post, we will have a look at what kind of tools one could use to find the skeletons hidden in the closet.

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