Month: May 2018

Using ‘printf’ in microcontrollers

We, as electronics enthusiasts, daily write hundreds of firmware code segments for various microcontrollers. Unlike software, when it comes to debugging microcontroller code, the challenges we face are much more fundamental. I believe that the most common method for debugging firmware is using the good old printf (just like the cout in C++ and println in Java).

When we develop conventional C code for Linux systems, printf works without any hassle. However, to enable the same functionality in microcontrollers, we need to peel away a layer in the C library and find out how exactly printf works.

How printf works?

As you may already know, printf function is implemented within the C library. I will not go through the full printf function definition. If you want you can read http://blog.hostilefork.com/where-printf-rubber-meets-road/. It’s one of the best write-ups I have seen.

However, the important part is, at the end of this function chain, printf calls another function called write. This is a standard system call in Linux, a part of kernel API. However, for microcontrollers, we don’t have such liberties and thus, we have to implement this function ourselves.

(more…)

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