Good Old printf()

13. April 2009 by pilot.

Good old printf() is probably the oldest debugging tool ever used, I mean beside a light bulb (nowadays replaced by an LED) … yet it represents a pretty sophisticated one when working in a deeply embedded control project. If you take the standard definition of the printf() function (as in the ANSI C standard) it assumes that you will be able to convert and print integers and floating point numbers of any size, and use a myriad of formatting options.

Assuming you have a serial port (UART) to spare for the interface with a terminal (Hyper- if you use a PC) it is the code space requirements (even excluding the floating point support) for a full implementation that makes it a difficult choice. It could be pretty large (several K of code), comparable if not more than the entire program memory available on some 8-bit microcontrollers.

So in the past I have used a bit of everything to avoid relying on printf() for my debugging/diagnostic output.  Mostly macros including itoa() followed by puts() and a mix of other hand made optimizations for simple hex output.

In the 16-bit and 32-bit world, there is a little bit more room to breathe, and  with a smart compiler’s help, things get manageable. Read the rest of this entry »

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