Re: Purchase microcontroller dev. kit

David Brown <david.brown@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

Nico Coesel wrote:
David Brown <david.brown@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

Nico Coesel wrote:
"David L. Jones" <altzone@xxxxxxxxx> wrote:


try to compile the following on an AVR:
const char a[]={"hello world"}
char b[30];
char *p;

p=a;
strcpy(b,p);
strcat(b, "?");
printf("%s %s", a, b);

It won't work because the different memory areas will screw-up the
pointers. Some very smart and expensive compilers may be able to solve
these problems at the expense of speed.

That works perfectly well using avrgcc. Even on compilers which don't
support it directly, the way to deal with code like that is clearly
explained in user manuals and FAQs. You weren't suggesting that a
beginner should just wade in without looking at the manuals?

Of course, no one doing embedded development on a small microcontroller
would write code like that anyway - using printf is a sure sign you
don't know what you are doing.

Is it? All of my projects use printf (which usually comes in several
grades to tailor memory requirements) to print status information,
debug information and responses to commands send to a tiny command
line interpreter (a little more than a string compare on a list with
strings). And this is not even my idea.

Being able to have a sensible dialog with your hardware makes testing
and debugging much easier. Having a command line interface is also
very handy for field service. For instance: implement a command to
have it print the version & build date, and presto, you know exactly
which software is in the device.


Communication with your embedded system is an important aid to
debugging, and a small CLI is often useful. But printf is not the way
to go about it on a small microcontroller - the overhead is too big.
It's frequently (though not always) a sign that the programmer is used
to PC programming and PC "printf debugging", and has not thought about
the costs. Look through any FAQ or mailing list for small
microcontrollers - they are full of questions about why the code is so
big, with the answer being either the use of printf, or the use of
floating point. Of course, as with floating point, there are times when
printf is the right choice, even on a small microcontroller - but it's a
rarity, and not something to encourage in newbies.

The amount of program space used to be a problem and I did have my own
printing routines, but in the end printf turned out to be more
efficient to use. Most devices have plenty of flash nowadays. A decent
(basic, non-floating point) printf implementation may cost around 1500
bytes of flash. Not really a problem anymore IMHO. It may become an
issue in extremely cost sensitive products, then again, time to market
is also an important factor.

--
Reply to nico@nctdevpuntnl (punt=.)
Bedrijven en winkels vindt U op www.adresboekje.nl
.

Relevant Pages

  • Re: Purchase microcontroller dev. kit
    ... Even on compilers which don't support it directly, the way to deal with code like that is clearly explained in user manuals and FAQs. ... no one doing embedded development on a small microcontroller would write code like that anyway - using printf is a sure sign you don't know what you are doing. ... Having a command line interface is also ...
    (sci.electronics.design)
  • Re: Why do i get runtime error ?
    ... I get runtime error for the above code. ... it's because you're not honest with printf(). ... some compilers warn you for e.g. ... But it can only do that if it gets a format string that is known ...
    (comp.lang.c)
  • Re: About Visual C++ 2005 Express Edition
    ... Here are the executable image sizes, in bytes (implementations with ... program* for other compilers. ... right, together with gcc's printf. ...
    (comp.lang.c)
  • Re: LPC213x IDE
    ... to be aware of the impact GNU libraries such as printf can have ... handicapped by a very complete printf library that serves little ... ARM Compilers produced similar, ... "If you want to post a followup via groups.google.com, don't use the broken "Reply" link at the bottom of the article. ...
    (comp.arch.embedded)
  • Re: workaround to make korn shell aliases that can take parameters
    ... It does require the apply command, ... printf>&2 '\n' ...
    (comp.unix.shell)