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[Reply #15 on:]

sprintf returns an integer, not a char array. I can't do something like this:

No, you can't. But, you can (and should) do:

Code:

char buffer[20];
sprintf(buffer, "L%05d",altitude);
ea.drawText(100,100, buffer);

As I wrote, I have to display a rather big amount of various numerical data, so I'm looking at some major rewriting... *sigh*

Quit moaning and get started.  

The fact that you started out in the wrong direction doesn't help you.

You may be able to write some functions to minimize the amount of work involved.

[Reply #16 on:]

Try what I said in reply #11. That might fix the crashes.

In any case it shouldn't be hard to rewrite your function to work. Here's an example:

Code:

const char * leadingZero (const int data, const int len)
  {
  static char buf [11];
  sprintf (buf, "%010d", data);
  return &buf [strlen (buf) - len];
  }  // end of leadingZero

void setup ()
  {
  Serial.begin (115200);
  Serial.println (leadingZero (42, 3));
  Serial.println (leadingZero (42, 4));
  Serial.println (leadingZero (42, 5));
  Serial.println (leadingZero (42, 6));
  }  // end of setup

void loop () {}  

Test output:

Code:

042
0042
00042
000042

[Reply #17 on:]

May I ask, why the 'const' as the type and in the parameters. I'm asking because I tried to write a function that returns a char array before and it didn't work.

[Reply #18 on:]

The const just means you promise not to change it (the value is read-only).

I don't know how you tried to return the char array, but if it was a local automatic variable then it will have been allocated on the stack and the content becomes undefined as soon as the function returns.

[Reply #19 on:]

I tried it basically like in that example, just without the 'const' and the 'static'. With ints and chars that works...

[Reply #20 on:]

Don't get rid of "static". I put it there for a reason. Without it you are returning the address of a variable on the stack, which no longer exists.