Problem with special characters in Strings (like ä, ü, ß, €)

Projects Programming
1

Hi,

I wanted to edit this library so that it can also display special characters (like ä, ö, ß, €) on my tft display.
My problem is that the library uses an 1 byte-identifier for charachter drawing (ASCII).
So i thought i could implement the ISO 8859-15 standard in only one byte as it has all the characters I need.
Arduino can display these special characters as it uses UTF-8.
In UTF-8 some characters are represented with more than one byte ( € is 0x E8 82 AC).

So I wrote a simple convert function that tries to solve the problem mentioned above:

String convertAscii(String input)
{
  String ret = "";
  Serial.println(input);
  Serial.println("Length: " + String(input.length()));
  for (int i = 0; i < input.length(); i ++)
  {
    char c = input.charAt(i);
    //ret = ????
    Serial.println(String(c) + " , " + String(isAscii(c)) + ", " + String((c), HEX));
  }
  return ret;
}

When I call the function with e.g. "€" I get this output:

€
Length: 3
⸮ , 0, e2
⸮ , 0, 82
⸮ , 0, ac

So stuff with char and String.length() doesn't work on those strings.
Now I have no clue what I should do about it.
Could You please help me?

2

Wow. You are way off in the weeds.

Instead of trying to include the special characters in your source code just use the ISO 8859-15 byte value...

#define SYMBOL_EURO  "\xA4"

Serial.println( SYMBOL_EURO "42" );
3

The problem is that I have a given string ( from an external source) where I can't change the formatting like in your post.

Edit: I tried Your code but my result is ⸮42

4

In which case you have excluded critical information.

5

So after a bit of thinking I updated the function:

String convertAscii(String input)
{
  bool nextReadChar = false;
  String ret = "";
  Serial.println("Input: " + input);
  Serial.println("Length: " + String(input.length()));
  for (int i = 0; i < input.length(); i ++)
  {
    char c = input.charAt(i);
    Serial.println(c, HEX);
    if (nextReadChar)
    {
      nextReadChar = false;
      ret += c;
    }
    else
    {
      if (c < 127)
      {
        ret += c;
      }
      else
      {
        if (c == 0xC3) //latin-9 table
        {;
          nextReadChar = true;
        }
        else if (c == 0xE2) //€
        {
          nextReadChar = true;
          i++;
        }
      }
    }
  }
  return ret;
}

Now my problem is solved. Note that it uses UTF-8 as standard as it's apperantly a little bit different to the special char ASCII

6 
        {;

I don't think I've seen THAT done before.

7

PaulS:

        {;

I don't think I've seen THAT done before.

Compiler will optimize that out. But yes, that is a first.