Printing utf8 strings from progmem arrays

Projects Programming
1

Hello, I'm making a project with multilanguage menu. Everything works great but when I tried making the multilanguage part, I got stuck when I need to print strings that have non-English(latin alphabet) letters in it. I made an example here that If you run it, it will print fine the English(latin alphabet) strigs, but when I print some greek words, everything gets problematic.

#include <avr/pgmspace.h>


const char speedView [5] [12] PROGMEM = { { "TAXYTHTA:" }, { "SPEED:   " }, { "Vitesse: " }, { "Velocità:" }, { "Drehzahl:" } };  //gr, en, fr, it, ge
const char speedSel [5] [12] PROGMEM = { { "ΡΥΘΜ ΤΑΧ: " }, { "SET SPEED:" }, { "Vitesse: " }, { "Velocità: " }, { "Drehzahl: " } };  //gr, en, fr, it, ge
const char remaining [5] [12] PROGMEM = { { "ΥΠΟΛΟΙΠΟ:" }, { "REMAIN:  " }, { "Vitesse: " }, { "Velocità:" }, { "Drehzahl:" } };  //gr, en, fr, it, ge
const char endingAt [5] [12] PROGMEM = { { "ΤΕΛΕΙΩΜΑ:" }, { "ENDING:  " }, { "Vitesse: " }, { "Velocità:" }, { "Drehzahl:" } };  //gr, en, fr, it, ge


void setup() {

  Serial.begin(115200);


  
  for (byte k = 0; k < strlen_P(speedView[2]); k++) {
    Serial.print((char)pgm_read_word(speedView[2] + k));
  }
  Serial.println();

  for (byte k = 0; k < strlen_P(speedSel[0]); k++) {
    Serial.print((char)pgm_read_word(speedSel[0] + k));
  }
  Serial.println();

  for (byte k = 0; k < strlen_P(remaining[1]); k++) {
    Serial.print((char)pgm_read_word(remaining[1] + k));
  }
  Serial.println();

  for (byte k = 0; k < strlen_P(endingAt[0]); k++) {
    Serial.print((char)pgm_read_word(endingAt[0] + k));
  }
  Serial.println();

  
}

void loop() {
  // put your main code here, to run repeatedly:
}

That's the output:
image

You'll see that whenever a greek word is printed, somehow it gets printed with the next string of the array.

Any help would be much appreciated!

2

The array does not have enough space to store the text, utf8 characters can be two or more bytes each. The compiler should be warning about the text being truncated.

1 Like
3

Hi David, the compiler doesn't give me any errors. With what you've said though I increased the space from all arrays to 20 from 12 and now it works fine.

Thank's a lot!

4

The for loops are not really necessary you should be able to cast the array element to __FlashStringHelper* and print the string directly, such as

Serial.println((__FlashStringHelper*)speedView[2]);
1 Like
5

Go to Preferences... and set "Compiler warnings" to "All".

Then, for each array where the compiler tells you a string is too long, increase the size. I found that the first array is OK but the other three need 18 bytes:

const char speedView [5] [12] PROGMEM = { { "TAXYTHTA:" }, { "SPEED:   " }, { "Vitesse: " }, { "Velocità:" }, { "Drehzahl:" } };  //gr, en, fr, it, ge
const char speedSel [5] [18] PROGMEM = { { "ΡΥΘΜ ΤΑΧ: " }, { "SET SPEED:" }, { "Vitesse: " }, { "Velocità: " }, { "Drehzahl: " } };  //gr, en, fr, it, ge
const char remaining [5] [18] PROGMEM = { { "ΥΠΟΛΟΙΠΟ:" }, { "REMAIN:  " }, { "Vitesse: " }, { "Velocità:" }, { "Drehzahl:" } };  //gr, en, fr, it, ge
const char endingAt [5] [18] PROGMEM = { { "ΤΕΛΕΙΩΜΑ:" }, { "ENDING:  " }, { "Vitesse: " }, { "Velocità:" }, { "Drehzahl:" } };  //gr, en, fr, it, ge
1 Like
6

That should save me many lines. Thank's again!

7

I have already been stuck with array spacing problems in the past. Now with compiler warnings informing me, I believe I'll be trouble free in the future.

Thank's for the info!

8

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