Array of strings locks up program

Projects Programming
1

I have a sketch to measure frequency and I want to display the name of the note. As my input comes from a celtic harp I have approx 40 strings (although digital strings that represent names of real life strings is a bit confusing :wink: ). I decided to give them frequencies and names with two arrays.

Everything locks up! :o I painstakingly commented all lines and found that the instruction that gives problems is the definition "String stringName etc." - I mean - when I activate it the display does not show the initializing screens and no further results come out. As soon as I comment it returns to normal. No problem with the int array. No messages at compile time though it looks like a memory problem - writing over some reserved area or such.

Any hints on how to go ahead?
Tks
F

…

//variables for tuning *** Mib Eb scale
//frequenza nota "esatta" moltiplicata per dieci
int stringFreq[40] = {1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1};

//nome della nota
String stringNAME[40] = {"A# LA#5","abcd","abcd","abcd","abcd","abcd","abcd","abcd","abcd","abcd",
"abcd","abcd","abcd","abcd","abcd","abcd","abcd","abcd","abcd","abcd",
"abcd","abcd","abcd","abcd","abcd","abcd","abcd","abcd","abcd","abcd",
"abcd","abcd","abcd","abcd","abcd","abcd","abcd","abcd","abcd","abcd"};

void setup(){

Serial.begin(9600);
Serial.println("Inizialize...");

display.begin(SSD1306_SWITCHCAPVCC, 0x3C); //Impostare l'indirizzo i2c annotato in precedenza
display.clearDisplay(); //Pulisce il buffer da inviare al display
display.setTextSize(2); //Imposta la grandezza del testo
display.setTextColor(WHITE); //Imposta il colore del testo (Solo bianco)
display.setCursor(0,0); //Imposta la posizione del cursore (Larghezza,Altezza)
display.println("aaaaa"); //Stringa da visualizzare
display.display(); //Invia il buffer da visualizzare al display
delay(1000);

...

2

The general advice here is not to use Strings with the limited amount of memory available on most Arduinos but to use zero terminated arrays of chars (aka C strings) instead

Please post a complete program that illustrates the problem and please use code tags when you do

3

With the alternative char definition it works.

I suppose that zero terminated means that the string lenght must be one less than the definition and can be implicit or do I have to add it at the end of each string?

My strings are all long 9 chars or less. "-2 Eb MIb"

char stringNAME[40][10] = {"-2 Eb MIb","abcd","abcd ...

Thanks
Flavio

4

You could simplify things by using an array of pointers to the strings
An example :

char * names[] = {"-2 Eb MIb", "abcd", "efgh"};

void setup()
{
  Serial.begin(115200);
  while (!Serial);
  for (int name = 0; name < sizeof(names) / 2; name++)
  {
    Serial.println(names[name]);
  }
}

void loop()
{
}
5

I tried, the line:

char * stringNAME[] = {"-2 Eb MIb","-2 F  FA","-2 G  SOL","-2 Ab LAb","-2 Bb SIb","-2 C  DO","-2 D  RE","-1 Eb MIb","-1 F  FA","-1 G  SOL",
                           "-1 Ab LAb","-1 Bb SIb","-1 C  DO","-1 D  RE","** Eb MIb","** F  FA","** G  SOL","** Ab LAb","** Bb SIb","** C  DO",
                           "** D  RE","+1 Eb MIb","+1 F  FA","+1 G  SOL","+1 Ab LAb","+1 Bb SIb","+1 C  DO","+1 D  RE","+2 Eb MIb","+2 F  FA",
                           "+2 G  SOL","+2 Ab LAb","+2 Bb SIb","+2 C  DO","+2 D  RE","+3 Eb MIb","+3 F  FA","+3 G  SOL","+3 Ab LAb","+3 Bb SIb"};

It gives a warning error at compile time as follows:
Tuner_v1_conOLED.ino:141:144: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]
"+2 G SOL","+2 Ab LAb","+2 Bb SIb","+2 C DO","+2 D RE","+3 Eb MIb","+3 F FA","+3 G SOL","+3 Ab LAb","+3 Bb SIb"};
^

I can revert to "char stringNAME[40][10]" but am still not sure how to null terminate each individual string.
Flavio

6

am still not sure how to null terminate each individual string

When you use double quotes to delimit the string, the zero is automatically added at the end.

7

flavios:
I tried, the line:

char * stringNAME[] = {"-2 Eb MIb","-2 F  FA","-2 G  SOL","-2 Ab LAb","-2 Bb SIb","-2 C  DO","-2 D  RE","-1 Eb MIb","-1 F  FA","-1 G  SOL",

"-1 Ab LAb","-1 Bb SIb","-1 C  DO","-1 D  RE","** Eb MIb","** F  FA","** G  SOL","** Ab LAb","** Bb SIb","** C  DO",
                          "** D  RE","+1 Eb MIb","+1 F  FA","+1 G  SOL","+1 Ab LAb","+1 Bb SIb","+1 C  DO","+1 D  RE","+2 Eb MIb","+2 F  FA",
                          "+2 G  SOL","+2 Ab LAb","+2 Bb SIb","+2 C  DO","+2 D  RE","+3 Eb MIb","+3 F  FA","+3 G  SOL","+3 Ab LAb","+3 Bb SIb"};




It gives a warning error at compile time as follows:
Tuner_v1_conOLED.ino:141:144: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]
"+2 G SOL","+2 Ab LAb","+2 Bb SIb","+2 C DO","+2 D RE","+3 Eb MIb","+3 F FA","+3 G SOL","+3 Ab LAb","+3 Bb SIb"};

Use:

const char * const stringNAME[] = {"-2 Eb MIb", "-2 F  FA", "-2 G  SOL", "-2 Ab LAb", "-2 Bb SIb", "-2 C  DO", "-2 D  RE", "-1 Eb MIb", "-1 F  FA", "-1 G  SOL",
                       "-1 Ab LAb", "-1 Bb SIb", "-1 C  DO", "-1 D  RE", "** Eb MIb", "** F  FA", "** G  SOL", "** Ab LAb", "** Bb SIb", "** C  DO",
                       "** D  RE", "+1 Eb MIb", "+1 F  FA", "+1 G  SOL", "+1 Ab LAb", "+1 Bb SIb", "+1 C  DO", "+1 D  RE", "+2 Eb MIb", "+2 F  FA",
                       "+2 G  SOL", "+2 Ab LAb", "+2 Bb SIb", "+2 C  DO", "+2 D  RE", "+3 Eb MIb", "+3 F  FA", "+3 G  SOL", "+3 Ab LAb", "+3 Bb SIb"
                      };
8

It gives a warning error at compile time

What is "it" ?
Please post your complete program

9

gfvalvo:
Use:

const char * const stringNAME[] = {"-2 Eb MIb",...

It works perfectly - no errors at compile time. Now that you have stated it, yes they are constants and not variables.

To extract the full description I use the following lines after making all description exactly long 9. I tried with '<sizeof((stringNAME*[aa])' as it was more "elegant" but it does not work.*
* *     stringN = "";      for (int aa = 0; aa < 10; aa++){        stringN += (stringNAME[i][aa]);      }* *
I did not enclose earlier the complete sketch as it exceed the total lenght allowed. I have now a much shorter sample but the question is satisfied and the issue closed.
Many thanks.
Flavio

10 
        stringN += (stringNAME[i][aa]);

I see that you have gone back to the use of Strings for this. Why not use C strings throughout ?

11

I needed to store the description in a separate string to get it out of the loop and display it.

I should confess my ignorance of C and just say that this was the first way it worked… I would know no better. :wink: I am learning "on the job". And some critical moments were overcome thanks to this forum.
Flavio

UKHeliBob:

        stringN += (stringNAME[i][aa]);

I see that you have gone back to the use of Strings for this. Why not use C strings throughout ?

12

I needed to store the description in a separate string to get it out of the loop and display it.

I have no idea what that means, but why do you need to copy a string from the array to another one and why do it character by character anyway ? Note that I am referring to strings not Strings