My function does not retrun me the correct value

Using Arduino Programming Questions
#1

Good evening!

First here is my function code:

char * SIM908::get_value(char * chaine, byte index)
{

  // +CENG:0,0872,21,99,228,02,11,7979,10,00,1770,255 <= ind

  // Initiate the 
  byte ind = 0; // position where "are" in the above char
  byte x = 0;   // index of the variable val. which return the desired value
  byte ic = 0;  // Index of the variable chaine.
  bool flag = false;  // True when we are in the position to return (for exemple 7979)
  char val[10]; // Variable which contain the value to return

  // if the need the first block (+CENG1), flag must be true at the begining
  if(index == 0)
  { 
    flag = true;
  }

  
  do // Read 'chaine' carcater by carater
  {
    switch(chaine[ic]){
      case ',':                 // if it read a comma, it increment ind, because we will go to the next block
        ind++;                  // See fefault:
        ic++;                    
        continue;               // Retunr to the begining of the do loop
      
      default:
        if(ind == index)        // if ind is egal to index (index is the block we want to return)
        {
          val[x] = chaine[ic];  // The store the carater to val 
         // Serial.print(F("Def")); Serial.println(val[x]);
          x++;
        }
    }
    
    ic++;                      
    //Serial.print(F("co")); Serial.println(co);

  }while( ic < strlen(chaine)); // Do as long as ix is smaller than the lenght of 'chaine
  val[x]='\0';  // Terminate the char with  \0
  
  Serial.print(F("sr:"));Serial.println(val);
  return val;   // return the caracter/value we want to treat.
}

This is the value (char) which pass to *chaine of the function

+CENG:0,0872,21,99,228,02,11,7979,10,00,1770,255

My goal is the return 228,02,7979 and 1770.

Serial.println(get_value(response[2],4));
Serial.println(get_value(response[2],5));
Serial.println(get_value(response[2],7));
Serial.println(get_value(response[2],10));

response[1] contains +CENG:0,0872,21,99,228,02,11,7979,10,00,1770,255.

Explication
This code works partialy and the problem is around the return.
Before the return I print the value of 'val

Serial.println(val);

and this display what I expected for.
However, when I

Serial.println(get_value(response[2],4));

it print nothing correct. (keep in mind that response[1] contain CENG:0,0872,21,99,228,02,11,7979,10,00,1770,255.

Here is what display my terminal with this code

Serial.println(response[2]);
      Serial.println(get_value(response[2],0));
      Serial.println(get_value(response[2],4));
      Serial.println(get_value(response[2],5));
      Serial.println(get_value(response[2],7));
      Serial.println(get_value(response[2],10));

+CENG:0,0875,25,99,228,02,12,750d,28,00,1388,255
sr:+CENG:0
=�v�
sr:228

sr:02

sr:750d

sr:1388

You can observe that the “sr:” display the correct value but

Serial.println(get_value(response[2],7));

dont display the same value.

I am asking my self if it’s because I am using a local variable. But the local variable is return before the function ends???

How can you suggest me to perfect my function?

Many thanks

#2

PS Just be ware, the actually correct value of response[2] is
+CENG:0,0875,25,99,228,02,12,750d,28,00,1388,255

and not
+CENG:0,0872,21,99,228,02,11,7979,10,00,1770,255

It just a detail and not the issue :slight_smile: . I can not edit my post any more :frowning:

#3 
char * SIM908::get_value(char * chaine, byte index)
{

...
  char val[10]; // Variable which contain the value to return
...

  return val;   // return the caracter/value we want to treat.
}

No.

Trap 18

I am asking my self if it's because I am using a local variable.

Yes it is, see the link.

#4