Flattening a multi-dimensional char array to an char* array

Projects Programming
1

Hello,
I have been trying to read a file from an SD card into an array. I now have this array, but it is not in the format I would like. I want it ion a char* string array. This is what I have so far:

char IRCodes[4][5];
// I want to replace the numbers with the IRcodes
// to end up with:  char* irCommand[] = {"C0E8","C091","C061","C001"}; 
char* irCommand[] = {"0000","0001","0002","0003"}; 

void setup() {
  IRCodes[0][0] = 'C';  // this array is what I get after I have
  IRCodes[0][1] = '0';  // read the file from the SD card.
  IRCodes[0][2] = 'E';
  IRCodes[0][3] = '8';
  IRCodes[0][4] = '\0';
  IRCodes[1][0] = 'C';
  IRCodes[1][1] = '0';
  IRCodes[1][2] = '9';
  IRCodes[1][3] = '1';
  IRCodes[1][4] = '\0';
  IRCodes[2][0] = 'C';
  IRCodes[2][1] = '0';
  IRCodes[2][2] = '6';
  IRCodes[2][3] = '1';
  IRCodes[2][4] = '\0';
  IRCodes[3][0] = 'C';
  IRCodes[3][1] = '0';
  IRCodes[3][2] = '0';
  IRCodes[3][3] = '1';
  IRCodes[3][4] = '\0';


  Serial.begin(19200);

  char* strCmd;
  int cc = 0;
  for (int i=0; i < 4; i++) {
    Serial.print(i);
    Serial.print(". ");
    strCmd = "";
    for (int ii = 0; ii < 5; ii++) {
      Serial.print(IRCodes[i][ii]);
      strCmd += IRCodes[i][ii];      // does not work
    }

    Serial.print("\n");
    Serial.println(strCmd);
    
    irCommand[i] = strCmd; 
  }
  
  Serial.println("-----------");
  for (int i=0; i < 4; i++) {
    Serial.print(i);
    Serial.print(". ");
    Serial.println(irCommand[i]);   
  }
}
void loop()
{
  // nothing happens after setup
}

as you can see, the variable strCmd is not picking up the element from IRcodes.

Can you help?
Thanks
Karl.

2

(1) You cant just add char arrays, there is no such operator defined:

      strCmd += IRCodes[i][ii];      // does not work

(2) You have declared strCmd as a pointer. This means that the compiler has allocated only two bytes of memory to store a pointer to a char. This is not an array, it is just a pointer, so the compiler doesn't know to allocate a block of memory for an array

 char* strCmd;
  int cc = 0;
  for (int i=0; i < 4; i++) {
    Serial.print(i);
    Serial.print(". ");
    strCmd = "";

(3)In the last part of that code snippet you try to assign a string to your pointer, this cannot be done in C. And again in this bit:

    irCommand[i] = strCmd;

Try making some adjustments, such as:

  char irCommand[4][5] = {"0000","0001","0002","0003"}; 

...

  int cc = 0;
  for (int i=0; i < 4; i++) {
    Serial.print(i);
    Serial.print(". ");
    strCmd[0] = '\0';
    strcpy(irCommand[i], IRCodes[i]); //copy from ircodes into ircommand

    Serial.println();
    Serial.println(strCmd);
  }
3

Hello Tom
Thanks for the reply, I now have my program working as I want to.

It was the change to char irCommand[4][5] and using strcpy(irCommand_, IRCodes*); that made all the difference.*_
Karl.