Reading SD card data

@winddance

This is a function I wrote a very long time ago to do just that. 

You would call it like:

   // char char_var_to_store_result_in should be an array large enough for the value.

    getstrfld (your_line_to_parse_from, 0, 0, ",", char_var_to_store_result_in);

    // Do something with the data...

    getstrfld (your_line_to_parse_from, 1, 0, ",", char_var_to_store_result_in);

    // Do something with the data...

 You will have to do an atoi on the char_var_to_store_result_in to get the real number value.

 The field number is zero-based, so the first field would be 0 the next 1 and so on.

char *getstrfld (char *strbuf, int fldno, int ofset, char *sep, char *retstr)
{
   char *offset, *strptr;
   int curfld;

   if (!*strbuf) {
      *retstr = 0;
      return (retstr);
   }

   offset = strptr = (char *) NULL;
   curfld = 0;

   strbuf += ofset;

   while (*strbuf) {
      strptr = !offset ? strbuf : offset;
      offset = strpbrk ((!offset ? strbuf : offset), sep);

      if (offset)
         offset++;
      else if (curfld != fldno) {
         *retstr = (char) 0;
         break;
      }

      if (curfld == fldno) {
         strncpy (retstr, strptr,
         (int)(!offset ? strlen (strptr) + 1 : (int) (offset - strptr)));
         if (offset)
            retstr[offset - strptr - 1] = 0;

         break;
      }
      curfld++;
   }   
   return retstr;
}

Hi Triform,

Thanks for the reply. However my programing level is low enough that the code you posted looks like a foreign language to me.

Right from the first line I have no idea What all these things mean?? (char *strbuf, int fldno, int ofset, char *sep, char *retstr) { char *offset, *strptr; int curfld; if (!*strbuf) { *retstr = 0; return (retstr); }

Is there a Dumbed down version.

Thanks 

Cheers

L

@triform

This is the way your code came out in my email.  I thought before I read you actual msg that you were making a joke.  My response was going to be " Ok that is just cruel" 🙂

After all this is how c programmers would write their code in some competitions.

char *getstrfld (char *strbuf, int fldno, int ofset, char *sep, char *retstr); void setup() { char val_buffer[10]; int val_one = 0, val_two = 0; Serial.begin (9600); getstrfld ("123,456", 0, 0, ",", val_buffer); val_one = atoi (val_buffer); Serial.println (val_one); getstrfld ("123,456", 1, 0, ",", val_buffer); val_two = atoi (val_buffer); Serial.println (val_two); } void loop() { // put your main code here, to run repeatedly: } char *getstrfld (char *strbuf, int fldno, int ofset, char *sep, char *retstr) { char *offset, *strptr; int curfld; if (!*strbuf) { *retstr = 0; return (retstr); } offset = strptr = (char *) NULL; curfld = 0; strbuf += ofset; while (*strbuf) { strptr = !offset ? strbuf : offset; offset = strpbrk ((!offset ? strbuf : offset), sep); if (offset) offset++; else if (curfld != fldno) { *retstr = (char) 0; break; } if (curfld == fldno) { strncpy (retstr, strptr, (int)(!offset ? strlen (strptr) + 1 : (int) (offset - strptr))); if (offset) retstr[offset - strptr - 1] = 0; break; } curfld++; } return retstr; }

@winddance

Here is an example that uses C++, the language of choice, that the Arduino designers and implementer's wanted to, and intended for you to use:

void setup() {
  Serial.begin(9600);

  String line  = "  Left  ,  Right   ";
  int delimPos = line.indexOf(',');
  
  // Start from position 0, and read up to, not including "delimPos" characters
  String left = line.substring(0, delimPos);
  
  // Start from next character following "delimPos", and read remaining characters
  String right = line.substring(delimPos + 1);

  // Remove leading and trailing spaces
  left.trim();
  right.trim();
  
  Serial.print(left);
  Serial.print(right); 
 }

Although Arduino supports code written in both "Assembly" and "C" as shown, I suggest you stick to the "C++" language unless you have a need to do otherwise!

By the way, you can easily incorporate the above example I provided into a loop too, if you need to read and work with multiple lines from a an SD file in real time.

Hope this help's!

Hi Frogandtoad,

Great handle by the way.

Thanks for the code. It gives me a good starting point. I'll play around with it and let you know how it goes.

Cheers

L

@winddance

No problem!

Here is a good reference to bookmark, for all Arduino programmers who wish to understand most parts of the language:

Arduino Language Reference

Cheers!