Reading a .csv file element wise

Question

I'm fairly new to arduino programming and C/C++. I would like to read a .csv file element wise, and send each element via. a nRF24L01 tranceiver to a raspberry pi. Right now I'm able to read the .csv file with Serial.write(<file>.read()). I was wondering if there's a way to read each element one at a time, if so how would i do that?

My thoughts (Pseudo code-ish):

loop through every element in .csv file {
    save the current element to X.
    send X to raspberry pi (I already have a function for sending)
}

I hope someone can help. Thanks in advance.

Answer 1

The read() method works character-wise, not element-wise. Then you have to rethink your algorithm to loop over characters:

• store each character in a buffer
• send the whole buffer (i.e. a single element) when you see a delimiter

Example:

const size_t BUFFER_SZ = ...;
char buffer[BUFFER_SZ];
size_t pos = 0;    // current write position in buffer
int c;

// While we can read a character:
while ((c = <file>.read()) != -1) {

    // If we get a delimiter, then we have a complete element.
    if (c == ',' || c == '\n') {
        buffer[pos] = '\0';         // terminate the string
        raspberry.println(buffer);  // send to the RPi
        pos = 0;                    // ready for next element
    }

    // Otherwise, store the character in the buffer.
    else if (pos < BUFFER_SZ-1) {
        buffer[pos++] = c;
    }
}

Here the buffer is sent as a string. If you want to parse it into a number, you can use sscanf.

This code assumes Unix text-file conventions, i.e. each line of the file (including the last one) being terminated by an LF character. You may have to adapt if your file is different.