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.

• brtiberio: Take a look at this post. Since the file is csv, you can construct a similar approach using a sscanf on each line you read.
• Majenko: Are all your CSV values all numeric, or do you have textual data in there as well?

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円'; // 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.