Reading CSV files from a SD Card with An Arduino

Writing CSV files to an SD card is a fairly easy matter, build a string, adding a comma between each number and send that string to the SD card. However, getting that data off the card and loaded back into use is not such an easy matter.

Here is a simple sketch that reads a CSV file with four numbers and two strings on each line.  It doesn't use the dangerous String class.

gps.csv

The following sketch successfully loads numbers and strings from an SD Card and is completely print values in serial (Serial Monitor).

Change the "gps.csv" file name according to your file name.

	#include <SoftwareSerial.h>
	#include <SD.h>
	#include <SPI.h>
	/* CSV File Reading */
	File file;
	int SC = 53; //SC - Pin 53 Arduino Mega
	char location;
	bool readLine(File &f, char* line, size_t maxLen) {
	for (size_t n = 0; n < maxLen; n++) {
	int c = f.read();
	if ( c < 0 && n == 0) return false; // EOF
	if (c < 0 || c == '\n') {
	line[n] = 0;
	return true;
	}
	line[n] = c;
	}
	return false; // line too long
	}
	bool readVals(long* v1, long* v2, long* v3, long* v4, String* loc,String* loc2) {
	char line[200], *ptr, *str;
	if (!readLine(file, line, sizeof(line))) {
	return false; // EOF or too long
	}
	*v1 = strtol(line, &ptr, 10);
	if (ptr == line) return false; // bad number if equal
	while (*ptr) {
	if (*ptr++ == ',') break;
	}
	*v2 = strtol(ptr, &str, 10);
	while (*ptr) {
	if (*ptr++ == ',') break;
	}
	*v3 = strtol(ptr, &str, 10);
	while (*ptr) {
	if (*ptr++ == ',') break;
	}
	*v4 = strtol(ptr, &str, 10);
	while (*ptr) {
	if (*ptr++ == ',') break;
	}
	String a = strtok_r(ptr, ",", &str);
	String first(str);
	*loc = first;
	String let(a);
	*loc2 = let;
	return str != ptr; // true if number found
	}
	/* Close CSV File Reading */
	void setup()
	{
	// Open serial communications and wait for port to open:
	Serial.begin(9600);
	//SD Card Reader Setup
	Serial.begin(9600);
	if (!SD.begin(SC)) {
	Serial.println("begin error");
	return;
	}
	file = SD.open("gps.CSV", FILE_READ);
	if (!file) {
	Serial.println("open error");
	return;
	}
	}
	void loop() // run over and over
	{
	long x, y, z, k;
	String loc,loc2;
	while (readVals(&x, &y, &z, &k, &loc, &loc2)) {
	//First 4 Long datatype variables
	Serial.println(x);
	Serial.println(y);
	Serial.println(z;
	Serial.println(k);
	//Last 2 String type variables
	Serial.println(loc);
	Serial.println(loc2);
	}
	}

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Arduino sd read CSV file.

If you have any questions please post your comments below.

Thank you!