sdcard_reader.ino

#include <SPI.h>
#include <SD.h>
File myFile;

void setup() {
    // Open serial communications and wait for port to open:
    Serial.begin(115200);
    SPI.begin(PA4);
    Serial.print("Initializing SD card...");
    if (!SD.begin(PA15)) {
        Serial.println("initialization failed!");
        while (1);
    }
    Serial.println("initialization done.");
    // open the file. note that only one file can be open at a time,
    // so you have to close this one before opening another.
    myFile = SD.open("got.txt", FILE_WRITE);
    // if the file opened okay, write to it:
    if (myFile) {
        Serial.print("Writing to test.txt...");
        myFile.println("This is a test file :)");
        myFile.println("testing 1, 2, 3.");
        for (int i = 0; i < 20; i++) {
            myFile.println(i);
        }
        // close the file:
        myFile.close();
        Serial.println("done.");
    } else {
        // if the file didn't open, print an error:
        Serial.println("error opening test.txt");
    }
}

void loop() {
    // nothing happens after setup
}