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SD Card Module with Arduino: How to Read/Write Data

In this tutorial, you’ll learn how to use SD and micro SD cards with Arduino in a simple project to measure the environment temperature.

BeginnerProtip1 hour45,345
SD Card Module with Arduino: How to Read/Write Data

Things used in this project

Hardware components

Arduino UNO R3
×1
ElectroPeak Micro SD TF Card Adapter Module
×1
ElectroPeak DS3231 I2C RTC Module
×1
ElectroPeak Male to Female jumper wire
×1
ElectroPeak micro SD card
×1

Software apps and online services

Arduino IDE

Story

Read more

Code

code 1

Arduino
Writing data on SD card with Arduino.
#include <SPI.h>
#include <SD.h>
File myFile;
void setup() {
// Open serial communications and wait for port to open:
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
}
Serial.print("Initializing SD card...");
if (!SD.begin(10)) {
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("test.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
}

Code 2

Arduino
Reading data from SD card with Arduino
#include <SPI.h>
#include <SD.h>
File myFile;
void setup() {
// Open serial communications and wait for port to open:
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
}
Serial.print("Initializing SD card...");
if (!SD.begin(10)) {
Serial.println("initialization failed!");
while (1);
}
Serial.println("initialization done.");
// open the file for reading:
myFile = SD.open("test.txt");
if (myFile) {
Serial.println("test.txt:");
// read from the file until there's nothing else in it:
while (myFile.available()) {
Serial.write(myFile.read());
}
// close the file:
myFile.close();
} else {
// if the file didn't open, print an error:
Serial.println("error opening test.txt");
}
}
void loop() {
// nothing happens after setup
}

code 3

Arduino
Code for project
/*
Save temperature in SD/microSD card every hour with DS3231 + SD/microSD module + Arduino
modified on 15 Apr 2019
by Mohammadreza Akbari @ Electropeak
https://electropeak.com/learn/
*/
#include <SPI.h>
#include <SD.h>
#include <Wire.h>
#include "Sodaq_DS3231.h"
File myFile;
DateTime now;
int newHour = 0;
int oldHour = 0;
void save_temperature() {
myFile = SD.open("temp.txt", FILE_WRITE);
now = rtc.now();
myFile.print(now.hour());
myFile.print(":");
myFile.print(now.minute());
rtc.convertTemperature(); //convert current temperature into registers
myFile.print(",");
myFile.println(rtc.getTemperature()); //read registers and save temperature on deg C
myFile.close();
}
void setup ()
{
Wire.begin();
rtc.begin();
Serial.begin(9600);
Serial.print("Initializing SD card...");
if (!SD.begin(10)) {
Serial.println("initialization failed!");
while (1);
}
Serial.println("initialization done.");
now = rtc.now();
oldHour = now.hour();
}
void loop ()
{
now = rtc.now();
newHour = now.hour();
if (oldHour != newHour) {
save_temperature();
oldHour = newHour;
}
}

Credits

ElectroPeak

ElectroPeak

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