Just a quick walk through how to use the SD card module with Arduino. It is the same for Micro SD card modules. The Arduino official site provide a library for this purpose, and I will describe how I used this library and explain what each function does.

Some of the links on this page are affiliate links. I receive a commission (at no extra cost to you) if you make a purchase after clicking on one of these affiliate links. This helps support the free content for the community on this website. Please read our Affiliate Link Policy for more information.

• Buy the Arduino from: Banggood | Amazon
• Buy SD Card Module from: Amazon | Banggood

The Type of SD Card Module

I have not tested this library with all the SD card modules, but I think it should work for majority of them, unless you are told by the seller that you should use a different library.

The Library uses standard SPI interface for communication, which hasSPI buses, MISO, MOSI, SCK (CLK) and a chip select signal pin, CS.

Connection With Arduino

[pic]

** MOSI – pin 11
** MISO – pin 12
** SCK (CLK) – pin 13
** CS – pin 4

Libraries

The default Arduino library for SD card is huge! With the example read/write sketch, when compiled it’s 13690 Bytes which is half of the available flash space on an Arduino pro mini!

So if you are tight in sketch space, it’s a good idea to find a smaller library. Depends on the SD cards you have and the format you want to use, you have these options.

FAT32 Format (larger than 2GB)

• Arduino SD
• Adafruit SD (almost the same as Arduino SD, except a few optimization on SRAM memory)
• SDFatLib

FAT16 Format (smaller than 2GB)

• Fat16Lib
• Arduino-Filelogger
• tinyFat

I haven’t tested all of these libraries, so do your research and test them before using it. Here I will show you how to use the Arduino SD library.

How To Use the Arduino SD Library

The SD library comes with the Arduino IDE, so you don’t need to download it. It needs to be include at the beginning of the sketch.

#include <SD.h>

Including `SD.h` automatically creates a global “SD” object which can be interacted within a similar
manner to other standard global objects like “Serial”.

The Available SD Card Module Functions

Read from SD card

First you need top open the file first.

File dataFile = SD.open("datalog.txt");

It will return false if it fails to open the file, so check dataFile before using it. The “read” function reads the file line by line, so you will have to use a while loop, until it fail to reach the end of the file. Now you can write to the file using this.

if (dataFile) { while (dataFile.available()) { Serial.write(dataFile.read()); } dataFile.close(); } else { // if the file isn't open, pop up an error: }

Note that you need to close the file after finished reading it. Also, you can only open one file at a time, if you want to read the next file, you need to close the current file first.

Write to SD card

First you need to open the file  you want to write to with “FILE_WRITE” parameter.

File dataFile  = SD.open("test.txt", FILE_WRITE);

The “open” function takes two parameters, file location and  mode (only required for “Write”, if missing by default it opens the file in Read-Only mode). It will return false if it fails to open the file, so check dataFile before using it. Now you can write to the file using this.

if (dataFile) { dataFile.println("writing data to test file"); dataFile.close(); } else { // if the file didn't open, do something here }

Note that you need to close the file after writing to it. Also, you can only open one file at a time, if you want to open the next file, you need to close the current file first.

Check if a File Exists

// Check to see if the file exists: if (SD.exists("example.txt")) {     // example.txt exists } else {     // example.txt doesn't exist }

Create a Text File on SD Card

There isn’t a function for this purposes, but you can open a file with “FILE_WRITE” mode to create a file, if this file doesn’t exist.

// To create a text file, we can open a new file and immediately close it: dataFile = SD.open("example.txt", FILE_WRITE); dataFile.close();

Delete a File on SD card

SD.remove("example.txt");

List All the files on SD card

There isn’t a function for this in the library, but we can create a custom function to achieve this purpose. This function is from the example sketch in the Library. It prints the file directory to serial monitor.

void printDirectory(File dir, int numTabs) { while(true) { File entry = dir.openNextFile(); if (! entry) { // no more files break; } for (uint8_t i=0; i<numTabs; i++) { Serial.print('t'); } Serial.print(entry.name()); if (entry.isDirectory()) { Serial.println("/"); printDirectory(entry, numTabs+1); } else { // files have sizes, directories do not Serial.print("tt"); Serial.println(entry.size(), DEC); } entry.close(); } }

Testing SD card or Get SD Card Information

Sd2Card card; SdVolume volume; SdFile root; const int chipSelect = 4; // 4 for Arduino boards, might be different in other non-Arduino boards. // we'll use the initialization code from the utility libraries // since we're just testing if the card is working! if (!card.init(SPI_HALF_SPEED, chipSelect)) { Serial.println("initialization failed. Things to check:"); Serial.println("* is a card is inserted?"); Serial.println("* Is your wiring correct?"); Serial.println("* did you change the chipSelect pin to match your shield or module?"); return; } else { Serial.println("Wiring is correct and a card is present."); } // print the type of card Serial.print("nCard type: "); switch(card.type()) { case SD_CARD_TYPE_SD1: Serial.println("SD1"); break; case SD_CARD_TYPE_SD2: Serial.println("SD2"); break; case SD_CARD_TYPE_SDHC: Serial.println("SDHC"); break; default: Serial.println("Unknown"); } // Now we will try to open the 'volume'/'partition' - it should be FAT16 or FAT32 if (!volume.init(card)) { Serial.println("Could not find FAT16/FAT32 partition.nMake sure you've formatted the card"); return; } // print the type and size of the first FAT-type volume uint32_t volumesize; Serial.print("nVolume type is FAT"); Serial.println(volume.fatType(), DEC); Serial.println(); volumesize = volume.blocksPerCluster(); // clusters are collections of blocks volumesize *= volume.clusterCount(); // we'll have a lot of clusters volumesize *= 512; // SD card blocks are always 512 bytes Serial.print("Volume size (bytes): "); Serial.println(volumesize); Serial.print("Volume size (Kbytes): "); volumesize /= 1024; Serial.println(volumesize); Serial.print("Volume size (Mbytes): "); volumesize /= 1024; Serial.println(volumesize); Serial.println("nFiles found on the card (name, date and size in bytes): "); root.openRoot(volume); // list all files in the card with date and size root.ls(LS_R | LS_DATE | LS_SIZE);