Get microSD card size<\/a>;<\/li>\n<\/ul>\n\n\n\nAlternatively, you can use the SD_MMC<\/strong> examples – these are similar to the SD examples, but use the SDMMC driver. For the SDMMC driver, you need a compatible microSD card module. The module we’re using in this tutorial doesn’t support SDMMC.<\/p>\n\n\n\nHow the Code Works<\/h3>\n\n\n\n First, you need to include the following libraries: FS.h<\/span> to handle files, SD.h<\/span> to interface with the microSD card and SPI.h<\/span> to use SPI communication protocol.<\/p>\n\n\n\n#include \"FS.h\"\n#include \"SD.h\"\n#include \"SPI.h\"<\/code><\/pre>\n\n\n\nThe example provides several functions to handle files on the microSD card.<\/p>\n\n\n\n
List a directory<\/h4>\n\n\n\n The listDir()<\/span> function lists the directories on the SD card. This function accepts as arguments the filesystem (SD<\/span>), the main directory’s name, and the levels to go into the directory.<\/p>\n\n\n\nvoid listDir(fs::FS &fs, const char * dirname, uint8_t levels){\n Serial.printf(\"Listing directory: %s\\n\", dirname);\n\n File root = fs.open(dirname);\n if(!root){\n Serial.println(\"Failed to open directory\");\n return;\n }\n if(!root.isDirectory()){\n Serial.println(\"Not a directory\");\n return;\n }\n\n File file = root.openNextFile();\n while(file){\n if(file.isDirectory()){\n Serial.print(\" DIR : \");\n Serial.println(file.name());\n if(levels){\n listDir(fs, file.name(), levels -1);\n }\n } else {\n Serial.print(\" FILE: \");\n Serial.print(file.name());\n Serial.print(\" SIZE: \");\n Serial.println(file.size());\n }\n file = root.openNextFile();\n }\n}<\/code><\/pre>\n\n\n\nHere’s an example of how to call this function. The \/<\/span> corresponds to the microSD card root directory.<\/p>\n\n\n\nlistDir(SD, \"\/\", 0);<\/code><\/pre>\n\n\n\nCreate a Directory<\/h4>\n\n\n\n The createDir()<\/span> function creates a new directory. Pass as an argument the SD<\/span> filesystem and the directory name path.<\/p>\n\n\n\nvoid createDir(fs::FS &fs, const char * path){\n Serial.printf(\"Creating Dir: %s\\n\", path);\n if(fs.mkdir(path)){\n Serial.println(\"Dir created\");\n } else {\n Serial.println(\"mkdir failed\");\n }\n}<\/code><\/pre>\n\n\n\nFor example, the following command creates a new directory on the root called mydir<\/span>.<\/p>\n\n\n\ncreateDir(SD, \"\/mydir\");<\/code><\/pre>\n\n\n\nRemove a Directory<\/h4>\n\n\n\n To remove a directory from the microSD card, use the removeDir()<\/span> function and pass as an argument the SD filesystem and the directory name path.<\/p>\n\n\n\nvoid removeDir(fs::FS &fs, const char * path){\n Serial.printf(\"Removing Dir: %s\\n\", path);\n if(fs.rmdir(path)){\n Serial.println(\"Dir removed\");\n } else {\n Serial.println(\"rmdir failed\");\n }\n}<\/code><\/pre>\n\n\n\nHere is an example:<\/p>\n\n\n\n
removeDir(SD, \"\/mydir\");<\/code><\/pre>\n\n\n\nRead File Content<\/h4>\n\n\n\n The readFile()<\/span> function reads the content of a file and prints the content in the Serial Monitor. As with previous functions, pass as an argument the SD<\/span> filesystem and the file path.<\/p>\n\n\n\nvoid readFile(fs::FS &fs, const char * path){\n Serial.printf(\"Reading file: %s\\n\", path);\n\n File file = fs.open(path);\n if(!file){\n Serial.println(\"Failed to open file for reading\");\n return;\n }\n\n Serial.print(\"Read from file: \");\n while(file.available()){\n Serial.write(file.read());\n }\n file.close();\n}<\/code><\/pre>\n\n\n\nFor example, the following line reads the content of the hello.txt<\/span> file.<\/p>\n\n\n\nreadFile(SD, \"\/hello.txt\")<\/code><\/pre>\n\n\n\nWrite Content to a File<\/h4>\n\n\n\n To write content to a file, you can use the writeFile()<\/span> function. Pass as an argument, the SD<\/span> filesystem, the file path and the message <\/p>\n\n\n\nvoid writeFile(fs::FS &fs, const char * path, const char * message){\n Serial.printf(\"Writing file: %s\\n\", path);\n\n File file = fs.open(path, FILE_WRITE);\n if(!file){\n Serial.println(\"Failed to open file for writing\");\n return;\n }\n if(file.print(message)){\n Serial.println(\"File written\");\n } else {\n Serial.println(\"Write failed\");\n }\n file.close();\n}<\/code><\/pre>\n\n\n\nThe following line writes Hello <\/span> in the hello.txt<\/span> file.<\/p>\n\n\n\nwriteFile(SD, \"\/hello.txt\", \"Hello \");<\/code><\/pre>\n\n\n\nAppend Content to a File<\/h4>\n\n\n\n Similarly, you can append content to a file (without overwriting previous content) using the appendFile()<\/span> function.<\/p>\n\n\n\nvoid appendFile(fs::FS &fs, const char * path, const char * message){\n Serial.printf(\"Appending to file: %s\\n\", path);\n\n File file = fs.open(path, FILE_APPEND);\n if(!file){\n Serial.println(\"Failed to open file for appending\");\n return;\n }\n if(file.print(message)){\n Serial.println(\"Message appended\");\n } else {\n Serial.println(\"Append failed\");\n }\n file.close();\n}<\/code><\/pre>\n\n\n\nThe following line appends the message World!\\n<\/span> in the hello.txt<\/span> file. The \\n<\/span> means that the next time you write something to the file, it will be written in a new line.<\/p>\n\n\n\nappendFile(SD, \"\/hello.txt\", \"World!\\n\");<\/code><\/pre>\n\n\n\nRename a File<\/h4>\n\n\n\n You can rename a file using the renameFile()<\/span> function. Pass as arguments the SD filesystem, the original filename, and the new filename.<\/p>\n\n\n\nvoid renameFile(fs::FS &fs, const char * path1, const char * path2){\n Serial.printf(\"Renaming file %s to %s\\n\", path1, path2);\n if (fs.rename(path1, path2)) {\n Serial.println(\"File renamed\");\n } else {\n Serial.println(\"Rename failed\");\n }\n}<\/code><\/pre>\n\n\n\nThe following line renames the hello.txt<\/span> file to foo.txt<\/span>.<\/p>\n\n\n\nrenameFile(SD, \"\/hello.txt\", \"\/foo.txt\");<\/code><\/pre>\n\n\n\nDelete a File<\/h4>\n\n\n\n Use the deleteFile()<\/span> function to delete a file. Pass as an argument the SD<\/span> filesystem and the file path of the file you want to delete.<\/p>\n\n\n\nvoid deleteFile(fs::FS &fs, const char * path){\n Serial.printf(\"Deleting file: %s\\n\", path);\n if(fs.remove(path)){\n Serial.println(\"File deleted\");\n } else {\n Serial.println(\"Delete failed\");\n }\n}<\/code><\/pre>\n\n\n\nThe following line deletes the foo.txt<\/span> file from the microSD card.<\/p>\n\n\n\ndeleteFile(SD, \"\/foo.txt\");<\/code><\/pre>\n\n\n\nTest a File<\/h4>\n\n\n\n The testFileIO()<\/span> functions shows how long it takes to read the content of a file.<\/p>\n\n\n\nvoid testFileIO(fs::FS &fs, const char * path){\n File file = fs.open(path);\n static uint8_t buf[512];\n size_t len = 0;\n uint32_t start = millis();\n uint32_t end = start;\n if(file){\n len = file.size();\n size_t flen = len;\n start = millis();\n while(len){\n size_t toRead = len;\n if(toRead > 512){\n toRead = 512;\n }\n file.read(buf, toRead);\n len -= toRead;\n }\n end = millis() - start;\n Serial.printf(\"%u bytes read for %u ms\\n\", flen, end);\n file.close();\n } \n else {\n Serial.println(\"Failed to open file for reading\");\n }\n\n file = fs.open(path, FILE_WRITE);\n if(!file){\n Serial.println(\"Failed to open file for writing\");\n return;\n }\n\n size_t i;\n start = millis();\n for(i=0; i<2048; i++){\n file.write(buf, 512);\n }\n end = millis() - start;\n Serial.printf(\"%u bytes written for %u ms\\n\", 2048 * 512, end);\n file.close();\n}<\/code><\/pre>\n\n\n\nThe following function tests the test.txt<\/span> file.<\/p>\n\n\n\ntestFileIO(SD, \"\/test.txt\");<\/code><\/pre>\n\n\n\nInitialize the microSD Card<\/h4>\n\n\n\n In the setup()<\/span>, the following lines initialize the microSD card with SD.begin()<\/span>.<\/p>\n\n\n\nSerial.begin(115200);\nif(!SD.begin()){\n Serial.println(\"Card Mount Failed\");\n return;\n}\nuint8_t cardType = SD.cardType();\n\nif(cardType == CARD_NONE){\n Serial.println(\"No SD card attached\");\n return;\n}<\/code><\/pre>\n\n\n\nIf you don’t pass any argument to the begin()<\/span> function, it will try to initialize SPI communication with the microSD card on the default chip select (CS) pin. If you want to use another CS pin, you can pass it as an argument to the begin()<\/span> function. For example, if you wanted to use GPIO 17 as a CS pin, you should use the following lines of code:<\/p>\n\n\n\nSerial.begin(115200);\nif(!SD.begin(17)){\n Serial.println(\"Card Mount Failed\");\n return;\n}\nuint8_t cardType = SD.cardType();<\/code><\/pre>\n\n\n\nIf you want to use custom SPI pins with the microSD card, go to this section<\/a>.<\/p>\n\n\n\nGet microSD Card Type<\/h4>\n\n\n\n The following lines print the microSD card type on the Serial Monitor.<\/p>\n\n\n\n
Serial.print(\"SD Card Type: \");\nif(cardType == CARD_MMC){\n Serial.println(\"MMC\");\n} else if(cardType == CARD_SD){\n Serial.println(\"SDSC\");\n} else if(cardType == CARD_SDHC){\n Serial.println(\"SDHC\");\n} else {\n Serial.println(\"UNKNOWN\");\n}<\/code><\/pre>\n\n\n\nGet microSD Card Size<\/h4>\n\n\n\n You can get the microSD card size by calling the cardSize()<\/span> method:<\/p>\n\n\n\nuint64_t cardSize = SD.cardSize() \/ (1024 * 1024);\nSerial.printf(\"SD Card Size: %lluMB\\n\", cardSize);<\/code><\/pre>\n\n\n\nTesting MicroSD Card Functions<\/h4>\n\n\n\n The following lines call the functions we’ve seen previously.<\/p>\n\n\n\n
listDir(SD, \"\/\", 0);\ncreateDir(SD, \"\/mydir\");\nlistDir(SD, \"\/\", 0);\nremoveDir(SD, \"\/mydir\");\nlistDir(SD, \"\/\", 2);\nwriteFile(SD, \"\/hello.txt\", \"Hello \");\nappendFile(SD, \"\/hello.txt\", \"World!\\n\");\nreadFile(SD, \"\/hello.txt\");\ndeleteFile(SD, \"\/foo.txt\");\nrenameFile(SD, \"\/hello.txt\", \"\/foo.txt\");\nreadFile(SD, \"\/foo.txt\");\ntestFileIO(SD, \"\/test.txt\");\nSerial.printf(\"Total space: %lluMB\\n\", SD.totalBytes() \/ (1024 * 1024));\nSerial.printf(\"Used space: %lluMB\\n\", SD.usedBytes() \/ (1024 * 1024));<\/code><\/pre>\n\n\n\nDemonstration<\/h3>\n\n\n\n Upload the previous sketch to your ESP32 board. After that, open the Serial Monitor and press the ESP32 on-board RST button. If the initialization succeeds, you’ll get similar messages on the Serial Monitor.<\/p>\n\n\n
\n
\n
Use Custom SPI Pins with the MicroSD Card<\/h2>\n\n\n\n The SD.h<\/span> and SD_MMC.h<\/span> libraries use the VSPI SPI pins (23, 19, 18, 5) by default. You can set other pins as SPI pins. The ESP32 features two SPI interfaces: HSPI and VSPI on the following pins:<\/p>\n\n\n\n
![\"ESP32](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2021\/02\/ESP32-Guide-microSD-Card-Module.jpg?resize=1200%2C675&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"MicroSD](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2021\/02\/microSD-card-module-ESP32-Arduino-ESP8266.jpg?resize=750%2C421&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"MicroSD](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2021\/02\/microSD-card-module-ESP32-ESP8266-Arduino.png?resize=317%2C288&quality=100&strip=all&ssl=1\")
<\/a><\/figure><\/div>\n\n\n![\"ESP32](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2021\/02\/ESP32-microSD-card-module-wiring-breadboard.jpg?resize=750%2C421&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/10\/header-200.png?w=1200&quality=100&strip=all&ssl=1\")
<\/a><\/p>\n\n\n\n![\"ESP32](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2021\/02\/ESP32-microSD-Card-Wiring-Diagram.png?resize=742%2C910&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"MicroSD](\"https:\/\/i0.wp.com\/rntlab.com\/wp-content\/uploads\/2018\/05\/format-SD-card-1.png?w=1200&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"MicroSD](\"https:\/\/i0.wp.com\/rntlab.com\/wp-content\/uploads\/2018\/05\/format-SD-card-2.png?w=1200&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"ESP32](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2021\/02\/microSD-car-ESP32-Example-Handle-Files-Read-Write_ESP32-microSD-card-read-write.png?resize=800%2C269&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"ESP32](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2021\/02\/microSDCard.-Serial-Monitor-Example-ESP32.png?resize=958%2C761&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n![\"ESP32](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2021\/02\/microSDCard.-Serial-Monitor-Example-ESP32-2.png?resize=958%2C761&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n