项目笔记：Arduino读取SD卡

1 硬件连接（使用Arduino Uno）：

CS -> 10
SCK -> 13
MOSI -> 11
MISO -> 12
VCC ->5V
GND -> GND

2 让Arduino检测到SD卡

官方测试程序：检测SD卡连接并输出卡型号

/*
  SD card test

  This example shows how use the utility libraries on which the'
  SD library is based in order to get info about your SD card.
  Very useful for testing a card when you're not sure whether its working or not.

  The circuit:
    SD card attached to SPI bus as follows:
 ** MOSI - pin 11 on Arduino Uno/Duemilanove/Diecimila
 ** MISO - pin 12 on Arduino Uno/Duemilanove/Diecimila
 ** CLK - pin 13 on Arduino Uno/Duemilanove/Diecimila
 ** CS - depends on your SD card shield or module.
 		Pin 4 used here for consistency with other Arduino examples


  created  28 Mar 2011
  by Limor Fried
  modified 9 Apr 2012
  by Tom Igoe
*/
// include the SD library:
#include 
#include 

// set up variables using the SD utility library functions:
Sd2Card card;
SdVolume volume;
SdFile root;

// change this to match your SD shield or module;
// Arduino Ethernet shield: pin 4
// Adafruit SD shields and modules: pin 10
// Sparkfun SD shield: pin 8
// MKRZero SD: SDCARD_SS_PIN
const int chipSelect = 4;

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("\nInitializing SD card...");

  // 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 inserted?");
    Serial.println("* is your wiring correct?");
    Serial.println("* did you change the chipSelect pin to match your shield or module?");
    while (1);
  } else {
    Serial.println("Wiring is correct and a card is present.");
  }

  // print the type of card
  Serial.println();
  Serial.print("Card 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");
    while (1);
  }

  Serial.print("Clusters:          ");
  Serial.println(volume.clusterCount());
  Serial.print("Blocks x Cluster:  ");
  Serial.println(volume.blocksPerCluster());

  Serial.print("Total Blocks:      ");
  Serial.println(volume.blocksPerCluster() * volume.clusterCount());
  Serial.println();

  // print the type and size of the first FAT-type volume
  uint32_t volumesize;
  Serial.print("Volume type is:    FAT");
  Serial.println(volume.fatType(), DEC);

  volumesize = volume.blocksPerCluster();    // clusters are collections of blocks
  volumesize *= volume.clusterCount();       // we'll have a lot of clusters
  volumesize /= 2;                           // SD card blocks are always 512 bytes (2 blocks are 1KB)
  Serial.print("Volume size (Kb):  ");
  Serial.println(volumesize);
  Serial.print("Volume size (Mb):  ");
  volumesize /= 1024;
  Serial.println(volumesize);
  Serial.print("Volume size (Gb):  ");
  Serial.println((float)volumesize / 1024.0);

  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);
}

void loop(void) {
}

如果测试失败，要注意以下操作：

1 Initializing failed:
确认接线：对于Arduino Uno，SD卡读卡器的CS引脚要连接4.
如果接线正确，确认chipSelect值也为4

2 Could not find FAT16/FAT32 partition.\nMake sure you’ve formatted the card：
这一步需要对SD卡进行格式化，一定要选择FAT16或FAT32格式。对于内存大于32G的SD卡，windows自带的格式化工具不会提供FAT32选项，因此需要借用第三方工具：
http://ridgecrop.co.uk/index.htm?guiformat.htm

测试成功结果如下

2 利用SD卡读写文件

#include 
#include 

const int chipSelect = 10;
String fileName = "test.txt";
File myFile;

void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  pinMode(chipSelect, OUTPUT);
  // wait for Serial Monitor to connect. Needed for native USB port boards only:
  while (!Serial);

  Serial.print("Initializing SD card...");

  if (!SD.begin(chipSelect)) {
    Serial.println("initialization failed. Things to check:");
    Serial.println("1. is a card inserted?");
    Serial.println("2. is your wiring correct?");
    Serial.println("3. did you change the chipSelect pin to match your shield or module?");
    Serial.println("Note: press reset button on the board and reopen this Serial Monitor after fixing your issue!");
    while (true);
  }

  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(fileName, FILE_WRITE);

  // if the file opened okay, write to it:
  if (myFile) {
    Serial.print("Writing to test.txt...");
    myFile.println("testing 1, 2, 3.");
    if (SD.exists(fileName)) {
      Serial.println("file exists");
    }
    // close the file:
    myFile.close();
    Serial.println("done.");
  } else {
    // if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  }

  Serial.println("reopening...");
  // re-open the file for reading:
  myFile = SD.open(fileName);
  if (myFile) {
    Serial.println(fileName + ":");

    // read from the file until there's nothing else in it:
    while (myFile.available()) {
      Serial.write(myFile.read());
    }
    // close the file:
    Serial.println("done.");
    myFile.close();
  } else {
    // if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  }
}


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

里面调用的SD类方法：
1

SD.begin(chipSelect)

启动SD类，chipSelect为SD读卡器CS引脚连接的Arduino引脚。返回值为boolean，代表SD卡是否成功启动

2

SD.open(fileName, FILE_WRITE)

打开文件，参数为（文件名，读取方式）。注意文件名采用8.3格式，即文件名最多8字符，文件拓展名最多3字符，不区分大小写。如果文件名长度超过限制可能造成文件创建失败。

读取方式分为FILE_READ和FILE_WRITE，如果该参数不填默认为FILE_READ。在FILE_READ为只读状态，而FILE_WRITE允许修改文件。在FILE_WRITE状态下如果open的文件名不存在会创建新文件。

在FILE_READ模式下默认从文件头读取，在FILE_WRITE模式下默认从文件末尾读取

该方法返回值为一个文件（File类型），代表打开的文件。File类型支持被作为boolean，true代表存在文件，false代表不存在文件

3

SD.exists(fileName)

判断文件是否存在，返回boolean

文件操作方法：

myFile.println()

在文件里打印信息

myFile.close()

关闭并退出当前文件

上述测试程序运行结果：

注：我在测试中调用了程序多次，导致test.txt里面有多行内容。第一次运行后test.txt中只会有一行testing 1 2 3