将SD卡连接到Arduino并获取卡信息
在本教程中,我们将Arduino Uno连接到SD卡并提取卡信息。
电路图
电路图如下所示:
如您所见,您需要进行以下连接:
SD卡座 | Arduino Uno |
---|---|
Vcc | 5V |
GND | GND |
MISO | 12 |
MOSI | 11 |
SCK | 13 |
CS | 10 |
只有对于Vcc,请确保您的SD卡座输入电压为5V。如果输入电压为3.3V,请将其连接到Arduino Uno上的3.3V引脚。
代码详解
我们将逐步讲解内置SD库附带的示例代码。您可以从文件→示例→SD→CardInfo中访问它。
或者,您也可以在GitHub上访问它:https://github.com/arduinolibraries/SD/blob/master/examples/CardInfo/CardInfo.ino
我们首先包含SPI和SD库:
#include <SPI.h> #include <SD.h>
接下来,我们根据SD库中定义的对象定义一些变量。
Sd2Card card; SdVolume volume; SdFile root;
接下来,我们定义芯片选择引脚。示例代码将芯片选择设置为4号引脚。但是,我们将CS引脚连接到Arduino Uno的10号引脚。因此,我们将更改它。
const int chipSelect = 10;
在Setup中,我们首先初始化Serial,然后初始化SD卡(使用芯片选择引脚和SPI协议,SPI协议的其他引脚MISO、MOSI、SCK在SPI库中默认定义)。
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..."); // 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."); }
接下来,我们使用.type()函数获取并打印卡的类型。
// 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"); }
接下来,我们初始化卡的卷,获取卡中的簇总数和每个簇的块数,从而获得卡中的块总数。
// 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.
Make 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();
之后,我们打印卷是FAT 16还是FAT 32类型。此外,我们还计算总容量(以kB为单位),利用一个块始终为512字节或0.5 kB这一事实。
// 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);
最后,我们使用openRoot()函数列出卡上找到的所有文件,并打印日期、大小以及文件名。
Serial.println("
Files 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);
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