教程八 SD卡读取例程

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各模块使用教程

SD卡读写

General Driver for Robots板载有SD卡模块，可对SD卡进行读写操作，以下提供SD卡读写程序。

例程

上传程序

首先将SD卡格式化为FAT32格式。
Gdfr07.png
下载压缩包后打开SDCard.ino，打开文件夹进入路径C:\Users\用户名\AppData\Local\Arduino15\libraries，删除SD文件夹。
六1.png
删除后切回到Arduino IDE，用USB线将多功能驱动板和计算机连接起来（此处插入的是多功能驱动板USB的Type-C接口），点击“工具”→“端口”，再点击新出现的COM（我这里新出现的COM为COM26）。
六2.png
在Arduino IDE中，点击“工具”→“开发板”→“ESP32”→“ESP32 Dev Module”。开发板以及端口都选择好后上传程序。上传程序后将SD卡插入到驱动板上的SD卡槽，需要先上传程序再插入SD卡，不然会出现上传程序失败的结果。打开串口监视器，若出现SD卡读取失败的情况则断开USB线重新连接。
六3.png Gdfr09.png

程序解析

#include "FS.h"
#include "SD.h"
#include "SPI.h"

#define SCK  14
#define MISO  12
#define MOSI  13
#define CS  15

void readFile(fs::FS &fs, const char * path){
  Serial.printf("Reading file: %s\n", path);

  File file = fs.open(path);
  if(!file){
    Serial.println("Failed to open file for reading");
    return;
  }

  Serial.print("Read from file: ");
  while(file.available()){
    Serial.print((char)file.read());
  }
  file.close();
}

void writeFile(fs::FS &fs, const char * path, const char * message){
  Serial.printf("Writing file: %s\n", path);

  File file = fs.open(path, FILE_WRITE);
  if(!file){
    Serial.println("Failed to open file for writing");
    return;
  }
  if(file.print(message)){
    Serial.println("File written");
  } else {
    Serial.println("Write failed");
  }
  file.close();
}

void appendFile(fs::FS &fs, const char * path, const char * message){
  Serial.printf("Appending to file: %s\n", path);

  File file = fs.open(path, FILE_APPEND);
  if(!file){
    Serial.println("Failed to open file for appending");
    return;
  }
  if(file.print(message)){
    Serial.println("Message appended");
  } else {
    Serial.println("Append failed");
  }
  file.close();
}

void deleteFile(fs::FS &fs, const char * path){
  Serial.printf("Deleting file: %s\n", path);
  if(fs.remove(path)){
    Serial.println("File deleted");
  } else {
    Serial.println("Delete failed");
  }
}

void testFileIO(fs::FS &fs, const char * path){
  File file = fs.open(path);
  static uint8_t buf[512];
  size_t len = 0;
  uint32_t start = millis();
  uint32_t end = start;
  if(file){
    len = file.size();
    size_t flen = len;
    start = millis();
    while(len){
      size_t toRead = len;
      if(toRead > 512){
        toRead = 512;
      }
      file.read(buf, toRead);
      len -= toRead;
    }
    end = millis() - start;
    Serial.printf("%u bytes read for %u ms\n", flen, end);
    file.close();
  } else {
    Serial.println("Failed to open file for reading");
  }


  file = fs.open(path, FILE_WRITE);
  if(!file){
    Serial.println("Failed to open file for writing");
    return;
  }

  size_t i;
  start = millis();
  for(i=0; i<2048; i++){
    file.write(buf, 512);
  }
  end = millis() - start;
  Serial.printf("%u bytes written for %u ms\n", 2048 * 512, end);
  file.close();
}

void setup(){
  Serial.begin(115200);
  SPIClass spi = SPIClass(HSPI);
  spi.begin(SCK, MISO, MOSI, CS);

  if (!SD.begin(CS,spi,80000000)) {
    Serial.println("Card Mount Failed");
    return;
  }
  uint8_t cardType = SD.cardType();

  if(cardType == CARD_NONE){
    Serial.println("No SD card attached");
    return;
  }

  Serial.print("SD Card Type: ");
  if(cardType == CARD_MMC){
    Serial.println("MMC");
  } else if(cardType == CARD_SD){
    Serial.println("SDSC");
  } else if(cardType == CARD_SDHC){
    Serial.println("SDHC");
  } else {
    Serial.println("UNKNOWN");
  }

  uint64_t cardSize = SD.cardSize() / (1024 * 1024);
  Serial.printf("SD Card Size: %lluMB\n", cardSize);
  delay(2000);

  deleteFile(SD, "/hello.txt");
  writeFile(SD, "/hello.txt", "Hello ");
  appendFile(SD, "/hello.txt", "World!\n");
  readFile(SD, "/hello.txt");
  testFileIO(SD, "/test.txt");
  Serial.printf("Total space: %lluMB\n", SD.totalBytes() / (1024 * 1024));
  Serial.printf("Used space: %lluMB\n", SD.usedBytes() / (1024 * 1024));
}

void loop(){

}

资料

取自“https://www.waveshare.net/w/index.php?title=教程八_SD卡读取例程&oldid=92948”