不删除AdodioC++上的文件

我有两个草图，我正在一个计算机上运行。第一个将文件转储到序列号（如果存在）。这是Arduino附带的示例之一，但我对其进行了如下修改：

/*
    SD card file dump

    This example shows how to read a file from the SD card using the
    SD library and send it over the serial port.

    The circuit:
    * SD card attached to SPI bus as follows:
    ** MOSI - pin 11
    ** MISO - pin 12
    ** CLK - pin 13
    ** CS - pin 4

    Created  22 December 2010 by Limor Fried
    Modified 9 Apr 2012 by Tom Igoe

    This example code is in the public domain.
 */

#include <SD.h>

// On the Ethernet Shield, CS is pin 4. Note that even if it's not
// used as the CS pin, the hardware CS pin (10 on most Arduino boards,
// 53 on the Mega) must be left as an output or the SD library
// functions will not work.
const int chipSelect = 4;

void setup()
{
    // Open serial communications and wait for port to open:
    Serial.begin(115200);
    while (!Serial) {
        ; // Wait for serial port to connect. Needed for Leonardo only.
    }

    Serial.print("Initializing SD card...");
    // Make sure that the default chip select pin is set to
    // output, even if you don't use it:
    pinMode(10, OUTPUT);

    // See if the card is present and can be initialized:
    if (!SD.begin(chipSelect)) {
        Serial.println("Card failed, or not present");
        // Don't do anything more:
        return;
    }
    Serial.println("card initialized.");

    // Open the file. note that only one file can be open at a time,
    // so you have to close this one before opening another.
    File dataFile = SD.open("datalog.txt");

    // If the file is available, write to it:
    if (dataFile) {
        while (dataFile.available()) {
          Serial.write(dataFile.read());
        }
        dataFile.close();
    }
    // If the file isn't open, pop up an error:
    else {
        Serial.println("error opening datalog.txt");
    }
}

void loop()
{
}

因此，新的删除示意图如下所示：

#include <SD.h>

const int chipSelect = 4;

void setup(){
    Serial.begin(115200);

    Serial.print("Initializing SD card...");
    // Make sure that the default chip select pin is set to
    // output, even if you don't use it:
    pinMode(10, OUTPUT);

    if(SD.exists("datalog.txt"))
    {
        SD.remove("datalog.txt");
        Serial.println("file removed");
    }
    else
    {
        Serial.println("no file to remove");
    }
}

void loop(){

}

#include <SD.h>

const int chipSelect = 4;

void setup(){
    Serial.begin(115200);

    Serial.print("Initializing SD card...");
    // Make sure that the default chip select pin is set to
    // output, even if you don't use it:
    pinMode(10, OUTPUT);

    // See if the card is present and can be initialized:
    if (!SD.begin(chipSelect)) {
        Serial.println("Card failed, or not present");
        // Don't do anything more:
        return;
    }
    Serial.println("card initialized.");

    if(SD.exists("datalog.txt"))
    {
        SD.remove("datalog.txt");
        Serial.println("file removed");
    }
    else
    {
        Serial.println("no file to remove");
    }
}

void loop(){

}

运行该草图后，它现在将删除文件。为什么新版本可以运行，而旧版本不能运行？

添加SD.begin并不能使其具有容错性。它初始化库。您需要在调用其他函数之前调用该函数。从：

begin初始化SD库和卡。这就开始使用 大多数Arduino板上的SPI总线数字引脚11、12和13；50, 51, Mega和chip select引脚上有52个，默认为 大多数Arduino板上的硬件SS引脚10，Mega板上的53

---

啊，我在想，这只不过是看看卡是否准备好了，但没有意识到它正在这样做，并提供状态。我的错。。。。

#include <SD.h>

const int chipSelect = 4;

void setup(){
    Serial.begin(115200);

    Serial.print("Initializing SD card...");
    // Make sure that the default chip select pin is set to
    // output, even if you don't use it:
    pinMode(10, OUTPUT);

    // See if the card is present and can be initialized:
    if (!SD.begin(chipSelect)) {
        Serial.println("Card failed, or not present");
        // Don't do anything more:
        return;
    }
    Serial.println("card initialized.");

    if(SD.exists("datalog.txt"))
    {
        SD.remove("datalog.txt");
        Serial.println("file removed");
    }
    else
    {
        Serial.println("no file to remove");
    }
}

void loop(){

}