我在Arduino Uno上运行了两个草图。第一个将文件转储到串行（如果存在）。这是 Arduino 附带的示例之一，但我已将其修改为：
/*
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()
{
}
我的另一个草图应该删除一个文件。当我运行这个删除草图时，它说没有找到文件。然而，我可以继续运行上面的草图并将内容转储到连续剧中。我的删除草图如下：
#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(){
}
我在这里错过了什么吗？
就在发布这个之后，我意识到我没有让这个删除草图容错，并在该pinmode行之后添加了以下代码：
// 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.");
因此，新的删除草图如下：
#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，它现在会删除文件。为什么新版能用，旧版不能用？