SD ReadWrite example writes too often

Other Hardware Storage
1

That's the best way I can describe it.....

I am using the ReadWrite sketch in the IDE. There is nothing in the loop, so I understand this is one pass through the setup section.
The initialisation and the write is confirmed on the monitor as OK.
The monitor showed:

test.txt:

testing 1, 2, 3.
testing 1, 2, 3.

I added two exclamation marks and started over. The extra print added was:

testing 1, 2, 3.
testing 1, 2, 3. !!
testing 1, 2, 3. !!

i.e. a third line as original, plus two with exclamation marks. It appears that very time I restart I get three lines of text.

2

I am using the ReadWrite sketch in the IDE.

But...

I added two exclamation marks and started over. The extra print added was:

So, where IS your code?

3

Hello. This is just the example in the 1.0.1 IDE

Thanks

NP

/*
  SD card read/write
 
 This example shows how to read and write data to and from an SD card file 	
 The circuit:
 * SD card attached to SPI bus as follows:
 ** MOSI - pin 11
 ** MISO - pin 12
 ** CLK - pin 13
 ** CS - pin 4
 
 created   Nov 2010
 by David A. Mellis
 modified 9 Apr 2012
 by Tom Igoe
 
 This example code is in the public domain.
 	 
 */
 
#include <SD.h>

File myFile;

void setup()
{
 // Open serial communications and wait for port to open:
  Serial.begin(9600);
   while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only
  }


  Serial.print("Initializing SD card...");
  // On the Ethernet Shield, CS is pin 4. It's set as an output by default.
  // Note that even if it's not used as the CS pin, the hardware SS pin 
  // (10 on most Arduino boards, 53 on the Mega) must be left as an output 
  // or the SD library functions will not work. 
   pinMode(10, OUTPUT);
   
  if (!SD.begin(4)) {
    Serial.println("initialization failed!");
    return;
  }
  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("test.txt", FILE_WRITE);
  
  // if the file opened okay, write to it:
  if (myFile) {
    Serial.print("Writing to test.txt...");
    myFile.println("testing 1, 2, 3.");
	// close the file:
    myFile.close();
    Serial.println("done.");
  } else {
    // if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  }
  
  // re-open the file for reading:
  myFile = SD.open("test.txt");
  if (myFile) {
    Serial.println("test.txt:");
    
    // read from the file until there's nothing else in it:
    while (myFile.available()) {
    	Serial.write(myFile.read());
    }
    // close the file:
    myFile.close();
  } else {
  	// if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  }
}

void loop()
{
	// nothing happens after setup
}
4

Further to this matter, confusion has reigned, not helped by my flailing around with alternatives, but I have now gotten some order into the problem.

The Arduino example works in that it will at least consistently initialise the card. The Jeremy Blum sketch does not work in that it consistently fails to initialise the same card.

Neither sketch works with the LCD shield in place. I will put that down to the shield.

On startup with a fresh, clean, card, The Arduino sketch will write "testing 1,2,3." three times. When I press reset, it will write one new line only. So it is only on startup that I have a problem.

5

An Arduino sketch starts when you power up or load a sketch. The Arduino is reset when you open the serial monitor. This means the sketch runs several times, not just once.

Change this:

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

To this:

 Serial.println("Type any character");
 while (Serial.read() < 0);
 Serial.print("Initializing SD card...");

This will prevent writing to the SD before the serial monitor is running.

Then run the sketch and type a character when this message prints.

Type any character