[136] | 1 | /*
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| 2 | SD card read/write
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| 3 |
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| 4 | This example shows how to read and write data to and from an SD card file
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| 5 | The circuit:
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| 6 | * SD card attached to SPI bus as follows:
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| 7 | ** MOSI - pin 11
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| 8 | ** MISO - pin 12
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| 9 | ** CLK - pin 13
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| 10 | ** CS - pin 4
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| 11 |
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| 12 | created Nov 2010
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| 13 | by David A. Mellis
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| 14 | modified 9 Apr 2012
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| 15 | by Tom Igoe
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| 16 |
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| 17 | This example code is in the public domain.
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| 18 |
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| 19 | */
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| 20 |
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| 21 | #include <SPI.h>
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| 22 | #include <SD.h>
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| 23 |
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| 24 | File myFile;
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| 25 |
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| 26 | void setup()
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| 27 | {
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| 28 | // Open serial communications and wait for port to open:
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| 29 | Serial.begin(9600);
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| 30 | while (!Serial) {
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| 31 | ; // wait for serial port to connect. Needed for Leonardo only
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| 32 | }
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| 33 |
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| 34 |
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| 35 | Serial.print("Initializing SD card...");
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| 36 | // On the Ethernet Shield, CS is pin 4. It's set as an output by default.
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| 37 | // Note that even if it's not used as the CS pin, the hardware SS pin
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| 38 | // (10 on most Arduino boards, 53 on the Mega, 14 on the Leonardo) must be left as an output
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| 39 | // or the SD library functions will not work.
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| 40 |
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| 41 | if (!SD.begin(4)) {
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| 42 | Serial.println("initialization failed!");
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| 43 | return;
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| 44 | }
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| 45 | Serial.println("initialization done.");
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| 46 |
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| 47 | // open the file. note that only one file can be open at a time,
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| 48 | // so you have to close this one before opening another.
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| 49 | myFile = SD.open("test.txt", FILE_WRITE);
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| 50 |
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| 51 | // if the file opened okay, write to it:
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| 52 | if (myFile) {
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| 53 | Serial.print("Writing to test.txt...");
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| 54 | myFile.println("testing 1, 2, 3.");
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| 55 | // close the file:
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| 56 | myFile.close();
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| 57 | Serial.println("done.");
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| 58 | } else {
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| 59 | // if the file didn't open, print an error:
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| 60 | Serial.println("error opening test.txt");
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| 61 | }
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| 62 |
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| 63 | // re-open the file for reading:
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| 64 | myFile = SD.open("test.txt");
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| 65 | if (myFile) {
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| 66 | Serial.println("test.txt:");
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| 67 |
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| 68 | // read from the file until there's nothing else in it:
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| 69 | while (myFile.available()) {
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| 70 | Serial.write(myFile.read());
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| 71 | }
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| 72 | // close the file:
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| 73 | myFile.close();
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| 74 | } else {
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| 75 | // if the file didn't open, print an error:
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| 76 | Serial.println("error opening test.txt");
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| 77 | }
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| 78 | }
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| 79 |
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| 80 | void loop()
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| 81 | {
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| 82 | // nothing happens after setup
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| 83 | }
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| 84 |
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| 85 |
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