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I tried to use Arduino SD Library, I was able to run Datalogger and Dumpfile sample application to verify that the bits and bytes are written perfectly in the SD card. When I tried to read from windows, everything is null. Is there an Arduino library that can write text file compatible to windows text format?

  • Add a link to the library you are using. The example sketches might be generating a file with binary data. It would look strange if displayed with as text. – Mikael Patel Sep 12 '16 at 5:15
  • I'm guessing that the way you read the file in Windows is the issue. The file encoding at the beginning of the file is probably not specified by the Arduino program. – Code Gorilla Sep 12 '16 at 8:02
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    Maybe if you showed us what isn't working we could help you see why it isn't working and how to fix it. – Majenko Sep 12 '16 at 10:15
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Notepad in Windows will show the raw data in a file - in all its hideous glory. However, there are things to make sure of:

  1. Make sure that what you write to a file is ASCII characters. By that I mean do not simply write a byte or word value, convert it to a string first:

    byte value; ...

    value = Sensor.read(); // Return a value from 0-99 Card.write(value);

The above code will write a byte of 0 to 99 to the file - but you probably don't want that! The byte 32 is a space; 65 is the capital letter A; and 97 is the lower case letter a. Say what?

Every byte is represented by a different character in Notepad, so you need to convert the byte 97 into TWO bytes - first the byte (character) 9, and then the byte (character) 7. How do you do that?

One easy way is to use the following:

byte value;
char buffer[8]; // Define once for temporary use

...
value = Sensor.read();
sprintf(buffer, " %d", value); // Store value in buffer as chars - with a leading space
Card.write(buffer);

The above will write one (or more) characters into the file depending on the value you want to print. If your existing data was just a series of 0 bytes, your old code would have been nothing but NULLs. This will (at least) print 0 0 0 0 0 0 0 0 0 0

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