modified the Datalogger example

Author: Fede85

hardware/arduino/avr/libraries/Bridge/examples/Datalogger/Datalogger.ino

@@ -2,11 +2,15 @@
   SD card datalogger
  
  This example shows how to log data from three analog sensors 
- to an SD card mounted on the Arduino Yun using the Bridge library.
+ to an SD card mounted on the Arduino Yún using the Bridge library.
  	
  The circuit:
- * analog sensors on analog ins 0, 1, and 2
- * SD card attached to SD card slot of the Arduino Yun
+ * analog sensors on analog pins 0, 1 and 2
+ * SD card attached to SD card slot of the Arduino Yún
+ 
+ Prepare your SD card creating an empty folder in the SD root 
+ named "arduino". This will ensure that the Yún will create a link 
+ to the SD to the "/mnt/sd" path.
  
  You can remove the SD card while the Linux and the 
  sketch are running but be careful not to remove it while
@@ -15,7 +19,7 @@
  created  24 Nov 2010
  modified 9 Apr 2012
  by Tom Igoe
- adapted to the Yun Bridge library 20 Jun 2013
+ adapted to the Yún Bridge library 20 Jun 2013
  by Federico Vanzati
  modified  21 Jun 2013
  by Tom Igoe
@@ -25,7 +29,6 @@
  */
 
 #include <FileIO.h>
-#include <Serial.h>
 
 void setup() {
   // Initialize the Bridge and the Serial
@@ -34,29 +37,29 @@ void setup() {
   FileSystem.begin();
 
   while(!Serial);  // wait for Serial port to connect.
-  Serial.println("Filesystem datalogger");
+  Serial.println("Filesystem datalogger\n");
 }
 
 
 void loop () {
   // make a string that start with a timestamp for assembling the data to log:
-  String dataString = "";
-  dataString += addTimeStamp();
+  String dataString;
+  dataString += getTimeStamp();
   dataString += " = ";
 
   // read three sensors and append to the string:
   for (int analogPin = 0; analogPin < 3; analogPin++) {
     int sensor = analogRead(analogPin);
     dataString += String(sensor);
     if (analogPin < 2) {
-      dataString += ","; 
+      dataString += ",";  // separate the values with a comma
     }
   }
 
   // open the file. note that only one file can be open at a time,
   // so you have to close this one before opening another.
   // The FileSystem card is mounted at the following "/mnt/FileSystema1"
-  File dataFile = FileSystem.open("/mnt/sda1/datalog.txt", FILE_APPEND);
+  File dataFile = FileSystem.open("/mnt/sd/datalog.txt", FILE_APPEND);
 
   // if the file is available, write to it:
   if (dataFile) {
@@ -74,17 +77,23 @@ void loop () {
 
 }
 
-// This function append a time stamp to the string passed as argument
-String addTimeStamp() {
+// This function return a string with the time stamp
+String getTimeStamp() {
   String result;
   Process time;
-  time.begin("date"); 
-  time.addParameter("+%D-%T");
-  time.run();
+  // date is a command line utility to get the date and the time 
+  // in different formats depending on the additional parameter 
+  time.begin("date");
+  time.addParameter("+%D-%T");  // parameters: D for the complete date mm/dd/yy
+                                //             T for the time hh:mm:ss    
+  time.run();  // run the command
 
+  // read the output of the command
   while(time.available()>0) {
     char c = time.read();
     if(c != '\n')
       result += c;
   }
+  
+  return result;
 }