modified SDclass.begin() check for sd presence and added the Datalogger example

hardware/arduino/avr/libraries/Bridge/FileIO.cpp

@@ -160,7 +160,13 @@ const char *File::name() {
 
 
 boolean SDClass::begin() {
-  return true;
+  Process chksd;
+  int res = chksd.runShellCommand(F("cat /sys/bus/scsi/drivers/sd/*/block/sda/size"));
+  if (res == 0) {
+    if (chksd.peek() != '0')
+    return true; 
+  }
+  return false;
 }
 
 File SDClass::open(const char *filename, uint8_t mode) {

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

@@ -0,0 +1,96 @@
+/*
+  SD card datalogger
+ 
+ This example shows how to log data from three analog sensors 
+ to an SD card mounted on the Linux 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
+ 
+ You are allowed to remove the SD card while the Linux and the 
+ sketch is running but becareful to don't remove it while
+ the system is writing on it.
+ 
+ created  24 Nov 2010
+ modified 9 Apr 2012
+ by Tom Igoe
+ adapted to the Yun Bridge library 20 Jun 2013
+ by Federico Vanzati
+ 
+ This example code is in the public domain.
+ 	 
+ */
+
+#include <FileIO.h>
+#include <Console.h>
+
+void setup() {
+  // Initialize the Bridge and the Console
+  Bridge.begin();
+  Console.begin();
+
+  while(!Console){
+    ;  // wait for Console port to connect.
+  }
+
+  // see if the card is present and can be initialized:
+  if (!SD.begin()) {
+    Console.println("SD card failed, or not present");
+    // don't do anything more:
+    return;
+  }
+  Console.println("SD card initialized."); 
+
+}
+
+
+void loop () {
+  // make a string that start with a timestamp for assembling the data to log:
+  String dataString = "";
+  addTimeStamp(dataString);
+  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 += ","; 
+    }
+  }
+
+  // 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 SD card is mounted at the following "/mnt/sda1"
+  File dataFile = SD.open("/mnt/sda1/datalog.txt", FILE_APPEND);
+
+  // if the file is available, write to it:
+  if (dataFile) {
+    dataFile.println(dataString);
+    dataFile.close();
+    // print to the serial port too:
+    Console.println(dataString);
+  }  
+  // if the file isn't open, pop up an error:
+  else {
+    Console.println("error opening datalog.txt");
+  } 
+  
+  delay(15000);
+
+}
+
+// This function append a time stamp to the string passed as argument
+void addTimeStamp(String &string) {
+  Process time;
+  time.begin("date"); 
+  time.addParameter("+%D-%T");
+  time.run();
+
+  while(time.available()>0) {
+    char c = time.read();
+    if(c != '\n')
+      string += c;
+  }
+}