Update librairies + optimizations

loop time and memory optimization

libraries/RTClib/examples/ds1307nvram/ds1307nvram.ino

@@ -0,0 +1,59 @@
+// Example of using the non-volatile RAM storage on the DS1307.
+// You can write up to 56 bytes from address 0 to 55.
+// Data will be persisted as long as the DS1307 has battery power.
+
+#include <Wire.h>
+#include "RTClib.h"
+
+RTC_DS1307 rtc;
+
+void printnvram(uint8_t address) {
+  Serial.print("Address 0x");
+  Serial.print(address, HEX);
+  Serial.print(" = 0x");
+  Serial.println(rtc.readnvram(address), HEX); 
+}
+
+void setup () {
+  Serial.begin(57600);
+#ifdef AVR
+  Wire.begin();
+#else
+  Wire1.begin(); // Shield I2C pins connect to alt I2C bus on Arduino Due
+#endif
+  rtc.begin();
+
+  // Print old RAM contents on startup.
+  Serial.println("Current NVRAM values:");
+  for (int i = 0; i < 6; ++i) {
+     printnvram(i);
+  }
+
+  // Write some bytes to non-volatile RAM storage.
+  // NOTE: You can only read and write from addresses 0 to 55 (i.e. 56 byte values).
+  Serial.println("Writing NVRAM values.");
+  // Example writing one byte at a time:
+  rtc.writenvram(0, 0xFE);
+  rtc.writenvram(1, 0xED);
+  // Example writing multiple bytes:
+  uint8_t writeData[4] = { 0xBE, 0xEF, 0x01, 0x02 };
+  rtc.writenvram(2, writeData, 4);
+  
+  // Read bytes from non-volatile RAM storage.
+  Serial.println("Reading NVRAM values:");
+  // Example reading one byte at a time.
+  Serial.println(rtc.readnvram(0), HEX);
+  Serial.println(rtc.readnvram(1), HEX);
+  // Example reading multiple bytes:
+  uint8_t readData[4] = {0};
+  rtc.readnvram(readData, 4, 2);
+  Serial.println(readData[0], HEX);
+  Serial.println(readData[1], HEX);
+  Serial.println(readData[2], HEX);
+  Serial.println(readData[3], HEX);
+  
+}
+
+void loop () {
+  // Do nothing in the loop.
+}