Added R2-D2 mailbox project, basic code that plays sounds in a loop

arduino_projects/r2d2_mailbox/README.md

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+R2-D2 Mailbox
+=============
+
+This project is a mailbox made from an old gas bottle to look like R2-D2 from Star Wars. 
+I've also added some electronics to it so it plays sounds when a person goes near it, to amuse the mailman and local dog walkers!

arduino_projects/r2d2_mailbox/r2d2_mailbox/r2d2_mailbox.ino

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+#include "Arduino.h"
+#include "DFRobotDFPlayerMini.h"
+
+#define DFPSerial Serial1
+
+#define DFP_VOLUME 3 // from 0 to 30
+#define DFP_RX_PIN 16  
+#define DFP_TX_PIN 17  
+
+DFRobotDFPlayerMini myDFPlayer;
+void printDetail(uint8_t type, int value);
+
+void setup()
+{
+  Serial.begin(115200);
+
+  DFPSerial.begin(9600, SERIAL_8N1, DFP_RX_PIN, DFP_TX_PIN);
+
+
+  Serial.println();
+  Serial.println(F("DFRobot DFPlayer Mini Demo"));
+  Serial.println(F("Initializing DFPlayer ... (May take 3~5 seconds)"));
+
+  if (!myDFPlayer.begin(DFPSerial, /*isACK = */true, /*doReset = */true)) {
+    Serial.println(F("Unable to begin:"));
+    Serial.println(F("1.Please recheck the connection!"));
+    Serial.println(F("2.Please insert the SD card!"));
+    while(true){
+      delay(0);
+    }
+  }
+  Serial.println(F("DFPlayer Mini online."));
+
+  myDFPlayer.volume(DFP_VOLUME);
+  myDFPlayer.play(1);
+}
+
+void loop()
+{
+  static unsigned long timer = millis();
+
+  if (millis() - timer > 5000) {
+    timer = millis();
+    myDFPlayer.next();  //Play next mp3 every x seconds.
+  }
+
+  if (myDFPlayer.available()) {
+    printDetail(myDFPlayer.readType(), myDFPlayer.read()); //Print the detail message from DFPlayer to handle different errors and states.
+  }
+}
+
+void printDetail(uint8_t type, int value){
+  switch (type) {
+    case TimeOut:
+      Serial.println(F("Time Out!"));
+      break;
+    case WrongStack:
+      Serial.println(F("Stack Wrong!"));
+      break;
+    case DFPlayerCardInserted:
+      Serial.println(F("Card Inserted!"));
+      break;
+    case DFPlayerCardRemoved:
+      Serial.println(F("Card Removed!"));
+      break;
+    case DFPlayerCardOnline:
+      Serial.println(F("Card Online!"));
+      break;
+    case DFPlayerUSBInserted:
+      Serial.println("USB Inserted!");
+      break;
+    case DFPlayerUSBRemoved:
+      Serial.println("USB Removed!");
+      break;
+    case DFPlayerPlayFinished:
+      Serial.print(F("Number:"));
+      Serial.print(value);
+      Serial.println(F(" Play Finished!"));
+      break;
+    case DFPlayerError:
+      Serial.print(F("DFPlayerError:"));
+      switch (value) {
+        case Busy:
+          Serial.println(F("Card not found"));
+          break;
+        case Sleeping:
+          Serial.println(F("Sleeping"));
+          break;
+        case SerialWrongStack:
+          Serial.println(F("Get Wrong Stack"));
+          break;
+        case CheckSumNotMatch:
+          Serial.println(F("Check Sum Not Match"));
+          break;
+        case FileIndexOut:
+          Serial.println(F("File Index Out of Bound"));
+          break;
+        case FileMismatch:
+          Serial.println(F("Cannot Find File"));
+          break;
+        case Advertise:
+          Serial.println(F("In Advertise"));
+          break;
+        default:
+          break;
+      }
+      break;
+    default:
+      break;
+  }
+
+}