Add USB examples

examples/HardwareTesting/PassThroughUSB/PassThroughUSB.ino

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+#include <Audio.h>
+#include <Wire.h>
+#include <SPI.h>
+#include <SD.h>
+#include <SerialFlash.h>
+
+AudioInputUSB            usb1;           //xy=200,69
+AudioOutputI2S           i2s1;           //xy=365,94
+AudioConnection          patchCord1(usb1, 0, i2s1, 0);
+AudioConnection          patchCord2(usb1, 1, i2s1, 1);
+AudioControlSGTL5000     sgtl5000_1;     //xy=302,184
+
+void setup() {                
+  AudioMemory(12);
+  sgtl5000_1.enable();
+  sgtl5000_1.volume(0.6);
+}
+
+void loop() {
+  // TODO: make PC's volume setting control the SGTL5000 volume...
+}

examples/HardwareTesting/WavFilePlayerUSB/WavFilePlayerUSB.ino

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+#include <Audio.h>
+#include <Wire.h>
+#include <SPI.h>
+#include <SD.h>
+#include <SerialFlash.h>
+
+AudioPlaySdWav           playWav1;
+AudioOutputUSB           audioOutput;
+AudioOutputAnalog        dac;
+AudioConnection          patchCord1(playWav1, 0, audioOutput, 0);
+AudioConnection          patchCord2(playWav1, 1, audioOutput, 1);
+AudioConnection          patchCord3(playWav1, 0, dac, 0);
+
+// Use these with the audio adaptor board
+#define SDCARD_CS_PIN    10
+#define SDCARD_MOSI_PIN  7
+#define SDCARD_SCK_PIN   14
+
+void setup() {
+  Serial.begin(9600);
+
+  // Audio connections require memory to work.  For more
+  // detailed information, see the MemoryAndCpuUsage example
+  AudioMemory(20);
+
+  SPI.setMOSI(SDCARD_MOSI_PIN);
+  SPI.setSCK(SDCARD_SCK_PIN);
+  if (!(SD.begin(SDCARD_CS_PIN))) {
+    // stop here, but print a message repetitively
+    while (1) {
+      Serial.println("Unable to access the SD card");
+      delay(500);
+    }
+  }
+}
+
+void playFile(const char *filename)
+{
+  playWav1.play(filename);
+  // A brief delay for the library read WAV info
+  delay(5);
+  // Simply wait for the file to finish playing.
+  while (playWav1.isPlaying()) {
+  }
+}
+
+void loop() {
+  playFile("SDTEST1.WAV");  // filenames are always uppercase 8.3 format
+  delay(500);
+  playFile("SDTEST2.WAV");
+  delay(500);
+  playFile("SDTEST3.WAV");
+  delay(500);
+  playFile("SDTEST4.WAV");
+  delay(1500);
+}