Add SimultaneousPlay for testing SD card and SD/SdFat library

examples/HardwareTesting/SimultaneousPlay/SimultaneousPlay.ino

+#include <Audio.h>
+#include <SD.h>
+
+// Reducing this delay will attempt to play the files simultaneously.
+// The clips are about 3.0 to 3.4 seconds, even though the voice is
+// heard only for the about the first half second.
+const int milliseconds = 3500;
+
+// GUItool: begin automatically generated code
+AudioPlaySdWav           playSdWav4;     //xy=259,267
+AudioPlaySdWav           playSdWav3;     //xy=260,218
+AudioPlaySdWav           playSdWav5;     //xy=260,317
+AudioPlaySdWav           playSdWav6;     //xy=261,369
+AudioPlaySdWav           playSdWav2;     //xy=262,169
+AudioPlaySdWav           playSdWav1;     //xy=263,118
+AudioMixer4              mixer1;         //xy=460,176
+AudioMixer4              mixer2;         //xy=571,271
+AudioOutputI2S           i2s1;           //xy=763,245
+AudioConnection          patchCord1(playSdWav4, 0, mixer1, 3);
+AudioConnection          patchCord2(playSdWav3, 0, mixer1, 2);
+AudioConnection          patchCord3(playSdWav5, 0, mixer2, 1);
+AudioConnection          patchCord4(playSdWav6, 0, mixer2, 2);
+AudioConnection          patchCord5(playSdWav2, 0, mixer1, 1);
+AudioConnection          patchCord6(playSdWav1, 0, mixer1, 0);
+AudioConnection          patchCord7(mixer1, 0, mixer2, 0);
+AudioConnection          patchCord8(mixer2, 0, i2s1, 0);
+AudioConnection          patchCord9(mixer2, 0, i2s1, 1);
+AudioControlSGTL5000     sgtl5000_1;     //xy=625,368
+// GUItool: end automatically generated code
+
+// Use these with the Teensy 3.x Audio Shield (Rev C)
+#define SDCARD_CS_PIN    10
+#define SDCARD_MOSI_PIN  7
+#define SDCARD_SCK_PIN   14
+
+// Use these with the Teensy 3.5 & 3.6 SD card
+//#define SDCARD_CS_PIN    BUILTIN_SDCARD
+//#define SDCARD_MOSI_PIN  11  // not actually used
+//#define SDCARD_SCK_PIN   13  // not actually used
+
+void setup() {
+  AudioMemory(40);
+  sgtl5000_1.enable();
+  sgtl5000_1.volume(0.6);
+  mixer1.gain(0, 0.167);
+  mixer1.gain(1, 0.167);
+  mixer1.gain(2, 0.167);
+  mixer1.gain(3, 0.167);
+  mixer2.gain(0, 1.0);
+  mixer2.gain(1, 0.167);
+  mixer2.gain(2, 0.167);
+
+  SPI.setMOSI(SDCARD_MOSI_PIN);
+  SPI.setSCK(SDCARD_SCK_PIN);
+  if (!(SD.begin(SDCARD_CS_PIN))) {
+    // stop here if no SD card, but print a message repetitively
+    while (1) {
+      Serial.println("Unable to access the SD card");
+      delay(500);
+    }
+  }
+}
+
+AudioPlaySdWav * const playerlist[6] = {
+  &playSdWav1, &playSdWav2, &playSdWav3, &playSdWav4, &playSdWav5, &playSdWav6
+};
+
+void playNumber(int n)
+{
+  String filename = String("NUM") + n + ".WAV";
+  Serial.print("Playing File: ");
+  Serial.println(filename);
+  Serial.flush();
+  playerlist[n]->play(filename.c_str());
+}
+
+void loop() {
+  for (int i=1; i <= 6; i++) {
+    playNumber(i);
+    delay(milliseconds);
+  }
+}