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libraries/WaveHC/examples/openByIndex/openByIndex.ino

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+/*
+ * This sketch illustrates opening files by index
+ * which can significantly reduce latency.
+ *
+ * How to prepare a test SD:
+ * Start with a clean newly formatted SD.
+ * First copy the 400 files in the 'fill' folder to the SD.
+ * Next copy the 16 files in the 'DTMF' folder to the SD.
+ * There should be 416 files in the SD root directory.
+ *
+ * You must copy the files in the above order so the 'fill'
+ * files occur in the directory before the DTMF files.
+ *
+ * Run this sketch using the prepared SD.  Notice the
+ * difference in latency between play by name and
+ * play by index.
+ */
+
+#include <WaveHC.h>
+#include <WaveUtil.h>
+
+SdReader card;    // This object holds the information for the card
+FatVolume vol;    // This holds the information for the partition on the card
+FatReader root;   // This holds the information for the volumes root directory
+FatReader file;   // This object represent the WAV file 
+WaveHC wave;      // This is the only wave (audio) object, since we will only play one at a time
+
+// time to play each tone in milliseconds
+#define PLAY_TIME 200
+
+/*
+ * Define macro to put error messages in flash memory
+ */
+#define error(msg) error_P(PSTR(msg))
+
+//////////////////////////////////// SETUP
+void setup() {
+  Serial.begin(9600);
+
+  if (!card.init()) error("card.init");
+
+  // enable optimized read - some cards may timeout
+  card.partialBlockRead(true);
+
+  if (!vol.init(card)) error("vol.init");
+
+  if (!root.openRoot(vol)) error("openRoot");
+
+  PgmPrintln("Index files");
+  indexFiles();
+
+  PgmPrintln("Play files by index");
+  playByIndex();
+
+  PgmPrintln("Play files by name");
+  playByName();
+}
+
+//////////////////////////////////// LOOP
+void loop() { }
+
+/////////////////////////////////// HELPERS
+/*
+ * print error message and halt
+ */
+void error_P(const char *str) {
+  PgmPrint("Error: ");
+  SerialPrint_P(str);
+  sdErrorCheck();
+  while(1);
+}
+/*
+ * print error message and halt if SD I/O error, great for debugging!
+ */
+void sdErrorCheck(void) {
+  if (!card.errorCode()) return;
+  PgmPrint("\r\nSD I/O error: ");
+  Serial.print(card.errorCode(), HEX);
+  PgmPrint(", ");
+  Serial.println(card.errorData(), HEX);
+  while(1);
+}
+
+// Number of files.
+#define FILE_COUNT 16
+
+// Files are 'touch tone phone' DTMF tones, P = #, S = *
+// Most phones don't have A, B, C, and D tones.
+// file names are of the form DTMFx.WAV where x is one of
+// the letters from fileLetter[]
+char fileLetter[] =  {'0', '1', '2', '3', '4', '5', '6', 
+      '7', '8', '9', 'A', 'B', 'C', 'D', 'P', 'S'}; 
+      
+// index of DTMF files in the root directory
+uint16_t fileIndex[FILE_COUNT];
+/*
+ * Find files and save file index.  A file's index is is the
+ * index of it's directory entry in it's directory file. 
+ */
+void indexFiles(void) {
+  char name[10];
+  
+  // copy flash string to RAM
+  strcpy_P(name, PSTR("DTMFx.WAV"));
+  
+  for (uint8_t i = 0; i < FILE_COUNT; i++) {
+    
+    // Make file name
+    name[4] = fileLetter[i];
+    
+    // Open file by name
+    if (!file.open(root, name)) error("open by name");
+    
+    // Save file's index (byte offset of directory entry divided by entry size)
+    // Current position is just after entry so subtract one.
+    fileIndex[i] = root.readPosition()/32 - 1;   
+  }
+  PgmPrintln("Done");
+}
+/*
+ * Play file by index and print latency in ms
+ */
+void playByIndex(void) {
+  for (uint8_t i = 0; i < FILE_COUNT; i++) {
+    
+    // start time
+    uint32_t t = millis();
+    
+    // open by index
+    if (!file.open(root, fileIndex[i])) {
+      error("open by index");
+    }
+    
+    // create and play Wave
+    if (!wave.create(file)) error("wave.create");
+    wave.play();
+    
+    // print time to open file and start play
+    Serial.println(millis() - t);
+    
+    // stop after PLAY_TIME ms
+    while((millis() - t) < PLAY_TIME);
+    wave.stop();
+    
+    // check for play errors
+    sdErrorCheck();
+  }
+  PgmPrintln("Done");
+}
+/*
+ * Play file by name and print latency in ms
+ */
+void playByName(void) {
+  char name[10];
+  
+  // copy flash string to RAM
+  strcpy_P(name, PSTR("DTMFx.WAV"));
+  
+  for (uint8_t i = 0; i < FILE_COUNT; i++) {
+    // start time
+    uint32_t t = millis();
+    
+    // make file name
+    name[4] = fileLetter[i];
+    
+    // open file by name
+    if (!file.open(root, name)) error("open by name"); 
+    
+    // create wave and start play
+    if (!wave.create(file))error("wave.create");
+    wave.play();
+    
+    // print time
+    Serial.println(millis() - t);
+    
+    // stop after PLAY_TIME ms
+    while((millis() - t) < PLAY_TIME);
+    wave.stop();
+    
+    // check for play errors
+    sdErrorCheck();
+  }
+  PgmPrintln("Done");
+}