Fixing example: this works now.

Author: aentinger

examples/Beginner/Audio_Playback/Audio_Playback.ino

@@ -2,20 +2,24 @@
  * GIGA R1 - Audio Playback
  * Simple wav format audio playback via 12-Bit DAC output by reading from a USB drive.
  * In order for this sketch to work you need to rename 'USB_DRIVE' to the name of your USB stick drive.
+ * Furthermore you need to store the provided audio file AUDIO_SAMPLE.wav on it.
 */
 
 #include <Arduino_AdvancedAnalog.h>
 #include <DigitalOut.h>
 #include <USBHostMbed5.h>
 #include <FATFileSystem.h>
 
-#include "wav_seeker.h"
-
 AdvancedDAC dac1(A12);
 
 USBHostMSD msd;
 mbed::FATFileSystem usb("USB_DRIVE");
 
+FILE * file = nullptr;
+int sample_size = 0;
+int samples_count = 0;
+
+
 void setup()
 {
   Serial.begin(115200);
@@ -38,28 +42,116 @@ void setup()
   }
 
   Serial.println("Opening audio file ...");
-  
-  // 16-bit PCM Mono 16kHz realigned noise reduction
-  FILE * f = fopen("/USB_DRIVE/AUDIO_SAMPLE.wav", "r");
-  if (f == nullptr)
+
+  /* 16-bit PCM Mono 16kHz realigned noise reduction */
+  file = fopen("/USB_DRIVE/AUDIO_SAMPLE.wav", "rb");
+  if (file == nullptr)
   {
     Serial.print("Error opening audio file: ");
     Serial.println(strerror(errno));
     return;
   }
 
-  Serial.println("Playing audio file ...");
-  wav_play_rl(f, dac1, false);
- 
-  Serial.println("Cleaning up ...");
-  fclose(f);
-  int const rc_umount = usb.unmount();
-  if (rc_umount < 0)
+  Serial.println("Reading audio header ...");
+  struct wav_header_t
   {
-    Serial.print("Error unmounting USB drive: ");
-    Serial.println(rc_umount);
+    char chunkID[4]; //"RIFF" = 0x46464952
+    unsigned long chunkSize; //28 [+ sizeof(wExtraFormatBytes) + wExtraFormatBytes] + sum(sizeof(chunk.id) + sizeof(chunk.size) + chunk.size)
+    char format[4]; //"WAVE" = 0x45564157
+    char subchunk1ID[4]; //"fmt " = 0x20746D66
+    unsigned long subchunk1Size; //16 [+ sizeof(wExtraFormatBytes) + wExtraFormatBytes]
+    unsigned short audioFormat;
+    unsigned short numChannels;
+    unsigned long sampleRate;
+    unsigned long byteRate;
+    unsigned short blockAlign;
+    unsigned short bitsPerSample;
+  };
+
+  wav_header_t header;
+  fread(&header, sizeof(header), 1, file);
+
+  Serial.println("WAV File Header read:");
+  char msg[64] = {0};
+  snprintf(msg, sizeof(msg), "File Type: %s", header.chunkID);
+  Serial.println(msg);
+  snprintf(msg, sizeof(msg), "File Size: %ld", header.chunkSize);
+  Serial.println(msg);
+  snprintf(msg, sizeof(msg), "WAV Marker: %s", header.format);
+  Serial.println(msg);
+  snprintf(msg, sizeof(msg), "Format Name: %s", header.subchunk1ID);
+  Serial.println(msg);
+  snprintf(msg, sizeof(msg), "Format Length: %ld", header.subchunk1Size);
+  Serial.println(msg);
+  snprintf(msg, sizeof(msg), "Format Type: %hd", header.audioFormat);
+  Serial.println(msg);
+  snprintf(msg, sizeof(msg), "Number of Channels: %hd", header.numChannels);
+  Serial.println(msg);
+  snprintf(msg, sizeof(msg), "Sample Rate: %ld", header.sampleRate);
+  Serial.println(msg);
+  snprintf(msg, sizeof(msg), "Sample Rate * Bits/Sample * Channels / 8: %ld", header.byteRate);
+  Serial.println(msg);
+  snprintf(msg, sizeof(msg), "Bits per Sample * Channels / 8: %hd", header.blockAlign);
+  Serial.println(msg);
+  snprintf(msg, sizeof(msg), "Bits per Sample: %hd", header.bitsPerSample);
+  Serial.println(msg);
+
+  /* Find the data section of the WAV file. */
+  struct chunk_t
+  {
+    char ID[4];
+    unsigned long size;
+  };
+
+  chunk_t chunk;
+  snprintf(msg, sizeof(msg), "id\t" "size");
+  Serial.println(msg);
+  /* Find data chunk. */
+  while (true)
+  {
+    fread(&chunk, sizeof(chunk), 1, file);
+    snprintf(msg, sizeof(msg), "%c%c%c%c\t" "%li", chunk.ID[0], chunk.ID[1], chunk.ID[2], chunk.ID[3], chunk.size);
+    Serial.println(msg);
+    if (*(unsigned int *) &chunk.ID == 0x61746164)
+      break;
+    /* Skip chunk data bytes. */
+    fseek(file, chunk.size, SEEK_CUR);
+  }
+
+  /* Determine number of samples. */
+  sample_size = header.bitsPerSample / 8;
+  samples_count = chunk.size * 8 / header.bitsPerSample;
+  snprintf(msg, sizeof(msg), "Sample size = %i", sample_size); Serial.println(msg);
+  snprintf(msg, sizeof(msg), "Samples count = %i", samples_count); Serial.println(msg);
+
+  /* Configure the advanced DAC. */
+  if (!dac1.begin(AN_RESOLUTION_12, header.sampleRate, 256, 16))
+  {
+    Serial.println("Failed to start DAC1 !");
     return;
   }
 }
 
-void loop() {}
+void loop()
+{
+  if (dac1.available() && !feof(file))
+  {
+    /* Read data from file. */
+    uint16_t sample_data[256] = {0};
+    fread(sample_data, sample_size, 256, file);
+
+    /* Get a free buffer for writing. */
+    SampleBuffer buf = dac1.dequeue();
+
+    /* Write data to buffer. */
+    for (size_t i = 0; i < buf.size(); i++)
+    {
+      /* Scale down to 12 bit. */
+      uint16_t const dac_val = ((static_cast<unsigned int>(sample_data[i])+32768)>>4) & 0x0fff;
+      buf[i] = dac_val;
+    }
+
+    /* Write the buffer to DAC. */
+    dac1.write(buf);
+  }
+}