Diff: main.cpp

Revision:

0:0ba4b5723199

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sun Jun 16 15:20:07 2013 +0000
@@ -0,0 +1,46 @@
+/* Program Example 11.5: 16-bit mono wave player
+                                                             */
+#include "mbed.h"
+#include "SDFileSystem.h"
+#define BUFFERSIZE 4096              // number of data in circular buffer
+SDFileSystem sd(p5, p6, p7, p8, "sd");
+AnalogOut DACout(p18);
+Ticker SampleTicker;
+int SampleRate;
+float SamplePeriod;                       // sample period in microseconds
+int CircularBuffer[BUFFERSIZE];           // circular buffer array
+int ReadPointer=0;
+int WritePointer=0;
+bool EndOfFileFlag=0;
+
+void DACFunction(void);                   // function prototype
+
+int main() {
+  FILE  *fp = fopen("/sd/testa.wav", "rb");     // open wave file
+  fseek(fp, 24, SEEK_SET);                      // move to byte 24
+  fread(&SampleRate, 4, 1, fp);                 // get sample frequency
+  SamplePeriod=(float)1/SampleRate;   // calculate sample period as float
+  SampleTicker.attach(&DACFunction,SamplePeriod);   // start output tick
+
+  while (!feof(fp)) {          // loop until end of file is encountered 
+    fread(&CircularBuffer[WritePointer], 2, 1, fp);
+    WritePointer=WritePointer+1;        // increment Write Pointer
+    if (WritePointer>=BUFFERSIZE) {     // if end of circular buffer
+        WritePointer=0;                 // go back to start of buffer   
+    }
+  }
+  EndOfFileFlag=1;
+  fclose(fp);
+}
+
+// DAC function called at rate SamplePeriod
+void DACFunction(void) {
+  if ((EndOfFileFlag==0)|(ReadPointer>0)) { // output while data available
+    DACout.write_u16(CircularBuffer[ReadPointer]);   // output to DAC
+    ReadPointer=ReadPointer+1;                       // increment pointer
+    if (ReadPointer>=BUFFERSIZE) {
+      ReadPointer=0;                      // reset pointer if necessary
+    }
+  }
+}
+