Diff: main.cpp

Revision:

0:7610d342c76e

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sun Jan 08 17:28:24 2012 +0000
@@ -0,0 +1,140 @@
+// Hello World example for the USBMIDI library (circular buffer)
+
+#include "mbed.h"
+#include "USBAudio.h"
+#include "CircBuffer.h"
+
+Serial pc(USBTX, USBRX);
+
+// frequency: 48 kHz
+#define FREQ 32000
+
+// 1 channel: mono
+#define NB_CHA 1
+
+// length computed: each ms, we receive 48 * 16bits ->48 * 2 bytes. as there is one channel, the length will be 48 * 2 * 1
+#define LENGTH_AUDIO_PACKET 32 * 2 * 1
+
+#define USR_POWERDOWN    (0x104)
+
+int semihost_powerdown() {
+    uint32_t arg;
+    return __semihost(USR_POWERDOWN, &arg);
+}
+ 
+
+// USBAudio
+USBAudio USBaudio(FREQ, NB_CHA, 0x7186, 0x7507);
+
+// speaker connected to the AnalogOut output. The audio stream received over USb will be sent to the speaker
+AnalogOut speaker(p18);
+
+AnalogIn mic(p19);
+
+// ticker to send data to the speaker at the good frequency
+Ticker tic;
+
+// circular buffer where will be stored data to be sent to the speaker
+CircBuffer<int16_t> cbuf(LENGTH_AUDIO_PACKET);
+
+// previous value sent to the speaker
+uint16_t p_val = 0;
+
+// function executed each 1/FREQ s
+void tic_handler() {
+    int16_t val;
+    float speaker_value;
+    unsigned short PlaySample;
+
+
+    if (cbuf.available() >= 1) {
+        cbuf.dequeue(&val);
+        speaker_value = (float)val;
+
+        // speaker_value between 0 and 65535
+        speaker_value +=  32768.0;
+
+        // adjust according to current volume
+        speaker_value *= USBaudio.getVolume();
+    } else {
+        speaker_value = p_val;
+    }
+    p_val = speaker_value;
+    
+    /* ADAMGR: Inserting my May 30th reversing code here!!! */
+  {
+    static const unsigned int   BufferSize = 20 * 640;
+    static unsigned short Buffer[BufferSize];
+    
+    static int           Index = 0;
+    static int           Direction = 1;
+    static int           Playback = false;
+    static int           ChunkSize = BufferSize;
+ 
+    unsigned short       ReadSample;
+ 
+    /* Default PlaySample to the current sample from USB buffer. */
+    PlaySample =  speaker_value;
+
+    
+    
+    /* Read out the sample from the buffer to be played back */
+    if (Playback)
+    {
+        PlaySample = Buffer[Index];
+    }
+    
+    /* Obtain current audio sample from the USB buffer. */
+    ReadSample = (unsigned short)speaker_value;
+    
+    /* Record the sample into the buffer right where a space was freed up from the PlaySample read above */
+    Buffer[Index] = ReadSample  += mic.read_u16();
+    
+     /* Increment the buffer pointer */
+    Index += Direction;
+    
+    /* Check to see if the chunk has been filled */
+    if (Index < 0)
+    {
+        /* Now have a chunk to be played back */
+        Playback = true;
+        /* Reverse the direction of playback and recording */
+        Direction *= -1;//Direction;
+        Index = 0;
+    }
+    else if (Index >= ChunkSize)
+    
+    
+
+    {
+       /* Now have a chunk to be played back */
+        Playback = true;
+        /* Reverse the direction of playback and recording */
+        Direction *= -1;//Direction;
+        Index = ChunkSize - 1;
+    }
+  }
+  
+
+    // send value to the speaker
+    speaker.write_u16((uint16_t)PlaySample);
+}
+
+int main() {
+    int16_t buf[LENGTH_AUDIO_PACKET/2];
+    
+    semihost_powerdown();
+
+    // attach a function executed each 1/FREQ s
+    tic.attach_us(tic_handler, 1000000.0/(float)FREQ);
+
+    while (1) {
+        // read an audio packet
+        USBaudio.read((uint8_t *)buf);
+
+        // put buffer in the circ buffer
+        for(int i = 0; i < LENGTH_AUDIO_PACKET/2; i++) {
+            cbuf.queue(buf[i]);
+        }
+    }
+}