Diff: main.cpp

Revision:

0:5c44ff47ac5c

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sat Sep 27 15:17:51 2014 +0000
@@ -0,0 +1,47 @@
+#include "mbed.h"
+ 
+#define MAX_QUEUE 512          // Indexed from 0 to 511
+ 
+AnalogOut speaker(PA_4);        // DAC for the speaker/output
+AnalogIn  mic(A2);            // ADC for the microphone/input
+//AnalogIn  pot(p20);            // ADC for the pot
+
+int main()
+{
+    int queue[MAX_QUEUE];      // Will be a circular buffer
+
+    int ii = 0;                // Queue write position
+    int jj = 0;                // Q read position
+    int offset = 0;            // Delay (number of samples)
+    int oo;                    // The analogue data read or written
+    
+    while(1)                   // For ever
+    {
+        oo = mic.read_u16() - 32767;    // Read ADC and remove DC offset
+      
+        queue[ii] = oo;                 // Add sample to queue
+        
+        jj = ii - offset;               // Calculate playback position
+        
+        if (jj < 0) jj = jj + MAX_QUEUE;// If queue pointer is negative, wrap it around.
+        
+        ii = (ii + 1) % MAX_QUEUE;      // Next position in the circular queue
+        
+        if (ii == 0)                    // Read the potentiometer
+        {
+            offset = MAX_QUEUE * 32767 / 65535;  // Scale the reading to fit the queue
+            
+            if (offset >= MAX_QUEUE) offset = MAX_QUEUE - 1;  // Limit the upper value
+        }
+
+        oo = oo + queue[jj];            // Add zero referenced signals: input + delayed_input
+
+        oo = oo + 32767;                // Restore the DC Offset.
+        
+        speaker.write_u16(oo);          // DAC output
+        //printf();
+        
+        if (!(ii % 16)) printf("oo = %5d | ii = %5d | jj = %5d | offset = %5d \n\r", oo, ii, jj, offset);
+        // FOR DEBUGGING if (!(ii % 16)) printf("oo = %5d | ii = %5d | jj = %5d | offset = %5d \n\r", oo, ii, jj, offset);
+    }
+}
\ No newline at end of file