Diff: main.cpp

Revision:

0:97643e5b2d5e

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sun Mar 28 11:23:11 2010 +0000
@@ -0,0 +1,50 @@
+#include "mbed.h"
+
+#define MAX_DELAY   15000
+#define MIN_DELAY   50
+
+#define MAX_GAIN    25
+#define MIN_GAIN    2
+
+/* ADC for the microphone/input, DAC for the speaker/output */
+AnalogIn mic(p19);
+AnalogOut speaker(p18);
+/* Two potentiometer voltage dividers for the delay/gain control knobs */
+AnalogIn delay_knob(p15);
+AnalogIn gain_knob(p16);
+
+unsigned short buffer[MAX_DELAY];
+
+/* inv_gain = 1 / gain; it's faster to avoid floating point during the main loop */
+int inv_gain = 3;
+int delay = MAX_DELAY;
+
+void read_knobs(void) {
+    delay = delay_knob*MAX_DELAY;
+    //gain = gain_knob*MAX_GAIN;
+    if (delay < MIN_DELAY)
+        delay = MIN_DELAY;
+    /*if (gain < MIN_GAIN)
+        gain = MIN_GAIN;
+    if (gain == MAX_GAIN)
+        gain -= 1;*/
+}
+
+int main() {
+    int i;
+    /* Fill up the sample buffer first */
+    for (i = 0; i < delay; i++)
+        buffer[i] += mic.read_u16();
+
+    for (i = 0; ; ) {
+        /* Multiply old data by the gain, add new data */
+        buffer[i] = buffer[i]/inv_gain + mic.read_u16();
+        /* Write to speaker */
+        speaker.write_u16(buffer[i]);
+        /* Increment index and wrap around, effectively only using "delay" length of the buffer */
+        i = (i+1) % delay;
+        /* Occasionally read the knobs */
+        if (i == 0)
+            read_knobs();
+    }
+}
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