commit 3def7bd1c8fa37b11168b91cfa0e1805ccbc572a
Author: Alexey Skobkin <x@skobkin.ru>
Date:   Sun Jul 28 07:43:43 2013 +0400

    initial

diff --git a/guitar.ino b/guitar.ino
new file mode 100644
index 0000000..a95db11
--- /dev/null
+++ b/guitar.ino
@@ -0,0 +1,34 @@
+int edge = 15;
+const long d = 5;
+int analogInPin = A0;
+const int audioOutPin = 12;
+
+void setup() {
+  Serial.begin(115200);
+}
+
+void loop() {
+  int freq = measureFrequency();
+  if (freq != 0)
+    tone(audioOutPin, freq);
+  else 
+    noTone(audioOutPin);
+  Serial.println(freq);
+}
+
+int measureFrequency() {
+  long t = millis();
+  int n = 0;
+  boolean o = analogRead(analogInPin) <= edge;
+
+  while(millis() - t <= d)
+    if ((analogRead(analogInPin) <= edge) != o) {
+      o = !o;
+      n++;
+    }
+  return n * 1000 / d;
+}
+
+
+
+