add week 9

content/docs/2023/code-design/9/examples/tone_random_flip/tone_random_flip.ino

@@ -0,0 +1,32 @@
+const int button_pin = 2;
+const int sound_pin = 9;
+
+bool is_playing = false;
+int button_prev= LOW;
+float freq = 440;
+
+float midiToFreq(int midi){
+  return 440.*pow(2.,(midi-69.)/12.);
+}
+
+void setup() {
+  pinMode(button_pin,INPUT);
+  pinMode(sound_pin, OUTPUT);
+}
+
+void loop() {
+  auto button_state = digitalRead(button_pin);
+
+  if(button_prev == LOW && button_state==HIGH){
+    is_playing = !is_playing;
+    freq = midiToFreq(random(65,100));
+  }
+  if(is_playing){
+    tone(sound_pin,freq);
+  }else{
+    noTone(sound_pin);
+  }
+
+  delay(20);
+  button_prev = button_state;
+}