1  // SPDX-FileCopyrightText: 2017 Limor Fried/ladyada for Adafruit Industries
 2  // SPDX-FileCopyrightText: 2017 Phillip Burgess for Adafruit Industries
 3  //
 4  // SPDX-License-Identifier: MIT
 5  /* Adafruit Trinket/Gemma Example: Simple Theramin
 6  
 7    Read the voltage from a Cadmium Sulfide (CdS) photocell voltage
 8    divider and output a corresponding tone to a piezo buzzer
 9  
10    Wiring: Photocell voltage divider center wire to GPIO #2
11    (analog 1) and output tone to GPIO #0 (digital 0)
12  
13    Note: The Arduino tone library does not work for the ATTiny85 on the
14    Trinket and Gemma.  The beep function below is similar.  The beep
15    code is adapted from Dr. Leah Buechley at
16    http://web.media.mit.edu/~leah/LilyPad/07_sound_code.html
17  */
18  
19  #define SPEAKER   0    // Speaker connected to this DIGITAL pin #
20  #define PHOTOCELL 1    // CdS photocell connected to this ANALOG pin #
21  #define SCALE     2.0  // You can change this to change the tone scale
22  
23  void setup() {
24    // Set SPEAKER pin to output to drive the piezo buzzer (important)
25    pinMode(SPEAKER, OUTPUT);
26  }
27  
28  void loop() {
29    // Read PHOTOCELL analog pin for the current CdS divider voltage
30    int reading = analogRead(PHOTOCELL);
31    // Change the voltage to a frequency.  You can change the values
32    // to scale your frequency range.
33    int freq = 220 + (int)(reading * SCALE);
34    // Output the tone to SPEAKER pin.  You can change the '400'
35    // to different times (in milliseconds).
36    beep(SPEAKER, freq, 400);
37    delay(50); // Delay a bit between notes (also adjustable to taste)
38  }
39  
40  // The sound-producing function
41  void beep (unsigned char speakerPin, int frequencyInHertz, long timeInMilliseconds)
42  { // http://web.media.mit.edu/~leah/LilyPad/07_sound_code.html
43    int  x;
44    long delayAmount = (long)(1000000 / frequencyInHertz);
45    long loopTime = (long)((timeInMilliseconds * 1000) / (delayAmount * 2));
46    for (x = 0; x < loopTime; x++) {
47      digitalWrite(speakerPin, HIGH);
48      delayMicroseconds(delayAmount);
49      digitalWrite(speakerPin, LOW);
50      delayMicroseconds(delayAmount);
51    }
52  }