Air Piano

// Air piano: hold your hand over the ultrasonic sensor and move it up and down.// Each 2-inch step is a different note, from C (closest) up to the next C// (furthest). Take your hand away and it goes quiet.////   2 to 4 in = C    4 to 6 = D    6 to 8 = E    8 to 10 = F//  10 to 12 = G     12 to 14 = A  14 to 16 = B  16 to 18 = high C//// Wiring is the same as the distance meter, plus the buzzer:// Ultrasonic sensor (HC-SR04), 4 female-to-male wires://   Vcc -> 5V     Trig -> pin 8     Echo -> pin 7     Gnd -> GND//   (Trig and Echo can go in 7 and 8 either way round, the program checks.)// Screen (LCD1602), pin by pin. Pin 1 is the one marked VSS://    1 VSS -> GND         2 VDD -> A0          3 V0 -> pin 9       4 RS -> pin 12//    5 RW  -> A1          6 E   -> pin 11      7 to 10 -> nothing//   11 D4  -> pin 5      12 D5  -> pin 4      13 D6 -> pin 3      14 D7 -> pin 2//   15 A   -> pin 10     16 K   -> A2// Buzzer (the starter kit's passive one, no sticker), 2 female-to-male wires://   one leg -> pin 13, the other leg -> the GND right next to pin 13.//   Either way round works. The board's "L" light blinks along with the notes.// The screen is optional: without it the piano still plays.//// From the computer://   "c 40"   screen contrast, 0 to 255 (lower = darker letters)//   "b 160"  backlight brightness, 0 to 255//   "m"      mute / unmute (the screen still shows the notes)//   "?"      is the sensor connected, and how far away is the nearest thing//   "f"      blink the "L" light 3 times (to find this board)// Contrast, backlight and mute are saved.#include <EEPROM.h>// ---------- Pins ----------const byte SENSOR_PINS[2] = {7, 8};byte trigPin = 7;byte echoPin = 8;const byte BUZZER = 13;const byte LCD_POWER = A0;const byte LCD_RW = A1;const byte LCD_GROUND = A2;  // the backlight's K pinconst byte LCD_RS = 12;const byte LCD_E = 11;const byte LCD_DATA[4] = {5, 4, 3, 2};  // the screen's D4, D5, D6, D7const byte LCD_CONTRAST = 9;const byte LCD_LIGHT = 10;// ---------- Notes ----------// One octave of C major. These are an octave above middle C's octave, because// the little buzzer is much louder at higher pitches.const byte NOTE_COUNT = 8;const char NOTE_NAMES[NOTE_COUNT] = {'C', 'D', 'E', 'F', 'G', 'A', 'B', 'C'};const unsigned int NOTE_HZ[NOTE_COUNT] = {1047, 1175, 1319, 1397, 1568, 1760, 1976, 2093};const float FIRST_NOTE_AT = 2.0;  // inches from the sensor where the first C startsconst float NOTE_WIDTH = 2.0;     // inches per noteconst float WOBBLE = 0.4;         // a hand has to move this far past a line to change noteconst int NO_NOTE = -1;// ---------- Measuring ----------const float MICROS_PER_INCH = 148.0;  // sound out and back, per inch, at room temperatureconst unsigned long LISTEN_MICROS = 4500;  // stop listening after ~30 inchesconst unsigned long PING_GAP_MS = 30;      // short rest so old echoes die awayconst unsigned long QUIET_AFTER_MS = 150;  // a hand has to be gone this long before it goes quiet// ---------- Saved settings ----------struct Settings {  byte check;  byte contrast;  byte backlight;  byte muted;};const byte SETTINGS_CHECK = 0xA9;Settings settings;int playing = NO_NOTE;unsigned long lastHandSeen = 0;float recent[3] = {0, 0, 0};  // last 3 readings, so one stray echo can't jump the notebyte recentNext = 0;          // which of the 3 gets the next readingbyte recentCount = 0;         // how many fresh readings there are (stops at 3)void setup() {  Serial.begin(9600);  Serial.println("Air piano starting");  EEPROM.get(0, settings);  if (settings.check != SETTINGS_CHECK) {    settings = {SETTINGS_CHECK, 40, 160, 0};    EEPROM.put(0, settings);  }  // Pins 9 and 10 flicker very fast (31,000 times a second) to set contrast  // and brightness without the screen shimmering.  TCCR1B = (TCCR1B & 0b11111000) | 0b001;  pinMode(LCD_CONTRAST, OUTPUT);  pinMode(LCD_LIGHT, OUTPUT);  analogWrite(LCD_CONTRAST, settings.contrast);  analogWrite(LCD_LIGHT, settings.backlight);  pinMode(LCD_RW, OUTPUT);  digitalWrite(LCD_RW, LOW);  pinMode(LCD_GROUND, OUTPUT);  digitalWrite(LCD_GROUND, LOW);  pinMode(LCD_POWER, OUTPUT);  digitalWrite(LCD_POWER, HIGH);  delay(100);  lcdBegin();  makeNoteSymbol();  pinMode(BUZZER, OUTPUT);  findSensorPins();  playStartTune();  showIdle();  Serial.println(settings.muted ? "Ready (muted)" : "Ready");}void loop() {  readComputer();  float inches = readInches();  if (inches > 0) {    recent[recentNext] = inches;    recentNext = (recentNext + 1) % 3;    if (recentCount < 3) recentCount++;  } else {    findSensorPins();  // in case the wires were swapped or plugged in late  }  int note = NO_NOTE;  if (inches > 0 && recentCount >= 3) {    note = pickNote(middleOf3());  }  if (note != NO_NOTE) {    lastHandSeen = millis();    if (note != playing) startNote(note);  } else if (playing != NO_NOTE && millis() - lastHandSeen > QUIET_AFTER_MS) {    stopNote();  }  delay(PING_GAP_MS);}// ---------- Notes ----------// Turns a distance into a note number (0 = low C ... 7 = high C), or NO_NOTE.// Near a line between two notes it keeps the current note, so it doesn't flutter.int pickNote(float inches) {  if (playing != NO_NOTE) {    float low = FIRST_NOTE_AT + playing * NOTE_WIDTH - WOBBLE;    float high = FIRST_NOTE_AT + (playing + 1) * NOTE_WIDTH + WOBBLE;    if (inches >= low && inches < high) return playing;  }  if (inches < FIRST_NOTE_AT) return NO_NOTE;  int note = (int)((inches - FIRST_NOTE_AT) / NOTE_WIDTH);  return note < NOTE_COUNT ? note : NO_NOTE;}void startNote(int note) {  playing = note;  if (!settings.muted) tone(BUZZER, NOTE_HZ[note]);  showNote(note);  Serial.print("Note ");  Serial.print(NOTE_NAMES[note]);  if (note == NOTE_COUNT - 1) Serial.print(" (high)");  Serial.print("  at ");  Serial.print(middleOf3(), 1);  Serial.println(" in");}void stopNote() {  playing = NO_NOTE;  noTone(BUZZER);  digitalWrite(BUZZER, LOW);  recentCount = 0;  showIdle();  Serial.println("Quiet");}void playStartTune() {  if (settings.muted) return;  const byte tune[] = {0, 2, 4, 7};  for (byte i = 0; i < sizeof(tune); i++) {    tone(BUZZER, NOTE_HZ[tune[i]], 110);    delay(140);  }  noTone(BUZZER);}// ---------- Measuring ----------// Pins 7 and 8: with a pull-up on, the Echo pin still reads LOW because the// sensor holds it there; the Trig pin reads HIGH. If it can't tell, it keeps// the last choice.void findSensorPins() {  pinMode(SENSOR_PINS[0], INPUT_PULLUP);  pinMode(SENSOR_PINS[1], INPUT_PULLUP);  delay(2);  bool low0 = digitalRead(SENSOR_PINS[0]) == LOW;  bool low1 = digitalRead(SENSOR_PINS[1]) == LOW;  if (low0 != low1) {    echoPin = low0 ? SENSOR_PINS[0] : SENSOR_PINS[1];    trigPin = low0 ? SENSOR_PINS[1] : SENSOR_PINS[0];  }  pinMode(echoPin, INPUT);  pinMode(trigPin, OUTPUT);  digitalWrite(trigPin, LOW);}// One ping. Returns the distance in inches, or 0 if nothing answered within ~30 in.float readInches() {  digitalWrite(trigPin, LOW);  delayMicroseconds(2);  digitalWrite(trigPin, HIGH);  delayMicroseconds(10);  digitalWrite(trigPin, LOW);  unsigned long microseconds = pulseIn(echoPin, HIGH, LISTEN_MICROS);  return microseconds == 0 ? 0 : microseconds / MICROS_PER_INCH;}float middleOf3() {  float a = recent[0], b = recent[1], c = recent[2];  if ((a <= b && b <= c) || (c <= b && b <= a)) return b;  if ((b <= a && a <= c) || (c <= a && a <= b)) return a;  return c;}// ---------- Screen ----------//   top row:     ♪  E  ♪          (or "Air Piano" when quiet)//   bottom row:  C D E F G A B C   with a solid block on the note being played// The music note lives in the screen's custom character slot 0. The screen// shows slot 0 for code 0 or code 8; using 8 keeps it from ending the text.const byte NOTE_SYMBOL_SLOT = 0;const char NOTE_SYMBOL = 8;void showNote(int note) {  char top[17] = "                ";  top[4] = NOTE_SYMBOL;  top[11] = NOTE_SYMBOL;  top[7] = NOTE_NAMES[note];  if (note == NOTE_COUNT - 1) {  // high C    top[7] = 'C';    top[8] = '\'';  }  lcdWake();  lcdPrintRow(0, top);  lcdPrintRow(1, keyboardRow(note));}void showIdle() {  lcdWake();  lcdPrintRow(0, settings.muted ? " Air Piano  mute" : "   Air Piano");  lcdPrintRow(1, "Hand 2-18in away");}const char *keyboardRow(int note) {  static char row[17];  for (byte i = 0; i < NOTE_COUNT; i++) {    row[i * 2] = ' ';    row[i * 2 + 1] = (i == note) ? (char)0xFF : NOTE_NAMES[i];  // 0xFF = solid block  }  row[16] = '\0';  return row;}// A little music note, drawn dot by dot (5 wide, 8 tall).void makeNoteSymbol() {  const byte rows[8] = {    0b00100,    0b00110,    0b00101,    0b00100,    0b00100,    0b01100,    0b11100,    0b01000,  };  lcdSend(0x40 | (NOTE_SYMBOL_SLOT << 3), false);  for (byte i = 0; i < 8; i++) lcdSend(rows[i], true);  lcdSend(0x80, false);  // back to writing letters}// "?" from the computer: is the sensor there, and what does it see right now?// With a pull-up on, a powered sensor holds its Echo pin LOW; with no sensor// (or no power), both pins read HIGH.void reportStatus() {  pinMode(SENSOR_PINS[0], INPUT_PULLUP);  pinMode(SENSOR_PINS[1], INPUT_PULLUP);  delay(2);  bool low0 = digitalRead(SENSOR_PINS[0]) == LOW;  bool low1 = digitalRead(SENSOR_PINS[1]) == LOW;  findSensorPins();  Serial.print("Sensor: ");  if (low0 != low1) {    Serial.print("found (Trig ");    Serial.print(trigPin);    Serial.print(", Echo ");    Serial.print(echoPin);    Serial.print(")");  } else if (low0 && low1) {    Serial.print("NOT found: pins 7 and 8 both pulled LOW (wires in, but no power? check 5V/GND)");  } else {    Serial.print("NOT found: pins 7 and 8 both HIGH (Trig/Echo wires not connected?)");  }  delay(60);  float inches = readInches();  Serial.print("   sees: ");  if (inches > 0) {    Serial.print(inches, 1);    Serial.print(" in");  } else {    Serial.print("nothing within 30 in");  }  Serial.println(settings.muted ? "   sound: muted" : "   sound: on");}// ---------- Settings from the computer ----------void readComputer() {  static char line[20];  static byte length = 0;  while (Serial.available()) {    char ch = Serial.read();    if (ch == '\n' || ch == '\r') {      line[length] = '\0';      if (length > 0) handleCommand(line);      length = 0;    } else if (length < sizeof(line) - 1) {      line[length++] = ch;    }  }}void handleCommand(const char *line) {  int value = constrain(atoi(line + 1), 0, 255);  if (line[0] == 'c') {    settings.contrast = value;    analogWrite(LCD_CONTRAST, settings.contrast);  } else if (line[0] == 'b') {    settings.backlight = value;    analogWrite(LCD_LIGHT, settings.backlight);  } else if (line[0] == '?') {    reportStatus();    return;  } else if (line[0] == 'f') {    // Three quick blinks of the "L" light, to find which board this is.    noTone(BUZZER);    for (byte i = 0; i < 3; i++) {      digitalWrite(BUZZER, HIGH);      delay(150);      digitalWrite(BUZZER, LOW);      delay(150);    }    if (playing != NO_NOTE && !settings.muted) tone(BUZZER, NOTE_HZ[playing]);    Serial.println("Blinked");    return;  } else if (line[0] == 'm') {    settings.muted = !settings.muted;    if (settings.muted) noTone(BUZZER);    else if (playing != NO_NOTE) tone(BUZZER, NOTE_HZ[playing]);    if (playing == NO_NOTE) showIdle();  } else {    return;  }  EEPROM.put(0, settings);  Serial.print("Saved: contrast ");  Serial.print(settings.contrast);  Serial.print(", backlight ");  Serial.print(settings.backlight);  Serial.println(settings.muted ? ", muted" : ", sound on");}// ---------- Screen driver ----------// The screen takes letters 4 bits at a time on its D4-D7 pins. RS picks// between a command (LOW) and a letter (HIGH), and a pulse on E sends it.void lcdBegin() {  pinMode(LCD_RS, OUTPUT);  pinMode(LCD_E, OUTPUT);  for (byte i = 0; i < 4; i++) pinMode(LCD_DATA[i], OUTPUT);  digitalWrite(LCD_E, LOW);  digitalWrite(LCD_RS, LOW);  delay(50);  lcdWake();  lcdSend(0x01, false);  // clear the screen  delay(2);}// The screen's start-up routine. Repeating it before each update gets a// screen that had a glitch back in step, without clearing it.void lcdWake() {  digitalWrite(LCD_RS, LOW);  lcdNibble(0x3);  delay(5);  lcdNibble(0x3);  delayMicroseconds(150);  lcdNibble(0x3);  delayMicroseconds(150);  lcdNibble(0x2);  delayMicroseconds(150);  lcdSend(0x28, false);  // 2 lines of text  lcdSend(0x0C, false);  // screen on, no cursor  lcdSend(0x06, false);  // move right after each letter}void lcdNibble(byte bits) {  for (byte i = 0; i < 4; i++) digitalWrite(LCD_DATA[i], (bits >> i) & 1);  digitalWrite(LCD_E, HIGH);  delayMicroseconds(1);  digitalWrite(LCD_E, LOW);  delayMicroseconds(100);}void lcdSend(byte value, bool isLetter) {  digitalWrite(LCD_RS, isLetter ? HIGH : LOW);  lcdNibble(value >> 4);  lcdNibble(value & 0x0F);}// Writes a whole row: the text, then spaces to fill all 16 places.void lcdPrintRow(byte row, const char *text) {  lcdSend(0x80 | (row ? 0x40 : 0), false);  bool ended = false;  for (byte i = 0; i < 16; i++) {    if (text[i] == '\0') ended = true;    lcdSend(ended ? ' ' : text[i], true);  }}