Wi-Fi Piano Instrument

#include <Arduino.h>
#include <WiFi.h>
#include <Preferences.h>
#include <AsyncTCP.h>
#include <ESPAsyncWebServer.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include "piano_page.h"

#define OLED_SCL 18

// The supplied buzzer is intentionally not connected: its electrical type is unverified.

struct PhysicalKey { bool stable = false, sampled = false; uint32_t changed = 0, order = 0; } physical[6];

struct BrowserClient { uint32_t id = 0, lastSeen = 0, order[6] = {}; } clients[8];


// Forward declarations
void sendState();
void updateOutputs();
void chooseActiveKey();
void stopAll();
void cancelDemo();
void scanButtons();
void updatePotentiometer();
void runDemo();
void beginAccessPoint();
void startHomeWiFi();
void handleMessage(AsyncWebSocketClient *client, void *arg, uint8_t *data, size_t len);
void onWsEvent(AsyncWebSocket *, AsyncWebSocketClient *client, AwsEventType type, void *arg, uint8_t *data, size_t len);

constexpr uint8_t POT_PIN = 1;
constexpr uint8_t BTN_PINS[6] = {4, 5, 6, 7, 15, 16};
constexpr uint8_t LED_PINS[6] = {8, 9, 10, 11, 12, 13};
constexpr uint8_t OLED_SDA = 17, OLED_SCL = 18;
constexpr uint32_t DEBOUNCE_MS = 25, CLIENT_TIMEOUT_MS = 4500;
constexpr char NOTE_NAMES[6] = {'C', 'D', 'E', 'F', 'G', 'A'};

AsyncWebServer server(80);
AsyncWebSocket ws("/ws");
Preferences prefs;
Adafruit_SSD1306 display(128, 64, &Wire, -1);
bool oledReady = false;



uint32_t sequenceNumber = 1;
uint8_t octave = 4;
int activeKey = -1;
int potFiltered = 0, lastPotControl = 0;
bool demoPlaying = false;
uint8_t demoStep = 0;
uint32_t demoNext = 0;
const int8_t demoNotes[] = {0,0,4,4,5,5,4, -1,3,3,2,2,1,1,0, -1, 4,4,3,3,2,2,1, -1,4,4,3,3,2,2,1};

BrowserClient *clientSlot(uint32_t id, bool create) {
  for (auto &c : clients) if (c.id == id) return &c;
  if (!create) return nullptr;
  for (auto &c : clients) if (c.id == 0) { c.id = id; c.lastSeen = millis(); return &c; }
  return nullptr;
}

void sendState() {
  char note[4] = "";
  if (activeKey >= 0) snprintf(note, sizeof(note), "%c%d", NOTE_NAMES[activeKey], octave);
  char json[100];
  snprintf(json, sizeof(json), "{\"note\":\"%s\",\"octave\":%u,\"demo\":%s}", note, octave, demoPlaying ? "true" : "false");
  ws.textAll(json);
}

void updateOutputs() {
  for (uint8_t i = 0; i < 6; ++i) digitalWrite(LED_PINS[i], i == activeKey ? HIGH : LOW);
  if (oledReady) {
    display.clearDisplay(); display.setTextColor(SSD1306_WHITE); display.setTextSize(1);
    display.setCursor(0, 0); display.println(WiFi.status() == WL_CONNECTED ? "Home Wi-Fi" : "Piano access point");
    display.println(WiFi.status() == WL_CONNECTED ? WiFi.localIP().toString() : WiFi.softAPIP().toString());
    display.setTextSize(2); display.setCursor(0, 28);
    if (activeKey >= 0) { display.print(NOTE_NAMES[activeKey]); display.print(octave); } else display.print("--");
    display.setTextSize(1); display.setCursor(0, 54); display.print("Octave "); display.print(octave);
    display.display();
  }
  sendState();
}

void chooseActiveKey() {
  int chosen = -1; uint32_t newest = 0;
  for (uint8_t i = 0; i < 6; ++i) if (physical[i].stable && physical[i].order >= newest) { newest = physical[i].order; chosen = i; }
  for (auto &c : clients) for (uint8_t i = 0; i < 6; ++i) if (c.order[i] >= newest) { newest = c.order[i]; chosen = i; }
  if (chosen != activeKey) { activeKey = chosen; updateOutputs(); }
}

void stopAll() {
  for (auto &p : physical) p.stable = false;
  for (auto &c : clients) for (uint8_t i = 0; i < 6; ++i) c.order[i] = 0;
  demoPlaying = false; activeKey = -1; updateOutputs();
}

void cancelDemo() { if (demoPlaying) { demoPlaying = false; demoStep = 0; } }

void scanButtons() {
  uint32_t now = millis();
  for (uint8_t i = 0; i < 6; ++i) {
    bool pressed = digitalRead(BTN_PINS[i]) == LOW;
    if (pressed != physical[i].sampled) { physical[i].sampled = pressed; physical[i].changed = now; }
    if (physical[i].stable != physical[i].sampled && now - physical[i].changed >= DEBOUNCE_MS) {
      physical[i].stable = physical[i].sampled;
      if (physical[i].stable) { cancelDemo(); physical[i].order = sequenceNumber++; }
      chooseActiveKey();
    }
  }
}

void updatePotentiometer() {
  static uint32_t lastRead = 0;
  if (millis() - lastRead < 40) return;
  lastRead = millis();
  int raw = analogRead(POT_PIN);
  potFiltered = potFiltered == 0 ? raw : (potFiltered * 7 + raw) / 8;
  if (abs(potFiltered - lastPotControl) < 130) return; // noise cannot steal website control
  lastPotControl = potFiltered;
  uint8_t next = potFiltered < 1250 ? 3 : (potFiltered > 2850 ? 5 : 4);
  if (next != octave) { octave = next; updateOutputs(); }
}

void runDemo() {
  if (!demoPlaying || millis() < demoNext) return;
  int8_t n = demoNotes[demoStep++];
  activeKey = n; updateOutputs();
  demoNext = millis() + (n < 0 ? 160 : 360);
  if (demoStep >= sizeof(demoNotes)) { demoPlaying = false; activeKey = -1; updateOutputs(); }
}

void beginAccessPoint() {
  uint64_t mac = ESP.getEfuseMac();
  char ssid[32]; snprintf(ssid, sizeof(ssid), "Schematik-Piano-%04X", (uint16_t)mac);
  WiFi.mode(WIFI_AP_STA);
  WiFi.softAP(ssid, "piano1234");
}

void startHomeWiFi() {
  prefs.begin("piano", true);
  String ssid = prefs.getString("ssid", ""), pass = prefs.getString("pass", "");
  prefs.end();
  if (ssid.length()) WiFi.begin(ssid.c_str(), pass.c_str());
}

void handleMessage(AsyncWebSocketClient *client, void *arg, uint8_t *data, size_t len) {
  AwsFrameInfo *info = (AwsFrameInfo *)arg;
  if (!info->final || info->index || info->len != len || len == 0 || len > 96) return;
  data[len] = 0;
  String m((char *)data); uint32_t id = client->id();
  BrowserClient *c = clientSlot(id, true); if (!c) return; c->lastSeen = millis();
  if (m.indexOf("\"t\":\"on\"") >= 0 || m.indexOf("\"t\":\"off\"") >= 0) {
    int p = m.indexOf("\"n\":"); if (p < 0) return; int n = m.substring(p + 4).toInt(); if (n < 0 || n > 5) return;
    cancelDemo();
    if (m.indexOf("\"t\":\"on\"") >= 0) c->order[n] = sequenceNumber++; else c->order[n] = 0;
    chooseActiveKey();
  } else if (m.indexOf("\"t\":\"octave\"") >= 0) {
    int p = m.indexOf("\"o\":"); if (p < 0) return; int o = m.substring(p + 4).toInt();
    if (o >= 3 && o <= 5 && o != octave) { octave = o; lastPotControl = potFiltered; updateOutputs(); }
  } else if (m.indexOf("\"t\":\"demo\"") >= 0) { stopAll(); demoPlaying = true; demoStep = 0; demoNext = millis(); }
  else if (m.indexOf("\"t\":\"stop\"") >= 0) stopAll();
  else if (m.indexOf("\"t\":\"state\"") >= 0) sendState();
}

void onWsEvent(AsyncWebSocket *, AsyncWebSocketClient *client, AwsEventType type, void *arg, uint8_t *data, size_t len) {
  if (type == WS_EVT_CONNECT) { clientSlot(client->id(), true); sendState(); }
  else if (type == WS_EVT_DATA) handleMessage(client, arg, data, len);
  else if (type == WS_EVT_DISCONNECT) { BrowserClient *c = clientSlot(client->id(), false); if (c) { *c = BrowserClient(); chooseActiveKey(); } }
}

void setup() {
  Serial.begin(115200); analogReadResolution(12);
  for (uint8_t i = 0; i < 6; ++i) { pinMode(BTN_PINS[i], INPUT_PULLUP); pinMode(LED_PINS[i], OUTPUT); digitalWrite(LED_PINS[i], LOW); }
  Wire.begin(OLED_SDA, OLED_SCL); oledReady = display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  beginAccessPoint(); startHomeWiFi();
  ws.onEvent(onWsEvent); server.addHandler(&ws);
  server.on("/", HTTP_GET, [](AsyncWebServerRequest *r) { r->send_P(200, "text/html", PAGE); });
  server.on("/setup", HTTP_POST, [](AsyncWebServerRequest *r) {
    if (!r->hasParam("ssid", true) || !r->hasParam("pass", true)) { r->send(400, "text/plain", "Enter a network name and password."); return; }
    String ssid = r->getParam("ssid", true)->value(), pass = r->getParam("pass", true)->value();
    if (ssid.length() > 32 || pass.length() > 63) { r->send(400, "text/plain", "Those details are too long."); return; }
    prefs.begin("piano", false); prefs.putString("ssid", ssid); prefs.putString("pass", pass); prefs.end();
    r->send(200, "text/plain", "Saved. Restart the board to try the home network; the Piano access point remains available if it cannot connect.");
  });
  server.begin(); updateOutputs();
}

void loop() {
  scanButtons(); updatePotentiometer(); runDemo(); ws.cleanupClients();
  uint32_t now = millis();
  for (auto &c : clients) if (c.id && now - c.lastSeen > CLIENT_TIMEOUT_MS) { c = BrowserClient(); chooseActiveKey(); }
}