ESP32 Wi-Fi Stopwatch with LED Matrix Display

// ESP32 Wi-Fi Stopwatch
// Full source available on GitHub

#include <WiFi.h>
#include <WebServer.h>
#include <SPIFFS.h>
#include <SPI.h>
#include <Max72xxPanel.h>
#include "html.h"
#include "css.h"
#include "js.h"

// ---- Wi-Fi AP config ----
const char* AP_SSID = "ESP32-Stopwatch";
const char* AP_PASS = "stopwatch123";

// ---- Hardware pins ----
const int PIN_CS    = 5;
const int PIN_BUZZ  = 27;
const int PANELS    = 4;

Max72xxPanel matrix = Max72xxPanel(PIN_CS, PANELS, 1);
WebServer server(80);
String resultLog = "";

// ---- Timing state ----
bool running = false;
unsigned long startMs = 0;
unsigned long elapsedMs = 0;

String formatTime(unsigned long ms) {
  unsigned long total = ms / 10;
  unsigned long hs = total % 100;
  unsigned long sec = (total / 100) % 60;
  unsigned long min = total / 6000;
  char buf[16];
  snprintf(buf, sizeof(buf), "%lu:%02lu:%02lu", min, sec, hs);
  return String(buf);
}

void updateMatrix() {
  unsigned long now = running ? elapsedMs + (millis() - startMs) : elapsedMs;
  String t = formatTime(now);
  matrix.fillScreen(0);
  matrix.setCursor(0, 0);
  matrix.print(t);
  matrix.write();
}

void beep(int ms) {
  digitalWrite(PIN_BUZZ, HIGH);
  delay(ms);
  digitalWrite(PIN_BUZZ, LOW);
}

void setup() {
  Serial.begin(115200);
  pinMode(PIN_BUZZ, OUTPUT);

  // Matrix init
  matrix.setIntensity(5);
  matrix.setRotation(0, 1);
  matrix.fillScreen(0);
  matrix.write();

  // SPIFFS
  if (!SPIFFS.begin(true)) {
    Serial.println("SPIFFS mount failed");
  } else {
    File f = SPIFFS.open("/results.csv", "r");
    if (f) { resultLog = f.readString(); f.close(); }
  }

  // Wi-Fi AP
  WiFi.softAP(AP_SSID, AP_PASS);
  Serial.print("AP IP: "); Serial.println(WiFi.softAPIP());

  // Routes
  server.on("/",        handleRoot);
  server.on("/app.css", [](){ server.send_P(200, "text/css", APP_CSS); });
  server.on("/app.js",  [](){ server.send_P(200, "application/javascript", APP_JS); });

  server.on("/start", []() {
    if (!running) { running = true; startMs = millis(); beep(100); }
    server.send(200, "text/plain", "ok");
  });

  server.on("/stop", []() {
    if (running) { elapsedMs += millis() - startMs; running = false; }
    server.send(200, "text/plain", "ok");
  });

  server.on("/reset", []() {
    running = false; elapsedMs = 0;
    server.send(200, "text/plain", "ok");
  });

  server.on("/time", []() {
    unsigned long now = running ? elapsedMs + (millis() - startMs) : elapsedMs;
    server.send(200, "text/plain", formatTime(now));
  });

  server.on("/finish", []() {
    if (running) { elapsedMs += millis() - startMs; running = false; }
    String name     = server.arg("name");
    String pool     = server.arg("pool");
    String stroke   = server.arg("stroke");
    String distance = server.arg("distance");
    String t        = formatTime(elapsedMs);
    String entry    = name + "," + pool + "," + stroke + "," + distance + "," + t + "\n";
    resultLog += entry;
    File f = SPIFFS.open("/results.csv", "a");
    if (f) { f.print(entry); f.close(); }
    elapsedMs = 0;
    server.sendHeader("Location", "/"); server.send(303);
  });

  server.on("/download", []() {
    server.sendHeader("Content-Disposition", "attachment; filename=results.csv");
    server.send(200, "text/csv", resultLog);
  });

  server.on("/clear", HTTP_POST, []() {
    resultLog = "";
    SPIFFS.remove("/results.csv");
    server.send(200, "text/plain", "ok");
  });

  server.on("/results.json", []() {
    server.send(200, "application/json", "[" + resultLog + "]");
  });

  server.begin();
  Serial.println("Server started");
}

void loop() {
  server.handleClient();
  updateMatrix();
}