用手机控制 ESP32 小灯：做第一个局域网页面

arduino-cli compile --fqbn 'esp32:esp32:esp32s3:FlashSize=8M,PSRAM=opi,FlashMode=qio,PartitionScheme=default_8MB,CDCOnBoot=default,USBMode=hwcdc' .
arduino-cli upload --fqbn 'esp32:esp32:esp32s3:FlashSize=8M,PSRAM=opi,FlashMode=qio,PartitionScheme=default_8MB,CDCOnBoot=default,USBMode=hwcdc' -p PORT .
arduino-cli monitor -p PORT --config baudrate=115200

// SPDX-License-Identifier: MIT
// N02: same fixed Wi-Fi retry policy as N01; HTTP and GPIO run in loop().
#include <Arduino.h>
#include <WiFi.h>
#include <WebServer.h>
#include <freertos/FreeRTOS.h>
#include <freertos/queue.h>
#include <freertos/task.h>
#include <atomic>
#include <cstring>
#if __has_include("wifi_secrets.h")
#include "wifi_secrets.h"
#else
#include "wifi_secrets.example.h"
#endif
constexpr uint8_t LED_PIN = 4;
constexpr uint32_t CONNECT_WINDOW_MS = 10000, FIRST_BACKOFF_MS = 2000, MAX_BACKOFF_MS = 30000;
enum class Phase : uint8_t { CONFIG_MISSING, START_FAILED, CONNECTING, ONLINE, BACKOFF };
struct Report { Phase phase; uint32_t attempt, windowAt, backoffMs, ip; int status; };
struct Notice { uint32_t at; uint16_t event; uint8_t reason; };
QueueHandle_t reportQueue = nullptr, noticeQueue = nullptr;
std::atomic<uint32_t> droppedNotices{0};
bool wifiTaskReady = false;
const char *phaseName(Phase phase) {
  switch (phase) {
    case Phase::CONFIG_MISSING: return "CONFIG_MISSING";
    case Phase::START_FAILED: return "START_FAILED";
    case Phase::CONNECTING: return "CONNECTING";
    case Phase::ONLINE: return "ONLINE";
    case Phase::BACKOFF: return "BACKOFF";
  }
  return "UNKNOWN";
}
void onWifiEvent(arduino_event_id_t event, arduino_event_info_t info) {
  if (event != ARDUINO_EVENT_WIFI_STA_DISCONNECTED && event != ARDUINO_EVENT_WIFI_STA_GOT_IP) return;
  Notice notice{millis(), uint16_t(event), uint8_t(event == ARDUINO_EVENT_WIFI_STA_DISCONNECTED ? info.wifi_sta_disconnected.reason : 0)};
  if (xQueueSend(noticeQueue, &notice, 0) != pdTRUE) ++droppedNotices;
}
void wifiTask(void *) {
  Report r{Phase::CONFIG_MISSING, 0, millis(), 0, 0, WL_DISCONNECTED};
  if (!std::strcmp(WIFI_SSID, "REPLACE_WITH_2G4_SSID") || !std::strcmp(WIFI_PASSWORD, "REPLACE_WITH_PASSWORD") || !*WIFI_SSID) {
    xQueueOverwrite(reportQueue, &r);
    vTaskDelete(nullptr);
    return;
  }
  WiFi.persistent(false);
  WiFi.onEvent(onWifiEvent);
  if (!WiFi.mode(WIFI_STA)) {
    r.phase = Phase::START_FAILED;
    xQueueOverwrite(reportQueue, &r);
    vTaskDelete(nullptr);
    return;
  }
  WiFi.setAutoReconnect(false);  // core 3.3.12 still has one internal first-connect retry
  uint32_t nextBackoff = FIRST_BACKOFF_MS;
  bool startAttempt = true;
  for (;;) {
    uint32_t now = millis();
    if (startAttempt) {
      startAttempt = false;
      ++r.attempt;
      r.phase = Phase::CONNECTING;
      r.backoffMs = 0;
      r.ip = 0;
      r.windowAt = now;
      WiFi.begin(WIFI_SSID, WIFI_PASSWORD);  // no waitForConnectResult / while waiting
      xQueueOverwrite(reportQueue, &r);
    }
    r.status = WiFi.status();
    now = millis();
    if (r.phase == Phase::CONNECTING) {
      if (r.status == WL_CONNECTED && uint32_t(WiFi.localIP()) != 0) {
        r.phase = Phase::ONLINE;
        r.ip = uint32_t(WiFi.localIP());
        nextBackoff = FIRST_BACKOFF_MS;
        xQueueOverwrite(reportQueue, &r);
      } else if (uint32_t(now - r.windowAt) >= CONNECT_WINDOW_MS) {
        WiFi.disconnect(false, false, 0);  // no deliberate connection-wait timeout
        r.phase = Phase::BACKOFF;
        r.windowAt = millis();
        r.backoffMs = nextBackoff;
        nextBackoff = min(nextBackoff * 2, MAX_BACKOFF_MS);
        xQueueOverwrite(reportQueue, &r);
      }
    } else if (r.phase == Phase::ONLINE && r.status != WL_CONNECTED) {
      WiFi.disconnect(false, false, 0);
      r.phase = Phase::BACKOFF;
      r.ip = 0;
      r.windowAt = millis();
      r.backoffMs = FIRST_BACKOFF_MS;
      nextBackoff = min(FIRST_BACKOFF_MS * 2, MAX_BACKOFF_MS);
      xQueueOverwrite(reportQueue, &r);
    } else if (r.phase == Phase::BACKOFF && uint32_t(now - r.windowAt) >= r.backoffMs) {
      startAttempt = true;
    }
    vTaskDelay(pdMS_TO_TICKS(10));
  }
}

WebServer server(80);
bool serverStarted = false;
const char PAGE[] PROGMEM = R"PAGE(<!doctype html><html lang="zh-CN"><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1"><title>ESP32 局域网小灯</title><style>body{font-family:system-ui,sans-serif;max-width:38rem;margin:3rem auto;padding:0 1.2rem;background:#f7f8f3;color:#203b29;line-height:1.7}main{padding:1.5rem;border:1px solid #a8baa0;border-radius:1rem;background:white}h1{font-size:1.8rem;line-height:1.4}button{min-height:48px;min-width:100px;margin:8px 12px 8px 0;padding:10px 18px;border:1px solid #436b45;border-radius:6px;background:#e5efdf;color:#203b29;font:inherit}button:focus-visible,a:focus-visible{outline:3px solid #245d91;outline-offset:4px}output{font-weight:700}small{display:block;color:#4d5f49}</style><main><h1>ESP32 局域网小灯</h1><p>GPIO4 当前输出：<output id="state" aria-live="polite">%STATE%</output></p><form method="post" action="/api/led"><button name="on" value="1">打开小灯</button><button name="on" value="0">关闭小灯</button></form><p id="feedback" role="status"></p><a href="/">刷新设备状态</a><small>这里只读回 GPIO 数字电平；没有光学或电流检测。请在同一可信局域网使用，不做公网端口映射。</small></main><script>const form=document.querySelector('form'),state=document.querySelector('#state'),feedback=document.querySelector('#feedback');form.addEventListener('submit',async event=>{if(!event.submitter)return;event.preventDefault();const buttons=[...form.querySelectorAll('button')];buttons.forEach(b=>b.disabled=true);feedback.textContent='正在请求设备…';try{const response=await fetch('/api/led',{method:'POST',headers:{'Content-Type':'application/x-www-form-urlencoded','Accept':'application/json'},body:'on='+event.submitter.value});if(!response.ok)throw new Error('HTTP '+response.status);const data=await response.json();state.textContent=data.on?'开（HIGH）':'关（LOW）';feedback.textContent='设备已返回当前 GPIO 状态。';}catch(error){feedback.textContent='请求未确认，请保持同网并刷新状态。';}finally{buttons.forEach(b=>b.disabled=false);}});</script></html>)PAGE";
void sendState() {
  const bool on = digitalRead(LED_PIN) == HIGH;
  server.sendHeader("Cache-Control", "no-store");
  server.send(200, "application/json; charset=utf-8", String("{\"on\":") + (on ? "true" : "false") + ",\"pin\":4,\"meaning\":\"gpio-digital-read\"}");
}
void handleSetLed() {
  if (server.args() != 1 || !server.hasArg("on") || (server.arg("on") != "0" && server.arg("on") != "1")) {
    server.send(400, "application/json; charset=utf-8", "{\"error\":\"exactly one on=0 or on=1 is required\"}");
    return;
  }
  digitalWrite(LED_PIN, server.arg("on") == "1" ? HIGH : LOW);
  if (server.header("Accept").indexOf("application/json") >= 0) sendState();
  else { server.sendHeader("Location", "/"); server.send(303, "text/plain", "See /"); }
}
void setup() {
  Serial.begin(115200);
  pinMode(LED_PIN, OUTPUT); digitalWrite(LED_PIN, LOW);
  const char *headers[] = {"Accept"}; server.collectHeaders(headers, 1);
  server.on("/", HTTP_GET, []() {
    String html = FPSTR(PAGE); html.replace("%STATE%", digitalRead(LED_PIN) ? "开（HIGH）" : "关（LOW）");
    server.sendHeader("Cache-Control", "no-store"); server.send(200, "text/html; charset=utf-8", html);
  });
  server.on("/api/led", HTTP_GET, []() { if (server.args()) server.send(400, "application/json", "{\"error\":\"GET takes no parameters\"}"); else sendState(); });
  server.on("/api/led", HTTP_POST, handleSetLed);
  server.onNotFound([]() { server.send(404, "application/json", "{\"error\":\"not found\"}"); });
  reportQueue = xQueueCreate(1, sizeof(Report)); noticeQueue = xQueueCreate(16, sizeof(Notice));
  if (reportQueue && noticeQueue) wifiTaskReady = xTaskCreate(wifiTask, "n02-wifi", 6144, nullptr, 1, nullptr) == pdPASS;
  Serial.printf("N02 core=3.3.12 task=%u HTTP=80 GPIO4 starts LOW; no credentials logged\n", wifiTaskReady);
}
void loop() {
  if (serverStarted) server.handleClient();
  Report report;
  if (wifiTaskReady && xQueueReceive(reportQueue, &report, 0) == pdTRUE) {
    Serial.printf("STATE=%s attempt=%lu backoff_ms=%lu status=%d IP=%s\n",phaseName(report.phase),(unsigned long)report.attempt,(unsigned long)report.backoffMs,report.status,IPAddress(report.ip).toString().c_str());
    if (report.phase == Phase::ONLINE && !serverStarted) { server.begin(); serverStarted = true; }
    if (report.phase == Phase::ONLINE) Serial.printf("OPEN http://%s/ from same LAN\n",IPAddress(report.ip).toString().c_str());
  }
  Notice notice;
  while (wifiTaskReady && xQueueReceive(noticeQueue, &notice, 0) == pdTRUE)
    if (notice.event == ARDUINO_EVENT_WIFI_STA_DISCONNECTED) Serial.printf("DISCONNECTED reason=%u at=%lu\n",notice.reason,(unsigned long)notice.at);
  const uint32_t dropped = droppedNotices.exchange(0);
  if (dropped) Serial.printf("NOTICE_OVERFLOW dropped=%lu\n",(unsigned long)dropped);
  delay(1);
}