diff --git a/aa-settings.h b/aa-settings.h
new file mode 100644
index 0000000..2713ea6
--- /dev/null
+++ b/aa-settings.h
@@ -0,0 +1,674 @@
+#ifndef SETTINGS_H
+#define SETTINGS_H
+
+const char settings_html PROGMEM = R"rawliteral(
+<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
+    <title>Settings - Byun CAN Logger v2.5</title>
+    <style>
+        * { margin: 0; padding: 0; box-sizing: border-box; }
+        body {
+            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
+            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+            min-height: 100vh;
+            padding: 10px;
+        }
+        .container {
+            max-width: 900px;
+            margin: 0 auto;
+            background: white;
+            border-radius: 15px;
+            box-shadow: 0 20px 60px rgba(0,0,0,0.3);
+            overflow: hidden;
+        }
+        .header {
+            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+            color: white;
+            padding: 20px;
+            text-align: center;
+        }
+        .header h1 { font-size: 1.8em; margin-bottom: 5px; }
+        .header p { opacity: 0.9; font-size: 0.9em; }
+        .nav {
+            background: #2c3e50;
+            padding: 10px;
+            display: flex;
+            gap: 10px;
+            flex-wrap: wrap;
+            justify-content: center;
+        }
+        .nav a {
+            color: white;
+            text-decoration: none;
+            padding: 10px 15px;
+            border-radius: 5px;
+            transition: all 0.3s;
+            font-size: 0.9em;
+            white-space: nowrap;
+        }
+        .nav a:hover { background: #34495e; }
+        .nav a.active { background: #3498db; }
+        .content { padding: 25px; }
+        
+        .settings-section {
+            background: #f8f9fa;
+            padding: 25px;
+            border-radius: 10px;
+            margin-bottom: 20px;
+            box-shadow: 0 2px 8px rgba(0,0,0,0.05);
+            border: 2px solid #e0e0e0;
+        }
+        
+        .section-title {
+            color: #333;
+            font-size: 1.3em;
+            margin-bottom: 20px;
+            padding-bottom: 10px;
+            border-bottom: 3px solid #667eea;
+            display: flex;
+            align-items: center;
+            gap: 10px;
+        }
+        
+        .subsection-title {
+            color: #555;
+            font-size: 1.05em;
+            margin: 20px 0 15px 0;
+            font-weight: 700;
+            display: flex;
+            align-items: center;
+            gap: 8px;
+        }
+        
+        .form-group {
+            margin-bottom: 18px;
+        }
+        
+        .form-group:last-child {
+            margin-bottom: 0;
+        }
+        
+        label {
+            display: block;
+            font-weight: 600;
+            color: #333;
+            margin-bottom: 8px;
+            font-size: 0.95em;
+        }
+        
+        .help-text {
+            font-size: 0.85em;
+            color: #666;
+            margin-top: 5px;
+            line-height: 1.5;
+            padding-left: 5px;
+        }
+        
+        input[type="text"],
+        input[type="password"] {
+            width: 100%;
+            padding: 12px 15px;
+            border: 2px solid #e1e8ed;
+            border-radius: 8px;
+            font-size: 0.95em;
+            transition: all 0.3s;
+            background: white;
+            font-family: inherit;
+        }
+        
+        input[type="text"]:focus,
+        input[type="password"]:focus {
+            outline: none;
+            border-color: #667eea;
+            box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
+        }
+        
+        input[type="checkbox"] {
+            width: 20px;
+            height: 20px;
+            cursor: pointer;
+            margin-right: 10px;
+            accent-color: #667eea;
+        }
+        
+        .checkbox-group {
+            display: flex;
+            align-items: center;
+            margin-bottom: 12px;
+            padding: 10px;
+            background: white;
+            border-radius: 8px;
+            border: 2px solid #e1e8ed;
+            transition: all 0.3s;
+        }
+        
+        .checkbox-group:hover {
+            border-color: #667eea;
+        }
+        
+        .checkbox-group label {
+            margin-bottom: 0;
+            cursor: pointer;
+            user-select: none;
+            flex: 1;
+        }
+        
+        .sta-settings {
+            background: linear-gradient(135deg, rgba(102, 126, 234, 0.05) 0%, rgba(118, 75, 162, 0.05) 100%);
+            padding: 20px;
+            border-radius: 8px;
+            margin-top: 15px;
+            border-left: 4px solid #667eea;
+            transition: all 0.3s;
+        }
+        
+        .sta-settings.disabled {
+            opacity: 0.4;
+            pointer-events: none;
+        }
+        
+        .sta-status {
+            margin-top: 15px;
+            padding: 12px 15px;
+            border-radius: 8px;
+            font-weight: 600;
+            display: flex;
+            align-items: center;
+            gap: 10px;
+        }
+        
+        .sta-status.connected {
+            background: linear-gradient(135deg, rgba(17, 153, 142, 0.1) 0%, rgba(56, 239, 125, 0.1) 100%);
+            border: 2px solid #11998e;
+            color: #0d6d62;
+        }
+        
+        .sta-status.disconnected {
+            background: linear-gradient(135deg, rgba(235, 51, 73, 0.1) 0%, rgba(244, 92, 67, 0.1) 100%);
+            border: 2px solid #eb3349;
+            color: #b8262f;
+        }
+        
+        .button-group {
+            display: flex;
+            gap: 12px;
+            margin-top: 25px;
+            flex-wrap: wrap;
+        }
+        
+        button {
+            flex: 1;
+            min-width: 180px;
+            padding: 14px 28px;
+            border: none;
+            border-radius: 8px;
+            font-size: 1em;
+            font-weight: 700;
+            cursor: pointer;
+            transition: all 0.3s;
+            text-transform: uppercase;
+            letter-spacing: 0.5px;
+        }
+        
+        .btn-save {
+            background: linear-gradient(135deg, #11998e 0%, #38ef7d 100%);
+            color: white;
+            box-shadow: 0 4px 15px rgba(17, 153, 142, 0.3);
+        }
+        
+        .btn-save:hover {
+            transform: translateY(-2px);
+            box-shadow: 0 6px 20px rgba(17, 153, 142, 0.4);
+        }
+        
+        .btn-cancel {
+            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+            color: white;
+            box-shadow: 0 4px 15px rgba(102, 126, 234, 0.3);
+        }
+        
+        .btn-cancel:hover {
+            transform: translateY(-2px);
+            box-shadow: 0 6px 20px rgba(102, 126, 234, 0.4);
+        }
+        
+        .btn-reboot {
+            background: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
+            color: white;
+            box-shadow: 0 4px 15px rgba(240, 147, 251, 0.3);
+        }
+        
+        .btn-reboot:hover {
+            transform: translateY(-2px);
+            box-shadow: 0 6px 20px rgba(240, 147, 251, 0.4);
+        }
+        
+        button:active {
+            transform: translateY(0);
+        }
+        
+        .alert {
+            padding: 15px 20px;
+            border-radius: 8px;
+            margin-bottom: 20px;
+            display: none;
+            align-items: center;
+            gap: 12px;
+            animation: slideDown 0.3s ease-out;
+            box-shadow: 0 3px 10px rgba(0,0,0,0.1);
+        }
+        
+        @keyframes slideDown {
+            from {
+                opacity: 0;
+                transform: translateY(-10px);
+            }
+            to {
+                opacity: 1;
+                transform: translateY(0);
+            }
+        }
+        
+        .alert.show {
+            display: flex;
+        }
+        
+        .alert-success {
+            background: linear-gradient(135deg, #11998e 0%, #38ef7d 100%);
+            color: white;
+        }
+        
+        .alert-info {
+            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+            color: white;
+        }
+        
+        .alert-warning {
+            background: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
+            color: white;
+        }
+        
+        .alert-icon {
+            font-size: 1.5em;
+        }
+        
+        .alert-text {
+            flex: 1;
+            font-weight: 600;
+        }
+        
+        .info-box {
+            background: linear-gradient(135deg, rgba(102, 126, 234, 0.1) 0%, rgba(118, 75, 162, 0.1) 100%);
+            border-left: 4px solid #667eea;
+            padding: 18px 20px;
+            border-radius: 8px;
+            margin-top: 25px;
+        }
+        
+        .info-box-title {
+            font-weight: 700;
+            color: #333;
+            margin-bottom: 10px;
+            display: flex;
+            align-items: center;
+            gap: 8px;
+            font-size: 1.05em;
+        }
+        
+        .info-box-text {
+            color: #555;
+            font-size: 0.9em;
+            line-height: 1.7;
+        }
+        
+        .divider {
+            margin: 25px 0;
+            border: none;
+            border-top: 2px solid #e0e0e0;
+        }
+        
+        @media (max-width: 768px) {
+            .content { padding: 15px; }
+            .settings-section { padding: 18px; }
+            .section-title { font-size: 1.1em; }
+            button { min-width: 100%; }
+            .button-group { flex-direction: column; }
+        }
+    </style>
+</head>
+<body>
+    <div class="container">
+        <div class="header">
+            <h1>⚙️ System Settings</h1>
+            <p>Configure WiFi, Network, and System Parameters</p>
+        </div>
+        
+        <div class="nav">
+            <a href="/">📊 Monitor</a>
+            <a href="/transmit">📤 Transmit</a>
+            <a href="/graph">📈 Graph</a>
+            <a href="/graph-view">📊 Graph View</a>
+            <a href="/settings" class="active">⚙️ Settings</a>
+            <a href="/serial">📟 Serial</a>
+        </div>
+        
+        <div class="content">
+            <div id="alert-success" class="alert alert-success">
+                <span class="alert-icon">✓</span>
+                <span class="alert-text">Settings saved successfully! Reboot to apply.</span>
+            </div>
+            
+            <div id="alert-loading" class="alert alert-info">
+                <span class="alert-icon">⏳</span>
+                <span class="alert-text">Loading settings...</span>
+            </div>
+            
+            <div id="alert-warning" class="alert alert-warning">
+                <span class="alert-icon">⚠️</span>
+                <span class="alert-text">Warning message</span>
+            </div>
+            
+            <div class="settings-section">
+                <div class="section-title">
+                    <span>📶</span>
+                    <span>WiFi Configuration</span>
+                </div>
+                
+                <div class="subsection-title">
+                    <span>🔷</span>
+                    <span>AP Mode (Access Point)</span>
+                </div>
+                <p style="color: #666; font-size: 0.9em; margin-bottom: 15px;">
+                    ESP32가 생성하는 WiFi 네트워크 설정입니다. 기본적으로 항상 활성화됩니다.
+                </p>
+                
+                <div class="form-group">
+                    <label for="wifi-ssid">📡 AP SSID (Network Name)</label>
+                    <input type="text" id="wifi-ssid" placeholder="Byun_CAN_Logger" maxlength="31">
+                    <div class="help-text">WiFi 네트워크 이름 (1-31자)</div>
+                </div>
+                
+                <div class="form-group">
+                    <label for="wifi-password">🔒 AP Password</label>
+                    <input type="password" id="wifi-password" placeholder="Minimum 8 characters" minlength="8" maxlength="63">
+                    <div class="help-text">WiFi 비밀번호 (8-63자, 비워두면 개방 네트워크)</div>
+                </div>
+                
+                <hr class="divider">
+                
+                <div class="subsection-title">
+                    <span>🔶</span>
+                    <span>APSTA Mode (AP + Station)</span>
+                </div>
+                <p style="color: #666; font-size: 0.9em; margin-bottom: 15px;">
+                    외부 WiFi 공유기에 연결하여 인터넷 접속 및 NTP 시간 동기화를 사용할 수 있습니다.
+                </p>
+                
+                <div class="checkbox-group">
+                    <input type="checkbox" id="sta-enable" onchange="toggleSTASettings()">
+                    <label for="sta-enable">
+                        <strong>Enable Station Mode</strong> - Connect to external WiFi network
+                    </label>
+                </div>
+                
+                <div id="sta-settings" class="sta-settings disabled">
+                    <div class="form-group">
+                        <label for="sta-ssid">📡 WiFi SSID to Connect</label>
+                        <input type="text" id="sta-ssid" placeholder="Your router's WiFi name" maxlength="31">
+                        <div class="help-text">연결할 공유기의 WiFi 이름</div>
+                    </div>
+                    
+                    <div class="form-group">
+                        <label for="sta-password">🔒 WiFi Password</label>
+                        <input type="password" id="sta-password" placeholder="Router password" maxlength="63">
+                        <div class="help-text">공유기의 WiFi 비밀번호</div>
+                    </div>
+                    
+                    <div id="sta-status" class="sta-status disconnected" style="display: none;">
+                        <span id="sta-status-icon">✗</span>
+                        <div>
+                            <div id="sta-status-text">Not connected</div>
+                            <div id="sta-ip" style="font-size: 0.85em; opacity: 0.8; margin-top: 3px;"></div>
+                        </div>
+                    </div>
+                </div>
+            </div>
+            
+            <div class="button-group">
+                <button class="btn-save" onclick="saveSettings()">💾 Save Settings</button>
+                <button class="btn-reboot" onclick="rebootDevice()">🔄 Reboot Device</button>
+                <button class="btn-cancel" onclick="location.href='/'">← Back</button>
+            </div>
+            
+            <div class="info-box">
+                <div class="info-box-title">
+                    <span>💡</span>
+                    <span>Important Information</span>
+                </div>
+                <div class="info-box-text">
+                    <strong>WiFi 설정 변경 시:</strong><br>
+                    • 설정 저장 후 <strong>"Reboot Device"</strong> 버튼을 눌러 재부팅해야 적용됩니다.<br>
+                    • 재부팅 시 기존 AP 연결이 끊어지므로, 새로운 SSID로 다시 접속하세요.<br><br>
+                    
+                    <strong>APSTA 모드:</strong><br>
+                    • Station 모드 활성화 시 ESP32가 AP와 Station을 동시에 사용합니다.<br>
+                    • 외부 WiFi에 연결하면 NTP를 통한 자동 시간 동기화가 가능합니다.<br>
+                    • Station 연결 실패 시에도 AP 모드는 정상 동작합니다.<br><br>
+                    
+                    <strong>현재 접속 정보:</strong><br>
+                    • AP IP: <strong>192.168.4.1</strong> (기본값)<br>
+                    • WebSocket Port: <strong>81</strong><br>
+                    • HTTP Port: <strong>80</strong>
+                </div>
+            </div>
+        </div>
+    </div>
+    
+    <script>
+        let ws;
+        
+        function initWebSocket() {
+            ws = new WebSocket('ws://' + window.location.hostname + ':81/');
+            
+            ws.onopen = function() {
+                console.log('✓ WebSocket connected');
+                loadSettings();
+            };
+            
+            ws.onclose = function() {
+                console.log('✗ WebSocket disconnected');
+                showAlert('alert-warning', '⚠️ Connection lost. Reconnecting...', 'alert-warning');
+                setTimeout(initWebSocket, 3000);
+            };
+            
+            ws.onerror = function(error) {
+                console.error('WebSocket error:', error);
+            };
+            
+            ws.onmessage = function(event) {
+                try {
+                    const data = JSON.parse(event.data);
+                    
+                    if (data.type === 'settings') {
+                        handleSettingsResponse(data);
+                    } else if (data.type === 'settingsSaved') {
+                        if (data.success) {
+                            showAlert('alert-success', '✓ Settings saved! Reboot to apply changes.', 'alert-success');
+                        } else {
+                            showAlert('alert-warning', '✗ Failed to save settings', 'alert-warning');
+                        }
+                    }
+                } catch (e) {
+                    console.error('Parse error:', e);
+                }
+            };
+        }
+        
+        function handleSettingsResponse(data) {
+            document.getElementById('wifi-ssid').value = data.ssid || 'Byun_CAN_Logger';
+            document.getElementById('wifi-password').value = data.password || '';
+            
+            document.getElementById('sta-enable').checked = data.staEnable || false;
+            document.getElementById('sta-ssid').value = data.staSSID || '';
+            document.getElementById('sta-password').value = data.staPassword || '';
+            
+            toggleSTASettings();
+            
+            const staStatus = document.getElementById('sta-status');
+            const staStatusIcon = document.getElementById('sta-status-icon');
+            const staStatusText = document.getElementById('sta-status-text');
+            const staIpElement = document.getElementById('sta-ip');
+            
+            if (data.staConnected && data.staIP && data.staIP !== '0.0.0.0') {
+                staStatus.className = 'sta-status connected';
+                staStatus.style.display = 'flex';
+                staStatusIcon.textContent = '✓';
+                staStatusText.textContent = 'Connected to WiFi';
+                staIpElement.textContent = 'IP Address: ' + data.staIP;
+            } else if (data.staEnable) {
+                staStatus.className = 'sta-status disconnected';
+                staStatus.style.display = 'flex';
+                staStatusIcon.textContent = '✗';
+                staStatusText.textContent = 'Not connected (Station mode enabled)';
+                staIpElement.textContent = 'Check WiFi credentials';
+            } else {
+                staStatus.style.display = 'none';
+            }
+            
+            hideAlert('alert-loading');
+            console.log('✓ Settings loaded:', data);
+        }
+        
+        function loadSettings() {
+            if (ws && ws.readyState === WebSocket.OPEN) {
+                ws.send(JSON.stringify({cmd: 'getSettings'}));
+                showAlert('alert-loading', '⏳ Loading settings...', 'alert-info');
+            }
+        }
+        
+        function saveSettings() {
+            const ssid = document.getElementById('wifi-ssid').value.trim();
+            const password = document.getElementById('wifi-password').value;
+            const staEnable = document.getElementById('sta-enable').checked;
+            const staSSID = document.getElementById('sta-ssid').value.trim();
+            const staPassword = document.getElementById('sta-password').value;
+            
+            // 입력 검증
+            if (ssid.length === 0) {
+                alert('⚠️ Please enter AP SSID');
+                return;
+            }
+            
+            if (ssid.length > 31) {
+                alert('⚠️ AP SSID maximum length is 31 characters');
+                return;
+            }
+            
+            if (password.length > 0 && password.length < 8) {
+                alert('⚠️ AP Password must be at least 8 characters (or leave empty for open network)');
+                return;
+            }
+            
+            if (password.length > 63) {
+                alert('⚠️ AP Password maximum length is 63 characters');
+                return;
+            }
+            
+            if (staEnable) {
+                if (staSSID.length === 0) {
+                    alert('⚠️ Please enter Station WiFi SSID or disable Station mode');
+                    return;
+                }
+                if (staSSID.length > 31) {
+                    alert('⚠️ Station SSID maximum length is 31 characters');
+                    return;
+                }
+            }
+            
+            const settings = {
+                cmd: 'saveSettings',
+                ssid: ssid,
+                password: password,
+                staEnable: staEnable,
+                staSSID: staSSID,
+                staPassword: staPassword
+            };
+            
+            if (ws && ws.readyState === WebSocket.OPEN) {
+                ws.send(JSON.stringify(settings));
+                console.log('✓ Saving settings:', settings);
+            } else {
+                alert('⚠️ WebSocket disconnected. Please refresh the page.');
+            }
+        }
+        
+        function rebootDevice() {
+            if (!confirm('⚠️ Reboot the device?\n\nCurrent connections will be lost.\nAfter reboot, reconnect to WiFi (use new SSID if changed).')) {
+                return;
+            }
+            
+            if (ws && ws.readyState === WebSocket.OPEN) {
+                ws.send(JSON.stringify({cmd: 'reboot'}));
+                
+                showAlert('alert-info', '🔄 Rebooting device... Please wait 10 seconds.', 'alert-info');
+                
+                setTimeout(() => {
+                    alert('Reboot complete!\n\nIf SSID was changed, reconnect to the new network.\nThen access: http://192.168.4.1');
+                }, 3000);
+            }
+        }
+        
+        function showAlert(alertId, message, className) {
+            // 모든 알림 숨김
+            document.querySelectorAll('.alert').forEach(alert => {
+                alert.classList.remove('show');
+            });
+            
+            const alert = document.getElementById(alertId);
+            if (alert) {
+                const textElement = alert.querySelector('.alert-text');
+                if (textElement && message) {
+                    textElement.textContent = message;
+                }
+                
+                alert.className = 'alert ' + className;
+                alert.classList.add('show');
+                
+                if (className === 'alert-success') {
+                    setTimeout(() => {
+                        hideAlert(alertId);
+                    }, 5000);
+                }
+            }
+        }
+        
+        function hideAlert(alertId) {
+            const alert = document.getElementById(alertId);
+            if (alert) {
+                alert.classList.remove('show');
+            }
+        }
+        
+        function toggleSTASettings() {
+            const staEnable = document.getElementById('sta-enable').checked;
+            const staSettings = document.getElementById('sta-settings');
+            
+            if (staEnable) {
+                staSettings.classList.remove('disabled');
+            } else {
+                staSettings.classList.add('disabled');
+            }
+        }
+        
+        window.addEventListener('load', function() {
+            initWebSocket();
+        });
+    </script>
+</body>
+</html>
+)rawliteral";
+
+#endif
