diff --git a/ESP32_CAN_Logger-a.ino b/ESP32_CAN_Logger-a.ino
index 31e9763..4c5ad73 100644
--- a/ESP32_CAN_Logger-a.ino
+++ b/ESP32_CAN_Logger-a.ino
@@ -1736,16 +1736,26 @@ void webSocketEvent(uint8_t num, WStype_t type, uint8_t *payload, size_t length)
             }
         }
         else if (strcmp(cmd, "sendSerial") == 0) {
-            const char* data = doc["data"];
-            if (data && strlen(data) > 0) {
-                SerialComm.println(data);
-                SerialMessage msg;
+            const char* hexStr = doc["data"];
+            if (hexStr && strlen(hexStr) > 0) {
+                uint8_t rawBuf[MAX_SERIAL_LINE_LEN]; int rawLen = 0;
+                for (int i = 0; hexStr[i] && hexStr[i+1] && rawLen < MAX_SERIAL_LINE_LEN; i += 2) {
+                    while (hexStr[i] == ' ') i++;
+                    if (!hexStr[i] || !hexStr[i+1]) break;
+                    char h[3] = {hexStr[i], hexStr[i+1], 0};
+                    rawBuf[rawLen++] = (uint8_t)strtoul(h, NULL, 16);
+                }
+                SerialComm.write(rawBuf, rawLen);
+                totalSerialTxCount++;
+                // ★ TX echo: s1 패킷으로 즉시 전송 → JS handlePacket(true, hex, ts)
+                char txHex[MAX_SERIAL_LINE_LEN*2+1];
+                for (int i=0; i<rawLen; i++) snprintf(&txHex[i*2], 3, "%02X", rawBuf[i]);
+                txHex[rawLen*2] = '\0';
                 struct timeval tv; gettimeofday(&tv, NULL);
-                msg.timestamp_us = (uint64_t)tv.tv_sec * 1000000ULL + tv.tv_usec;
-                msg.length = min((int)(strlen(data)+2), MAX_SERIAL_LINE_LEN-1);
-                snprintf((char*)msg.data, MAX_SERIAL_LINE_LEN, "%s\r\n", data);
-                msg.isTx = true;
-                if (ring_serial_push(&serialRing, &msg)) totalSerialTxCount++;
+                uint32_t tsMs = (uint32_t)(tv.tv_sec*1000ULL + tv.tv_usec/1000ULL);
+                char s1pkt[MAX_SERIAL_LINE_LEN*2+80];
+                snprintf(s1pkt, sizeof(s1pkt), "{\"type\":\"s1\",\"tx\":true,\"ts\":%u,\"d\":\"%s\"}", tsMs, txHex);
+                webSocket.sendTXT(num, s1pkt);
             }
         }
         else if (strcmp(cmd, "setSerialConfig") == 0) {
@@ -1798,16 +1808,25 @@ void webSocketEvent(uint8_t num, WStype_t type, uint8_t *payload, size_t length)
             }
         }
         else if (strcmp(cmd, "sendSerial2") == 0) {
-            const char* data = doc["data"];
-            if (data && strlen(data) > 0) {
-                Serial2Comm.println(data);
-                SerialMessage msg;
+            const char* hexStr = doc["data"];
+            if (hexStr && strlen(hexStr) > 0) {
+                uint8_t rawBuf[MAX_SERIAL_LINE_LEN]; int rawLen = 0;
+                for (int i = 0; hexStr[i] && hexStr[i+1] && rawLen < MAX_SERIAL_LINE_LEN; i += 2) {
+                    while (hexStr[i] == ' ') i++;
+                    if (!hexStr[i] || !hexStr[i+1]) break;
+                    char h[3] = {hexStr[i], hexStr[i+1], 0};
+                    rawBuf[rawLen++] = (uint8_t)strtoul(h, NULL, 16);
+                }
+                Serial2Comm.write(rawBuf, rawLen);
+                totalSerial2TxCount++;
+                char txHex[MAX_SERIAL_LINE_LEN*2+1];
+                for (int i=0; i<rawLen; i++) snprintf(&txHex[i*2], 3, "%02X", rawBuf[i]);
+                txHex[rawLen*2] = '\0';
                 struct timeval tv; gettimeofday(&tv, NULL);
-                msg.timestamp_us = (uint64_t)tv.tv_sec * 1000000ULL + tv.tv_usec;
-                msg.length = min((int)(strlen(data)+2), MAX_SERIAL_LINE_LEN-1);
-                snprintf((char*)msg.data, MAX_SERIAL_LINE_LEN, "%s\r\n", data);
-                msg.isTx = true;
-                if (ring_serial_push(&serial2Ring, &msg)) totalSerial2TxCount++;
+                uint32_t tsMs = (uint32_t)(tv.tv_sec*1000ULL + tv.tv_usec/1000ULL);
+                char s2pkt[MAX_SERIAL_LINE_LEN*2+80];
+                snprintf(s2pkt, sizeof(s2pkt), "{\"type\":\"s2\",\"tx\":true,\"ts\":%u,\"d\":\"%s\"}", tsMs, txHex);
+                webSocket.sendTXT(num, s2pkt);
             }
         }
         else if (strcmp(cmd, "setSerial2Config") == 0) {
@@ -1824,6 +1843,9 @@ void webSocketEvent(uint8_t num, WStype_t type, uint8_t *payload, size_t length)
             r["stopBits"]=serial2Settings.stopBits;
             String j; serializeJson(r,j); webSocket.sendTXT(num,j);
         }
+        else if (strcmp(cmd, "ping") == 0) {
+            webSocket.sendTXT(num, "{\"type\":\"pong\"}");
+        }
         else if (strcmp(cmd, "setSpeed") == 0) {
             int si = doc["speed"];
             if (si >= 0 && si < 4) {
@@ -2244,89 +2266,87 @@ void webUpdateTask(void *parameter) {
                 }
             }
 
-            // ★ Serial RingBuffer pop (최대 10개)
-            SerialMessage serialMsg;
-            JsonArray serialMessages = doc.createNestedArray("serialMessages");
-            int serialCnt = 0;
-            while (serialCnt < 10 && ring_serial_pop(&serialRing, &serialMsg)) {
-                JsonObject so = serialMessages.createNestedObject();
-                so["timestamp"] = serialMsg.timestamp_us;
-                so["isTx"]      = serialMsg.isTx;
-                char ds[MAX_SERIAL_LINE_LEN+1];
-                memcpy(ds, serialMsg.data, serialMsg.length);
-                ds[serialMsg.length] = '\0';
-                so["data"] = ds;
-                serialCnt++;
-
-                // Serial SD 로깅
-                if (serialLoggingEnabled && sdCardReady) {
-                    if (xSemaphoreTake(sdMutex, pdMS_TO_TICKS(10)) == pdTRUE) {
-                        if (serialLogFormatCSV) {
-                            uint64_t rt = serialMsg.timestamp_us - serialLogStartTime;
-                            char csvLine[256];
-                            int ll = snprintf(csvLine, sizeof(csvLine),
-                                "%llu,%s,\"%s\"\n", rt, serialMsg.isTx?"TX":"RX", ds);
-                            if (serialCsvIndex + ll <= SERIAL_CSV_BUFFER_SIZE) {
-                                memcpy(&serialCsvBuffer[serialCsvIndex], csvLine, ll);
-                                serialCsvIndex += ll;
-                                currentSerialFileSize += ll;
-                            }
-                            if (serialCsvIndex >= SERIAL_CSV_BUFFER_SIZE - 256) {
-                                if (serialLogFile) { serialLogFile.write((uint8_t*)serialCsvBuffer, serialCsvIndex); serialLogFile.flush(); serialCsvIndex=0; }
-                            }
-                        } else {
-                            if (serialLogFile) {
-                                serialLogFile.write((uint8_t*)&serialMsg, sizeof(SerialMessage));
-                                currentSerialFileSize += sizeof(SerialMessage);
-                                static int bfc=0; if (++bfc>=50){serialLogFile.flush();bfc=0;}
+            // ★★★ Serial1/2 데이터: update 패킷 분리 → 별도 소형 s1/s2 패킷으로 즉시 전송
+            // 이유: update 패킷 JSON 크기 초과 시 전체 드롭됨 (8192 또는 12000 limit)
+            {
+                SerialMessage sMsg;
+                while (ring_serial_pop(&serialRing, &sMsg)) {
+                    // raw bytes → hex string (0x80+ UTF-8 안전)
+                    char hexBuf[MAX_SERIAL_LINE_LEN*2+1];
+                    for (int hi=0; hi<sMsg.length; hi++)
+                        snprintf(&hexBuf[hi*2], 3, "%02X", (uint8_t)sMsg.data[hi]);
+                    hexBuf[sMsg.length*2] = '\0';
+                    // s1 패킷 직접 포맷 (StaticJsonDocument heap 절약)
+                    uint32_t tsMs = (uint32_t)(sMsg.timestamp_us / 1000ULL);
+                    char s1pkt[MAX_SERIAL_LINE_LEN*2+80];
+                    snprintf(s1pkt, sizeof(s1pkt),
+                        "{\"type\":\"s1\",\"tx\":%s,\"ts\":%u,\"d\":\"%s\"}",
+                        sMsg.isTx ? "true":"false", tsMs, hexBuf);
+                    webSocket.broadcastTXT(s1pkt);
+                    // SD 로깅
+                    if (serialLoggingEnabled && sdCardReady) {
+                        if (xSemaphoreTake(sdMutex, pdMS_TO_TICKS(10)) == pdTRUE) {
+                            if (serialLogFormatCSV) {
+                                uint64_t rt = sMsg.timestamp_us - serialLogStartTime;
+                                char csv[256];
+                                int ll = snprintf(csv, sizeof(csv), "%llu,%s,\"%s\"\n",
+                                    rt, sMsg.isTx?"TX":"RX", hexBuf);
+                                if (serialCsvIndex+ll <= SERIAL_CSV_BUFFER_SIZE) {
+                                    memcpy(&serialCsvBuffer[serialCsvIndex], csv, ll);
+                                    serialCsvIndex += ll; currentSerialFileSize += ll;
+                                }
+                                if (serialCsvIndex >= SERIAL_CSV_BUFFER_SIZE-256 && serialLogFile)
+                                    { serialLogFile.write((uint8_t*)serialCsvBuffer, serialCsvIndex); serialLogFile.flush(); serialCsvIndex=0; }
+                            } else {
+                                if (serialLogFile) {
+                                    serialLogFile.write((uint8_t*)&sMsg, sizeof(SerialMessage));
+                                    currentSerialFileSize += sizeof(SerialMessage);
+                                    static int bfc=0; if (++bfc>=50){serialLogFile.flush();bfc=0;}
+                                }
                             }
+                            xSemaphoreGive(sdMutex);
                         }
-                        xSemaphoreGive(sdMutex);
                     }
                 }
             }
-
-            // ★ Serial2 RingBuffer pop
-            SerialMessage serial2Msg;
-            JsonArray serial2Messages = doc.createNestedArray("serial2Messages");
-            int s2Cnt = 0;
-            while (s2Cnt < 10 && ring_serial_pop(&serial2Ring, &serial2Msg)) {
-                JsonObject so = serial2Messages.createNestedObject();
-                so["timestamp"] = serial2Msg.timestamp_us;
-                so["isTx"]      = serial2Msg.isTx;
-                char ds[MAX_SERIAL_LINE_LEN+1];
-                memcpy(ds, serial2Msg.data, serial2Msg.length);
-                ds[serial2Msg.length] = '\0';
-                so["data"] = ds;
-                s2Cnt++;
-
-                if (serial2LoggingEnabled && sdCardReady) {
-                    if (xSemaphoreTake(sdMutex, pdMS_TO_TICKS(10)) == pdTRUE) {
-                        if (serial2LogFormatCSV) {
-                            uint64_t rt = serial2Msg.timestamp_us - serial2LogStartTime;
-                            char csvLine[256];
-                            int ll = snprintf(csvLine, sizeof(csvLine),
-                                "%llu,%s,\"%s\"\n", rt, serial2Msg.isTx?"TX":"RX", ds);
-                            if (serial2CsvIndex + ll <= SERIAL2_CSV_BUFFER_SIZE) {
-                                memcpy(&serial2CsvBuffer[serial2CsvIndex], csvLine, ll);
-                                serial2CsvIndex += ll;
-                                currentSerial2FileSize += ll;
-                            }
-                            if (serial2CsvIndex >= SERIAL2_CSV_BUFFER_SIZE - 256) {
-                                if (serial2LogFile) { serial2LogFile.write((uint8_t*)serial2CsvBuffer, serial2CsvIndex); serial2LogFile.flush(); serial2CsvIndex=0; }
-                            }
-                        } else {
-                            if (serial2LogFile) {
-                                serial2LogFile.write((uint8_t*)&serial2Msg, sizeof(SerialMessage));
-                                currentSerial2FileSize += sizeof(SerialMessage);
-                                static int bfc2=0; if (++bfc2>=50){serial2LogFile.flush();bfc2=0;}
+            {
+                SerialMessage sMsg2;
+                while (ring_serial_pop(&serial2Ring, &sMsg2)) {
+                    char hexBuf2[MAX_SERIAL_LINE_LEN*2+1];
+                    for (int hi=0; hi<sMsg2.length; hi++)
+                        snprintf(&hexBuf2[hi*2], 3, "%02X", (uint8_t)sMsg2.data[hi]);
+                    hexBuf2[sMsg2.length*2] = '\0';
+                    uint32_t tsMs2 = (uint32_t)(sMsg2.timestamp_us / 1000ULL);
+                    char s2pkt[MAX_SERIAL_LINE_LEN*2+80];
+                    snprintf(s2pkt, sizeof(s2pkt),
+                        "{\"type\":\"s2\",\"tx\":%s,\"ts\":%u,\"d\":\"%s\"}",
+                        sMsg2.isTx ? "true":"false", tsMs2, hexBuf2);
+                    webSocket.broadcastTXT(s2pkt);
+                    if (serial2LoggingEnabled && sdCardReady) {
+                        if (xSemaphoreTake(sdMutex, pdMS_TO_TICKS(10)) == pdTRUE) {
+                            if (serial2LogFormatCSV) {
+                                uint64_t rt = sMsg2.timestamp_us - serial2LogStartTime;
+                                char csv[256];
+                                int ll = snprintf(csv, sizeof(csv), "%llu,%s,\"%s\"\n",
+                                    rt, sMsg2.isTx?"TX":"RX", hexBuf2);
+                                if (serial2CsvIndex+ll <= SERIAL2_CSV_BUFFER_SIZE) {
+                                    memcpy(&serial2CsvBuffer[serial2CsvIndex], csv, ll);
+                                    serial2CsvIndex += ll; currentSerial2FileSize += ll;
+                                }
+                                if (serial2CsvIndex >= SERIAL2_CSV_BUFFER_SIZE-256 && serial2LogFile)
+                                    { serial2LogFile.write((uint8_t*)serial2CsvBuffer, serial2CsvIndex); serial2LogFile.flush(); serial2CsvIndex=0; }
+                            } else {
+                                if (serial2LogFile) {
+                                    serial2LogFile.write((uint8_t*)&sMsg2, sizeof(SerialMessage));
+                                    currentSerial2FileSize += sizeof(SerialMessage);
+                                    static int bfc2=0; if (++bfc2>=50){serial2LogFile.flush();bfc2=0;}
+                                }
                             }
+                            xSemaphoreGive(sdMutex);
                         }
-                        xSemaphoreGive(sdMutex);
                     }
                 }
             }
-
             String json;
             size_t jsonSize = serializeJson(doc, json);
             if (jsonSize > 0 && jsonSize < 8192) webSocket.broadcastTXT(json);
@@ -2655,8 +2675,8 @@ void setup() {
     xTaskCreatePinnedToCore(sdMonitorTask, "SD_MONITOR",  4096, NULL,  1, NULL,                  1);
     xTaskCreatePinnedToCore(sdFlushTask,   "SD_FLUSH",    4096, NULL,  9, &sdFlushTaskHandle,    0);
     xTaskCreatePinnedToCore(sdWriteTask,   "SD_WRITE",   18576, NULL,  8, &sdWriteTaskHandle,    0);
-    xTaskCreatePinnedToCore(serialRxTask,  "SERIAL_RX",   6144, NULL,  6, &serialRxTaskHandle,   0);
-    xTaskCreatePinnedToCore(serial2RxTask, "SERIAL2_RX",  6144, NULL,  6, &serial2RxTaskHandle,  0);
+    xTaskCreatePinnedToCore(serialRxTask,  "SERIAL_RX",   6144, NULL,  6, &serialRxTaskHandle,   1);
+    xTaskCreatePinnedToCore(serial2RxTask, "SERIAL2_RX",  6144, NULL,  6, &serial2RxTaskHandle,  1);
     if (timeSyncStatus.rtcAvailable)
         xTaskCreatePinnedToCore(rtcSyncTask,"RTC_SYNC",   3072, NULL,  0, &rtcTaskHandle,        0);
     // ★ canRxTask 마지막 생성 (Core 1 Pri 24 → 이 시점엔 setup() 완료 직전)