diff --git a/OtaUpdate/CdcUpdater.cpp b/OtaUpdate/CdcUpdater.cpp
index 0509d4d..a1ebb5d 100644
--- a/OtaUpdate/CdcUpdater.cpp
+++ b/OtaUpdate/CdcUpdater.cpp
@@ -87,13 +87,17 @@ bool CdcUpdater::write(Command command, const uint8_t *data, uint32_t size) {
 void CdcUpdater::timerEvent(QTimerEvent *event) {
     const auto serialPortInfos = QSerialPortInfo::availablePorts();
     for (const QSerialPortInfo &portInfo : serialPortInfos) {
+        LOG(info) << "portName:" << portInfo.portName().toStdString()
+                  << ", vendorIdentifier: " << portInfo.vendorIdentifier();
         if (portInfo.vendorIdentifier() == 0xffff) {
             LOG(info) << "founded device: " << portInfo.portName().toStdString();
             emit deviceDiscovered(portInfo);
             killTimer(m_timerId);
             m_timerId = -1;
+            break;
         }
     }
+    LOG(info) << "----------";
 }
 
 void CdcUpdater::transferBin() {
diff --git a/Peripheral/DeviceDiscovery.cpp b/Peripheral/DeviceDiscovery.cpp
index 28f1185..10a2035 100644
--- a/Peripheral/DeviceDiscovery.cpp
+++ b/Peripheral/DeviceDiscovery.cpp
@@ -54,7 +54,7 @@ std::shared_ptr<DeviceDiscovery::Device> DeviceDiscovery::find(const std::string
     }
     if (index >= 0) {
         IMFMediaSource *source = nullptr;
-        result = devices[0]->ActivateObject(IID_PPV_ARGS(&source));
+        result = devices[index]->ActivateObject(IID_PPV_ARGS(&source));
         if (FAILED(result)) {
         } else {
             ret = std::make_shared<Device>(source);
@@ -80,11 +80,11 @@ std::string DeviceDiscovery::deviceName(IMFActivate *device) {
 
 void DeviceDiscovery::enterOtaMode(const std::shared_ptr<Device> &device, std::error_code &error) {
     auto resolutions = deviceResolutions(device);
-    // for (auto &[w, h] : resolutions) {
-    //     LOG(info) << w << " " << h;
-    // }
+    LOG(info) << "device resolutions:";
+    for (auto &[w, h] : resolutions) {
+        LOG(info) << "\t" << w << "*" << h;
+    }
 
-    // LOG(info) << "resolutions: " << resolutions.size();
     int32_t otaSpecificHeight = -1;
     for (auto &[width, height] : resolutions) {
         if (width == OtaSpecificWidth) {
@@ -95,6 +95,8 @@ void DeviceDiscovery::enterOtaMode(const std::shared_ptr<Device> &device, std::e
     if (otaSpecificHeight <= 0) {
         LOG(error) << "cannot find ota specific resolution.";
         return;
+    } else {
+        LOG(info) << "found ota specific resolution: " << OtaSpecificWidth << "x" << otaSpecificHeight;
     }
 
     IMFMediaType *type = nullptr;