diff --git a/lib/switchbot-advertising.js b/lib/switchbot-advertising.js
index 95569d3c..3650322c 100644
--- a/lib/switchbot-advertising.js
+++ b/lib/switchbot-advertising.js
@@ -60,7 +60,7 @@ class SwitchbotAdvertising {
   * If the specified `Peripheral` does not represent any switchbot
   * device, this method will return `null`.
   * ---------------------------------------------------------------- */
-  parse(peripheral) {
+  parse(peripheral, onlog) {
     let ad = peripheral.advertisement;
     if (!ad || !ad.serviceData) {
       return null;
@@ -75,22 +75,28 @@ class SwitchbotAdvertising {
     let sd = null;
 
     if (model === 'H') { // WoHand
-      sd = this._parseServiceDataForWoHand(buf);
+      sd = this._parseServiceDataForWoHand(buf, onlog);
     } else if (model === 'e') { // WoHumi
-      sd = this._parseServiceDataForWoHumi(buf);
+      sd = this._parseServiceDataForWoHumi(buf, onlog);
     } else if (model === 'T') { // WoSensorTH
-      sd = this._parseServiceDataForWoSensorTH(buf);
+      sd = this._parseServiceDataForWoSensorTH(buf, onlog);
     } else if (model === 'c') { // WoCurtain
-      sd = this._parseServiceDataForWoCurtain(buf);
+      sd = this._parseServiceDataForWoCurtain(buf, onlog);
     } else if (model === 's') { // WoMotion
-      sd = this._parseServiceDataForWoPresence(buf);
+      sd = this._parseServiceDataForWoPresence(buf, onlog);
     } else if (model === 'd') { // WoContact
-      sd = this._parseServiceDataForWoContact(buf);
+      sd = this._parseServiceDataForWoContact(buf, onlog);
     } else {
+      if (onlog && typeof onlog === 'function') {
+        onlog(`[parseAdvertising.${peripheral.id}] return null, model "${model}" not available!`);
+      }
       return null;
     }
 
     if (!sd) {
+      if (onlog && typeof onlog === 'function') {
+        onlog(`[parseAdvertising.${peripheral.id}.${model}] return null, parsed serviceData empty!`);
+      }
       return null;
     }
     let address = peripheral.address || '';
@@ -114,11 +120,18 @@ class SwitchbotAdvertising {
       rssi: peripheral.rssi,
       serviceData: sd
     };
+    
+    if (onlog && typeof onlog === 'function') {
+      onlog(`[parseAdvertising.${peripheral.id}.${model}] return ${JSON.stringify(data)}`);
+    }
     return data;
   }
 
-  _parseServiceDataForWoHand(buf) {
+  _parseServiceDataForWoHand(buf, onlog) {
     if (buf.length !== 3) {
+      if (onlog && typeof onlog === 'function') {
+        onlog(`[_parseServiceDataForWoHand] Buffer length ${buf.length} !== 3!`);
+      }
       return null;
     }
     let byte1 = buf.readUInt8(1);
@@ -139,8 +152,11 @@ class SwitchbotAdvertising {
     return data;
   }
 
-  _parseServiceDataForWoHumi(buf) {
+  _parseServiceDataForWoHumi(buf, onlog) {
     if (buf.length !== 8) {
+      if (onlog && typeof onlog === 'function') {
+        onlog(`[_parseServiceDataForWoHumi] Buffer length ${buf.length} !== 8!`);
+      }
       return null;
     }
     let byte1 = buf.readUInt8(1);
@@ -164,8 +180,11 @@ class SwitchbotAdvertising {
     return data;
   }
 
-  _parseServiceDataForWoSensorTH(buf) {
+  _parseServiceDataForWoSensorTH(buf, onlog) {
     if (buf.length !== 6) {
+      if (onlog && typeof onlog === 'function') {
+        onlog(`[_parseServiceDataForWoSensorTH] Buffer length ${buf.length} !== 6!`);
+      }
       return null;
     }
     let byte2 = buf.readUInt8(2);
@@ -193,8 +212,11 @@ class SwitchbotAdvertising {
     return data;
   }
 
-  _parseServiceDataForWoPresence(buf) {
+  _parseServiceDataForWoPresence(buf, onlog) {
     if (buf.length !== 6) {
+      if (onlog && typeof onlog === 'function') {
+        onlog(`[_parseServiceDataForWoPresence] Buffer length ${buf.length} !== 6!`);
+      }
       return null;
     }
     let byte1 = buf.readUInt8(1);
@@ -218,8 +240,11 @@ class SwitchbotAdvertising {
     return data;
   }
 
-  _parseServiceDataForWoContact(buf) {
+  _parseServiceDataForWoContact(buf, onlog) {
     if (buf.length !== 9) {
+      if (onlog && typeof onlog === 'function') {
+        onlog(`[_parseServiceDataForWoContact] Buffer length ${buf.length} !== 9!`);
+      }
       return null;
     }
 
@@ -249,14 +274,18 @@ class SwitchbotAdvertising {
     return data;
   }
 
-  _parseServiceDataForWoCurtain(buf) {
-    if (buf.length !== 5) {
+  _parseServiceDataForWoCurtain(buf, onlog) {
+    if (buf.length !== 5 && buf.length !== 6) {
+      if (onlog && typeof onlog === 'function') {
+        onlog(`[_parseServiceDataForWoCurtain] Buffer length ${buf.length} !== 5 or 6!`);
+      }
       return null;
     }
     let byte1 = buf.readUInt8(1);
     let byte2 = buf.readUInt8(2);
     let byte3 = buf.readUInt8(3);
     let byte4 = buf.readUInt8(4);
+    // let byte5 = buf.readUInt8(5);
 
     let calibration = (byte1 & 0b01000000) ? true : false; // Whether the calibration is completed
     let battery = byte2 & 0b01111111; // %
diff --git a/lib/switchbot.js b/lib/switchbot.js
index 2dc7fb18..8721901a 100644
--- a/lib/switchbot.js
+++ b/lib/switchbot.js
@@ -34,6 +34,7 @@ class Switchbot {
     this.noble = noble;
     this.ondiscover = null;
     this.onadvertisement = null;
+    this.onlog = null;
 
     // Private properties
     this._scanning = false;
@@ -178,7 +179,7 @@ class Switchbot {
   }
 
   _getDeviceObject(peripheral, id, model) {
-    let ad = switchbotAdvertising.parse(peripheral);
+    let ad = switchbotAdvertising.parse(peripheral, this.onlog);
     if (this._filterAdvertising(ad, id, model)) {
       let device = null;
       switch (ad.serviceData.model) {
@@ -293,7 +294,7 @@ class Switchbot {
 
         // Set a handler for the 'discover' event
         this.noble.on('discover', (peripheral) => {
-          let ad = switchbotAdvertising.parse(peripheral);
+          let ad = switchbotAdvertising.parse(peripheral, this.onlog);
           if (this._filterAdvertising(ad, p.id, p.model)) {
             if (this.onadvertisement && typeof (this.onadvertisement) === 'function') {
               this.onadvertisement(ad);