diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 4e259e3..fa81d97 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -2,7 +2,7 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:versionCode="128"
-    android:versionName="4.2.1b">
+    android:versionName="4.2.1e">
     <!-- android:allowBackup="false" -->
     <uses-permission android:name="android.permission.BLUETOOTH" />
     <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
diff --git a/app/src/main/java/uk/org/openseizuredetector/SdDataSourceBLE.java b/app/src/main/java/uk/org/openseizuredetector/SdDataSourceBLE.java
index a56f059..09d4f27 100644
--- a/app/src/main/java/uk/org/openseizuredetector/SdDataSourceBLE.java
+++ b/app/src/main/java/uk/org/openseizuredetector/SdDataSourceBLE.java
@@ -83,16 +83,17 @@ public class SdDataSourceBLE extends SdDataSource {
 
     public static String SERV_DEV_INFO = "0000180a-0000-1000-8000-00805f9b34fb";
     public static String SERV_HEART_RATE = "0000180d-0000-1000-8000-00805f9b34fb";
-    public static String SERV_OSD = "000085e9-0000-1000-8000-00805f9b34fb";
     public static String CHAR_HEART_RATE_MEASUREMENT = "00002a37-0000-1000-8000-00805f9b34fb";
+
+    public static String SERV_OSD           = "000085e9-0000-1000-8000-00805f9b34fb";
+    public static String CHAR_OSD_ACC_DATA  = "000085e9-0001-1000-8000-00805f9b34fb";
+    public static String CHAR_OSD_BATT_DATA = "000085e9-0002-1000-8000-00805f9b34fb";
+    public static String CHAR_OSD_WATCH_ID = "000085e9-0003-1000-8000-00805f9b34fb";
+    public static String CHAR_OSD_WATCH_FW = "000085e9-0004-1000-8000-00805f9b34fb";
+
     public static String CHAR_MANUF_NAME = "00002a29-0000-1000-8000-00805f9b34fb";
     public static String CLIENT_CHARACTERISTIC_CONFIG = "00002902-0000-1000-8000-00805f9b34fb";
-    public static String CHAR_OSD_ACC_DATA = "000085ea-0000-1000-8000-00805f9b34fb";
-    public static String CHAR_OSD_BATT_DATA = "000085eb-0000-1000-8000-00805f9b34fb";
-
-    public final static UUID UUID_HEART_RATE_MEASUREMENT = UUID.fromString(CHAR_HEART_RATE_MEASUREMENT);
     private BluetoothGatt mGatt;
-    private BluetoothGattCharacteristic mBattChar;
     private BluetoothGattCharacteristic mOsdChar;
 
 
@@ -263,10 +264,13 @@ public class SdDataSourceBLE extends SdDataSource {
                                 setCharacteristicNotification(gattCharacteristic,true);
                             }
                             else if (charUuidStr.equals(CHAR_OSD_BATT_DATA)) {
-                                Log.v(TAG,"Saving battery characteristic for later");
                                 Log.v(TAG, "Subscribing to battery change Notifications");
                                 setCharacteristicNotification(gattCharacteristic,true);
                             }
+                            //else if (charUuidStr.equals(CHAR_OSD_HR_DATA)) {
+                            //    Log.v(TAG, "Subscribing to HR change Notifications");
+                            //    setCharacteristicNotification(gattCharacteristic,true);
+                            //.}
                         }
                     }
                 }
@@ -288,34 +292,42 @@ public class SdDataSourceBLE extends SdDataSource {
         }
 
         public void onDataReceived(BluetoothGattCharacteristic characteristic) {
-            Log.v(TAG, "onDataReceived uuid" + characteristic.getUuid().toString());
-
-            // FIXME - collect data until we have enough to do analysis, then use onDataReceived to process it.
+            /**
+             * onDataReceived - called whenever a BLE characteristic notifies us that its data has changed.
+             * If the data is acceleration data, we add it to a buffer - it is analysed once the buffer is full.
+             * Heart rate data is written directly to sdData to be used in future analysis.
+             */
             //Log.v(TAG,"onDataReceived: Characteristic="+characteristic.getUuid().toString());
             if (characteristic.getUuid().toString().equals(CHAR_HEART_RATE_MEASUREMENT)) {
                 int flag = characteristic.getProperties();
+                //Log.d(TAG,"onDataReceived() - flag = "+flag);
                 int format = -1;
                 if ((flag & 0x01) != 0) {
                     format = BluetoothGattCharacteristic.FORMAT_UINT16;
-                    Log.d(TAG, "Heart rate format UINT16.");
+                    //Log.d(TAG, "onDataReceived(): Heart rate format UINT16.");
                 } else {
                     format = BluetoothGattCharacteristic.FORMAT_UINT8;
-                    Log.d(TAG, "Heart rate format UINT8.");
+                    //Log.d(TAG, "onDataReceived(): Heart rate format UINT8.");
                 }
-                final int heartRate = characteristic.getIntValue(format, 1);
+                final int heartRate = characteristic.getIntValue(format, 1);  // heart rate is second byte
+                //byte[] rawDataBytes = characteristic.getValue();
+                //Log.d(TAG,"onDataReceived - len(rawDataBytes)="+rawDataBytes.length);
+                //for (int i=0;i<rawDataBytes.length;i++) {
+                //    Log.d(TAG,"onDataReceived - HR["+i+" = "+rawDataBytes[i]);
+                //}
                 mSdData.mHR = (double) heartRate;
-                Log.d(TAG, String.format("Received heart rate: %d", heartRate));
+                Log.d(TAG, String.format("onDataReceived(): CHAR_HEART_RATE_MEASUREMENT: %d", heartRate));
             }
             else if (characteristic.getUuid().toString().equals(CHAR_OSD_ACC_DATA)) {
                 //Log.v(TAG,"Received OSD ACC DATA"+characteristic.getValue());
                 byte[] rawDataBytes = characteristic.getValue();
-                Log.v(TAG, "CHAR_OSD_ACC_DATA: numSamples = " + rawDataBytes.length+" nRawData="+nRawData);
+                Log.v(TAG, "onDataReceived(): CHAR_OSD_ACC_DATA: numSamples = " + rawDataBytes.length+" nRawData="+nRawData);
                 for (int i = 0; i < rawDataBytes.length;i++) {
                     if (nRawData < MAX_RAW_DATA) {
                         rawData[nRawData] = 1000 * rawDataBytes[i] / 64;   // Scale to mg
                         nRawData++;
                     } else {
-                        Log.i(TAG, "RawData Buffer Full - processing data");
+                        Log.i(TAG, "onDataReceived(): RawData Buffer Full - processing data");
                         // Re-start collecting raw data.
                         mSdData.watchAppRunning = true;
                         for (i = 0; i < rawData.length; i++) {
@@ -334,7 +346,7 @@ public class SdDataSourceBLE extends SdDataSource {
             else if (characteristic.getUuid().toString().equals(CHAR_OSD_BATT_DATA)) {
                 byte batteryPc = characteristic.getValue()[0];
                 mSdData.batteryPc = batteryPc;
-                Log.v(TAG,"Received Battery Data" + String.format("%d", batteryPc));
+                Log.v(TAG,"onDataReceived(): CHAR_OSD_BATT_DATA: " + String.format("%d", batteryPc));
                 mSdData.haveSettings = true;
             }
             else {
@@ -356,7 +368,7 @@ public class SdDataSourceBLE extends SdDataSource {
         @Override
         public void onCharacteristicChanged(BluetoothGatt gatt,
                                             BluetoothGattCharacteristic characteristic) {
-            Log.v(TAG,"onCharacteristicChanged(): Characteristic "+characteristic.getUuid()+" changed");
+            //Log.v(TAG,"onCharacteristicChanged(): Characteristic "+characteristic.getUuid()+" changed");
             onDataReceived(characteristic);
         }