diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/devices/zetime/ZeTimeConstants.java b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/devices/zetime/ZeTimeConstants.java
index b36d8b000..4a0cd8e26 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/devices/zetime/ZeTimeConstants.java
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/devices/zetime/ZeTimeConstants.java
@@ -19,8 +19,46 @@ public class ZeTimeConstants {
     public static final UUID UUID_SERVICE_HEART_RATE = UUID.fromString("0000180d-0000-1000-8000-00805f9b34fb");
 
     public static final byte CMD_PREAMBLE = (byte) 0x6f;
-    public static final byte CMD_GET_AVAIABLE_DATE = (byte) 0x52;
+    // list all available commands
+    public static final byte CMD_RESPOND = (byte) 0x01;
+    public static final byte CMD_WATCH_ID = (byte) 0x02;
+    public static final byte CMD_DEVICE_VERSION = (byte) 0x03;
+    public static final byte CMD_DATE_TIME = (byte) 0x04;
+    public static final byte CMD_TIME_SURFACE_SETTINGS = (byte) 0x05;
+    public static final byte CMD_SURFACE_DISPLAY_SETTIGNS = (byte) 0x06;
+    public static final byte CMD_SCREEN_BRIGHTNESS = (byte) 0x07;
+    public static final byte CMD_BATTERY_POWER = (byte) 0x08;
+    public static final byte CMD_VOLUME_SETTINGS = (byte) 0x09;
+    public static final byte CMD_SHOCK_MODE = (byte) 0x0A;
+    public static final byte CMD_LANGUAGE_SETTINGS = (byte) 0x0B;
+    public static final byte CMD_UNIT_SETTINGS = (byte) 0x0C;
+    public static final byte CMD_FACTORY_RESTORE = (byte) 0x0D;
+    public static final byte CMD_ENTER_UPGRADE_MODE = (byte) 0x0E;
+    public static final byte CMD_SHOCK_STRENGTH = (byte) 0x10;
+    public static final byte CMD_WORK_MODE = (byte) 0x12;
+    public static final byte CMD_SCREEN_ON_TIME = (byte) 0x13;
+    public static final byte CMD_SNOOZE = (byte) 0x14;
+    public static final byte CMD_DO_NOT_DISTURB = (byte) 0x15;
+    public static final byte CMD_USER_INFO = (byte) 0x30;
+    public static final byte CMD_USAGE_HABITS = (byte) 0x31;
+    public static final byte CMD_USER_NAME = (byte) 0x32;
+    public static final byte CMD_GOALS = (byte) 0x50;
+    public static final byte CMD_AVAIABLE_DATA = (byte) 0x52;
+    public static final byte CMD_DELETE_STEP_COUNT = (byte) 0x53;
+    public static final byte CMD_GET_STEP_COUNT = (byte) 0x54;
+    public static final byte CMD_DELETE_SLEEP_DATA = (byte) 0x55;
+    public static final byte CMD_GET_SLEEP_DATA = (byte) 0x56;
+    public static final byte CMD_DELETE_HEARTRATE_DATA = (byte) 0x5A;
+    public static final byte CMD_GET_HEARTRATE_DATA = (byte) 0x5B;
+    public static final byte CMD_AUTO_HEARTRATE = (byte) 0x5C;
+    public static final byte CMD_HEARTRATE_ALARM_LIMITS = (byte) 0x5D;
+    public static final byte CMD_INACTIVITY_ALERT = (byte) 0x5E;
+    public static final byte CMD_CALORIES_TYPE = (byte) 0x60;
+    public static final byte CMD_GET_HEARTRATE_EXDATA = (byte) 0x61;
+    // here are the action commands
     public static final byte CMD_REQUEST = (byte) 0x70;
+    public static final byte CMD_REQUEST_RESPOND = (byte) 0x80;
+    // further commands
     public static final byte CMD_END = (byte) 0x8f;
     public static final byte CMD_ACK_WRITE = (byte) 0x03;
 }
diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/zetime/ZeTimeDeviceSupport.java b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/zetime/ZeTimeDeviceSupport.java
index cec5284d0..bceed1721 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/zetime/ZeTimeDeviceSupport.java
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/zetime/ZeTimeDeviceSupport.java
@@ -26,6 +26,8 @@ import nodomain.freeyourgadget.gadgetbridge.service.btle.GattService;
 import nodomain.freeyourgadget.gadgetbridge.service.btle.TransactionBuilder;
 import nodomain.freeyourgadget.gadgetbridge.service.btle.actions.SetDeviceStateAction;
 
+import static nodomain.freeyourgadget.gadgetbridge.devices.zetime.ZeTimeConstants.CMD_AVAIABLE_DATA;
+
 /**
  * Created by Kranz on 08.02.2018.
  */
@@ -59,7 +61,7 @@ public class ZeTimeDeviceSupport extends AbstractBTLEDeviceSupport {
 
         // do this in a function
         builder.write(writeCharacteristic, new byte[]{ZeTimeConstants.CMD_PREAMBLE,
-                                                      ZeTimeConstants.CMD_GET_AVAIABLE_DATE,
+                                                      CMD_AVAIABLE_DATA,
                                                       ZeTimeConstants.CMD_REQUEST,
                                                       0x01,
                                                       0x00,
@@ -230,6 +232,11 @@ public class ZeTimeDeviceSupport extends AbstractBTLEDeviceSupport {
         UUID characteristicUUID = characteristic.getUuid();
         if (ZeTimeConstants.UUID_ACK_CHARACTERISTIC.equals(characteristicUUID)) {
             byte[] data = characteristic.getValue();
+            if(isMsgFormatOK(data)) {
+                switch (data[1]) {
+                    case ZeTimeConstants.CMD_AVAIABLE_DATA:
+                }
+            }
             return true;
         } else {
             LOG.info("Unhandled characteristic changed: " + characteristicUUID);
@@ -237,4 +244,24 @@ public class ZeTimeDeviceSupport extends AbstractBTLEDeviceSupport {
         }
         return false;
     }
+
+    private boolean isMsgFormatOK(byte[] msg)
+    {
+        if(msg[0] == ZeTimeConstants.CMD_PREAMBLE)
+        {
+            if((msg[3] != 0) && (msg[4] != 0))
+            {
+                int payloadSize = msg[4] * 256 + msg[3];
+                int msgLength = payloadSize + 6;
+                if(msgLength == msg.length)
+                {
+                    if(msg[msgLength - 1] == ZeTimeConstants.CMD_END)
+                    {
+                        return true;
+                    }
+                }
+            }
+        }
+        return false;
+    }
 }