diff --git a/apps/counter/api/mobile/serializers.py b/apps/counter/api/mobile/serializers.py
new file mode 100644
index 0000000..e969437
--- /dev/null
+++ b/apps/counter/api/mobile/serializers.py
@@ -0,0 +1,36 @@
+from typing import Optional
+from rest_framework import serializers
+from counter.models import DeviceCount, DeviceInfo
+from mosquito.models import DeviceInfo as MosquitoDeviceInfo
+
+
+class DeviceInfoMobileSerializer(serializers.ModelSerializer):
+    device_name = serializers.SerializerMethodField()
+    status = serializers.SerializerMethodField()
+    coordinate = serializers.SerializerMethodField()
+
+    class Meta:
+        model = DeviceInfo
+        fields = [
+            'device_id',
+            'device_name',
+            'status',
+            'coordinate',
+        ]
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.latest = None
+        self.cur_device = None
+
+    def get_device_name(self, obj) -> Optional[str]:
+        qs = MosquitoDeviceInfo.objects.filter(device_id=obj.device_id)
+        if qs.count() > 0:
+            device = qs.first()
+            self.cur_device = device
+            return device.device_name
+        return None
+
+    def get_status(self, obj) -> int:
+        return obj.online
+
diff --git a/apps/counter/api/mobile/urls.py b/apps/counter/api/mobile/urls.py
new file mode 100644
index 0000000..e69de29
diff --git a/apps/counter/api/mobile/views.py b/apps/counter/api/mobile/views.py
new file mode 100644
index 0000000..e69de29
diff --git a/apps/counter/api/serializers.py b/apps/counter/api/serializers.py
index 9cb51d3..25492ee 100644
--- a/apps/counter/api/serializers.py
+++ b/apps/counter/api/serializers.py
@@ -30,18 +30,29 @@ def get_vol(device_id, cur_vol):
     return '{}{}'.format(round(vol, 1), '%')
 
 
-def get_latest(device_id):
-    latest_key = 'device_latest_{}'.format(device_id)
+def get_device_latest_by_cache(device_id, key="device_latest_{}"):
+    """
+    Get latest device from cache
+    """
+    latest_key = key.format(device_id)
     latest = cache.get(latest_key)
     if latest:
         return latest
-    latest = DeviceCount.objects.filter(device_id=device_id).order_by('-data_time')[0]
+    latest = DeviceCount.objects.filter(device_id=device_id).order_by('-data_time').first()
+    if latest is None:
+        return None
     s = DeviceCountBaseSerializer(latest)
     data = s.data
-    cache.set(latest_key, data, 60 * 10)
+
+    # set cache before return
+    set_device_latest_cache(latest_key, data)
     return data
 
 
+def set_device_latest_cache(key: str, value: serializers.ModelSerializer, timeout=60 * 10):
+    cache.set(key, value, timeout)
+
+
 class DeviceCountBaseSerializer(serializers.ModelSerializer):
     class Meta:
         model = DeviceCount
@@ -262,20 +273,17 @@ class DeviceInfoSerializer(serializers.ModelSerializer):
     def get_device_name(self, obj):
         qs = MosquitoDeviceInfo.objects.filter(device_id=obj.device_id)
         if qs.count() > 0:
-            device = qs[0]
+            device = qs.first()
             self.cur_device = device
             return device.device_name
         return None
 
-    def get_status(self, obj):
+    @staticmethod
+    def get_status(obj):
         return obj.online
 
     def get_count(self, obj) -> str:
-        try:
-            # self.latest = DeviceCount.objects.filter(device_id=obj.device_id).order_by('-data_time')[0]
-            self.latest = get_latest(obj.device_id)
-        except IndexError:
-            self.latest = None
+        self.latest = get_device_latest_by_cache(obj.device_id)
         if self.latest:
             return self.latest['count']
         return '0'