diff --git a/lib/modbuzz/rtu/client/receiver.ex b/lib/modbuzz/rtu/client/receiver.ex
index 72fd66e..55e8299 100644
--- a/lib/modbuzz/rtu/client/receiver.ex
+++ b/lib/modbuzz/rtu/client/receiver.ex
@@ -5,6 +5,7 @@ defmodule Modbuzz.RTU.Client.Receiver do
 
   alias Modbuzz.PDU
   alias Modbuzz.RTU.ADU
+  alias Modbuzz.RTU.Log
 
   @server_device_failure 0x04
   @server_device_busy 0x06
@@ -78,7 +79,8 @@ defmodule Modbuzz.RTU.Client.Receiver do
       # already responded
       {:noreply, state}
     else
-      # something wrong, treat as server failure
+      Log.error("RTU server didn't respond.")
+      # treat as server device failure
       {:ok, req} = PDU.decode_request(adu.pdu)
       err = PDU.to_error(req, @server_device_failure)
       GenServer.reply(caller, {:error, err})
@@ -107,7 +109,8 @@ defmodule Modbuzz.RTU.Client.Receiver do
       {:error, :binary_is_short} ->
         {:noreply, %{state | binary: new_binary}}
 
-      {:error, %ADU{unit_id: unit_id, pdu: _pdu, crc_valid?: false}} ->
+      {:error, %ADU{unit_id: unit_id, pdu: _pdu, crc_valid?: false} = adu} ->
+        Log.warning("CRC error detected, #{inspect(adu)}.")
         caller = Enum.fetch!(callers, unit_id)
         if not is_nil(caller), do: GenServer.reply(caller, {:error, :crc_error})
 
diff --git a/lib/modbuzz/rtu/log.ex b/lib/modbuzz/rtu/log.ex
index 4e8a9b7..59d15ec 100644
--- a/lib/modbuzz/rtu/log.ex
+++ b/lib/modbuzz/rtu/log.ex
@@ -11,6 +11,10 @@ defmodule Modbuzz.RTU.Log do
     Logger.error(what_happend <> why(reason) <> where(state))
   end
 
+  def warning(what_happend) do
+    Logger.warning(what_happend)
+  end
+
   def warning(what_happend, reason, state) do
     Logger.warning(what_happend <> why(reason) <> where(state))
   end
diff --git a/lib/modbuzz/rtu/server.ex b/lib/modbuzz/rtu/server.ex
index b8c53ec..8e17508 100644
--- a/lib/modbuzz/rtu/server.ex
+++ b/lib/modbuzz/rtu/server.ex
@@ -5,6 +5,7 @@ defmodule Modbuzz.RTU.Server do
 
   alias Modbuzz.PDU
   alias Modbuzz.RTU.ADU
+  alias Modbuzz.RTU.Log
 
   @spec start_link(keyword()) :: GenServer.on_start()
   def start_link(args) when is_list(args) do
@@ -58,7 +59,8 @@ defmodule Modbuzz.RTU.Server do
       {:error, :binary_is_short} ->
         {:noreply, %{state | binary: new_binary}}
 
-      {:error, %ADU{unit_id: _unit_id, pdu: _pdu, crc_valid?: false}} ->
+      {:error, %ADU{unit_id: _unit_id, pdu: _pdu, crc_valid?: false} = adu} ->
+        Log.warning("CRC error detected, #{inspect(adu)}.")
         # ignore request
         {:noreply, %{state | binary: <<>>}}
     end