Update README.md

Author: bakercp

README.md

@@ -48,7 +48,7 @@ This is much more compact but can create problems when the user wants to send a
 
 ## PacketSerial
 
-The `PacketSerial` class wraps the standard Arduino `Serial` class to automatically encode and decode byte packets automatically.  Thus users can still call methods on the `Serial` object (e.g. `Serial.write()`, the built in `serialEvent()` callback etc), but it is not recommended.  Users are advised to let PacketSerial manage all Serial communication via the packet handler callback for incoming packets and the `send(const uint8_t* buffer, size_t size)` method for outgoing packets.
+The `PacketSerial` class wraps the standard Arduino `Serial` class to automatically encode and decode byte packets automatically.  Thus users can still call methods on the `Serial` object (e.g. `Serial.write()`, the built in `serialEvent()` callback etc), but it is not recommended.  Users are advised to let PacketSerial manage all Serial communication via the packet handler callback for incoming packets and the `send(const uint8_t* buffer, size_t size)` method for outgoing packets.  Mixing raw Serial calls with PacketSerial may lead to unexpected results, as the endpoint will not know what data is encoded and what data is not.
 
 
 ## Setup 
@@ -186,4 +186,4 @@ void reverse(uint8_t* buffer, size_t size)
 
 - openFrameworks
     - https://github.com/bakercp/ofxSerial
-    - See the `ofx::IO::PacketSerial` object which is directly compatible with this library. 
+    - See the `ofx::IO::PacketSerial` object which is directly compatible with this library.