title: Simple hashing/checksum function for message acknowledgment between two radio units
body: <p>I am trying to setup communications between a pair of Xbee radios with micro controllers. These radios have their own built in acknowledge and checksum functions but they are too simplistic and I still end up with incorrect messages out the other end anyways.</p>
  
  <p>I want to implement a more robust acknowledgment scheme in which the receiver sends a message containing a hash/checksum of the message and the sender looks up that value in a table of sent messages and clears the matching sent message (if a message has not been cleared for a set period of time, the message is resent until a match is found).</p>
  
  <p>My problem is I'm not familiar with checksums and hashing functions, both of which are similar but designed for different purposes.</p>
  
  <p>Is there a simple algorithm that would work well as both a hashing function (collision avoidance so that we don't clear the wrong sent message) and a checksum function (highly sensitive to transmission errors) at the same time that could be simply implemented on an 8-bit micro controller (programmed in C).</p>