>> I.e., what happens when the receiver has received the command (or frame) >> and executed tha action, and ACK'ed, but the Transmitter does not see >> the ACK? It will try again, and the receiver will execute again... and >> if it is SET -> no problem, but if it is a Toggle -> troubles! > > Ah yes! I have avoided toggle messages. But I should add that frame > index to my protocol as well. A protocol which doesn't have problems with repeated meessages is called 'idempotent'. Some remote file system protocols work that way. I often use this concept when designing protocols. -- Bob Ammerman RAm Systems -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist