Addressing with Dip Switch or ???

[rmteo]

You could store the Device ID (address) in EEPROM. As suggested by CocaColaKid, use ID 0 as the broadcast ID (every unit responds to this ID) to have the ability to change/add ID's. No need for switches, I/O's, etc. You can have up to 255 ID's - or if you use 2 bytes of EEPROM, up to 65535 ID's, if you should need that many.