Hi Matthew, What is the baudrate of your USART ? and does the printf function work with interrupt ? If not, you can lose some edges... Do not use this kind of output in an interrupt routine (just an advice). Regards, Nicolas -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads