I want to get a tri-level video sync to to act as a rising edge trigger on an Atmel AVR. The Tri-level signal is a square wave that goes from 0V->-300mV->300mv->0mV that is typically running at 24-60hz. The actual sync point is where the -300mV->300mV transition occurs. What I would like to do is shift and amplify this wave so that it falls into a 0-5V range (2.5V->0->5V->2.5V) thus falling into the range that would trigger an interrupt on the AVR. I am a software guy and am just beginning to get my head wrapped around the hardware side of things. From what I have seen it looks like an OpAmp circuit would be the way to go but I am having trouble working out the details. Any help would be appreciated.