I'm working on a project that needs to take an capacitively-coupled Manchester data steam and feed it though a slicer/limiter type circuit that will connect to an AVR series micro and use a pin change interrupt to process and decode the Manchester data steam. The design requirements, in order of importance are:
1. *Must Do* the circuit should not generate a transition that might trigger the pin change interrupt unless a signal meeting requirement #2's characteristics is present. That is, if nothing is connected to the input jack, the output from the circuit should be stable and unchanging and should not trigger a pin change interrupt.
2. the circuit needs to handle input signals that will typically range from perhaps 300mVpp to 4Vpp, but should, ideally protect against damage, or latch up that might result from higher input levels.
3. be as simple and as compact as possible, as space is limited on the PCB.
4. If possible, make use of the comparator built into the AVR micro, as this seems to be a standard feature.
I've looked at a lot of designs intended for conditioning and squaring up a Manchester data steam, but I've yet to find one that I think can reliably meet all my requirements, especially my #1 requirement. Can anyone else suggest an approach that might work?
Wayne