Matrix user forums

If you want to pick up the zero point of the AC mains, a novel method (see attachment) is to use an opto isolator with two emitters reverse connected in parallel. The only time a positive signal is available, is when both LED emitters are not conducting (mains is at zero).
RB0 interrupt will be evoked every time the AC gets to a zero condition.

The main transformer uses a diode to supply the rest of you circuitry via the 5v regulator so no extra transformer is required.

Uses -
Light intensity control
Accurate timing (divide by 50 for 1 second action (60 USA)
Counting
Mains synchronizing (Grid inter-tie etc)
State programming - Allows an interrupt to gather I/O information. Could eliminate the requirement to use input icons making the program easier to read.

It would be nice if you could attach a flowchart to complement the screen shots. Screen shots can be hard to read...

Not sure if my particular code will add anything so I have increased the resolution for a partial look at the development of "states" in the interrupt routine which can be used to determine what to do in the main program.