Light dimmer problem

[dhouston]

Full wave rectification of mains, I needed it for Zero-Crossing of mains.

You do not need full wave rectification for zero-crossing detection. The circuit shown on p3, FIG3 of AN236 works fine for zero crossing. The appnote even details the inaccuracies inherent in the circuit, saying...

On a rising edge, RB0 will go high about 64 µS after the zero-crossing, and on a falling edge, it will go low about 16 µS before the zero-crossing.

You'll find similar inaccuracies in most methods for zero-crossing detection. Their calculations are for 120VAC/60Hz. You'll need to adjust for 220V/50Hz (and maybe use a larger current limiting resistor).

One possible cause of flicker is failing to compensate for inaccurate zero crossing detection.

You can ignore the X10 communications circuitry and code but I suggest you study the code used for the triac dimmer circuit in AN236 (p6) or in the referenced PICREF-4 Reference Design, “PICDIM Lamp Dimmer for the PIC12C508”. The Microchip engineers frequently know what they are doing.