Tomorrow I'll have a little oscilloscope. Something its strange, because I verified with a simple way the level pulse: I put in parallel with portc.2 a simple device with 10F202 that turn ON a LED when signal is missing (< 0,5 ms) and turn OFF LED when signal is different to 0 (>0,5ms) and work perfectly.
Sometime , 1 from 15 tries, my code work good. Between tests I wait few minutes and I discharged the 10uF capacitor from Vcc line.