How can I measure Duty cycle ?

[skimask]

@skimask ,
I`ll take this picture only for you

Schmit trigger ;
Because I`m work on the table at home ,not on car ,
and use a 555 for signal not car enjector`s signal .
Im sure cars injector signal or ecu` injector out signal is Not clean ..

Thank you again.

If you want to use RB0 for the input, then use it, change the lines in the code. The schmidt trigger input will help to clean up a noisy signal a little bit, but I don't know if I'd go so far as to start messing with different pins and methods of reading the pulses until you've tried it in the car. I know the signals would be dirty being in an automotive environment...but... The injectors won't be firing at more than (give or take) 5,000/sec (10,000 rpm). So why not a simple opamp before the PIC with a 5khz rolloff or an even simpler R/C filter? Play with it and see what happens... that's the only way you'll figure out how much filtering you may or may not need.