I am developing a program to send and receive sigal to my circuit and pc. Actually I have to count the pulses or (frequency of high pulse) generated from a 555 timer IC in my circuit. When I connect a input pin of Parallel port to the ground pin or simply to a casing of the system it produce a input signal. I used transistor in the hardware side which let connect input pin to the ground on the production of High pulse. I think it is not a good method to do so.
Is there any way to do it directly by sending voltage to parallel port input pin?
What amount of current and voltage is required?
I am using 2x1.5 volt AA size batteries to supply power to the circuit.