joystick interface

ktor july/august 1983 26 joystick interface It happens from time to time that it would be nice to read the position of a potentiometer with a micro- processor. For those many computer enthusiasts we have designed a simple circuit to do this. Only one 555 and one input line to the processor are needed. Care must be taken in the construction to prevent hum. The interface should also be of interest to other computer enthusiasts who just want to experiment with their equipment. ntegrated circuit IC1 oscillates con- tinuously: capacitor Cl is charged via resistor R 1 and potentiometer Pl and then discharged through Pl. This means that the discharge time is dependent on the setting of Pl and this, in turn, means that the time during which the output ofICl (pin 3) is logic 0 is directly pro- portional to the resistance of Pl. If the resistance of Pl becomes less than 10 kS2, there is a likelihood that oscillations will cease. When the microprocessor measures the time that the output of I...