System using a digital timer for a joystick potentiometer readout

摘要

A system is provided for digitizing the setting of a potentiometer of the type used in an analog joystick for computer games. The analog output of the potentiometer is applied to one of two inputs of a voltage comparator. When a readout of the joystick position is desired, a "write" input is applied to a counter to permit it to commence counting at a predetermined frequency from an initial or zero count. The digital outputs of the counter are coupled to the inputs of a digital-to-analog converter, the output of which is coupled to the second input of the voltage comparator. When the count in the counter produces a voltage at the output of the digital-to-analog converter corresponding to the voltage setting of the potentiometer, the comparator provides an output signal. The time delay from the time the write pulse occurs until this signal is obtained is representative of the potentiometer setting. The system also provides a direct digital output from the counter by gating the counter outputs to a bus at the time the signal from the comparator is obtained. Thus, either a time interval representation of the potentiometer setting or a direct digital readout of the potentiometer setting may be obtained from the system.