Apparatus and method for bidirectional data communication in a game port

An apparatus for bidirectional communication between a pointing device and a computer game port interface having a timer with a timer input that changes from a first logic level to a second logic level when enabled by an output instruction to the game port interface, with a capacitor coupled to the timer input, the apparatus comprising:

• a resistance within the pointing device and coupled to the timer input to form a charging circuit with the capacitor, said charging circuit having a predetermined time constant determined by a fixed resistance value for said resistance and a fixed capacitance value for the capacitor;
• a level detector within the pointing device and coupled to the timer input to detect a first transition of the timer input from the first logic level to the second logic level, said level detector generating a first interrupt signal in response to detecting first transition;
• and
• an interface within the pointing device to process data in response to said first interrupt signal.

An apparatus for bidirectional communication between a digital pointing device and a computer game port interface having a first digital input and a timer with a timer input that changes from a first logic level to a second logic level when enabled by an output instruction to the game port interface, with a capacitor coupled to the timer input, the apparatus comprising:

• a fixed resistor within the pointing device and coupled to the timer input to form a charging circuit with the capacitor;
• a level detector within the pointing device and coupled to the timer input detecting a first transition of the timer input from the first logic level to the second logic level, said level detector generating a first interrupt signal in response to detecting said first transition;
• and
• a digital interface within the pointing device transmitting digital data from the pointing device to the first digital input in response to said first interrupt signal.

A positional control device having bidirectional communication with a game port on a computer, the game port having a first timer circuit with a timer input and analog circuitry to form a portion of a charging circuit coupled to the timer input, the timer being responsive to an output instruction from the computer to activate the charging circuit in response to the output instruction, the device comprising:

• a position sensing circuit operable by a user and generating positional data;
• a peripheral analog circuit coupled to the timer input to complete the charging circuit;
• a detector within the positional control device and coupled to the timer input to detect a predetermined charging level and generate a first interrupt signal in response to detecting said first predetermined level;
• and
• an interface within the positional control device to process said positional data in response to said first interrupt signal.

A method for bidirectional communication between a peripheral device and a computer game port interface having a timer with a timer input that changes from a first logic level to a second logic level when enabled by an output instruction to the game port interface, with a capacitor coupled to the timer input, the method comprising the steps of:

• coupling a resistance within the peripheral device to the timer input to form a charging circuit with the capacitor, said charging circuit having a predetermined time constant determined by a resistance value for said resistance and a capacitance value for the capacitor;
• detecting a first transition of the timer input from the first logic level to the second logic level;
• generating a first interrupt signal in response to detecting first transition;
• and
• processing said first interrupt signal as a first command from the game port.