Circuit for sensing and automatically switching between an inter

Details Circuit for sensing and automatically switching between an inter Circuit for sensing and automatically switching between an inter

1996-07-15

2000-05-16

Maung, Zarni

Electrical computers and digital data processing systems: input/

Input/output data processing

Peripheral monitoring

710103, G06F 300, G06F 1300

Patent

active

060650699

ABSTRACT:
A circuit for sensing when an external pointing device is connected to a portable computer system detects the device's power consumption and automatically switches to it without requiring that the computer system to be power cycled or reset. Further, the circuit can detect when an external pointer device is disconnected and, in response, automatically switch to the computer system's internal pointer device. The sensor comprises a small resistor in series with the power supply for the external device. When the external device is attached, the power consumption of the external device results in a voltage drop across the resistor, which may be detected with a voltage comparator. In one embodiment, when the sensor detects that an external pointer device has been connected it generates a static signal to control the operation of a switch. Based upon input from the sensor, the switch routes all appropriate signals from either the internal or external pointer device to a standard microcontroller device. In an alternative embodiment, sensor output is connected directly to a microcontroller which is modified (via its firmware) to select either the computer system's internal pointer device or external pointer device based on sensor output.

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