HDMI source detection

A circuit for detection of an HDMI source device to an HDMI sink device through an HDMI sink connector without regard for the activity state of the HDMI source device, comprising in combination:

• a pull-up resistor having first and second terminals with the first terminal coupled to a DC power source;
• a junction transistor switch device coupled between the pull-up resistor's second terminal and ground at a circuit node;
• the junction transistor switch being switched on to couple the circuit node to ground when power is applied to a base terminal thereof from the HDMI sink connector power pin, and being switched off otherwise;
• the circuit node being further coupled to a DDC/CEC GROUND pin of the HDMI sink connector;
• and
• the circuit node being readable as a binary signal to indicate the presence of a source device to the HDMI sink connector, wherein the node exhibits a logic low signal when either the node is grounded by the DDC/CEC GROUND pin connection to a source device or when the junction transistor switch is switched on.

A circuit for detection of an HDMI source device to an HDMI sink device through an HDMI sink connector without regard for the activity state of the HDMI source device, comprising in combination:

• a pull-up resistor having first and second terminals with the first terminal coupled to a DC power source;
• an NPN junction transistor switch device coupled between the pull-up resistor's second terminal and ground at a circuit node, wherein the node is coupled to the transistor's collector, the HDMI sink connector's power pin is coupled to the transistor's base and the transistor's emitter is grounded;
• the NPN junction transistor switch being switched on to couple the circuit node to ground when power is applied to a base terminal thereof from the HDMI sink connector power pin, and being switched off otherwise;
• the circuit node being further coupled to a DDC/CEC GROUND pin of the HDMI sink connector;
• and
• the circuit node being readable as a binary signal to indicate the presence of a source device to the HDMI sink connector, wherein the node exhibits a logic low signal when either the node is grounded by the DDC/CEC GROUND pin connection to a source device or when the NPN junction transistor switch is switched on.

A circuit for detection of an HDMI source device to an HDMI sink device through one of a plurality of HDMI sink connectors without regard for the activity state of the HDMI source device, comprising in combination:

• for each HDMI sink connector, a pull-up resistor having first and second terminals with the first terminal coupled to a DC power source;
• a plurality of switching devices, each coupled between one of the pull-up resistor's second terminal and ground at a circuit node for each HDMI sink connector;
• each switching device being switched on to couple the circuit node to ground when power is applied to a control terminal thereof from the HDMI sink connector power pin, and being switched off otherwise;
• each circuit node being further coupled to a DDC/CEC GROUND pin of each respective HDMI sink connector;
• and
• each circuit node being readable as a binary signal to indicate the presence of a source device to the respective HDMI sink connector, wherein each node exhibits a logic low signal when either the node is grounded by the DDC/CEC GROUND pin connection to a source device or when the switching device is switched on.

An arrangement for detecting a connection state of a plurality of HDMI sink connectors, comprising:

• a plurality of sink connectors residing on an HDMI sink device;
• a corresponding plurality of connection state detectors that detect a state of connection of each of the sink connectors by detecting a DDC/CEC ground state that is produced either by a ground connection through the respective sink connector from an HDMI source or by detecting a switched ground state at the DDC/CEC ground connection created within the sink device by a switch controlled by virtue of power applied to the sink connectors from connection to the HDMI source;
• a storage device that stores the state of each respective connector;
• and
• a polling circuit that polls each of the connection detectors and stores the state of connection of each of the connection detectors to the memory.

A method for detecting a connection state of a plurality of HDMI sink connectors, comprising:

• providing a plurality of connection state detectors that detect a state of connection of each of a plurality of sink connectors by detecting a DDC/CEC ground state that is produced either by a ground connection through the respective sink connector from an HDMI source or by detecting a switched ground state at the DDC/CEC ground connection created within the sink device by a switch controlled by virtue of power applied to the sink connectors from connection to the HDMI source;
• polling each of the connection detectors to determine its state of connection;
• and
• storing the state of connection of each of the connection detectors to the memory.

A circuit for detection of an HDMI source device to an HDMI sink device through an HDMI sink connector without regard for the activity state of the HDMI source device, comprising in combination:

• an HDMI sink connector having a DDC/CEC GROUND pin;
• a pull-up resistor having first and second terminals with the first terminal coupled to a DC power source;
• the second terminal being further coupled to a DDC/CEC GROUND pin of the HDMI sink connector and forming a circuit node;
• and
• the circuit node being readable as a binary signal to indicate the presence of a source device to the HDMI sink connector, wherein the node exhibits a logic low signal when the circuit node is grounded by the DDC/CEC GROUND pin connection to a source device.