System and method for detecting accessory connection and accessory class

A method comprising:

• disabling a video digital-to-analog converter (DAC) that is configured to provide an output current representative of a video signal to an output node of an accessory connector in an enabled state, the accessory connector coupleable to an accessory device;
• determining, while the video DAC is disabled, whether the accessory connector is coupled to the accessory device based on a first voltage at the output node while the output node is connected to a first voltage reference via a first resistor having a first resistance;
• and
• in response to determining the accessory connector is coupled to the accessory device, determining an impedence class of the accessory device by:
• disconnecting the output node from the first voltage reference;
• configuring the video DAC to provide a predetermined first current to the output node while the output node is disconnected from the first voltage reference;
• and
• determining the accessory device is of a first impedance class in response to determining a first reference voltage is greater than a second voltage at the output node resulting from provision of the first current to the output node.

A video processing device comprising:

• an accessory connector coupleable to an accessory device;
• a video digital-to-analog converter (DAC) to convert a video signal to a corresponding output current and provide the output current to an output node of the accessory connector;
• a comparator comprising a first input connected to the output node, a second input to receive a reference voltage, and an output to provide a value based on a comparison of a voltage at the first input to a voltage at the second input;
• a first resistor comprising a first terminal coupled to a first voltage reference and a second terminal, the first resistor having a first resistance;
• a first switch comprising a first terminal coupled to the second terminal of the first resistor and a second terminal coupled to the output node;
• and
• a connect detect module configured to:
• disable the video DAC;
• enable the first switch to connect the output node to the first voltage reference via the first resistor while the video DAC is disabled;
• and
• determine whether the accessory connector is coupled to the accessory device based on the output of the comparator when the output node is connected to the first voltage reference via the first resistor.

A video processing system comprising:

• a video digital-to-analog converter (DAC) configured to provide an output current representative of a video signal to an output node of an accessory connector in an enabled state, the accessory connector coupleable to an accessory device;
• means for configuring the video DAC to provide a predetermined first current to the output node;
• means for determining the accessory device is of a first impedance class in response to determining a reference voltage is greater than a first voltage at the output node resulting from provision of the first current to the output node;
• means for connecting the output node to a voltage reference via a resistor;
• means for configuring the video DAC to provide a predetermined second current to the output node while the output node is connected to the voltage reference via the resistor;
• means for determining the accessory device is of a second impedance class in response to determining the reference voltage is greater than a second voltage at the output node resulting from provision of the second current to the output node, the second impedance class comprising an impedance range higher than an impedance range of the first impedance class;
• and
• means for determining the accessory device is of a third impedance class in response to determining the reference voltage is not greater than the second voltage, the third impedance class comprising an impedance range higher than the impedance range of the second impedance class.