Method and system for detecting displayport source device connections to sink device

• US 20090179883A1
• Filed: 04/21/2008
• Published: 07/16/2009
• Est. Priority Date: 01/15/2008
• Status: Active Grant

• Current Assignee: Dell Products LP (Dell Technologies Inc.)
• Original Assignee: Dell Products LP (Dell Technologies Inc.)
• Inventors: Cheong, Seen Yee Cindy, Goodart, Joe E., Lee, Jae-Ik
• Granted Patent: US 8,200,855 B2
• Time in Patent Office: Days
• US Class Current: 345/211
• CPC Class Codes: G09G 2370/14 Use of low voltage differential signaling [LVDS] for display data communication
• CPC Class Codes: G09G 5/006 Details of the interface to the display terminal specific for a display terminal using a CRT G09G1/167; using a flat panel G09G3/2096; circuits for interfacing with colour displays G09G5/04

Abstract

Methods and systems are disclosed for detecting DisplayPort (DP) source device connection to sink devices. When the DP link is active, no measurements are made to determine source device connections. When a DP link is not active, a signal line for the auxiliary channel for a DP connection is measured to determine if a source device is connected. More particularly, the auxiliary channel is a differential auxiliary channel, and the positive signal line is measured to make the determination of whether a source device is connected. Still further, an indication is made that a source device is connected if the positive signal line is at a low level, and an indication is made that a source device is not connected if the positive signal line is at a high level.

Claims

1. A method for determining connections to a DisplayPort source device, comprising:

providing a first device configured to be a sink device according to the DisplayPort standard and to have a sink connector including a main link, a hot plug detect signal line, and an auxiliary channel;

determining if a DisplayPort link is active between the first device and a second device, the second device being configured to be a source device according to the DisplayPort standard;

only if the DisplayPort link is not active, measuring a voltage on a signal line for the auxiliary channel to determine if a second device is connected or not.

2. The method of claim 1, wherein measuring step comprises measuring a positive signal line for a differential auxiliary channel.

3. The method of claim 2, wherein the measuring step further comprises determining that a second device is not connected to the first device if the voltage is a high level, and determining that a second device is connected to the first device if the voltage is a low level.

4. The method of claim 2, wherein the measuring step comprises utilizing level detection circuitry to generate a source detection signal based upon the voltage on the signal line for the auxiliary channel.

5. The method of claim 4, further comprising powering the level detection circuitry only when the DisplayPort link is not active.

6. The method of claim 4, further comprising placing inputs to the level detection circuitry circuitry in a high impedance state while the DisplayPort link is not active.

7. The method of claim 1, wherein the first device is a display device.

8. The method of claim 4, wherein the second device is an information handling system.

9. A DisplayPort sink device having source detection capabilities, comprising:

receive circuitry configured for the DisplayPort standard;

a sink connector coupled to the receive circuitry and including a main link, a hot plug detect signal line, and an auxiliary channel;

level detection circuitry within the receive circuitry coupled to a signal line for the auxiliary channel; and

detection control circuitry within the receive circuitry coupled to receive an output from the level detection circuitry and to receive a signal indicating whether or not a DisplayPort link is active for the DisplayPort sink device;

wherein the detection control circuitry is further configured to output a signal indicating whether or not a source device is connected only when the DisplayPort link is not active.

10. The DisplayPort sink device of claim 9, wherein the level detection circuitry is coupled to a positive signal line for a differential auxiliary channel.

11. The DisplayPort sink device of claim 10, wherein the detection control circuitry is further configured to indicate that a source device is not connected if a voltage level for the positive signal line for the differential auxiliary channel is a high level and to indicate that a source device is connected if a voltage level for the positive signal line for the differential auxiliary channel is a low level.

12. The DisplayPort sink device of claim 9, wherein the sink device is a display device.

13. The DisplayPort sink device of claim 12, wherein the source device is an information handling system.

14. The DisplayPort sink device of claim 9, wherein the level detection circuitry is configured to be powered only when the DP link is not active.

15. The DisplayPort sink device of claim 9, wherein the inputs to the level detection circuitry are configured to be in a high impedance state while the DP link is not active.

16. Receive circuitry for a DisplayPort sink device, comprising:

level detection circuitry coupled to a signal line for an auxiliary channel within a DisplayLink connection for a DisplayPort sink device; and

detection control circuitry within the receive circuitry coupled to receive an output from the level detection circuitry;

wherein the detection control circuitry is further configured to output a signal indicating whether or not a source device is connected only when a DisplayPort link is not active.

17. The receive circuitry of claim 16, wherein the level detection circuitry is coupled to a positive signal line for a differential auxiliary channel.

18. The receive circuitry of claim 17, wherein the detection control circuitry is further configured to indicate that a source device is not connected if a voltage level for the positive signal line for the differential auxiliary channel is a high level and to indicate that a source device is connected if a voltage level for the positive signal line for the differential auxiliary channel is a low level.

19. The receive circuitry of claim 16, wherein the level detection circuitry is configured to be powered only when the DP link is not active.

20. The receive circuitry of claim 16, wherein the inputs to the level detection circuitry are configured to be in a high impedance state while the DP link is active.