Single line dock status autoidentification

1. A portable computing device, comprising:

a dock detector circuit having a pull down circuit and an interface pin configured to be coupled to a docking station via a single line dock connection, wherein the dock detector circuit is configured to:

reset a passive component in the docking station when the portable computing device is connected to the docking station via the single line dock connection and by operation of the pull down circuit;

switch a dock connection driver in the portable device to operate as an input device;

after a predetermined time period, measure a voltage level on the single line dock connection;

in response to the measured voltage level being above a certain threshold, wait for a first time step state;

in response to the measured voltage being at or below the certain threshold, wait a second time step; and

return a number of second time steps for the passive component to reach a voltage above a high voltage threshold.

2. The portable computing device of claim 1 , wherein the dock detector circuit comprises a resistor and a Schmitt trigger.

3. The portable computing device of claim 1 , wherein the passive component in the docking station comprises a capacitor.

4. The portable computing device of claim 3 , wherein the capacitor is configured to be discharged via the single line dock connection when the portable computing device is coupled to the docking station.

5. The portable computing device of claim 1 , wherein the dock detector circuit comprises a calibration capacitor.

6. The portable computing device of claim 1 , wherein the characteristic comprises a type of the docking station, and wherein the voltage level is related to an RC-time constant of a resistor in the dock detector circuit and a capacitor in the docking station.

7. The portable computing device of claim 6 , wherein the resistor is coupled to a power supply.

8. The portable computing device of claim 1 , wherein the pull down circuit comprises:

an active device with a first terminal connected to ground, a second terminal connected to a common node, and a control terminal; and

an impedance with a first terminal connected to a power supply and a second terminal connected the common node; wherein the single line dock connection.

9. A method of determining a characteristic of a docking station, the method comprising:

connecting a portable computing device to the docking station via a single line dock connection, wherein the portable computing device comprises a dock detector circuit coupled to the single line dock connection, wherein the detector circuit includes a pull down circuit;

reset a passive component in the docking station when the portable computing device is connected to the docking station via the single line dock connection, wherein the pull down circuit couples a resistor connected to a power supply and the passive device to ground;

switching a dock connection driver in the portable device to operate as an input device;

waiting a first time step;

measuring a voltage level on the single line dock connection;

in response to the measured voltage level being below a certain threshold, waiting another time period equal to the first time step;

in response to the measured voltage being at or above the certain threshold, waiting a second time step;

measuring the voltage level on the single line dock connection; and

return a number of second time steps for the passive component to reach a voltage above the high voltage threshold, wherein the returned number of second time steps indicates the characteristic of the docking station.

10. The method of claim 9 , wherein the dock detector circuit comprises a resistor and a Schmitt trigger.

11. The method of claim 9 , wherein the connecting comprises coupling a capacitor in the docking station to the single line dock connection.

12. The method of claim 11 , wherein the placing the single line dock connection in the reset state comprises discharging the capacitor using an NMOS device.

13. The method of claim 12 , wherein the determining the characteristic by the sampling comprises using an RC-time constant of a resistor in the dock detector circuit and the capacitor.

14. The method of claim 9 , wherein the characteristic comprises a type of the docking station.

15. The method of claim 9 , wherein the portable computing device comprises an embedded controller coupled to the single line dock connection.

16. The method of claim 9 , further comprising:

measuring the single line dock connection voltage; and

determining whether the measured single line dock connection voltage is above a certain threshold based on a characteristic of the passive device.

17. The method of claim 9 , further comprising:

switching a dock connection driver in the portable device to operate as an output device.

18. The method of claim 9 , further comprising:

in response to the measured voltage being above a high voltage threshold, waiting for a further time period equal to the second time step.

19. A system comprising:

a single line dock connection coupled to a docking station; and

a portable computing device having a dock detector circuit including a pull down circuit, wherein the dock detector circuit is coupled to the single line dock connection, and wherein the dock detector circuit is configured to:

reset a passive component in the docking station when the portable computing device is connected to the docking station via the single line dock connection and by operation of the pull down circuit;

switching a dock connection driver in the portable device to operate as an input device;

after a predetermined time period, measuring a voltage level on the single line dock connection;

in response to the measured voltage level being above a certain threshold, waiting for a first time step state;

in response to the measured voltage being at or below the certain threshold, waiting a second time step; and

return a number of second time steps for the passive component to reach a voltage above a high voltage threshold, wherein the number of second time steps indicates a characteristic of the docking station.

20. The system of claim 19 , wherein the passive component in the docking station comprises a capacitor.

21. The system of claim 19 , wherein the characteristic comprises a type of the docking station, and wherein the voltage level is related to an RC-time constant of a resistor in the dock detector circuit and a capacitor in the docking station.

22. The system of claim 21 , wherein the capacitor is configured to be discharged via the single line dock connection upon connection to the docking station.

23. The system of claim 19 , wherein the pull down circuit comprises:

an active device with a first terminal connected to ground, a second terminal connected to a common node, and a control terminal; and

an impedance with a first terminal connected to a power supply and a second terminal connected the common node; wherein the single line dock connection.