Method and system for charge cradle lock control

1. A mobile computing device, comprising:

a housing having a recess configured to receive a latch of a charging cradle to lock the mobile computing device in the charging cradle;

a set of charging contacts configured to engage with corresponding power connectors of the charging cradle; and

a processor configured to:

responsive to detecting an unlock event, determine whether an unlock condition is satisfied; and

when the unlock condition is satisfied, cause the charging cradle to release the latch by: generating a current profile at the set of charging contacts, the current profile corresponding to an unlock command, and causing the charging cradle to release the latch responsive to extracting the unlock command from the current profile.

2. The mobile computing device of claim 1 , further comprising:

a power supply subsystem connected with a battery, wherein the set of charging contacts is connected to the power supply subsystem; and

a signaling switch connected between the charging contacts.

3. The mobile computing device of claim 2 , wherein when the unlock condition is satisfied, the processor is further configured to toggle the signaling switch according to the unlock command a command.

4. The mobile computing device of claim 3 , wherein when the unlock condition is satisfied, the processor is further configured to disconnect the power supply subsystem from the charging contacts.

5. The mobile computing device of claim 4 , wherein the processor is further configured to disconnect the power supply subsystem from the charging contacts by opening a switch connected between the charging contacts and the power supply subsystem.

6. The mobile computing device of claim 3 , wherein the mobile computing device further comprises a memory storing a plurality of command identifiers; and

wherein the processor is further configured, when the unlock condition is satisfied, to select an active one of the command identifiers and to generate the unlock command according to the active command identifier.

7. The mobile computing device of claim 6 , wherein the processor is further configured, in order to generate the unlock command, to binary-encode the active command identifier.

8. The mobile computing device of claim 7 , wherein the processor is further configured, in order to generate the unlock command, to binary-encode the active command identifier and a command parameter.

9. The mobile computing device of claim 8 , wherein the command parameter indicates a timeout period for the unlock command.

10. The mobile computing device of claim 7 , wherein the processor is further configured, in order to toggle the signaling switch according to the unlock command, to:

activate the signaling switch for a first predetermined time period for a first binary value; and

activate the signaling switch for a second predetermined time period for a second binary value.

11. The mobile computing device of claim 3 , wherein the processor is configured to toggle the signaling switch according to the unlock command to generate the current profile across the charging contacts, to cause the charging cradle to (i) release the latch and (ii) activate an indicator output responsive to detection of the current profile at the power connectors.

12. A method in a mobile computing device, comprising:

receiving electrical power from a charging cradle via a set of charging contacts configured to engage with corresponding power connectors of the charging cradle, wherein the charging cradle includes a latch received in a recess of a housing of the mobile computing device to lock the mobile computing device in the charging cradle;

responsive to detecting an unlock event, determining whether an unlock condition is satisfied; and

when the unlock condition is satisfied, causing the charging cradle to release the latch by: generating a current profile at the set of charging contacts, the current profile corresponding to an unlock command, and causing the charging cradle to release the latch responsive to extracting the unlock command from the current profile.

13. The method of claim 12 , further comprising:

when the unlock condition is satisfied, disconnecting a power supply subsystem of the mobile computing device from the set of charging contacts.

14. The method of claim 13 , further comprising:

toggling a signaling switch connected between the charging contacts according to the unlock command.

15. The method of claim 13 , further comprising: disconnecting the power supply subsystem from the charging contacts by opening a switch connected between the charging contacts and the power supply subsystem.

16. The method of claim 12 , further comprising:

storing a plurality of command identifiers in a memory of the mobile computing device; and

when the unlock condition is satisfied, selecting an active one of the command identifiers and generating the unlock command according to the active command identifier.

17. The method of claim 16 , further comprising generating the unlock command by binary-encoding the active command identifier.

18. The method of claim 17 , further comprising generating the unlock command by binary-encoding the active command identifier and a command parameter.

19. The method of claim 18 , wherein the command parameter indicates a timeout period for the unlock command.

20. The method of claim 14 , further comprising, to toggle the signaling switch according to the unlock command:

activating the signaling switch for a first predetermined time period for a first binary value; and

activating the signaling switch for a second predetermined time period for a second binary value.

21. A charging cradle for a mobile computing device, the charging cradle comprising:

a cradle body defining a slot to receive the mobile computing device;

a set of power connectors in the slot configured to engage with corresponding charging contacts on a housing of the mobile computing device;

a latch movable between (i) an extended position to engage with the housing and lock the mobile computing device into the slot, and (ii) a retracted position to disengage from the housing to unlock the mobile computing device for removal from the slot;

a current sensor coupled to the power connectors; and

a controller connected to the current sensor and the latch, wherein the controller is configured to:

receive a measured current profile from the current sensor;

extract command data from the measured current profile;

responsive to extracting the command data, move the latch from the extended position to the retracted position to unlock the mobile computing device.

22. The charging cradle of claim 21 , wherein the controller is further configured, prior to receiving the measured current profile, to monitor the power connectors for a current draw below a predetermined threshold.

23. The charging cradle of claim 21 , further comprising:

an actuator coupled to the latch;

wherein the controller is configured, in order to move the latch, to supply power to the actuator.

24. The charging cradle of claim 21 , wherein the extracted command data includes an extracted command identifier and an extracted command parameter.

25. The charging cradle of claim 24 , wherein the predefined command data includes at least a predefined unlock command identifier; and wherein the controller is further configured to:

when the extracted command identifier matches the unlock command identifier, return the latch to the extended position after a timeout period defined by the extracted command parameter.