Methods and systems for interfacing bus powered devices with host devices providing limited power levels
Various techniques are provided for interfacing external devices with host computer systems. In one example, hard drive parameters may be retrieved from a nonvolatile memory of an external hard drive enclosure device in order to register the external device with a host device while the host device provides a low power level to the external device. Following registration of the external device, the host device may provide a high power level to the external device to operate the registered external device. The hard drive parameters may be stored in the nonvolatile memory by a provider of the external device. In another example, the hard drive parameters may be loaded into the nonvolatile memory by appropriate software running on the host device. In yet another example, the external device may read the hard drive parameters from the hard drive while emulating another external device.
1. A method of interfacing an external device with a host device through a bus, the method comprising:
receiving a first power level at the external device from the host device through the bus, wherein the bus is configured to provide electrical power from the host device to the external device and further configured to provide data communications between the host device and the external device, wherein a hard drive of the external device does not operate while the first power level is received by the external device;
retrieving a set of device parameters from a nonvolatile memory of the external device, wherein the device parameters identify the hard drive;
providing the device parameters from the external device to the host device through the bus to register the external device with the host device, wherein said providing the device parameters is performed after said receiving the first power level and after said retrieving the set of device parameters, wherein said providing the device parameters allows the external device to receive a second power level that is higher than the first power level; and
receiving the second power level at the external device from the host device through the bus to operate the hard drive after the external device is registered with the host device using the device parameters.
2. The method of claim 1 , further comprising performing the following prior to retrieving the device parameters:
receiving the device parameters from the host device through the bus; and
storing the device parameters in the nonvolatile memory.
3. The method of claim 1 , wherein the external device is a first external device, the method further comprising performing the following prior to retrieving the device parameters:
emulating a second external device to receive the second power level at the first external device from the host device through the bus to operate the hard drive;
retrieving the device parameters from the hard drive while receiving the second power level at the first external device from the host device through the bus; and
storing the device parameters in the nonvolatile memory.
4. The method of claim 3 , wherein the emulated second external device is a mass storage device.
5. The method of claim 1 , wherein the set of device parameters is a first set of device parameters, wherein the external device is a first external device, the method further comprising performing the following prior to retrieving the first set of device parameters:
providing a second set of device parameters from the first external device to the host device to emulate a second external device, wherein the second device parameters identify the emulated second external device;
receiving the second power level at the first external device from the host device through the bus to operate the hard drive after the emulated second external device is registered with the host device using the second device parameters;
retrieving the first device parameters from the hard drive while receiving the second power level at the first external device from the host device through the bus; and
storing the first device parameters in the nonvolatile memory.
6. The method of claim 5 , further comprising performing the following prior to retrieving the first set of device parameters:
requesting the host device to unregister the emulated second external device;
receiving the first power level at the first external device from the host device through the bus;
requesting the host device to register the first external device; and
receiving a request for the first device parameters from the host device through the bus.
7. The method of claim 1 , wherein the bus is configured to support a Universal Serial Bus (USB) 2.0 interface, the first power level is approximately 100 mA, and the second power level is approximately 500 mA.
8. The method of claim 1 , wherein the bus is configured to support a Universal Serial Bus (USB) 3.0 interface, the first power level is approximately 150 mA, and the second power level is approximately 900 mA.
9. The method of claim 1 , wherein the bus is configured to support a Firewire interface.
10. The method of claim 1 , wherein the external device is a hard drive enclosure device.
11. The method of claim 1 , wherein the hard drive is selectively removable from the external device.
12. The method of claim 1 , wherein the nonvolatile memory is a flash memory.
13. An external device coupled to a host device via a bus, the external device comprising:
a port adapted to couple to the bus, wherein the port is configured to receive a first power level from the host device through the bus before the external device is registered with the host device, wherein the port is further configured to receive a second power level from the host device through the bus after the external device is registered with the host device, wherein the second power level is greater than the first power level, and wherein the port is further configured to pass data communications between the host device and the external device through the bus;
a hard drive configured to not operate while the first power level is received from the host device through the bus and operate while the second power level is received from the host device through the bus;
a nonvolatile memory configured to selectively store device parameters that identify the hard drive; and
a controller configured to retrieve the device parameters from the nonvolatile memory and provide the device parameters from the external device to the host device through the port to register the external device with the host device, wherein the first power level is provided prior to the controlling the device parameters, and wherein the second power level is provided in response to the controller providing the device parameters.
14. The external device of claim 13 , wherein the external device is configured to receive the device parameters from the host device through the bus and store the device parameters in the nonvolatile memory.
15. The external device of claim 13 , wherein the external device is a first external device, wherein the first external device is configured to:
emulate a second external device to receive the second power level from the host device through the bus to operate the hard drive;
retrieve the device parameters from the hard drive while the second power level is received from the host device through the bus; and
store the device parameters in the nonvolatile memory.
16. The external device of claim 15 , wherein the emulated second external device is a mass storage device.
17. The external device of claim 13 , wherein the set of device parameters is a first set of device parameters, wherein the external device is a first external device, wherein the first external device is configured to:
provide a second set of device parameters to the host device to emulate a second external device, wherein the second device parameters identify the emulated second external device;
receive the second power level from the host device through the bus to operate the hard drive after the emulated second external device is registered with the host device using the second device parameters;
retrieve the first device parameters from the hard drive while the second power level is received from the host device through the bus; and
store the first device parameters in the nonvolatile memory.
18. The external device of claim 17 , wherein the first external device is configured to:
request the host device to unregister the emulated second external device;
receive the first power level from the host device through the bus;
request the host device to register the first external device; and
receive a request for the first device parameters from the host device through the bus.
19. The external device of claim 13 , wherein the bus is configured to support a Universal Serial Bus (USB) 2.0 interface, wherein the first power level is approximately 100 mA, and wherein the second power level is approximately 500 mA.
20. The external device of claim 13 , wherein the bus is configured to support a Universal Serial Bus (USB) 3.0 interface, wherein the first power level is approximately 150 mA, and wherein the second power level is approximately 900 mA.
21. The external device of claim 13 , wherein the bus is configured to support a Firewire interface.
22. The external device of claim 13 , wherein the external device is a hard drive enclosure device.
23. The external device of claim 13 , wherein the hard drive is selectively removable from the external device.
24. The external device of claim 13 , wherein the nonvolatile memory is a flash memory.
25. An external device coupled to a host device via a bus, the external device comprising:
means for interfacing the external device with the bus, wherein the bus is configured to provide electrical power from the host device to the external device and wherein the bus is further configured to pass data communications between the host device and the external device;
means for receiving a first power level at the external device from the host device through the bus, wherein an electrical component of the external device does not operate while the first power level is received by the external device;
means for storing a set of device parameters, wherein the device parameters identify the electrical component;
means for retrieving the device parameters from the storing means;
means for providing the device parameters from the external device to the host device through the bus to register the external device with the host device, wherein said providing the device parameters is performed after receiving the first power level and after retrieving the device parameters, wherein said providing the device parameters allows the external device to receive a second power level that is higher than the first power level; and
means for receiving the second power level at the external device from the host device through the bus to operate the electrical component after the external device is registered with the host device using the device parameters.
26. The external device of claim 25 , further comprising means for receiving the device parameters from the host device through the bus.
27. The external device of claim 25 , wherein the external device is a first external device, wherein the first external device further comprises:
means for emulating a second external device to receive the second power level at the first external device from the host device through the bus to operate the electrical component;
means for retrieving the device parameters from the electrical component while
receiving the second power level at the first external device from the host device through the bus; and
means for storing the device parameters in the nonvolatile memory.
28. The external device of claim 25 , wherein the set of device parameters is a first set of device parameters, wherein the external device is a first external device, wherein the first external device further comprises:
means for providing a second set of device parameters from the first external device to the host device to emulate a second external device, wherein the second device parameters identify the emulated second external device;
means for receiving the second power level at the first external device from the host device through the bus to operate the electrical component after the emulated second external device is registered with the host device using the second device parameters;
means for retrieving the first device parameters from the electrical component while receiving the second power level at the first external device from the host device through the bus; and
means for storing the first device parameters in the nonvolatile memory.
29. The external device of claim 28 , wherein the first external device further comprises:
means for requesting the host device to unregister the emulated second external device;
means for receiving the first power level at the first external device from the host device through the bus;
means for requesting the host device to register the first external device; and
means for receiving a request for the first device parameters from the host device through the bus.