Devices and methods for enabling USB communication over extension media
USB extension devices that transmit USB 3.0 differential signaling over an extension medium that supports serial communication are provided. In some embodiments, an electrical idle or suspend is detected from a transmit conductor of a USB host or device, and a corresponding USB extension device is reconfigured to couple a receive conductor of the USB host or device to a null data source instead of an extension medium transceiver. Once the electrical idle or suspend state ceases, the receive conductor of the USB host or device is reconnected to the extension medium transceiver. In some embodiments, a transmit input of the extension medium transceiver is coupled to a null data source upon detection of electrical idle or suspend from the USB host or device.
1. A USB extension device, comprising:
a USB port;
an extension medium transceiver configured to:
receive outgoing differential signals from the USB port;
transmit outgoing signals representing the outgoing differential signals over an extension medium; and
receive incoming signals from the extension medium representing incoming differential signals; and
a multiplexer selectively configurable to:
transmit the incoming differential signals from the extension medium transceiver to the USB port while configured in a first state; and
transmit a signal from a null data source to the USB port while configured in a second state.
2. The USB extension device of claim 1 , further comprising logic circuitry configured to control whether the multiplexer is in the first state or the second state.
3. The USB extension device of claim 2 , wherein the logic circuitry is further configured to cause the multiplexer to be in the first state in response to detecting an electrical idle differential signal from the USB port.
4. The USB extension device of claim 2 , wherein the logic circuitry is further configured to cause the multiplexer to be in the second state in response to detecting a valid incoming signal from the extension medium transceiver.
5. The USB extension device of claim 2 , wherein the logic circuitry is further configured to control whether extension medium transmission functionality of the extension medium transceiver is enabled or disabled.
6. The USB extension device of claim 5 , wherein the logic circuitry is further configured to disable the extension medium transmission functionality of the extension medium transceiver after a predetermined period of time has elapsed since detecting the electrical idle differential signal from the USB port.
7. The USB extension device of claim 1 , wherein the null data source includes at least one of a ground contact and a constant frequency signal generator.
8. The USB extension device of claim 1 , wherein the extension medium includes one of a fiber optic cable and a coaxial cable.
9. The USB extension device of claim 1 , wherein the USB port is an upstream facing port coupled to a host device or a hub device.
10. The USB extension device of claim 1 , wherein the USB port is a downstream facing port coupled to a peripheral device or a hub device.
11. A method implemented in a USB extension device of translating USB signals for transmission to and reception from an extension medium, wherein the USB extension device is coupled via a USB port to a device, the method comprising:
coupling a data receive differential pair of the USB port to a null data source in response to determining that the device is in a suspend state; and
coupling the data receive differential pair of the USB port to a data receive output of an extension medium transceiver in response to determining that either:
the device coupled to the USB port is not in the suspend state; or
a valid signal is being received from the extension medium.
12. The method of claim 11 , wherein the device coupled to the USB port of the USB extension device is one of a host device, a hub device, or a peripheral USB device.
13. The method of claim 11 , wherein determining that the device is in a suspend state includes detecting an electrical idle state on a data transmit differential pair of the USB port.
14. The method of claim 11 , wherein determining that the device is in a suspend state includes detecting a suspend acknowledgement signal transmitted by the device.
15. The method of claim 14 , wherein the suspend acknowledgement signal includes an LAU packet.
16. The method of claim 11 , further comprising:
disabling data transmission functionality of the extension medium transceiver in response to determining that the device has been in the suspend state for a predetermined period of time.
17. The method of claim 16 , further comprising:
enabling data transmission functionality of the extension medium transceiver in response to at least one of:
determining that the device is not in the suspend state; and
detecting a valid signal from the extension medium.
18. A USB extension device, comprising:
a USB port; and
logic circuitry configured to cause a null signal to be presented to an extension medium transceiver for transmission over an extension medium in response to detecting an electrical idle differential signal from the USB port.
19. The USB extension device of claim 18 , wherein the null signal is a substantially constant frequency differential signal.
20. The USB extension device of claim 19 , wherein a frequency of the substantially constant frequency differential signal is about 30 kilohertz.