Felxconnect disconnect detection
A USB hub includes a plurality of downstream ports; at least one dual mode port, the dual mode port configured to be switchable from a downstream port to an upstream port; and host detection circuitry for detecting whether, when operating as an upstream port, a host is connected.
1. A USB hub comprising:
a plurality of dual mode ports each configured to be switchable between operating as an effective upstream port and an effective downstream port;
host detection circuitry for detecting, while a first dual mode port is operating as an effective upstream port and a second dual mode port is operating as an effective downstream port, whether a USB host is connected to the first dual mode port; and
a controller configured to, in response to detection that the USB host is not connected to the first dual mode port, (a) switch the first dual mode port to function as an effective downstream port and (b) switch the second dual mode port to function as an effective upstream port;
wherein:
the circuitry to detect whether a USB host is connected to the first dual mode port is operable to detect connections or disconnections of a USB element actively configured as a USB host after the first dual mode port has entered a suspend state and is operable while the first dual mode port has entered the suspend state and the USB element is actively configured as a USB host;
each dual mode port further comprises a D+ (DP) connection line and a D− (DM) connection line; and
the host detection circuitry comprises a current source coupled between the DM connection line and ground, the current source configured to source current to the DM connection line while the USB hub is configured to provide charging to the USB element.
2. The USB hub of claim 1 , wherein:
the DM connection line is coupled with the host detection circuitry;
when a respective dual mode port is operating as an effective upstream port, the host detection circuitry is configured to determine connection of the host; and
the host detection circuitry is configured to cause a predetermined logic value to be identified at the DM connection line when a host is disconnected.
3. The USB hub of claim 1 , wherein the current source is a 10 uA current source coupled between the DM connection line and ground.
4. The USB hub of claim 2 , wherein the host detection circuitry comprises a pull up resistor coupled to the DM connection line.
5. A method comprising:
in a USB hub including a plurality of dual mode ports each configured to be switchable between operating as an effective upstream port and an effective downstream port, switching a first USB port function of a first dual mode port from a first mode as an effective downstream port to a second mode as an effective upstream port, and switching a second USB port function of a second dual mode port from a first mode as an effective upstream port to a second mode as an effective downstream port;
upon entering a suspend state, periodically sampling a logic level of a D− (DM) connection line provided by host detection circuitry to determine if a USB host is still connected to the first dual mode port operating as an effective upstream port, wherein the host detection circuitry comprises a current source coupled between the DM connection line and ground, and the method includes sourcing current to the DM connection line while providing charging to the USB element;
in response to determining that a USB host is not connected to the first dual mode port, switching the first dual mode port back to functioning as an effective downstream port and switching the second dual mode port back to functioning as an effective upstream port; and
operating the circuitry to detect whether a USB host is connected to the first dual mode port is operable to detect connections or disconnections of a USB element actively configured as a USB host after the first dual mode port has entered a suspend state and is operable while the first dual mode port has entered the suspend state and the USB element is actively configured as a USB host.
6. The method according to claim 5 , wherein the current source comprises a 10 uA current source.
7. The method according to claim 5 , wherein the host detection circuitry comprises a pull up resistor coupled to the DM connection line.
8. The method according to claim 5 , further including a pull up resistor coupled to a D+ (DP) connection line, wherein the host is detected as being connected to the first dual mode port when the DP connection line and the DM connection line are determined to have the same predetermined logic levels.
9. A USB hub comprising:
a controller;
a plurality of dual mode ports each configured to be switchable between operating as an effective upstream port and an effective downstream port;
host detection circuitry for providing, while a first dual mode port is operating as an effective upstream port and a second dual mode port is operating as an effective downstream port, indicia to the controller of whether a USB host is connected to the first dual mode dport; and
wherein:
the controller is configured to, in response to receiving indicia from the host detection circuity indicating that the USB host is not connected to the first dual mode port operating as an effective upstream port, (a) switch the first dual mode port back to functioning as an effective downstream port and (b) switch the second dual mode port back to functioning as an effective upstream port;
the host detection circuitry to detect whether a USB host is connected to the first dual mode port is operable to detect connections or disconnections of a USB element actively configured as a USB host after the first dual mode port has entered a suspend state and is operable while the first dual mode port has entered the suspend state and the USB element is actively configured as a USB host;
the at least one dual mode port further comprises a D+ (DP) connection line and a D− (DM) connection line; and
the host detection circuitry comprises a current source coupled between the DM connection line and ground, the current source configured to source current to the DM connection line while the USB hub is configured to provide charging to the USB element.
10. The USB hub of claim 9 , wherein:
the DM connection line is coupled with the host detection circuitry; and
the host detection circuitry is configured to, when a respective dual mode port is operating as an effective upstream port, determine connection of the host, wherein said host detection circuitry is configured to cause a predetermined logic value to be identified at the DM connection line when a host is disconnected.
11. The USB hub of claim 9 , wherein the current source is a 10 uA current source coupled between the DM connection line and ground.
12. The USB hub of claim 10 , wherein the host detection circuitry comprises a pull up resistor coupled to the DM connection line.