Device disconnect detection
Systems and methods for operating a universal serial bus are described herein. The method includes sending packet data from a USB2 device to a USB2 host on a pair of signal lines, and after sending the packet data, sending an End-Of-Packet (EOP) signal from the USB2 device to the USB2 host. The method also includes, entering the USB2 device into idle state after sending the EOP signal. The method also includes sending a digital ping from the USB2 device to the USB2 host to indicate device presence during idle state.
1. A method of operating a universal serial bus, comprising:
sending packet data from a Universal Serial Bus 2.0 (USB2) host to a USB2 device on a pair of signal lines, and after sending the packet data, sending an End-Of-Packet (EOP) signal from the USB2 host to the USB2 device;
after sending the EOP signal, entering the USB2 device into idle state; and
during idle state, sending a digital ping from the USB2 device to the USB2 host to indicate device presence.
2. The method of claim 1 , comprising the USB2 device periodically sending additional digital pings over a specified time interval to indicate continued device presence.
3. The method of claim 1 , comprising the USB2 host declaring device disconnect if the USB2 host does not receive the digital ping from the USB2 device within a specified time period.
4. The method of claim 1 , comprising the USB2 host declaring device disconnect if the USB2 host does not receive the digital ping for three consecutive frames.
5. The method of claim 1 , comprising the USB2 device indicating device presence without using passive pull up resistors.
6. The method of claim 1 , the EOP signal is sent form the USB2 host to the USB2 device on a first signal line of the pair of signal lines, and the digital ping is sent from the USB2 device to the USB2 host on a second signal line of the pair of signal lines.
7. The method of claim 1 , comprising the USB2 host holding both signal lines of the pair of signal lines to ground during idle state.
8. A Universal Serial Bus 2.0 (USB2) host comprising:
a host port comprising a physical layer to send and receive data on a pair of signal lines to a device, the host port to:
send an End-Of-Packet (EOP) signal to the device following the transmission of packet data, wherein the EOP signal causes a port of the device to enter idle state; and
receive a digital ping from the device to determine the presence of the device.
9. The USB2 host of claim 8 , wherein the host port periodically receives additional digital pings over a specified time interval that indicates continued device presence.
10. The USB2 host of claim 8 , wherein the USB2 host is to declare device disconnect if the host port does not receive the digital ping from the device within a specified time period.
11. The USB2 host of claim 8 , wherein the USB2 host is to declare device disconnect if the host port does not receive the digital ping for three consecutive frames.
12. The USB2 host of claim 8 , wherein the host port sends the EOP signal on a first signal line of the pair of signal lines, and the digital ping is received from the device on a second signal line of the pair of signal lines.
13. The USB2 host of claim 8 , wherein the host port holds both signal lines of the pair of signal lines to ground during idle state.
14. A Universal Serial Bus 2.0 (USB2) device, comprising:
a device port comprising a physical layer to drive signals on a first signal line and a second signal line for communicating with a USB2 host;
wherein, upon entering an idle state, the device port sends a digital ping to the USB2 host on one of the pair of signal lines to indicate device presence.
15. The USB2 device of claim 14 , wherein the device port indicates device presence without using passive pull up resistors.
16. The USB2 device of claim 14 , wherein the device port periodically sends additional digital pings over a specified time interval to indicate continued device presence.
17. The USB2 device of claim 14 , wherein the time separation between the additional digital pings is less than three frames.
18. The USB2 device of claim 14 , wherein the device port enters the idle state upon receiving an EOP signal from the USB2 host on a first signal line of the pair of signal lines, and the digital ping is sent to the USB2 host on a second signal line of the pair of signal lines.
19. The USB2 device of claim 14 , wherein, the USB2 device is a chip disposed in a same motherboard as the USB2 host.
20. The USB2 device of claim 19 , wherein, during a Sleep (L1) or Suspend state, the USB2 device powers down a transmitter of the device port and does not send digital pings to the USB2 host while still maintaining device presence.