Using USB signaling to trigger a device to enter a mode of operation

Patent metadata

Field	Value
Publication number	US-9824046-B2
Application number	US-201414337844-A
Country	US
Kind code	B2
Filing date	Jul 22, 2014
Priority date	Jul 23, 2013
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

A method of triggering a desired operating mode in a universal serial bus (USB)-compatible client device is provided. A USB-compatible client device detects that it has been coupled to a USB-compatible host device via a USB bus. The USB-compatible client device attempts to pull a data line of the USB bus high. The USB-compatible client device then ascertains that the data line remains pulled low, thereby indicating that the USB-compatible client device should enter a first mode of operation. The USB-compatible client device operates according to the first mode of operation.

First claim

What is claimed is:

1. A method, operational at universal serial bus (USB)-compatible client device, of triggering a desired mode of operation the USB-compatible client device, comprising:
detecting that the USB-compatible client device has been coupled to a USB-compatible host device via a USB bus;
driving, from the USB-compatible client device, an interface to a data line of the USB bus to a logic high as a result of the detection;
determining that the data line remains at a logic low while the interface to the data line is being driven to a logic high, thereby indicating that the USB-compatible client device is to enter a first mode of operation; and
operating the USB-compatible client device according to the first mode of operation as a result of the determination that the data line remains at a logic low despite the USB-compatible client device driving the interface to the data line to a logic high.

2. The method of claim 1 , further comprising:
driving another data line of the USB bus to a logic high as a result of the determination that the data line is at a logic low.

3. The method of claim 2 , wherein:
the data line is a D+ line; and
the other data line is a D− line.

4. The method of claim 2 , wherein operating the USB-compatible client device according to the first mode of operation is triggered as a result of driving the other data line to a logic high.

5. The method of claim 2 , wherein the other data line is driven to a logic high within a threshold period of time after detecting that the USB-compatible client device has been coupled to the USB-compatible host device.

6. The method of claim 1 , wherein the determination that the data line is at a logic low is performed within a threshold period of time after detecting that the USB-compatible client device has been coupled to the USB-compatible host device.

7. The method of claim 1 , wherein the data line is driven to a logic high for a period of time that is less than a reset time period.

8. The method of claim 1 , wherein the detection comprises detecting presence of a voltage on a power line of the USB bus.

9. The method of claim 1 , wherein the data line is driven to a logic low, by an external device, prior to the USB-compatible client device being coupled to the USB-compatible host device.

10. The method of claim 1 , wherein the data line is driven to a logic low by externally coupling the data line to ground.

11. The method of claim 1 , wherein the data line is driven to a logic low by a switch on the USB bus that couples the data line to a ground line.

12. The method of claim 1 , wherein the data line is driven to a logic low at a transmit driver of the USB-compatible host device.

13. The method of claim 1 , further comprising:
entering an enumeration mode of operation following the first mode of operation.

14. The method of claim 1 , further comprising:
attempting to perform a key exchange with the USB-compatible host device; and
exiting the first mode of operation if the key exchange is not completed within a specified time period.

15. The method of claim 14 , further comprising:
using a key obtained during the key exchange to secure data transmissions between the USB-compatible client device and the USB-compatible host device.

16. A universal serial bus (USB)-compatible client device, comprising:
a USB interface for communicating with a USB-compatible host device over a USB bus; and
a USB processing circuit coupled to the USB interface, the USB processing circuit configured to
detect that the USB-compatible client device has been coupled to a USB-compatible host device via a USB bus,
drive, from the USB-compatible client device, an interface to a data line of the USB bus to a logic high as a result of the detection,
determine that the data line remains at a logic low while the interface to the data line is being driven to a logic high, thereby indicating that the USB-compatible client device is to enter a first mode of operation, and
operate the USB-compatible client device according to the first mode of operation as a result of the determination that the data line remains at a logic low despite the USB-compatible client device driving the interface to the data line to a logic high.

17. The device of claim 16 , wherein the USB processing circuit is further configured to:
drive another data line of the USB bus to a logic high as a result of the determination that the data line is at a logic low.

18. The device of claim 17 , wherein:
the data line is a D+ line; and
the other data line is a D− line.

19. The device of claim 17 , wherein the other data line is driven to a logic high within a threshold period of time after detecting that the USB-compatible client device has been coupled to the USB-compatible host device.

20. The device of claim 16 , wherein the determination that the data line is at a logic low is performed within a threshold period of time after detecting that the USB-compatible client device has been coupled to the USB-compatible host device.

21. The device of claim 16 , wherein the detection comprises detecting presence of a voltage on a power line of the USB bus.

22. The device of claim 16 , wherein the data line is driven to a logic low, by an external device, prior to the USB-compatible client device being coupled to the USB-compatible host device.

23. The device of claim 16 , wherein the USB processing circuit is further configured to:
enter an enumeration mode of operation following the first mode of operation.

24. The device of claim 16 , wherein the USB processing circuit is further configured to:
attempt to perform a key exchange with the USB-compatible host device; and
exit the first mode of operation if the key exchange is not completed within a specified time period.

25. The device of claim 24 , wherein the USB processing circuit is further configured to:
use a key obtained during the key exchange to secure data transmissions between the USB-compatible client device and the USB-compatible host device.

26. A universal serial bus (USB)-compatible client device, comprising:
means for detecting that the USB-compatible client device has been coupled to a USB-compatible host device via a USB bus;
means for driving, from the USB-compatible client device, an interface to a data line of the USB bus to a logic high as a result of the detection;
means for determining that the data line remains at a logic low while the interface to the data line is being driven to a logic high, thereby indicating that the USB-compatible client device is to enter a first mode of operation; and
means for operating the USB-compatible client device according to the first mode of operation as a result of the determination that the data line remains at a logic low despite the USB-compatible client device driving the interface to the data line to a logic high.

27. A non-transitory machine-readable storage medium having stored thereon instructions operational in a universal serial bus (USB)-compatible client device, which when executed by one or more processing circuits of the USB-compatible client device, causes one or more processing circuits to:
detect that the USB-compatible client device has been coupled to a USB-compatible host device via a USB bus;
drive, from the USB-compatible client device, an interface to a data line of the USB bus to a logic high as a result

Assignees

• Qualcomm Inc

Inventors

• Remple Terrence Brian
• Patnaik Devdutt
• Choi Jay Yu Jae
• Li Yanru

Classifications

• G06F2213/3854

  Control is performed at the peripheral side · CPC title

• H04L9/0838

  Key agreement, i.e. key establishment technique in which a shared key is derived by parties as a function of information contributed by, or associated with, each of these (network architectures or network communication protocols for key exchange in a packet data network H04L63/061) · CPC title

• G06F2213/0042

  Universal serial bus [USB] · CPC title

• G06F13/4291

  using a clocked protocol · CPC title

• G06F13/385 Primary

  for adaptation of a particular data processing system to different peripheral devices · CPC title