System and method for improved synchronization between devices

• US 10,394,349 B2
• Filed: 04/13/2018
• Issued: 08/27/2019
• Est. Priority Date: 03/06/2014
• Status: Active Grant

• Current Assignee: STMicroelectronics International N.V. (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV)
• Inventors: Cheong, Chee Weng, Dinu, Leonard Liviu, Guo, Dianbo, Tan, Kien Beng
• Primary Examiner(s): Ahn, Sung S
• Application Number:
  US15/953,017
• Publication Number:
  US 20180232071A1
• Time in Patent Office: 501 Days
• CPC Class Codes: G06F 2203/0384 Wireless input, i.e. hardware and software details of wireless interface arrangements for pointing devices
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/04162 for exchanging data with external devices, e.g. smart pens, via the digitiser sensing hardware
• CPC Class Codes: H04L 2027/0097 Adaptive synchronisation signals

Abstract

A system and method for synchronizing two devices in communication with each other. When communication between the two devices is to be established, a synchronization process may be invoked. In an embodiment, a first device may initiate sending synchronization signals having rising edge and falling edge pairs. The second device may include a controller configured to receive the synchronization signals. However, noise may inhibit the ability of the controller to correctly receive and/or interpret the synchronization signals. Noise may cause detection components to falsely detect noise as a synchronization signal or may cause detection components to miss detection of an actual synchronization signal. A window generator may be used to generate comparison windows for the controller to detect synchronization signals. Further, the detection window duration and start times may be adjusted based on previously detected (or undetected) synchronization signals in order to compensate for noise overshadowing synchronization signals.

Claims

1. A synchronization detector, comprising:

a receiver configured to receive a synchronization signal originating from a stylus external to the synchronization detector, the synchronization signal having a period and edges; and

a window generator configured to generate an activating signal for the receiver, the activating signal enabling the receiver to attempt detection during each of a plurality of time windows, the receiver being disabled outside each of the plurality of time windows, the plurality of time windows including;

a first time window for detecting a first subsequent synchronization signal edge in response to a first synchronization signal edge;

a second time window for detecting a second subsequent synchronization signal edge following the first subsequent synchronization signal edge in response to a failure to detect the first subsequent synchronization signal edge within the first time window, wherein the second time window has a duration that is greater than that of the first time window and that is related to the period of the synchronization signal; and

a third time window for detecting a third subsequent synchronization signal edge following the second subsequent synchronization edge signal in response to a failure to detect the second subsequent synchronization signal edge within the second time window, wherein the third time window has a duration that is greater than that of the second time window and that is related to the period of the synchronization signal;

a comparator configured to receive output from the receiver when the receiver is enabled, to compare that output to a reference threshold, to assert a detection signal when the output from the receiver is greater than the reference threshold, and to deassert the detection signal when the output from the receiver is less than the reference threshold; and

a counter receiving the detection signal, and configured to count a number of assertions of the detection signal.

2. The synchronization detector of claim 1, wherein a duration of the second time window is approximately one tenth of the period of the synchronization signal plus a detection delay time.

3. The synchronization detector of claim 1, wherein a duration of the second time window is approximately one fifth of the period of the synchronization signal plus a detection delay time.

4. The synchronization detector of claim 1, wherein the window generator asserts the activating signal during each of the plurality of time windows and deasserts the activating signal outside each of the plurality of time windows.

5. The synchronization detector of claim 1, wherein the first synchronization signal edge comprises a rising edge.

6. The synchronization detector of claim 1, wherein the first synchronization signal edge comprises a falling edge.

7. The synchronization detector of claim 1, wherein the receiver comprises a charge to voltage converter.

8. A synchronization detector comprising:

a receiver configured to receive a synchronization signal originating from a stylus external to the synchronization detector, the synchronization signal having a period and edges; and

a window generator configured to generate an activating signal for the receiver, the activating signal enabling the receiver to attempt detection during each of a plurality of time windows, the receiver being disabled outside each of the plurality of time windows, the plurality of time windows including;

a first time window for detecting a first subsequent synchronization signal edge in response to a first synchronization signal edge;

a second time window for detecting a second subsequent synchronization signal edge following the first subsequent synchronization signal edge in response to a failure to detect the first subsequent synchronization signal edge within the first time window, wherein the second time window has a duration that is greater than that of the first time window and that is related to the period of the synchronization signal; and

a third time window for detecting a third subsequent synchronization signal edge following the second subsequent synchronization edge signal in response to a failure to detect the second subsequent synchronization signal edge within the second time window, wherein the third time window has a duration that is greater than that of the second time window and that is related to the period of the synchronization signal;

wherein the window generator is configured to generate the activating signal after a delay time that is a function of half the period of the synchronization signal and a transient period representing a delay time between occurrence of an edge in the synchronization signal and detection of the edge by the receiver.

9. The synchronization detector of claim 8, wherein a duration of the second time window is approximately one tenth of the period of the synchronization signal plus a detection delay time.

10. The synchronization detector of claim 8, wherein a duration of the second time window is approximately one fifth of the period of the synchronization signal plus a detection delay time.

11. The synchronization detector of claim 8, wherein the window generator asserts the activating signal during each of the plurality of time windows and deasserts the activating signal outside each of the plurality of time windows.

12. The synchronization detector of claim 8, wherein the first synchronization signal edge comprises a rising edge.

13. The synchronization detector of claim 8, wherein the first synchronization signal edge comprises a falling edge.

14. The synchronization detector of claim 8, wherein the receiver comprises a charge to voltage converter.

15. A synchronization detector, comprising:

a receiver configured to receive a synchronization signal having a period and edges; and

a window generator configured to generate an activating signal for the receiver, the activating signal enabling the receiver to attempt detection during each of a plurality of time windows, the receiver being disabled outside each of the plurality of time windows, the plurality of time windows including;

a first time window for detecting a first subsequent synchronization signal edge in response to a first synchronization signal edge;

a second time window for detecting a second subsequent synchronization signal edge following the first subsequent synchronization signal edge in response to a failure to detect the first subsequent synchronization signal edge within the first time window, wherein the second time window has a duration that is greater than that of the first time window and that is related to the period of the synchronization signal; and

a third time window for detecting a third subsequent synchronization signal edge following the second subsequent synchronization edge signal in response to a failure to detect the second subsequent synchronization signal edge within the second time window, wherein the third time window has a duration that is greater than that of the second time window and that is related to the period of the synchronization signal;

a comparator configured to receive output from the receiver when the receiver is enabled, to compare that output to a reference threshold, to assert a detection signal when the output from the receiver is greater than the reference threshold, and to deassert the detection signal when the output from the receiver is less than the reference threshold; and

a counter receiving the detection signal, and configured to count a number of assertions of the detection signal.

16. The synchronization detector of claim 15, wherein a duration of the second time window is approximately one tenth of the period of the synchronization signal plus a detection delay time.

17. The synchronization detector of claim 15, wherein a duration of the second time window is approximately one fifth of the period of the synchronization signal plus a detection delay time.

18. The synchronization detector of claim 15, wherein the window generator asserts the activating signal during each of the plurality of time windows and deasserts the activating signal outside each of the plurality of time windows.

19. The synchronization detector of claim 15, wherein the first synchronization signal edge comprises a rising edge.

20. The synchronization detector of claim 15, wherein the first synchronization signal edge comprises a falling edge.

21. The synchronization detector of claim 15, wherein the receiver comprises a charge to voltage converter.

22. A synchronization detector, comprising:

a receiver configured to receive a synchronization signal having a period and edges; and

a window generator configured to generate an activating signal for the receiver, the activating signal enabling the receiver to attempt detection during each of a plurality of time windows, the receiver being disabled outside each of the plurality of time windows, the plurality of time windows including;

a first time window for detecting a first subsequent synchronization signal edge in response to a first synchronization signal edge;

a second time window for detecting a second subsequent synchronization signal edge following the first subsequent synchronization signal edge in response to a failure to detect the first subsequent synchronization signal edge within the first time window, wherein the second time window has a duration that is greater than that of the first time window and that is related to the period of the synchronization signal; and

a third time window for detecting a third subsequent synchronization signal edge following the second subsequent synchronization edge signal in response to a failure to detect the second subsequent synchronization signal edge within the second time window, wherein the third time window has a duration that is greater than that of the second time window and that is related to the period of the synchronization signal;

wherein the window generator is configured to generate the activating signal after a delay time that is a function of half the period of the synchronization signal and a transient period representing a delay time between occurrence of an edge in the synchronization signal and detection of the edge by the receiver.

23. The synchronization detector of claim 22, wherein a duration of the second time window is approximately one tenth of the period of the synchronization signal plus a detection delay time.

24. The synchronization detector of claim 22, wherein a duration of the second time window is approximately one fifth of the period of the synchronization signal plus a detection delay time.

25. The synchronization detector of claim 22, wherein the window generator asserts the activating signal during each of the plurality of time windows and deasserts the activating signal outside each of the plurality of time windows.

26. The synchronization detector of claim 22, wherein the first synchronization signal edge comprises a rising edge.

27. The synchronization detector of claim 22, wherein the first synchronization signal edge comprises a falling edge.

28. The synchronization detector of claim 22, wherein the receiver comprises a charge to voltage converter.