Capacitive stylus for a touch screen

• US 9,411,462 B2
• Filed: 07/22/2013
• Issued: 08/09/2016
• Est. Priority Date: 09/22/2010
• Status: Active Grant

• Current Assignee: Parade Technologies, Ltd.
• Original Assignee: Parade Technologies, Ltd.
• Inventors: Wright, David G., Vallis, Darrin
• Primary Examiner(s): SHERMAN, STEPHEN G
• Application Number:
  US13/947,596
• Publication Number:
  US 20140085257A1
• Time in Patent Office: 1,114 Days
• Field of Search: 345173-179, 345/104, 178 1801- 1809, 178/18.11, 178 1901- 1907
• US Class Current: 1/1
• 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 3/04162 for exchanging data with external devices, e.g. smart pens, via the digitiser sensing hardware
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0441 using active external devices, e.g. active pens, for receiving changes in electrical potential transmitted by the digitiser, e.g. tablet driving signals
• CPC Class Codes: G06F 3/0442 using active external devices, e.g. active pens, for transmitting changes in electrical potential to be received by the digitiser
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer

Abstract

A stylus having a transmit drive circuit configured to transmit a signal to a capacitance sensor via capacitive coupling between the stylus and a capacitive sense array which is coupled to the capacitance sensor, which is configured to synchronize to the stylus, the stylus being configured to act as a timing master.

Claims

1. A method comprising:

receiving a first signal at a capacitance sensor from a stylus via capacitive coupling between the stylus and a capacitive sense array coupled to the capacitance sensor; and

in response to the receiving of the first signal by the capacitance sensor, synchronizing a timing of the capacitance sensor to a timing of the first signal by adjusting the timing of the capacitance sensor using the timing of the first signal, wherein receive (RX) signals from the capacitive sense array remain active during the synchronizing of the timing of the capacitance sensor.

2. The method of claim 1, further comprising:

detecting in a first sensing operation a location of the stylus on the capacitive sense array; and

detecting in a second sensing operation a location of a passive touch object proximate to the capacitive sense array, wherein the second sensing operation comprises transmitting, by the capacitance sensor, to the capacitive sense array a second signal in response to the timing of the first signal.

3. The method of claim 2, further comprising initiating the second sensing operation in response to an end of the first sensing operation.

4. The method of claim 1, wherein receiving the first signal at the capacitance sensor from the stylus comprises receiving stylus tip force information.

5. The method of claim 1, wherein synchronizing the timing of the capacitance sensor to the timing of the first signal comprises:

transmitting, by the capacitance sensor, to at least part of the capacitive sense array a transmit (TX) signal;

receiving, by the capacitance sensor, a corresponding receive (RX) signal from the capacitive sense array;

operating an RX sense circuit of the capacitance sensor; and

receiving the first signal from the stylus using the RX sense circuit.

6. The method of claim 5, wherein synchronizing the timing of the capacitance sensor to the timing of the first signal comprises locking the RX sense circuit to the timing of the first signal using a phase locked loop (PLL).

7. The method of claim 5, wherein operating the RX sense circuit comprises configuring a multiplexor to couple an electrode of the capacitive sense array to the RX sense circuit.

8. The method of claim 5, wherein transmitting the TX signal comprises generating a signal having a different frequency from the frequency of the first signal, and transmitting the generated signal having a different frequency to the capacitive sense array.

9. An apparatus comprising:

a capacitive sense array coupled to a capacitance sensor, the capacitance sensor comprising a receive (RX) sense circuit and a transmit (TX) drive circuit, the capacitance sensor configured to;

detect a first signal from a stylus via capacitive coupling between the stylus and the capacitive sense array;

synchronize a timing of the capacitance sensor to a timing of the first signal by adjusting the timing of the capacitance sensor using the timing of the first signal in response to the detection of the first signal by the capacitance sensor, wherein RX signals from the capacitive sense array remain on during the synchronization of the timing of the capacitance sensor;

perform a first sensing operation to detect a location of the stylus on the capacitive sense array; and

perform a second sensing operation to detect a location of a passive touch object proximate to the capacitive sense array.

10. The apparatus of claim 9, wherein the TX drive circuit is configured to transmit a second signal to at least part of the capacitive sense array in response to the timing of the first signal.

11. The apparatus of claim 9, wherein the capacitance sensor is further configured to receive stylus tip force information from the stylus.

12. The apparatus of claim 9, wherein the capacitance sensor is further configured to perform the second sensing operation in response to an end of the first sensing operation.

13. The apparatus of claim 9, wherein the capacitance sensor is further configured to:

transmit a TX signal using the TX drive circuit;

receive a corresponding RX signal using the RX sense circuit;

continue to operate the RX sense circuit after the TX drive circuit has ceased transmitting the TX signal; and

receive the first signal from the stylus using the RX sense circuit.

14. The apparatus of claim 13, wherein the TX drive circuit is further configured to transmit the TX signal having a frequency different from the frequency of the first signal.

15. The apparatus of claim 9 further comprising a phase locked loop (PLL) to synchronize operation of the capacitance sensor to the first signal.

16. The apparatus of claim 9 further comprising a multiplexor, configured to couple the TX drive circuit and the RX sense circuit to the capacitive sense array.

17. A method comprising:

detecting a first signal at a capacitance sensor from a stylus via capacitive coupling between the stylus and a capacitive sense array coupled to the capacitance sensor;

in response to detecting the first signal by the capacitance sensor, receiving the first signal and synchronizing the capacitance sensor to the first signal by adjusting a timing of the capacitance sensor, wherein RX signals from the capacitive sense array remain on during the synchronizing of the capacitance sensor;

detecting in a first sensing operation a location of the stylus on the capacitive sense array; and

detecting in a second sensing operation a location of a passive touch object proximate to the capacitive sense array, wherein the second sensing operation comprises transmitting, by the capacitance sensor, to the capacitive sense array a second signal in response to a timing of the first signal.