MASTER/SLAVE CONTROL OF TOUCH SENSING

• US 20120056662A1
• Filed: 09/07/2010
• Published: 03/08/2012
• Est. Priority Date: 09/07/2010
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Wilson, Thomas James, Reeve, Richard James
• Granted Patent: US 8,823,657 B2
• Time in Patent Office: Days
• US Class Current: 327/517
• CPC Class Codes: G06F 1/12 Synchronisation of different clock signals provided by a plurality of clock generators
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers

Abstract

Touch sensing can be accomplished using master/slave touch controllers that transmit drive signals to a touch surface and process sense signals including superpositions resulting from master/slave drive signals. The master/slave can drive and sense different sets of lines, respectively, of the touch surface. A communication link between master/slave can be established by transmitting a clock signal between master/slave, transmitting a command including sequence information to the slave, and initiating a communication sequence from the clock signal and sequence information. The slave can receive/transmit communications from/to the master during first/second portions of the communication sequence, respectively. Touch sensing operations can be synchronized between master/slave by transmitting a command including phase alignment information from master to slave, and generating slave clock signals based on the clock signal and the phase alignment information, such that sense signal processing by master clock signals are in-phase with sense signal processing by slave clock signals.

Claims

1. A method of synchronizing touch sensing operations of a master controller and a slave controller for joint operation of a touch sensing surface, the method comprising:

transmitting a first clock signal from the master controller to the slave controller;

transmitting a first command from the master controller to the slave controller, the first command including phase alignment information;

generating a slave clock signal in the slave controller based on the first clock signal and the phase alignment information, wherein the slave clock signal is generated in a known phase relationship with a master clock signal of the master controller; and

performing touch sensing to detect touch on or near the touch sensing surface based on the master and slave clock signals, wherein the master controller operates a first portion of the touch sensing surface, and the slave controller operates a second portion of the touch sensing surface.

2. The method of claim 1, wherein the first portion of the touch sensing surface includes a set of first drive lines and a set of first sense lines and the second portion of the touch sensing surface includes a set of second drive lines and a set of second sense lines, and performing touch sensing includes the master controller applying one or more drive signals to one or more first drive lines and receiving one or more sense signals from the first sense lines, and the slave controller applying one or more drive signals to one or more second drive lines and receiving one or more sense signals from the second sense lines.

3. The method of claim 2, wherein one or more drive signals applied by the master controller are based on the master clock signal, and the one or more drive signals applied by the slave controller are based on the slave clock signal.

4. The method of claim 2, wherein performing touch sensing further includes demodulating the sense signals received by the master controller from the one or more first sense lines with one or more demodulation signals based on the master clock signal, and demodulating the sense signals received by the slave controller from the one or more second sense lines with one or more demodulation signals based on the slave clock signal.

5. The method of claim 2, wherein the drive signals are applied by the master and slave controllers such that the drive signals occur simultaneously on the one or more first drive lines and the one or more second drive lines during a first time period.

6. The method of claim 1, wherein the communication link is a serial link.

7. The method of claim 1, wherein the communication between the master and slave controllers includes alternating periods of transmission of the master controller and the slave controller.

8. The method of claim 7, wherein the communication between the master and slave controllers includes transmission of a second command that causes two consecutive periods of transmission for one of the master controller and the slave controller.

9. The method of claim 1, wherein the phase alignment information includes an identification of a clock cycle of the first clock signal, such that the slave controller sets the phase of the slave clock signal based on the identified clock cycle.

10. The method of claim 1, wherein performing touch sensing includes one of stimulating the touch sensing surface with in-phase drive signals of the master and slave controllers based on the phase relationship of the master and slave clock signals, demodulating sense signals received from the touch sensing surface with in-phase demodulation signals of the master and slave controllers based on the phase relationship of the master and slave clock signals, and applying sense signals received from the touch sensing surface to decimation filters of the master and slave controllers operating in-phase based on the phase relationship of the master and slave clock signals.

11. A touch sensing system comprising:

a touch sensing surface including first and second drive lines, and first and second sense lines;

a master controller that applies one or more drive signals to the first drive lines and receives one or more sense signals from the first sense lines;

a slave controller that applies one or more drive signals to the second drive lines and receives one or more sense signals from the second sense lines, wherein the sense signals received by the master controller and slave controller include one or more sense signals that include a superposition of signals resulting from drive signals applied by the master and slave controllers;

a communication link between the master controller and the slave controller; and

one or more processors that process touch information of the sense signals to sense a touch on or near the touch sensing surface.

12. The touch sensing system of claim 11, wherein the master controller transmits a first clock signal and a first command to the slave controller over the communication link, the first command including phase alignment information, and the slave controller generates a slave clock signal based on the first clock signal and the first command such that the slave clock signal is in a known phase relationship with a master clock signal of the master controller.

13. The touch sensing system of claim 12, wherein the one or more drive signals applied by the master controller are based on the master clock signal, and the one or more drive signals applied by the slave controller are based on the slave clock signal.

14. The method of claim 12, wherein the phase alignment information includes an identification of a clock cycle of the first clock signal, such that the slave controller sets the phase of the slave clock signal based on the identified clock cycle.

15. The touch sensing system of claim 12, wherein the drive signals of the master and slave controllers are in-phase when applied to the touch sensing surface based on the phase relationship of the master and slave clock signals.

16. The touch sensing system of claim 12, wherein the master and slave controllers demodulate the sense signals received from the touch sensing surface with in-phase demodulation signals of the master and slave controllers based on the phase relationship of the master and slave clock signals.

17. The touch sensing system of claim 12, wherein the master and slave controllers each include a decimation filter operating on the sense signals, and the decimation filters of the master and slave controllers operate in-phase with each other based on the phase relationship of the master and slave clock signals.

18. The touch sensing system of claim 11, wherein the master controller demodulates the one or more sense signals received from the first sense lines with one or more demodulation signals based on the master clock signal, and the slave controller demodulates the one or more sense signals received from the second sense lines with one or more demodulation signals based on the slave clock signal.

19. The touch sensing system of claim 11, wherein the drive signals are applied by the master and slave controllers such that the drive signals occur simultaneously on the one or more first drive lines and the one or more second drive lines during a first time period.

20. The touch sensing system of claim 11, wherein the communication link is a serial link.

21. The touch sensing system of claim 11, wherein the communication between the master and slave controllers includes alternating periods of transmission of the master controller and the slave controller.

22. The touch sensing system of claim 21, wherein the communication between the master and slave controllers includes transmission of a second command that causes two consecutive periods of transmission for one of the master controller and the slave controller.

23. A mobile computing device comprising:

a touch sensing system, including a touch sensing surface including first and second drive lines, and first and second sense lines, a master controller that applies one or more drive signals to the first drive lines and receives one or more sense signals from the first sense lines, a slave controller that applies one or more drive signals to the second drive lines and receives one or more sense signals from the second sense lines, wherein the sense signals received by the master controller and slave controller include one or more sense signals that include a superposition of signals resulting from drive signals applied by the master and slave controllers, a communication link between the master controller and the slave controller, and one or more processors that process touch information of the sense signals to sense a touch on or near the touch sensing surface.

24. A method of training communication between a master controller and a slave controller for joint operation of a touch sensing surface, the method comprising:

transmitting a first clock signal from the master controller to the slave controller;

transmitting a first command from the master controller to the slave controller, the first command including sequence information; and

initiating a communication sequence in the slave controller, the communication sequence based on the first clock signal and the sequence information, wherein the receives communications from the master during a first portion of the communication sequence, and the slave controller transmits communications to the master during a second portion of the communication sequence.

25. The method of claim 24, wherein the sequence information includes information of one of a beginning clock cycle of the communication sequence, a length of the communication sequence, the first portion of the communication sequence, and the second portion of the communication sequence.

26. The method of claim 24, wherein predetermined sequence information is pre-stored in a local memory in the slave controller, the method further comprising:

reading the predetermined sequence information from the local memory, wherein initiating the communication sequence includes initiating the sequence based on the predetermined information.

27. The method of claim 26, wherein the predetermined sequence information includes one of the length of the communication sequence, the first portion of the communication sequence, and the second portion of the communication sequence.