Master/slave control of touch sensing

• US 8,823,657 B2
• Filed: 09/07/2010
• Issued: 09/02/2014
• Est. Priority Date: 09/07/2010
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Wilson, Thomas James, Reeve, Richard James
• Primary Examiner(s): Chang, Kent
• Assistant Examiner(s): BRITTINGHAM, NATHANIEL P
• Application Number:
  US12/877,056
• Publication Number:
  US 20120056662A1
• Time in Patent Office: 1,456 Days
• Field of Search: 345/173
• US Class Current: 345/173
• 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 touch sensing system comprising:

a touch sensing panel 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;

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,

wherein the master controller and the slave controller apply drive signals simultaneously at least part of the time to the first and second sense lines such that the drive signals on both the first and second drive lines interact with one of the first and second sense lines at the same time, resulting in a superposition sense signal based on an interaction of each drive signal with the sense line, wherein the superposition sense signal comprises composite information associated with an amount of touch at one or more pixels on the sense line.

2. The touch sensing system of claim 1, 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.

3. The touch sensing system of claim 2, 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.

4. The touch sensing system of claim 2, 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.

5. The touch sensing system of claim 2, 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.

6. The touch sensing system of claim 2, wherein the master and slave controllers demodulate the sense signals received from the touch sensing panel with in-phase demodulation signals of the master and slave controllers based on the phase relationship of the master and slave clock signals.

7. The touch sensing system of claim 2, 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.

8. The touch sensing system of claim 1, 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.

9. The touch sensing system of claim 1, 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.

10. The touch sensing system of claim 1, wherein the communication link is a serial link.

11. The touch sensing system 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.

12. The touch sensing system of claim 11, 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.

13. 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,

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,

wherein the master controller and the slave controller apply drive signals simultaneously at least part of the time to the first and second sense lines such that the drive signals on both the first and second drive lines interact with one of the first and second sense lines at the same time, resulting in a superposition sense signal based on an interaction of each drive signal with the sense line, and

wherein the superposition sense signal comprises composite information associated with an amount of touch at one or more pixels on the sense line.

14. The mobile computing device of claim 13, 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.

15. The mobile computing device of claim 14, 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.

16. The mobile computing device of claim 14, 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.

17. The mobile computing device of claim 14, 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.

18. The mobile computing device of claim 14, wherein the master and slave controllers demodulate the sense signals received from the touch sensing panel with in-phase demodulation signals of the master and slave controllers based on the phase relationship of the master and slave clock signals.

19. The mobile computing device of claim 14, 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.

20. The mobile computing device of claim 13, 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.

21. The mobile computing device of claim 13, 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.