Device and method for synchronizing display and touch controller with host polling

1. A method for coordinating the interaction between a touch screen controller and a display controller in an electronic device of the type including a host processor, the touch screen controller configured to acquire capacitive measurements from a touch screen, and the display controller configured to update a display at a refresh frequency and phase, the method comprising:

sending a synchronization signal from the display controller to the host processor, the synchronization signal indicative of the refresh frequency and phase, the synchronization signal comprising a VSYNC signal;

polling the touch screen controller, by the host processor, as triggered by the synchronization signal; and

in response to the polling, acquiring the capacitive measurements by the touch screen controller at a sampling rate and phase determined by the refresh frequency and phase.

2. The method of claim 1 , wherein acquiring comprises sampling capacitive measurements from the touch screen, processing the sampled measurements using the touch screen controller, and sending the processed measurements in the form of data frames to the host processor.

3. The method of claim 1 , wherein the refresh frequency comprises an integer multiple of the sampling rate.

4. The method of claim 1 , wherein:

the electronic device is of the type which further includes a software driver running on the host processor and configured to coordinate communication between the touch screen controller and the host processor; and

the touch screen controller comprises a hardware module which is separate from the host processor.

5. The method of claim 1 , wherein the VSYNC signal is sent at the sampling frequency.

6. The method of claim 1 , wherein the electronic device is of the type which further includes a communications bus extending between the host processor and the touch screen controller, and wherein polling comprises sending a data request from the host processor to the touch controller using the communications bus.

7. The method of claim 6 , further comprising sending, in response to the data request, a data frame comprising indicia of a capacitive measurement from the touch screen controller to the host processor.

8. The method of claim 7 , further comprising sending, in response to sending the data frame to the host processor, refresh image data to be displayed from the host processor to the display controller.

9. The method of claim 1 , wherein:

the electronic device is of the type which further includes an attention signal wire extending from the touch screen controller to the host processor;

the host processor is configured to enter a sleep mode following a predetermined period of inactivity and to suspend polling during sleep mode; and

the touch screen controller is configured to wake the host processor from sleep mode using the attention line in response to detection of an input object interacting with the touch screen during sleep mode.

10. The method of claim 9 , further comprising resuming polling by the host processor upon being awakened by the touch screen controller.

11. The method of claim 1 , further comprising synchronizing, by the touch screen controller in response to polling, the sampling rate to the refresh frequency.

12. The method of claim 11 , wherein synchronizing comprises maintaining synchronous operation between the touch screen controller and the display controller using a feedback loop to maintain synchronous phase operation.

13. The method of claim 1 , further comprising:

configuring a driver module to intercept the synchronization signal operating between the display controller and the host processor, generate a polling signal based on the synchronization signal, and send the polling signal to the touchscreen controller; and

installing the driver module on the host processor for operation by the host processor.

14. The method of claim 1 , wherein the touch screen at least partially overlays the display screen.

15. An input device comprising:

a touch controller operating at a sampling rate;

a display controller operating at a refresh frequency; and

a host controller configured to detect synchronization signals indicative of the refresh frequency and phase from the display controller, and to generate polling requests to the touch controller based on the synchronization signals, the synchronization signals comprising a VSYNC signal;

wherein the touch controller is configured to adapt the sampling rate and phase to the refresh frequency and phase in response to the polling requests.

16. The input device of claim 15 , wherein the touch controller is further configured to synchronize the sampling rate to the refresh frequency such that the refresh frequency comprises an integer multiple of the sampling rate.

17. The input device of claim 15 , wherein the touch controller is further configured to maintain synchronous operation between the touch controller and the display controller using at least one of a phase lock loop and a delay lock loop.

18. The input device of claim 15 wherein, in response to the polling requests, the touch controller is configured to send corresponding respective data frames to the display controller, the data frames comprising information relating to at least one object interacting with a touch screen associated with the touch controller.

19. A touch controller for a capacitive sensing device, the touch controller configured to:

acquire a touch data frames from the capacitive sensing device at a sensing rate;

receive polling requests from a host processor at a refresh frequency,

the polling requests being based on a VSYNC signal sent from a display controller to the host processor, the VSYNC signal indicative of the refresh frequency and phase of the display controller; and

synchronize the sensing rate to the refresh frequency and phase.