Capacitive touch screen interference detection and operation
View Patent ↗A processing system for a capacitive touch screen comprises sensor circuitry and control logic. The sensor circuitry is configured to communicatively couple with sensor electrodes of the capacitive touch screen. The control logic is configured to operate the capacitive touch screen in a first mode comprising interference sensing at a first level and input object sensing. The control logic is also configured to operate the capacitive touch screen in a second mode instead of the first mode in response to: interference measured in the first mode meeting an interference condition; and a determination that input is in a sensing region of the capacitive touch screen. Operating in the first mode, interference sensing is performed during a non-display update time. Operating in the second mode, interference sensing with the capacitive touch screen is either not performed or is performed at a second level, lower in fidelity than the first level.
1. A processing system for a capacitive touch screen, said processing system comprising:
sensor circuitry configured to be communicatively coupled with sensor electrodes of said capacitive touch screen;
display circuitry configured to update a display of said capacitive touch screen, wherein the sensor electrodes of the capacitive touch screen comprise a plurality of common electrodes configured to transmit transmitter signals to update the display and to perform capacitive sensing; and
control logic configured to:
operate said capacitive touch screen in a first frame type corresponding to a first capacitive sensing sequence that is performed by said plurality of common electrodes within a display sequence, said first frame type comprising a first period for interference detection and a second period for input object capacitive sensing;
determine, using said first capacitive sensing sequence of said first period of said first frame type, interference in said first frame type, wherein said interference comprises an input object coupled interference component;
determine, using said first capacitive sensing sequence of said second period of said first frame type, that an input object is in a sensing region of said capacitive touch screen;
operate, in response to determining that said input object is in the sensing region, said capacitive touch screen in a second frame type without interference detection, wherein said capacitive touch screen operates said plurality of common electrodes at a capacitive sensing frequency that is shifted from said first frame type to said the second frame type, and wherein the control logic is configured to select the second frame type based on said interference that is determined in said first period of said first frame type;
acquire, using a second capacitive sensing sequence of said second frame type, a capacitive image of the sensing region; and
filter, using said interference in said first period of said first frame type, the input object coupled interference component from said capacitive image to determine an input object signal in said capacitive image while operating said capacitive touch screen in said second frame type.
2. The processing system of claim 1 , wherein said plurality of common electrodes are maintained in a non-transmitting state during interference sensing in said first frame type.
3. The processing system of claim 1 , wherein said control logic is further configured to:
exit said second frame type in response to a second determination while in said second frame type that no input is in said sensing region.
4. The processing system of claim 1 , wherein said control logic is further configured to:
enter said first frame type in response to a second determination that no input has been sensed in said sensing region for a predetermined period.
5. The processing system of claim 1 , wherein said control logic is further configured to:
enter said first frame type in response to experiencing signal corruption while in said second frame type.
6. A capacitive touch screen comprising:
a display;
a plurality of common electrodes configured to transmit transmitter signals to update the display of said capacitive touch screen and to perform capacitive sensing; and
a processing system coupled with said plurality of sensor electrodes, said processing system configured to:
operate said capacitive touch screen in a first frame type corresponding to a first capacitive sensing sequence that is performed by said plurality of common electrodes within a display sequence, said first frame type comprising a first period for interference detection and a second period for input object capacitive sensing;
determine, using said first capacitive sensing sequence of said first period of said first frame type, interference in said first frame type, wherein said interference comprises an input object coupled interference component;
determine, using said first capacitive sensing sequence of said first period of said first frame type, that an input object is in a sensing region of said capacitive touch screen;
operate, in response to determining that said input object is in said sensing region, said capacitive touch screen in a second frame type without interference detection, wherein said capacitive touch screen operates said plurality of common electrodes at a capacitive sensing frequency that is shifted from said first frame type to said the second frame type, and wherein the processing system is configured to select the second frame type based on said interference that is determined in said first period of said first frame type;
acquire, using a second capacitive sensing sequence of said second frame type, a capacitive image of the sensing region; and
filter, using said interference in said first period of said first frame type, the input object coupled interference component from the capacitive image to determine an input object signal in said capacitive image while operating said capacitive touch screen in said second frame type.
7. The capacitive touch screen of claim 6 , wherein said processing system is further configured to:
exit said second frame type in response to a second determination while in said second frame type that no input is in said sensing region.
8. The capacitive touch screen of claim 6 , wherein said processing system is further configured to:
enter said first frame type in response to a second determination that no input has been sensed in said sensing region for a predetermined period.
9. The capacitive touch screen of claim 6 , wherein said processing system is further configured to:
enter said first frame type in response to experiencing signal corruption while in said second frame type.
10. A method comprising:
operate a capacitive touch screen in a first frame type corresponding to a first capacitive sensing sequence that is performed by a plurality of common electrodes within a display sequence, said first frame type comprising a first period for interference detection and a second period for input object capacitive sensing;
determine, using said first capacitive sensing sequence of said first period of said first frame type, interference in said first frame type;
determine, using said first capacitive sensing sequence of said second period of said first frame type, that an input object is in a sensing region of said capacitive touch screen;
operate, in response to determining that said input object is in said sensing region, said capacitive touch screen in a second frame type without interference detection, wherein said capacitive touch screen operates said plurality of common electrodes at a capacitive sensing frequency that is shifted from said first frame type to said the second frame type, and wherein the second frame type is selected based on said interference that is determined in said first period of said first frame type;
acquire, using a second capacitive sensing sequence of said second frame type, a capacitive image of the sensing region; and
filter, using said interference in said first period of said first frame type, said input object coupled interference component from the capacitive image to determine an input object signal in said capacitive image while operating said capacitive touch screen in said second frame type.
11. The method as recited in claim 10 , further comprising:
exiting said second frame type in response to a second determination, said second determination comprising that no input is sensed in said sensing region.
12. The method as recited in claim 10 , further comprising:
entering said first frame type in response to a second determination, said second determination comprising no input being sensed in said sensing region for a predetermined period.
13. The method as recited in claim 10 , further comprising:
entering said first frame type in response to experiencing signal corruption while in said second frame type.