Capacitive touchscreen system with reduced power consumption using modal focused scanning
View Patent ↗Disclosed herein are various embodiments of a capacitive touchscreen system that is capable of sensing finger touches made on a capacitive touchscreen according to various scanning modes that reduce power consumption of the capacitive touchscreen system. The disclosed power saving scanning modes are modally focused, and can be used not only to reduce system power consumption, but also to enhance the user experience with the capacitive touchscreen system.
1. A method of reducing power consumption in a capacitive touchscreen system, comprising:
providing, under control of a touchscreen processor, drive signals to a first plurality of electrically conductive drive traces, a second plurality of electrically conductive sense traces being located in proximity to the first plurality of drive traces such that mutual capacitances are developed between the first and second pluralities of traces by the drive signals at locations where the first and second pluralities of traces intersect to form pixels, such mutual capacitances changing in the presence of one or more fingers, hands or touch devices brought into proximity thereto at touch locations on the touchscreen;
sensing at a first scan rate in a full scan mode over a first predetermined period of time corresponding to a no touch timer, and under control of the touchscreen processor, mutual capacitances along the second plurality of sense traces;
when touches are detected on the touchscreen within the first predetermined period of time, resetting the no touch timer to zero and continuing to sense at the first scan rate in the full scan mode mutual capacitances along the second plurality of sense traces;
when no touches are detected on the touchscreen within the first predetermined period of time, sensing at a second scan rate in a first rest mode over a second predetermined period of time corresponding to a first rest timer, comprising:
scanning less than all the second plurality of traces;
when touches are detected on the touchscreen within the second predetermined period of time, resetting the no touch timer to zero and resuming sensing at the first scan rate in the full scan mode the mutual capacitances along the second plurality of sense traces;
when no touches are detected on the touchscreen within the second predetermined period of time, sensing at a third scan rate in a second rest mode over a third predetermined period of time corresponding to a second rest timer, the third scan rate being lower than the second scan rate;
when touches are detected on the touchscreen within the third predetermined period of time, resetting the no touch timer to zero and resuming sensing at the first scan rate in the full scan mode the mutual capacitances along the second plurality of sense traces;
when no touches are detected on the touchscreen within the third predetermined period of time, entering a locked mode in which a reduced number of the second plurality of traces are sensed.
2. The method of claim 1 , wherein sensing at the third reduced scan rate further comprises scanning less than all the second plurality of traces.
3. The method of claim 1 , further comprising detecting an unlocking gesture on the touchscreen.
4. The method of claim 1 , further comprising resuming sensing at the first full scan rate in the full scan mode the mutual capacitances along the second plurality of sense traces.
5. The method of claim 1 , further comprising sequentially acquiring frames corresponding to different portions of the touchscreen.