Baseline recalculation after frequency reconfiguration of a mutual capacitive touch controller
View Patent ↗Systems and methods are provided that allow a touch sensor, such as a mutual capacitive touch panel, to switch from an operative transmit (TX) frequency at which the mutual capacitive touch panel is driven to an alternative TX frequency. When switching to an alternative TX frequency, an alternative baseline capacitance value corresponding to the alternative TX frequency may be utilized to determine whether a touch event has occurred on the mutual capacitive touch panel. Frame scans can be repeatedly performed at the operative TX frequency and the alternative TX frequency in rapid succession, and an average difference of the frame scans can be calculated and utilized to generate the alternative baseline capacitance value which may be insensitive to sudden ambient changes and moving touch events affecting the mutual touch capacitive panel.
1. A method, comprising:
determining a first plurality baseline capacitance values of a capacitive touch panel corresponding to a first frequency;
capturing in rapid succession, a first frequency frame scan of the capacitive touch panel at the first frequency and a second frequency frame scan of the capacitive touch panel at a second frequency;
calculating differences in capacitance values of the capacitive touch panel between the first frequency frame scan and the second frequency frame scan;
repeating, for a predetermined number of times:
the capturing of the first frequency frame scan;
the capturing of the second frequency frame; and
the calculation of the differences in capacitance values of the capacitive touch panel between the first frequency frame scan and the second frequency frame scan,
determining average differences in capacitance values of the capacitive touch panel between the first frequency frame scans and the second frequency frame scans; and
generating a second plurality of baseline capacitance values of the capacitive touch screen corresponding to the second frequency by adding the determined average differences in capacitance values of the capacitive touch panel to the first plurality of baseline capacitance values of the capacitive touch screen corresponding to the first frequency.
2. The method of claim 1 further comprising:
simultaneously with the capturing of the first frequency frame scan and the second frequency frame scan, detecting if noise signals associated with the first frequency frame scans or the second frequency frame scans exist; and
discarding the calculated differences in capacitance values of the capacitive touch screen if a large noise signal is detected.
3. The method of claim 1 further comprising, retuning the capacitive touch panel to the second frequency from the first frequency upon detecting noise on the first frequency.
4. The method of claim 3 further comprising, utilizing the second plurality of baseline capacitances of the capacitive touch screen value instead of the first plurality of baseline capacitance values in determining whether to report a touch event occurring on the capacitive touch panel.
5. The method of claim 3 , wherein the generation of the second plurality of baseline capacitance values of the capacitive touch screen occurs prior to the detection of the noise on the first frequency.
6. The method of claim 3 , wherein the generation of the second plurality of baseline capacitance values of the capacitive touch screen occurs subsequent to the detection of the noise on the first frequency.
7. The method of claim 1 , wherein the first frequency comprises an active transmit frequency on which transmit channels of the capacitive touch panel are excited.
8. The method of claim 1 , wherein the second frequency comprises an alternative frequency determined from a table of known transmit frequencies.
9. The method of claim 1 , wherein the second plurality of baseline capacitance values of the capacitive touch screen are insensitive to sudden ambient changes and moving touch events affecting the capacitive touch panel.
10. A system, comprising:
a capacitive touch panel; and
a digital touch subsystem communicatively coupled to the capacitive touch panel and configured to:
determine a first plurality of baseline capacitance values of the capacitive touch panel corresponding to a first frequency;
repeat, for a predetermined number of times:
capture in rapid succession, a first frequency frame scan of the capacitive touch panel at the first frequency and a second frequency frame scan of the capacitive touch panel at a second frequency; and
calculate differences in capacitance values of the capacitive touch panel between the first frequency frame scan and the second frequency frame scan;
determine average differences in capacitance values of the capacitive touch panel between the first frequency frame scans and the second frequency frame scans; and
generate a second plurality of baseline capacitance values of the capacitive touch screen corresponding to the second frequency by adding the determined average differences in capacitance values of the capacitive touch panel to the first plurality of baseline capacitance values of the capacitive touch screen corresponding to the first frequency.
11. The system of claim 10 , the digital touch subsystem further configured to:
simultaneously with the capturing of the first frequency frame scan and the second frequency frame scan, detect if noise signals associated with the first frequency frame scans or the second frequency frame scans exist; and
discard the calculated differences in capacitance values of the capacitive touch screen if a large noise signal is detected.
12. The system of claim 10 , the digital touch subsystem further configured to retune the capacitive touch panel to the second frequency from the first frequency upon detecting noise on the first frequency.
13. The system of claim 12 , the digital touch subsystem further configured to use the second plurality of baseline capacitances of the capacitive touch screen value instead of the first plurality of baseline capacitance values in determining whether to report a touch event occurring on the capacitive touch panel.
14. The system of claim 12 , wherein the generation of the second plurality of baseline capacitance values of the capacitive touch screen occurs prior to the detection of the noise on the first frequency.
15. The system of claim 12 , wherein the generation of the second plurality of baseline capacitance values of the capacitive touch screen occurs subsequent to the detection of the noise on the first frequency.
16. The system of claim 10 , wherein the first frequency comprises an active transmit frequency on which transmit channels of the capacitive touch panel are excited.
17. The system of claim 10 , wherein the second frequency comprises an alternative frequency determined from a table of known transmit frequencies.
18. The system of claim 10 , wherein the second plurality of baseline capacitance values of the capacitive touch screen are insensitive to sudden ambient changes and moving touch events affecting the capacitive touch panel.
19. A method, comprising:
determining a first plurality of baseline capacitance values of a capacitive touch panel corresponding to a first frequency;
repeating, for a predetermined number of times:
capturing in rapid succession, a first frequency frame scan of the capacitive touch panel at the first frequency and a second frequency frame scan of the capacitive touch panel at a second frequency; and
calculating differences in capacitance values of the capacitive touch panel between the first frequency frame scan and the second frequency frame scan;
determining average differences in capacitance values of the capacitive touch panel between the first frequency frame scans and the second frequency frame scans; and
generating a second plurality of baseline capacitance values of the capacitive touch screen corresponding to the second frequency by adding the determined average differences in capacitance values of the capacitive touch panel to the first plurality of baseline capacitance values of the capacitive touch screen corresponding to the first frequency.
20. The method of claim 19 , further comprising retuning the capacitive touch panel to the second frequency from the first frequency upon detecting noise on the first frequency.