US 9,811,220 B2
Signal adaptive filtering for touch detection
Karel Povalac, Valasska Polanka (CZ); Petr Gargulak, Lidecko (CZ); and Lukas Vaculik, Valasske Mezirici (CZ)
Assigned to NXA USA, Inc., Austin, TX (US)
Filed by Freescale Semiconductor, Inc., Austin, TX (US)
Filed on Jun. 19, 2015, as Appl. No. 14/744,310.
Prior Publication US 2016/0370894 A1, Dec. 22, 2016
Int. Cl. G06F 3/044 (2006.01); G06F 3/041 (2006.01); G06F 3/0354 (2013.01)
CPC G06F 3/044 (2013.01) [G06F 3/03545 (2013.01); G06F 3/03547 (2013.01); G06F 3/0416 (2013.01); G06F 3/0418 (2013.01); G06F 2203/04106 (2013.01); G06F 2203/04808 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A method for performing touch detection within a capacitive touch sensor system, comprising:
receiving a measured capacitance signal from a capacitive touch sensor device;
updating a baseline capacitance signal by performing a first filtering of the measured capacitance signal, wherein a transfer function of the first filtering varies as a function of a current state of the capacitive touch sensor device;
performing a second filtering of the measured capacitance signal to create a noise signal;
creating a deadband filter as a function of the noise signal;
performing a third filtering of the measured capacitance signal to create a predicted signal; and
recognizing a touch event or a release event of the capacitive touch sensor device as a function of a comparison of the predicted signal to the measured capacitance signal when the measured capacitance signal lies outside of a range of the deadband filter.