Use of random sampling technique to reduce finger-coupled noise

Abstract

Random sampling techniques include techniques for reducing or eliminating errors in the output of capacitive sensor arrays such as touch panels. The channels of the touch panel are periodically sampled to determine the presence of one or more touch events. Each channel is individually sampled in a round robin fashion, referred to as a sampling cycle. During each sampling cycle, all channels are sampled once. Multiple sampling cycles are performed such that each channel is sampled multiple times. Random sampling techniques are used to sample each of the channels. One random sampling technique randomizes a starting channel in each sampling cycle. Another random sampling technique randomizes the selection of all channels in each sampling cycle. Yet another random sampling technique randomizes the sampling cycle delay period between each sampling cycle. Still another random sampling technique randomizes the channel delay period between sampling each channel.

What is claimed is: 
     
         1 . A method of detecting one or more touch events on a capacitive touch sensitive device comprising;
 configuring a plurality of channels, each channel corresponding to the capacitive touch sensitive device;   sampling each channel in the plurality of channels according to a randomization algorithm that includes performing multiple sampling cycles, each sampling cycle including sampling each channel in the plurality of channels;   for each channel, calculating a channel capacitance using sampled data; and   determining one or more touch events from the channel capacitances calculated for the plurality of channels.   
     
     
         2 . The method of  claim 1 , wherein the randomization algorithm further includes randomly selecting each channel within the sampling cycle. 
     
     
         3 . The method of  claim 1 , wherein a sampling cycle delay period is included between each sampling cycle, and the randomization algorithm further includes randomly changing the sampling cycle delay period between each sampling cycle. 
     
     
         4 . The method of  claim 1 , wherein a channel delay period is included between each channel sampling and the randomization algorithm further includes randomly changing the channel delay period. 
     
     
         5 . The method of  claim 4 , wherein the plurality of channels includes N channels, and the randomization algorithm further includes randomly generating the channel delay period every M channel samples such that a same channel delay period is applied for each of M channel samples before a new channel delay period is randomly generated and applied to a next M channel samples. 
     
     
         6 . The method of  claim 5 , wherein M is less than N. 
     
     
         7 . The method of  claim 6 , wherein M is greater than N. 
     
     
         8 . A method of detecting one or more touch events on a capacitive touch sensitive device comprising:
 configuring a plurality of channels, each channel corresponding to the capacitive touch sensitive device;   sampling each channel in the plurality of channels according to a randomization algorithm such that each channel is sampled, wherein sampling each channel includes measuring a capacitance of each channel;   performing multiple sampling cycles, wherein a sampling cycle includes sampling each channel in the plurality of channels one time;   for each channel, calculating a channel capacitance using the measured capacitances from the multiple sampling cycles for the channel; and   determining one or more touch events from the channel capacitances calculated for the plurality of channels.   
     
     
         9 . The method of  claim 8 , wherein the randomization algorithm includes randomly selecting each channel within the sampling cycle. 
     
     
         10 . The method of  claim 8 , wherein a sampling cycle delay period is included between each sampling cycle, and the randomization algorithm further includes randomly changing the sampling cycle delay period between each sampling cycle. 
     
     
         11 . The method of  claim 8 , wherein a channel delay period is included between each channel sampling, and the randomization algorithm further includes randomly changing the channel delay period. 
     
     
         12 . The method of  claim 11 , wherein the plurality of channels includes N channels, and the randomization algorithm further includes randomly generating the channel delay period every M channel samples such that a same channel delay period is applied for each of M channel samples before a new channel delay period is randomly generated and applied to a next M channel samples. 
     
     
         13 . The method of  claim 12 , wherein M is less than N. 
     
     
         14 . The method of  claim 12  wherein M is greater than N. 
     
     
         15 . An apparatus for detecting one or more touch events on a touch panel comprising;
 a capacitive touch sensitive device including a plurality of channels, each channel including a touch sensor;   a processor configured to implement a randomization algorithm that includes performing multiple sampling cycles, each sampling cycle including sampling each channel in the plurality of channels; and   a measuring circuit coupled to the capacitive touch sensitive device and to the processor, wherein the measuring circuit is configured to sample each channel in the plurality of channels according to the randomization algorithm, wherein the processor is configured to receive sampled data from the measuring circuit, to calculate a channel capacitance for each channel using the received sample data, and to determine one or more touch events from the channel capacitances calculated for the plurality of channels.   
     
     
         16 . The apparatus of  claim 15 , wherein the randomization algorithm further includes randomly selecting each channel within the sampling cycle. 
     
     
         17 . The apparatus of  claim 15 , wherein a sampling cycle delay period is included between each sampling cycle, and the randomization algorithm further includes randomly changing the sampling cycle delay period between each sampling cycle. 
     
     
         18 . The apparatus of  claim 15 , wherein a channel delay period is included between each channel sampling, and the randomization algorithm further includes randomly changing the channel delay period. 
     
     
         19 . The apparatus of  claim 18  wherein the plurality of channels includes N channels, and the randomization algorithm further includes randomly generating the channel delay period every M channel samples such that a same channel delay period is applied for each of M channel samples before a new channel delay period is randomly generated and applied to a next M channel samples. 
     
     
         20 . The apparatus of  claim 19 , wherein M is less than N. 
     
     
         21 . The apparatus of  claim 19 , wherein M is greater than N.