TECHNICAL FIELD

This disclosure is related to the field of capacitive touch sensing and, in particular, to the emulation of self capacitance sensing, using touch data collected with mutual capacitance sensing, to perform accurate ear detection.

BACKGROUND

Touch screens are prevalent in today's computing environment. Portable computers, desktop computers, tablets, smart phones, and smartwatches typically employ a touch screen to gain user input for navigation and control of these devices. Thus, discerning the intent of the user via touch inputs is an important feature of a touch screen device.

Touch screens typically operate based on capacitive touch sensing, and include a patterned array of conductive features. For instance, the patterned array of conductive features may include sets of lines, conductive pads, overlapping structures, interleaved structures, diamond structures, lattice structures, and the like. By evaluating changes in capacitance at different lines or sets of lines, a user touch or hover, such as by a finger or stylus, can be detected.

Two common capacitive touch sensing modes that may be performed on touch screens are mutual capacitance sensing and self capacitance sensing. In a mutual self capacitance sensing mode, a drive signal is applied to a subset of the lines referred to as drive lines, and capacitance values are measured at a subset of the lines referred to as sense lines, with it being understood that the sense lines cross the drive lines in a spaced apart fashion therefrom. Each crossing of a drive line and a sense line forms a capacitive node. Since bringing a finger or conductive stylus near the surface of the touch screen changes the local electric field, this causes a reduction in the capacitance between the drive lines and the sense lines (the “mutual” capacitance), and the capacitance change at every individual capacitive node can be measured and processed to accurately determine the touch location. Therefore, the output of mutual capacitance sensing is a two-dimensional matrix of values, with one value for each capacitive node (crossing between a drive line and a sense line). Thus, it can be appreciated that mutual capacitance sensing allows multi-touch operation where multiple fingers, palms or styli can be accurately tracked at the same time.

In a self capacitance sensing mode, the drive signal is applied to every line, regardless of orientation. Bringing a finger or conductive stylus near the surface of the sensor changes the local electric field, increasing the capacitance between the drive line or sense line of interest and ground (the “self capacitance”) in this instance. However, since all lines are driven, the capacitance change can only be measured on each line. Therefore, the output of self capacitance sensing is two one dimensional arrays of values, with one value for each line.

There is an increasing demand for smartphones having a touch screen that spans across the full front side of the smartphone, without large cutouts or large bezels permitting the presence of numerous sensors on the front side of the smartphone. In particular, it is desired to remove proximity sensors from the front side of smartphones, and to instead utilize the touch screen itself to perform the function of a proximity sensor (which is used by the smartphone to determine when the user is holding the smartphone next to their ear to make a voice call).

While conventional touch screens may be capable of performing the function of a proximity sensor when operating using self capacitance sensing, issues arise when it is desired to make a particularly thin touch screen perform the function of a proximity sensor. For example, in thin touch screen technology, the touch sensors themselves become more influenced by and exposed to display noise, resulting in signal to noise ratio too poor to utilize self capacitance sensing in performing the function of a proximity sensor. As such, further development is needed.

SUMMARY

Disclosed herein is a touch screen controller including processing circuitry. The processing circuitry is configured to perform mutual capacitance sensing to acquire touch strength values from a capacitive touch matrix formed by capacitively intersecting drive lines and sense lines, and for each sense line, sum the touch strength values associated with that sense line to thereby form an emulated self capacitance sense value for that sense line, and apply a weighting to that emulated self capacitance sense value, the weighting being based upon a position of that sense line compared to a location on the capacitive touch matrix adjacent which a user's ear is expected to be placed. For each drive line, the processing circuitry is further configured to sum the touch strength values associated with that drive line to thereby form an emulated self capacitance drive value for that drive line, and apply a weighting to that emulated self capacitance drive value, the weighting being based upon a position of that drive line compared to the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed. The processing circuitry is also configured to determine presence of the user's ear adjacent to the capacitive touch matrix based upon the emulated self capacitance sense values and the emulated self capacitance drive values.

The weighting of each emulated self capacitance sense value may be greater the closer its associated sense line is to the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed and lesser the farther its associated sense line is from the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed. The weighting of each emulated self capacitance drive value may be greater the closer its associated drive line is to the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed and lesser the farther its associated drive line is from the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed.

The weighting of each emulated self capacitance sense value may be a weighting of zero if its associated sense line is outside of the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed, and a weighting of one if its associated sense line is inside of the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed. The weighting of each emulated self capacitance drive value may be a weighting of zero if its associated drive line is outside of the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed, and a weighting of one if its associated drive line is inside of the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed.

The weighting of each emulated self capacitance sense value may be a weighting of zero if its associated sense line is inside of a location on the capacitive touch matrix adjacent which the user's hand is expected to be placed. The weighting of each emulated self capacitance drive value may be a weighting of zero if its associated sense line is inside of a location on the capacitive touch matrix adjacent which the user's hand is expected to be placed.

Also disclosed herein is a smartphone including a portable housing, and a touch screen carried by the portable housing on a front face thereof, with the touch screen including a capacitive touch matrix formed by capacitively intersecting drive lines and sense lines. A speaker is carried by the portable housing at a top of the front face. A touch screen controller within the portable housing includes drive circuitry configured to apply a drive signal to the drive lines, sense circuitry configured to sense mutual capacitances between the capacitive intersections of the drive lines and the sense lines, and processing circuitry. The processing circuitry is configured to acquire touch strength values from the sense lines while the drive signal is applied to the drive lines, and for each sense line, sum the touch strength values associated with that sense line to thereby form an emulated self capacitance sense value for that sense line, and apply a weighting to that emulated self capacitance sense value, the weighting being based upon a position of that sense line on the front face of the portable housing compared to the position of the speaker on the front face of the portable housing. The processing circuitry is also configured to, for each drive line, sum the touch strength values associated with that drive line to thereby form an emulated self capacitance drive value for that drive line, and apply a weighting to that emulated self capacitance drive value, the weighting being based upon a position of that drive line on the front face of the portable housing compared to the position of the speaker on the front face of the portable housing. The processing circuitry also determines presence of the user's ear adjacent to the capacitive touch matrix based upon the emulated self capacitance sense values and the emulated self capacitance drive values.

The weighting of each emulated self capacitance sense value may be greater the closer its associated sense line is to the position of that sense line on the front face of the portable housing and lesser the farther its associated sense line is from the position of the speaker on the front face of the portable housing. The weighting of each emulated self capacitance drive value may be greater the closer its associated drive line is to the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed and lesser the farther its associated drive line is from the position of the speaker on the front face of the portable housing.

The weighting of each emulated self capacitance sense value may be a weighting of zero if its associated sense line is outside of a zone defined around the speaker, and a weighting of one if its associated sense line is inside of the zone defined around the speaker.

The weighting of each emulated self capacitance sense value may be a weighting of zero if its associated sense line is inside of a location on the capacitive touch matrix adjacent which the user's hand is expected to be placed. The weighting of each emulated self capacitance drive value may be a weighting of zero if its associated sense line is inside of a location on the capacitive touch matrix adjacent which the user's hand is expected to be placed.

Also disclosed herein is a method including acquiring touch strength values from a capacitive touch matrix formed by capacitively intersecting drive lines and sense lines, using mutual capacitance sensing, and for each sense line, summing the touch strength values associated with that sense line to thereby form an emulated self capacitance sense value for that sense line, and apply a weighting to that emulated self capacitance sense value, the weighting being based upon the position of that sense line compared to a location on the capacitive touch matrix adjacent which a user's ear is expected to be placed. The method also includes for each drive line, summing the touch strength values associated with that drive line to thereby form an emulated self capacitance drive value for that drive line, and apply a weighting to that emulated self capacitance drive value, the weighting being based upon the position of that drive line compared to the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed. The method further includes determining presence of the user's ear adjacent to the capacitive touch matrix based upon the emulated self capacitance sense values and the emulated self capacitance drive values.

The weighting of each emulated self capacitance sense value may be greater the closer its associated sense line is to the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed and lesser the farther its associated sense line is from the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed. The weighting of each emulated self capacitance drive value may be greater the closer its associated drive line is to the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed and lesser the farther its associated drive line is from the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed.

The weighting of each emulated self capacitance sense value may be a weighting of zero if its associated sense line is outside of the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed, and a weighting of one if its associated sense line is inside of the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed. The weighting of each emulated self capacitance drive value may be a weighting of zero if its associated drive line is outside of the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed, and a weighting of one if its associated drive line is inside of the location on the capacitive touch matrix adjacent which the user's ear is expected to be placed.

The weighting of each emulated self capacitance sense value may be a weighting of zero if its associated sense line is inside of a location on the capacitive touch matrix adjacent which the user's hand is expected to be placed. The weighting of each emulated self capacitance drive value may be a weighting of zero if its associated sense line is inside of a location on the capacitive touch matrix adjacent which the user's hand is expected to be placed.

Also disclosed herein is a touch screen controller, including processing circuitry configured to perform mutual capacitance sensing to acquire touch strength values from a capacitive touch matrix formed by capacitively intersecting conductive lines, for each conductive line, generate an emulated self capacitance value from an associated touch strength value based upon a position of that conductive line compared to a location on the capacitive touch matrix adjacent to which a first touch type is expected to occur, and determine presence of the first touch type adjacent to the capacitive touch matrix based upon the emulated self capacitance values.

The processing circuitry may be configured to generate the emulated self capacitance values for each conductive line by weighting the acquired touch strength values based upon its closeness to the location on the capacitive touch matrix adjacent to which the first touch type is expected to occur.

The weighting applied to each acquired touch strength value may be a weighting of zero if its associated conductive line is outside of the location on the capacitive touch matrix adjacent which the first touch type is expected to occur, and a weighting of one if its associated conductive line is inside of the location on the capacitive touch matrix adjacent which the first touch type is expected to occur.

The weighting applied to each acquired touch strength value may be a weighting of one if its associated conductive line is outside of the location on the capacitive touch matrix adjacent which a second touch type is expected to occur, and a weighting of zero if its associated conductive line is inside of the location on the capacitive touch matrix adjacent which the first touch type is expected to occur, wherein the second touch type is different than the first touch type.

The first touch type may be a touch by a portion of a user's head, and the second touch type may be a touch by a portion of a user's hand.

The conductive lines may include capacitively intersecting drive lines and sense lines. The processing circuitry may be configured to generate the emulated self capacitance value for each conductive line by for each sense line, generating an emulated self capacitance sense value based upon a position of that sense line compared to a location on the capacitive touch matrix adjacent to which the first touch type is expected to occur, and for each drive line, generate an emulated self capacitance drive value based upon a position of that drive line compared to the location on the capacitive touch matrix adjacent to which the first touch type is expected to occur. The processing circuitry may be configured to determine the presence of the first touch type adjacent to the capacitive touch matrix based upon the emulated self capacitance sense values and emulated self capacitance drive values.

The processing circuitry may be configured to generate the emulated self capacitance sense values by acquiring touch strength values for the sense lines and weighting those touch strength values based on their closeness to the location on the capacitive touch matrix adjacent to which the first touch type is expected to occur. The processing circuitry may be configured to generate the emulated self capacitance drive values by acquiring touch strength values for the drive lines and weighting those touch strength values based on their closeness to the location on the capacitive touch matrix adjacent to which the first touch type is expected to occur.

The weighting applied to each touch strength value for the sense lines may be a weighting of zero if its associated sense line is outside of the location on the capacitive touch matrix adjacent which the first touch type is expected to occur, and a weighting of one if its associated sense line is inside of the location on the capacitive touch matrix adjacent which the first touch type is expected to occur.

The weighting applied to each touch strength value for the drive lines may be a weighting of zero if its associated drive line is outside of the location on the capacitive touch matrix adjacent which the first touch type is expected to occur, and a weighting of one if its associated drive line is inside of the location on the capacitive touch matrix adjacent which the first touch type is expected to occur.

The weighting applied to each touch strength value for the sense lines may be a weighting of one if its associated sense line is outside of the location on the capacitive touch matrix adjacent which a second touch type is expected to occur, and a weighting of zero if its associated sense line is inside of the location on the capacitive touch matrix adjacent which the second touch type is expected to occur.

The weighting applied to each touch strength value for the drive lines may be a weighting of one if its associated drive line is outside of the location on the capacitive touch matrix adjacent which a second touch type is expected to occur, and a weighting of zero if its associated drive line is inside of the location on the capacitive touch matrix adjacent which the second touch type is expected to occur.

