Multiple touch resolve

• US 8,564,546 B1
• Filed: 02/27/2009
• Issued: 10/22/2013
• Est. Priority Date: 02/27/2008
• Status: Active Grant

• Current Assignee: Parade Technologies, Ltd.
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Birch, Robert
• Primary Examiner(s): Feild, Joseph
• Assistant Examiner(s): HOFFNER, LINH NGUYEN
• Application Number:
  US12/395,304
• Time in Patent Office: 1,698 Days
• Field of Search: 345156-173, 382312-314, 178 1801- 1806
• US Class Current: 345/173
• CPC Class Codes: G06F 2203/04106 Multi-sensing digitiser, i.e. digitiser using at least two different sensing technologies simultaneously or alternatively, e.g. for detecting pen and finger, for saving power or for improving position detection
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• CPC Class Codes: G06F 3/044 by capacitive means

Abstract

An apparatus for and method of resolving multiple centroids from data received from a multi-touch sensor device are described.

Claims

1. A method comprising:

measuring a capacitance of a plurality of capacitance sensors;

identifying at least one peak sensor of the plurality of capacitance sensors;

in a first subtraction function, subtracting a first predetermined value from the measured capacitance of each of the plurality of capacitance sensors;

in a first summing function, summing the result of the first subtraction function for the plurality of capacitance sensors; and

in a first comparing function, comparing the result of the first summing function to a first threshold; and

if the result of the first summing function is greater than the first threshold, increasing the first predetermined value and repeating the first subtraction, summing, and comparing function, and

if the result of the first summing function is not greater than the first threshold, calculating a centroid for each of the at least one peak sensor.

2. The method of claim 1, further comprising:

in a second summing function, summing result of the first subtraction function for each capacitance sensor of the plurality of capacitance sensors of each centroid;

in a second comparing function, comparing the result of the second summing function to a second threshold; and

if the result of the second comparing function is greater the second threshold, proceeding to the calculating a centroid, and

if the result of the second comparing function is not greater than the second threshold, decreasing second threshold and repeating the first subtraction function and the first and second summing and comparing functions.

3. The method of claim 1, wherein the measured capacitances of the plurality of capacitance sensors is compared to a noise threshold and if the measured capacitances are less than the noise threshold, the measured capacitances are ignored.

4. The method of claim 1, wherein the peak sensor is identified by comparing each sensor to each of the plurality of sensors surrounding it and determining that the sensor is a peak if the measured capacitance is greater than the measured capacitance of the surrounding sensors.

5. The method of claim 1, wherein the first predetermined value and the first threshold are based on an empirical analysis of one or more manufactured touch sensor arrays.

6. The method of claim 1, wherein the first and second predetermined values and the first and second thresholds are based on an empirical analysis of one or more manufactured touch sensor arrays.

7. The method of claim 1, wherein the measuring the capacitance of the plurality of sensors comprises:

converting a the capacitance to a digital value;

subtracting a baseline value from each of the measured capacitance values for the plurality of sensors; and

generating a difference count value representative of the change in capacitance for each of the plurality of sensors.

8. A capacitance sensing circuit comprising:

a plurality of capacitance sensing inputs coupled to a plurality of capacitance sensors; and

a processing device configured to;

measure capacitance on a plurality of capacitance sensors,

identify at least one peak sensor of the plurality of capacitance sensors,

in a first subtraction function, subtract a first predetermined value from the measured capacitance of each of the plurality of capacitance sensors,

in a first summing function, sum the result of the first subtraction function for the plurality of capacitance sensors,

in a first comparing function, compare the result of the first summing function to a first threshold,

if the result of the first summing function is greater than the first threshold, increase the first predetermined value and repeat the first subtraction, summing, and comparing function, and

if the result of the first summing function is not greater than the first threshold, calculate a centroid for each of the at least one peak sensor.

9. The capacitance sensing circuit of claim 8, wherein the processing device is further comprising:

in a second summing function, sum result of the first subtraction function for each capacitance sensor of the plurality of capacitance sensors of each centroid;

in a second comparing function, compare the result of the second summing function to a second threshold; and

if the result of the second comparing function is greater the second threshold, proceed to the calculating a centroid, and

if the result of the second comparing function is not greater than the second threshold, decrease second threshold and repeat the first subtraction function and the first and second summing and comparing functions.

10. The capacitance sensing circuit of claim 9, wherein the processing device is configured to compare the measured capacitances to a noise threshold and if the measured capacitances are less than the noise threshold, ignore the measured capacitances.

11. The capacitance sensing circuit of claim 9, wherein the processing device is configured to compare the capacitance of each sensor to those surrounding it and identifying a capacitance sensor as a peak if the measured capacitance is greater than the measured capacitance of the surrounding sensors.

12. The capacitance sensing circuit of claim 8, wherein the first predetermined value and the first threshold are based on an empirical analysis of one or more manufactured touch sensor arrays.

13. The capacitance sensing circuit of claim 9, wherein the first and second predetermined values and the first and second thresholds are based on an empirical analysis of one or more manufactured touch sensor arrays.

14. The capacitance sensing circuit of claim 9, wherein for the measuring capacitance the processor is configured to:

convert a the capacitance to a digital value;

subtract a baseline value from each of the measured capacitance values for the plurality of sensors; and

generate a difference count value representative of the change in capacitance for each of the plurality of sensors.

15. An apparatus comprising:

a plurality of capacitance sensing inputs coupled to a plurality of capacitance sensors; and

a processing device configured to;

measure capacitance on a plurality of capacitance sensors;

identify at least one peak sensor of the plurality of capacitance sensors;

in a first subtraction function, subtract a first predetermined value from the measured capacitance of each of the plurality of capacitance sensors;

in a first summing function, sum the result of the first subtraction function for the plurality of capacitance sensors; and

in a first comparing function, compare the result of the first summing function to a first threshold; and

if the result of the first summing function is greater than the first threshold, increase the first predetermined value and repeat the first subtraction, summing, and comparing function, and

if the result of the first summing function is not greater than the first threshold, calculate a centroid for each of the at least one peak sensor.

16. The apparatus of claim 15, wherein the processing device is further comprising:

in a second summing function, sum result of the first subtraction function for each capacitance sensor of the plurality of capacitance sensors of each centroid;

in a second comparing function, compare the result of the second summing function to a second threshold; and

if the result of the second comparing function is greater the second threshold, proceed to the calculating a centroid, and

if the result of the second comparing function is not greater than the second threshold, decrease second threshold and repeat the first subtraction function and the first and second summing and comparing functions.

17. The apparatus of claim 16 wherein at least one operation performed by the processing device is performed by a host processor separate to the capacitance measurement processing device.

18. The apparatus of claim 16, wherein the processing device is configured to compare the capacitance of each sensor to those surrounding it and identifying a capacitance sensor as a peak if the measured capacitance is greater than the measured capacitance of the surrounding sensors.

19. The apparatus of claim 16, wherein for the measuring capacitance the processor is configured to:

convert a the capacitance to a digital value;

subtract a baseline value from each of the measured capacitance values for the plurality of sensors; and

generate a difference count value representative of the change in capacitance for each of the plurality of sensors.