TOUCHSCREEN DATA PROCESSING

• US 20140022211A1
• Filed: 09/05/2013
• Published: 01/23/2014
• Est. Priority Date: 07/19/2012
• Status: Active Grant

• Current Assignee: Parade Technologies, Ltd.
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Karpin, Oleksandr, Kolych, Igor, Maharyta, Andriy, Kremin, Victor, van de Waerdt, Jan-Willem, Musijchuk, lhor
• Granted Patent: US 9,377,909 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• 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 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

Capacitive touch sensors and touchscreen data processing methods are provided. In one embodiment, the method includes sequentially integrating and converting charge from each of a plurality of sensing capacitors in an array to digital data, the digital data including sample values corresponding to a measured capacitance for each of the plurality of sensing capacitors. Noise is then separated from useful information by filtering the sample values on a sample-by-sample basis. Finally, the filtered sample values are summed and a position of at least one contact on the array determined using the filtered capacitance values. Other embodiments are also provided.

Claims

1. A method comprising:

sequentially integrating and converting charge from each of a plurality of sensing capacitors in an array to digital data, the digital data including sample values corresponding to a measured capacitance for each of a plurality of sensing capacitors;

filtering the sample values on a sample-by-sample basis; and

summing the filtered sample values and determining a position of at least one contact on the array according to the filtered sample values.

2. The method of claim 1, wherein filtering the sample values comprises applying a first filter configured to limit amplitude of each of the sample values.

3. The method of claim 2, wherein the first filter is configured to replace sample values having a value greater than an upper limit value or less than a lower limit value.

4. The method of claim 3, wherein the first filter is configured to replace sample values having a value greater than the upper limit value with the upper limit value, and to replace sample values having a value less than the lower limit value with the lower limit value.

5. The method of claim 3, wherein the first filter is configured to replace sample values having a value greater than the upper limit value with the sample value of a last preceding sample having a sample value lower than the upper limit value, and to replace sample values having a value less than the lower limit value with the sample value of a last preceding sample having a sample value greater than the lower limit value.

6. The method of claim 2, wherein the first filter is configured to reject sample values having a value greater than an upper limit value or less than a lower limit value.

7. The method of claim 6, wherein the first filter is further configured to replace sample values having a value greater than an upper limit value or less than a lower limit value once a first number (N) of sample values have been rejected within second number (M) of the sample values.

8. The method of claim 2, wherein filtering the sample values further comprises applying a second filter configured to sort and multiply the sample values by at least one weighted value.

9. The method of claim 8, wherein the second filter is configured to sort a number (N) of sequential sample values into a sliding window including a first sample value and a number of boundary samples preceding or following the first sample value, multiply each of the first sample value and boundary samples by a weighted value, sum the products of the multiplied sample values and output a median of the weighted sample values as a new sample value for the first sample value.

10. The method of claim 9, wherein the second filter is configured to reject sample values from the number (N) of sequential sample values having a value greater than an upper limit value or less than a lower limit value.

11. A method comprising:

sequentially integrating and converting charge from each of a plurality of sensing capacitors in an array to digital data, the digital data including sample values corresponding to a measured capacitance for each of a plurality of sensing capacitors;

filtering the sample values on a sample-by-sample basis by applying a filter configured to sort and multiply the sample values by at least one weighted value; and

summing the filtered sample values and determining a position of at least one contact on the array according to the filtered sample values.

12. The method of claim 11, wherein the filter is configured to sort a number (N) of sequential sample values into a sliding window including a first sample value and a number of boundary samples preceding or following the first sample value, multiply each of the first sample value and boundary samples by a weighted value, sum the products of the multiplied sample values and output a median of the weighted sample values as a new sample value for the first sample value.

13. The method of claim 12, wherein the second filter is configured to reject sample values from the number (N) of sequential sample values having a value greater than an upper limit value or less than a lower limit value.

14. The method of claim 12, wherein the boundary samples include one or more mirrored sample values of sample values preceding or following the first sample value to extend the sliding window beyond boundaries of the sequence of sample values.

15. The method of claim 12, wherein the boundary samples include one or more copied sample values of the first sample value to extend the sliding window beyond boundaries of the sequence of sample values.

16. The method of claim 12, wherein the filter is further configured to sort the number (N) of sequential sample values into a first sequence of odd numbered sample values and a second sequence of even numbered sample values, and to output a median of the weighted odd sample values for the first sequence of odd numbered sample values and a median of the weighted even sample values for the second sequence of even numbered sample values.

17. The method of claim 12, wherein the filter is a conditional median filter configured to sort the number (N) of sequential sample values, calculate at least one condition of the sample values and if the condition is met output the median of the weighted sample values as a new sample value for the first sample value and, if the condition is not met output a mean of the weighted sample values as a new sample value for the first sample value.

18. A system comprising:

an analog front end configured to sequentially integrate and convert charge from each of a plurality of sensing capacitors in an array to digital data; and

a channel engine to receive digital data from the analog front end and generate of sample values corresponding to a measured capacitance for the plurality of sensing capacitors, the channel engine including;

a number of filters configured to filter the sample values on a sample-by-sample basis; and

a digital section configured to sum the filtered sample values and determine a position of at least one contact on the array according to the filtered sample values.

21. The system of claim 18, wherein the channel engine further comprises a hardware accelerator configured to store a subset of measured capacitance values, the subset of measured capacitance values comprising at least the capacitance values used for determination of a node as a local maximum.

19. The system of 18, wherein the number of filters comprises a first filter configured to limit amplitude of each of the sample values.

20. The system of claim 19, wherein the number of filters further comprises a second filter configured to sort and multiply the sample values by at least one weighted value.