Touch Finding Method and Apparatus

• US 20100097328A1
• Filed: 10/21/2008
• Published: 04/22/2010
• Est. Priority Date: 10/21/2008
• Status: Active Grant

• Current Assignee: Neodrón Limited (Atlantic IP Services Limited)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Simmons, Martin, Pickett, David
• Granted Patent: US 8,659,557 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 2203/04808 Several contacts: gestures triggering a specific function, e.g. scrolling, zooming, right-click, when the user establishes several contacts with the surface simultaneously; e.g. using several fingers or a combination of fingers and pen
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers

Abstract

A method of determining touches from a data set output from a touch screen comprising an array of sensing nodes. The method comprises analyzing the dataset and identifies a node with a maximum signal value among all unassigned nodes, and, if present, assigns that node to a touch. A logical test is applied to each node that is a neighbor to the assigned node to determine if that node should also be assigned to the touch and the logical test is repeatedly applied to the unassigned neighbors of each newly assigned node until there are no more newly assigned nodes, or no more unassigned nodes, thereby assigning a group of nodes to the touch defining its area. This process can be repeated until all of the nodes of a touch panel are assigned to a touch. The method is ideally suited to implementation on a microcontroller. Therefore, although the kind of processing power being considered is extremely modest in the context of a microprocessor or digital signal processor, it is not insignificant for a microcontroller, or other low specification item, which has memory as well as processing constraints.

Claims

1. A method of determining touches from a data set output from a touch screen comprising an array of sensing nodes, the method comprising:

a) identifying a node with a maximum signal value among all unassigned nodes, and, if present,

b) assigning that node to a touch,

c) applying a logical test to each node that is a neighbor to the assigned node to determine if that node should also be assigned to the touch, and

d) repeatedly applying the logical test to the unassigned neighbors of each newly assigned node until there are no more newly assigned nodes, or no more unassigned nodes, thereby assigning a group of nodes to the touch defining its area.

2. The method of claim 1, further comprising:

repeating the method of claim 1 as many times as is required until no node with a maximum signal value is identified, whereupon all touches have been identified and assigned respective groups of nodes defining their area.

3. The method of claim 1, further comprising:

repeating the method of claim 1 up to a fixed number of times or until no node with a maximum signal value is identified, whereafter up to the fixed number of touches have been identified and assigned respective groups of nodes defining their area.

4. The method of claim 1, wherein the logical test involves testing whether the as yet unassigned neighbor node has a signal value lower than that of the assigned node it is being compared with, and if yes provisionally deciding that the as yet unassigned neighbor node is to be assigned to the touch being processed, subject to outcomes of optional other parts of the logical test.

5. The method of claim 4, wherein the logical test additionally involves testing whether the as yet unassigned neighbor node has a signal value greater than a saturation threshold value, and if yes deciding that the as yet unassigned neighbor node is to be assigned to the touch being processed.

6. The method of claim 5, wherein the saturation threshold value is set at a level determined from a pre-calibrated measure of saturation levels for the touch screen.

7. The method of claim 5, wherein the saturation threshold value is set for each touch at a level having regard to the maximum signal value for the touch being processed.

8. The method of claim 4, wherein the logical test additionally involves testing whether the as yet unassigned neighbor node has a signal value lower than a detect threshold, and if yes deciding that the as yet unassigned neighbor node is not to be assigned to the touch being processed.

9. The method of claim 1, wherein prior to step a) all nodes having signal values lower than a detect threshold are tagged so as to be ignored by subsequent processing to assign nodes to touches, thereby to remain unassigned throughout.

10. The method of claim 1, wherein the touch screen is a capacitive touch screen.

11. A 2D touch-sensitive position sensor comprising:

a touch panel having a plurality of sensing elements distributed over its area to form an array of sensing nodes, each of which being configured to collect a location specific sense signal indicative of a touch,

a measurement circuit connected to the sensing elements and operable repeatedly to acquire a set of signal values, each set being made up of a signal value from each of the nodes,

a processor connected to receive the sets of signal values and operable to process each set to output touch data providing information on each touch, the processor being configured to carry out the method of claim 1.

12. Apparatus comprising the 2D touch-sensitive position sensor of claim 11.