Touch finding method and apparatus
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.
1. A method comprising:
accessing, for each sensing node of a plurality of sensing nodes of a touch sensor, a corresponding measured signal value of the sensing node;
assigning a first sensing node of the plurality of sensing nodes to a first touch based on the corresponding measured signal values of the plurality of sensing nodes, the first sensing node having a maximum corresponding measured signal value among unassigned sensing nodes, the first sensing node being an original start node for the first touch; and
determining, subsequent to determining that a second sensing node adjacent to the first sensing node should be assigned to the first touch and for each sensing node adjacent to the second sensing node, whether to assign the sensing node to the first touch by applying a logical test using the corresponding measured signal value of the sensing node, the logical test comprising:
determining whether the corresponding measured signal value of the sensing node is within a percentage range of the corresponding measured signal value of the first sensing node;
assigning the sensing node to the first touch when the corresponding measured signal value of the sensing node is within the percentage range;
determining, when the corresponding measured signal value of the sensing node is not within the percentage range, whether the corresponding measured signal value of the sensing node is lower than the corresponding measured signal value of the second sensing node and greater than a minimum detect threshold value; and
assigning the sensing node to the first touch when the corresponding measured signal value of the sensing node is lower than the corresponding measured signal value of the second sensing node and greater than the minimum detect threshold value.
2. The method of claim 1 , further comprising:
assigning a second sensing node of the plurality of sensing nodes to a second touch; and
determining, for each sensing node adjacent to the second sensing node, whether to assign the sensing node to the second touch by applying a logical test using the corresponding measured signal value of a sensing node that is adjacent to the second sensing node, the adjacent sensing node being assigned to the second touch when the corresponding measured signal value of the adjacent sensing node is lower than the corresponding measured signal value of the second sensing node.
3. The method of claim 2 , further comprising assigning a third sensing node of the plurality of sensing nodes to both the first touch and the second touch.
4. The method of claim 1 , comprising, prior to assigning the first sensing node to the first touch, for each of the plurality of sensing nodes:
determining whether the corresponding measured signal value of the sensing node is less than the minimum detect threshold, and
assigning, when the corresponding measured signal value of the sensing node is less than the minimum detect threshold, the sensing node to a null touch state such that the sensing node is not considered for assignment to any other touch for an analysis corresponding to a sample interval.
5. The method of claim 1 , comprising:
prior to determining for a particular sensing node that is adjacent to the first sensing node whether to assign the particular sensing node to the first touch, determining whether the corresponding measured signal value of the particular sensing node is less than the minimum detect threshold; and
assigning, when the corresponding measured signal value of the particular sensing node is less than the minimum detect threshold, the particular sensing node to a null touch state.
6. The method of claim 1 , wherein a total number of touches is limited based on an application user interface using the touch sensor.
7. The method of claim 1 , wherein the touch sensor comprises a capacitive touch screen.
8. The method of claim 1 , wherein:
the first sensing node and one or more other sensing nodes in the plurality of sensing nodes are assigned to the first touch; and
the method further comprises summing the measured signal values for each of the sensing nodes assigned to the first touch to quantify a strength of the first touch.
9. A touch sensor, comprising:
a plurality of sensing nodes;
a measurement circuit configured to acquire measured signal values from of the plurality of sensing nodes;
a processor configured to:
access, for each sensing node of the plurality of sensing nodes, a corresponding measured signal value of the sensing node;
assign a first sensing node of the plurality of sensing nodes to a first touch based on the corresponding measured signal values of the plurality of sensing nodes, the first sensing node having a maximum corresponding measured signal value among unassigned sensing nodes, the first sensing node being an original start node for the first touch; and
determine, subsequent to determining that a second sensing node adjacent to the first sensing node should be assigned to the first touch and for each sensing node adjacent to the second sensing node, whether to assign the sensing node to the first touch by applying a logical test using the corresponding measured signal value of the sensing node, the logical test comprising:
determining whether the corresponding measured signal value of the sensing node is within a percentage range of the corresponding measured signal value of the first sensing node;
assigning the sensing node to the first touch when the corresponding measured signal value of the sensing node is within the percentage range;
determining, when the corresponding measured signal value of the sensing node is not within the percentage range, whether the corresponding measured signal value of the sensing node is lower than the corresponding measured signal value of the second sensing node and greater than a minimum detect threshold value; and
assign the sensing node to the first touch when the corresponding measured signal value of the sensing node is lower than the corresponding measured signal value of the second sensing node and greater than the minimum detect threshold value.
10. The touch sensor of claim 9 , wherein the processor is further configured to:
assign a second sensing node of the plurality of sensing nodes to a second touch; and
determine, for each sensing node adjacent to the second sensing node, whether to assign the sensing node to the second touch by applying a logical test using the corresponding measured signal value of a sensing node that is adjacent to the second sensing node, the adjacent sensing node being assigned to the second touch when the corresponding measured signal value of the adjacent sensing node is lower than the corresponding measured signal value of the second sensing node.
11. The touch sensor of claim 10 , wherein the processor is configured to assign a third sensing node of the plurality of sensing nodes to both the first touch and the second touch.
12. The touch sensor of claim 9 , wherein the processor is configured to, prior to assigning the first sensing node to the first touch, for each of the plurality of sensing nodes:
determine whether the corresponding measured signal value of the sensing node is less than the minimum detect threshold, and
assign, when the corresponding measured signal value of the sensing node is less than the minimum detect threshold, the sensing node to a null touch state such that the sensing node is not considered for assignment to any other touch for an analysis corresponding to a sample interval.
13. The touch sensor of claim 9 , wherein the processor is configured to:
prior to determining for a particular sensing node that is adjacent to the first sensing node whether to assign the particular sensing node to the first touch, determine whether the corresponding measured signal value of the particular sensing node is less than the minimum detect threshold; and
assign, when the corresponding measured signal value of the particular sensing node is less than the minimum detect threshold, the particular sensing node to a null touch state.
14. A device, comprising:
a first processor;
a touch sensor comprising:
a plurality of sensing nodes;
a measurement circuit configured to acquire measured signal values from of the plurality of sensing nodes;
a second processor configured to:
access, for each sensing node of the plurality of sensing nodes, a corresponding measured signal value of the sensing node;
assign a first sensing node of the plurality of sensing nodes to a first touch based on the corresponding measured signal values of the plurality of sensing nodes the first sensing node having a maximum corresponding measured signal value among unassigned sensing nodes, the first sensing node being an original start node for the first touch; and
determine, subsequent to determining that a second sensing node adjacent to the first sensing node should be assigned to the first touch and for each sensing node adjacent to the second sensing node, whether to assign the sensing node to the first touch by applying a logical test using the corresponding measured signal value of the sensing node, the logical test comprising:
determining whether the corresponding measured signal value of the sensing node is within a percentage range of the corresponding measured signal value of the first sensing node;
assigning the sensing node to the first touch when the corresponding measured signal value of the sensing node is within the percentage range;
determining, when the corresponding measured signal value of the sensing node is not within the percentage range, whether the corresponding measured signal value of the sensing node is lower than the corresponding measured signal value of the second sensing node and greater than a minimum detect threshold value; and
assigning the sensing node to the first touch when the corresponding measured signal value of the sensing node is lower than the corresponding measured signal value of the second sensing node and greater than the minimum detect threshold value.