Hardware accelerator for touchscreen data processing
View Patent ↗A contact's interaction with a sensing array is subject to several external and internal stimuli which may impact a processing unit's confidence in the characteristics of that interaction or the presence of the interaction itself. Fidelity of user action is greatly improved with a step-wise and holistic analysis of a contact on an array of capacitance sensors, which allows for repetition of certain steps of processing or the entire operation if threshold confidence levels are not achieved.
1. A method of local maximum calculation for a touch sensing system, comprising:
at a hardware accelerator including a local memory array, wherein the hardware accelerator is distinct from a central processing unit (CPU) that is configured to execute commands and control an analog front end of the touch sensing system:
fetching a plurality of capacitance values corresponding to nodes of a grid of nodes of a capacitance sense array;
storing the plurality of capacitance values in the local memory array;
selecting a center node in a window of nodes within the grid of nodes, the center node having a second capacitance value, wherein the window of nodes includes a first number of nodes that is less than a total number of nodes in the grid;
identifying a first node adjacent to the center node along an axis and having a first capacitance value;
after determining that the first capacitance value of the first node is equal to the second capacitance value of the center node:
identifying a third node and a fourth node in the window of nodes, wherein the third node is adjacent to the first node along the axis and has a third capacitance value, and the fourth node is adjacent to the center node along the axis and has a fourth capacitance value;
comparing the third capacitance value of the third node to the fourth capacitance value of the fourth node;
in accordance with a determination that the third capacitance value is less than the fourth capacitance value, determining that the center node is the local maximum of the window of nodes; and
in accordance with a determination that the third capacitance value is greater than the fourth capacitance value, determining that the first node is the local maximum of the window of nodes.
2. The method of claim 1 , wherein the first node is located in a cardinal direction of the center node.
3. The method of claim 2 , wherein the axis is a cardinal axis relative to the center node.
4. The method of claim 1 , wherein the first node is located in a diagonal direction of the center node.
5. The method of claim 4 , wherein the axis is a diagonal axis relative to the center node.
6. The method of claim 1 , wherein the storing the plurality of capacitance values comprises storing the plurality of capacitance values in a plurality of next available cells of the memory array.
7. An apparatus comprising:
a capacitive sense array configured to receive a plurality of capacitance values corresponding to nodes of a grid of nodes;
a processing device, coupled to the capacitive sense array, wherein the processing device is distinct from a central processing unit (CPU) that is configured to execute commands and control an analog front end, and the processing device is configured to:
fetch the plurality of capacitance values corresponding to nodes of the grid of nodes of a capacitance sense array;
store the plurality of capacitance values in a memory array;
select a center node in a window of nodes within the grid of nodes, the center node having a second capacitance value, wherein the window of nodes includes a first number of nodes that is less than a total number of nodes in the grid;
identify a first node adjacent to the center node along an axis and having a first capacitance value;
after determining that the first capacitance value of the first node is equal to the second capacitance value of the center node:
identify a third node and a fourth node in the window of nodes, wherein the third node is adjacent to the first node along the axis and has a third capacitance value, and the fourth node is adjacent to the center node along the axis and has a fourth capacitance value;
compare the third capacitance value of the third node to the fourth capacitance value of the fourth node;
in accordance with a determination that the third capacitance value is less than the fourth capacitance value, determine that the center node is the local maximum of the window of nodes; and
in accordance with a determination that the third capacitance value is greater than the fourth capacitance value, determine that the first node is the local maximum of the window of nodes.
8. The apparatus of claim 7 , wherein the first node is located in a cardinal direction of the center node.
9. The apparatus of claim 8 , wherein the axis is a cardinal axis relative to the center node.
10. The apparatus of claim 7 , wherein the first node is located in a diagonal direction of the center node.
11. The apparatus of claim 10 , wherein the axis is a diagonal axis relative to the center node.
12. The apparatus of claim 7 , wherein the processing device is further configured to store the plurality of capacitance values in a plurality of next available cells of the memory array.