Touch sensing
One or more computing devices, systems, and/or methods are provided. In an embodiment of the techniques presented herein, a touch detection system, comprises a touch sensor array comprising unit cells, a transmit sequencer configured to generate an excitation signal, an analog-to-digital-converter unit configured to measure responses of the unit cells to the excitation signal and, a processing unit configured to generate a first capacitance map based on the responses, filter the first capacitance map, by rows, in a first band pass filter to generate a second capacitance map, and detect a touch event based on the second capacitance map.
1 . A method for touch detection, comprising:
scanning unit cells of a touch sensor array to generate a first capacitance map;
filtering the first capacitance map, by rows, in a first band pass filter to generate a second capacitance map, wherein filtering the first capacitance map comprises:
storing a first row of the first capacitance map in a memory block,
selecting a window of data elements in the memory block,
generating a filter output for the window, and
sliding the window through the memory block and iterating the generating of the filter output; and
detecting a touch event based on the second capacitance map.
2 . The method of claim 1 , comprising:
filtering the second capacitance map, by columns, in a second band pass filter to generate a third capacitance map; and
detecting the touch event based on the third capacitance map.
3 . The method of claim 2 , wherein:
the touch sensor array comprises transmit lines and receive lines perpendicular to the transmit lines;
the unit cells are defined at intersections between the transmit lines and the receive lines;
filtering the first capacitance map, by rows, comprises filtering the first capacitance map in a first direction corresponding to the receive lines; and
filtering the second capacitance map, by columns, comprises filtering the second capacitance map in a second direction corresponding to the transmit lines.
4 . The method of claim 1 , comprising:
performing a calibration process on the touch sensor array to generate a baseline map;
subtracting the baseline map from the first capacitance map to generate a third capacitance map; and
detecting the touch event based on the third capacitance map.
5 . The method of claim 1 , wherein:
filtering the first capacitance map, by rows, in the first band pass filter comprises:
mirroring data adjacent a first edge of the first row in the memory block; and
mirroring data adjacent a second edge of the first row in the memory block.
6 . The method of claim 1 , wherein:
filtering the first capacitance map, by rows, in the first band pass filter comprises:
applying a tap weighting factor to each of the data elements to generate weighted data elements; and
summing the weighted data elements to generate the filter output.
7 . The method of claim 1 , wherein:
filtering the first capacitance map, by rows, in the first band pass filter comprises:
storing the window of data elements in a shift register; and
storing the filter output in the memory block.
8 . A touch detection system, comprising:
a touch sensor array comprising unit cells;
a transmit sequencer configured to generate an excitation signal;
an analog-to-digital-converter unit configured to measure responses of the unit cells to the excitation signal; and
a processing unit configured to:
generate a first capacitance map based on the responses;
filter the first capacitance map, by rows, in a first band pass filter to generate a second capacitance map, wherein the filtering of the first capacitance map is by:
storing a first row of the first capacitance map in a memory block,
selecting a window of data elements in the memory block,
generating a filter output for the window, and
sliding the window through the memory block and iterating the generating of the filter output; and
detect a touch event based on the second capacitance map.
9 . The system of claim 8 , wherein:
the processing unit is configured to:
filter the second capacitance map, by columns, in a second band pass filter to generate a third capacitance map; and
detect the touch event based on the third capacitance map.
10 . The system of claim 9 , wherein:
the touch sensor array comprises transmit lines and receive lines perpendicular to the transmit lines;
the unit cells are defined at intersections between the transmit lines and the receive lines; and
the processing unit is configured to:
filter the first capacitance map, by rows, in a first direction corresponding to the receive lines; and
filter the second capacitance map, by columns, in a second direction corresponding to the transmit lines.
11 . The system of claim 8 , wherein:
the processing unit is configured to:
perform a calibration process on the touch sensor array to generate a baseline map;
subtract the baseline map from the first capacitance map to generate a third capacitance map; and
detect the touch event based on the third capacitance map.
12 . The system of claim 8 , wherein:
the processing unit is configured to filter the first capacitance map, by rows, in the first band pass filter by:
mirroring data adjacent a first edge of the first row in the memory block; and
mirroring data adjacent a second edge of the first row in the memory block.
13 . The system of claim 8 , wherein:
the processing unit is configured to filter the first capacitance map, by rows, in the first band pass filter by:
applying a tap weighting factor to each data elements to generate weighted data elements; and
summing the weighted data elements to generate the filter output.
14 . The system of claim 8 , wherein:
the processing unit is configured to filter the first capacitance map, by rows, in the first band pass filter by:
storing the window of data elements in a shift register; and
storing the filter output in the memory block.
15 . A touch detection system, comprising:
a display comprising a touch sensor array having transmit lines and receive lines;
a transmit sequencer configured to generate excitation signals, by transmit line, on the touch sensor array;
an analog-to-digital-converter unit configured to measure responses of the receive lines to the excitation signals; and
a processing unit configured to:
generate a first capacitance map based on the responses;
filter the first capacitance map, by rows, in a first band pass filter to generate a second capacitance map, wherein the filtering of the first capacitance map is by:
storing a first row of the first capacitance map in a memory block,
selecting a window of data elements in the memory block,
generating a filter output for the window, and
sliding the window through the memory block and iterating the generating of the filter output; and
detect a touch event based on the second capacitance map.
16 . The system of claim 15 , wherein:
the receive lines are perpendicular to the transmit lines;
the unit cells are defined at intersections between the transmit lines and the receive lines; and
the processing unit is configured to:
filter the first capacitance map, by rows, in a first direction corresponding to the receive lines;
filter the second capacitance map, by columns, in a second band pass filter in a second direction corresponding to the transmit lines to generate a third capacitance map; and
detect the touch event based on the third capacitance map.