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Mutual Capacitance Button
Create a User Board project for Mutualcap technology from Sensors > Button > Technology > Mutualcap from within the QTouch® Configurator. (Refer to the "Generate a QTouch Configurator Project" page for more details.)
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Pin Selection View
The mutual capacitance sensors are grouped down as per the Y-lines. If the total number of sensors for a given Y line is more than four, multiple groups are formed with four X-lines for each group. The group information can be found in touch.h file as illustrated below.
For a given Y line, if the number of sensors is less than four or if the number of sensors is not a multiple of four, virtual sensors named X_NONE are added to the group in that Y-line.
In the above example configuration, Y0 will not have X_NONE and the Y2 group will have two X_NONE as shown below.
The acquisition parameters (like filter level, prescaler, CSD etc) for the group is decided by the maximum values configured for the corresponding Y line.
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Node Mapping Information
If the number of sensors is not a multiple of four or if each Y line does not have a multiple of four sensors, then the total number of nodes and buttons does not match. Even if everything is multiple of four, the buttons may not be sequentially assigned for a given Y line. So, to map the node to an individual button, an array is created in the touch.c file. The array touch_key_node_mapping_4p in the touch.c file displays the button’s position in the group created.
Additional Group Example
If the sensors are interchanged as above, the following changes reflects in both touch.h and touch.c file.