12.1 Touchpad Resolution

The resolution is the number of positions to be reported for each sensor area. Its value can range from two to 12 bits (i.e., four to 4096 positions).

The total resolution for X-axis = number of X lines x the number of positions for one sensor.

The total resolution for Y-axis = number of Y lines x the number of positions for one sensor.

Touchpad resolution (dpi) = number of sensors available in one-inch area x the number of positions for one sensor.

The number of sensors available in the one-inch area = one-inch area in mm / one sensor area in mm.

The QT2 Xplained Pro extension board is used as a touch surface in this application. On it, one sensor area is 8 mm x 8 mm, and the firmware uses a 7-bit position resolution. Using the above calculation, the touchpad resolution for the QT2 touch surface design adds up to 102 dpi.

Table 12-2 shows the position and resolution that is possible with a 4X x 4Y sensor configuration, with one sensor area of 8 mm x 8 mm and for different resolution inputs.