Datasheet

Touchscreen controller STMPE811
34/65 Doc ID 14489 Rev 6
Window tracking
The -WDW_X and WDW_Y registers allow to pre-set a sub-window in the touchscreen such
that any touch position that is outside the sub-window is discarded.
Figure 10. Window tracking
FIFO
FIFO has a depth of 128 sectors. This is enough for 128 sets of touch data at maximum
resolution (2 x 12 bits). FIFO can be programmed to generate an interrupt when it is filled to
a pre-determined level.
Sampling
The STMPE811 touchscreen controller has an internal 180 kHz, 12-bit ADC able to execute
autonomous driving/sampling. Each "sample" consists of 4 ADC readings that provide the X
and Y locations, as well as the touch pressure.
Figure 11. Sampling
Active window
Top right coordinates
Bottom left coordinates
ADC
takes X reading
Settling
period
Drive X
ADC
takes Y reading
Settling
period
Drive Y