Datasheet

STMPE811 GPIO controller
Doc ID 14489 Rev 6 53/65
GPIO_RE Rising edge register
Address: 0x15
Type: R/W
Reset: 0x00
Description: GPIO rising edge detection enable register.
Setting this bit to ‘1’ would enable the detection of the rising edge transition.
The detection would be reflected in the GPIO edge detect status register.
GPIO_FE Falling edge detection enable register
Address: 0x16
Type: R/W
Reset: 0x00
Description: Setting this bit to ‘1’ would enable the detection of the falling edge transition.
The detection would be reflected in the GPIO edge detect status register.
GPIO_ALT_FUNCT Alternate function register
Address: 0x17
Type: R/W
Reset: 0x0F
Description: Alternate function register. "‘0’ sets the corresponding pin to function as
touchscreen/ADC, and ‘1’ sets it into GPIO mode.
13.0.1 Power supply
The STMPE811 GPIO operates from a separate supply pin (V
IO
). This dedicated supply pin
provides a level-shifting feature to the STMPE811. The GPIO remains valid until V
IO
is
removed.
The host system may choose to turn off V
cc
supply while keeping V
IO
supplied. However it is
not allowed to turn off supply to V
IO
, while keeping the Vcc supplied.
The touchscreen is always powered by V
IO
. For better resolution and noise immunity, V
IO
above 2.8 V is advised.
13.0.2 Power-up reset (POR)
The STMPE811 is equipped with an internal POR circuit that holds the device in reset state,
until the V
IO
supply input is valid. The internal POR is tied to the V
IO
supply pin.
On power-up reset, all GPIOs are set as input.