Datasheet

14
9502A–AT42–07/08
AT42QT2160
4.18 General Purpose Inputs/Outputs
There are three dedicated GPIOs (GPIO1...3) and eight GPOs shared with X lines (X0...7).
Shared GPOs are always outputs, whereas dedicated GPIOs can be set to be outputs or inputs.
GPIOs set to input can be used for reading dome switches or logic signals. Outputs can be used
to drive LEDs, or other devices. It is recommended driving external devices through the use of
bipolar transistors or MOSFETs, so as not to affect capacitive sensing if a load fluctuates the
power rail by drawing/sinking too much current.
All GPOs and GPIOs set to output can be PWM driven, if the corresponding PWM bit is set. Note
that the PWM duty cycle will be an approximation, as GPIOs will not be switched during
acquisition bursts.
The dedicated GPIOs have a Wake option, that if enabled will enable dedicated GPIOs set as
inputs, to be read in SLEEP mode.
Note that shared GPOs (X0...X7) are driven by the burst pulses during acquisition bursts, if the
corresponding X line is used in the keys/slider. A low pass filter can be inserted to eliminate
these burst pulses, as shown in Figure 4-9 on page 16.