El escenario
A TTP223 capacitive touch module is powered from the Raspberry Pi 3.3V rail, and its active-high output drives a GPIO pin through a series resistor while a pulldown resistor keeps the pin low when untouched.
Qué hay en este dibujo
Lee las decisiones que hay detrás.
01
Use the Raspberry Pi 3.3V header supply to stay within GPIO voltage tolerance.
02
Add a 100k pulldown on the GPIO input so the pin reads low when the touch pad is idle.
03
Use a 1k series resistor to protect the GPIO pin from transient output conditions.
Reusable for any 3.3V MCU GPIO when wiring a TTP223 active-high touch switch module with a local bypass capacitor and output conditioning.