qmk-firmware/docs/internals_gpio_control.md

# GPIO Control

QMK has a GPIO control abstraction layer which is microcontroller agnostic. This is done to allow easy access to pin control across different platforms.

## Functions

The following functions can provide basic control of GPIOs and are found in `quantum/quantum.h`.

|Function              |Description                                                       |
|----------------------|------------------------------------------------------------------|
|`setPinInput(pin)`    |Set pin as input with high impedance (High-Z)                     |
|`setPinInputHigh(pin)`|Set pin as input with build in pull-up                            |
|`setPinInputLow(pin)` |Set pin as input with build in pull-down (Supported only on STM32)|
|`setPinOutput(pin)`   |Set pin as output                                                 |
|`writePinHigh(pin)`   |Set pin level as high, assuming it is an output                   |
|`writePinLow(pin)`    |Set pin level as low, assuming it is an output                    |
|`writePin(pin, level)`|Set pin level, assuming it is an output                           |
|`readPin(pin)`        |Returns the level of the pin                                      |

## Advanced Settings

Each microcontroller can have multiple advanced settings regarding its GPIO. This abstraction layer does not limit the use of architecture-specific functions. Advanced users should consult the datasheet of their desired device and include any needed libraries. For AVR, the standard avr/io.h library is used; for STM32, the ChibiOS [PAL library](http://chibios.sourceforge.net/docs3/hal/group___p_a_l.html) is used.